text: Research and Development Laboratories of the Portland Cement Association RESEARCH DEPARTMENT Bulletin 91 Early High-Strength Concrete for Prestressing BY PAUL KLIK.I R MARCH, 195 Chicago Authorize*! Reprint from Proceedings, World Conference on Prestressed Concrete Sa\ Fkw UUFORNIA EARLY HIGH-STRENGTH CONCRETE FOR PRESTRESS1NG Paul Klieger* SYNOPSIS The continued growth of prestressed concrete de- pends to a large extent on its relative economy in com- parison with other structural materials. The cost of producing high -strength concrete and the resulting economies which can be effected by early application of prestress are important factors in this economic pic - ture. This report discusses the techniques which are pre- sently at our disposal for producing early high -strength concrete t Data on other properties of high -strength con- crete, such as elasticity, creep, drying shrinkage, bond to steel, and durability are presented. INTRODUCTION The use of prestressed concrete is growing rapidly. Continued growth is dependent to a large extent on its relative economy and suitability in comparison with other structural materials. Two important factors in the economics of pre- stressed concrete are the cost of producing early high - strength concrete and the resulting economies which can be effected by the early application of the prestress in either the pretensioned or post-tensioned methods. In the pretensioned method, early application of prestress permits more efficient utilization of forms and stressing equipment. The earlier the concrete reaches the re- quired strength, the earlier the prestress can be applied. This report deals with the means which are presently at our disposal for producing early high-strength con- crete. The choice of method for a particular situation will depend upon the availability of specific materials, mixing equipment, and compacting equipment and on the relative effectiveness of the method. When con- sidering these means for attaining early high strength. Important physical properties of the concrete other than strength must also be kept in mind. •Senior Research Engineer, Applied Research Section, Portland Cement Association, Chicago, FUNDAMENTAL BASIS OF STRENGTH DEVELOPMENT The cementing medium In concrete is produced by the chemical reaction between Portland cement and water. The inherent strength of this medium is primar- ily a function of the ratio of the amounts of these two components, normally expressed either on a weight ba- sis or in gallons per sack of cement. This is the fa- miliar "water -cement ratio". The manner in which this ratio influences the strength of the paste or gel, and hence the strength of the concrete, is illustrated in Fig. 1. The sol id -line curve is the familiar characterization of Abram's water-cement ratio law for "..... plastic, workable mixes ,....," or as we now realize for mixes fully compacted (minimum entrapped air voids). Actu- ally, this particular example represents the relationship between water-cement ratio and strength for an initially workable mix of fixed proportions. As the water-cement ratio of the mix is decreased, by decreasing the amount of water added, the mix becomes progressively less workable and full compaction by hand-placing methods becomes impossible, as indicated by the drop in strength when the water-cement ratio is decreased below a point characteristic of each particular mix. If at this point mechanical compaction is used, the strengths will con- tinue to increase until the particular method of mechan- ical compaction being used no longer produces full compaction. For fully compacted concrete, therefore, the strength is determined primarily by the water-cement ratio of the paste. The proportion of the potential or ultimate strength actually developed in a given concrete at a particular age is affected by many factors such as curing conditions, type of cement, and others. INFLUENCE OF MIX PROPORTIONS The amount of a given aggregate that can be ac- commodated in a cement paste of a particular water- cement ratio depends upon its influence on the workability of the resulting mixture. The limiting amount is that maximum amount which can be used and still attain full compaction of the concrete. In other words, the mix proportions (meaning the relative pro- proportions of cement and aggregate) are of importance mainly insofar as they influence the workability of the concrete. Increasing the proportion of aggregate in a mix with a fixed water-cement ratio progressively decreases the consistency and workability of the concrete. There are a number of advantages to using the maximum amount of aggregate per unit of cement consistent with avail- able placing techniques. Some of these advantages re- lative to certain physical properties of the resulting A5-I WORLD CONFERENCE ON PRESTRESSED CONCRETE concrete will be discussed later in this report. Of main interest, however, is the influence of mix proportions on the cement requirement of the concrete. An increase in the amount of aggregate per unit volume in a mix of fixed water-cement ratio results in a reduction in both the amount of cement and the amount of water per unit volume of concrete produced and therefore a more economical concrete with lower shrinkage character- istics. Considerably more economy, in addition to other benefits, can be effected by utilizing a more efficient placing technique, such as vibration, in order to use still greater amounts of aggregate. Fig. 2 shows some data obtained recently in our laboratory using a Type 1 port- land cement in concretes having net water- cement ratios ranging from 0.29 to 0.41 by weight. The hand- placed concretes required considerably more paste per unit volume in order to provide sufficient workability to enable compaction with relative ease. The cement contents of these hand -placed mixes ranged from 6 to 12 sacks per cubic yard. The concretes which were placed by external vibration, however, contained less paste per unit volume and though they were dry and unworkable by hand -placing standards, these concretes were easily compacted by this external vibration. The cement con- tents of these vibrated concretes ranged from 5 to 9£ sacks per cubic yard. The reductions in cement con- tent afforded by a change in mix proportions and a con- comitant change in placing technique ranged from 1 to 2\ sacks per cubic yard. The net saving effected by these reductions in cement content would depend upon additional costs which might be incurred in mixing these dry concretes, transporting and vibrating, and the cost of more substantial forms required for vibration. One other aspect of mix proportions is the proportion of sand in the total aggregate. Progressing from a hand- placing technique to more and more efficient methods of mechanical compaction, the amount of sand required for good placeability can be reduced materially. This reduction in sand percentage permits the use of less water per cubic yard for the same level of workability and consequently a greater amount of aggregate per unit of cement. The vibrated mixes had lower sand percent- ages than the hand -placed mixes, as shown in Fig. 2. ment. For prestressing, the time required to develop the necessary strength is of particular importance. 1 INFLUENCE OF CURING CONDITIONS Since the reaction between cement and water is chemical, the temperature at which the reaction takes place would be expected to influence the rate of the reaction. Both the availability of water and the tem- perature are extremely important aspects of curing, particularly with regard to early high -strength develop - Availability of Water When cement and water react, an internal defi- ciency of water in the system may occur unless addi- tional curing water is supplied^). If this deficiency (by self-desiccation) occurs, the rate and degree of ultimate hydration may be reduced. Such deficiencies are more likely to occur in low water-cement ratio mixes for prestressed concrete. The influence of this factor on strength development is greater at the later ages than it is at the age of one day. This effect is illustrated in Figs. 3 and 4. Fig. 3 shows data for hand -placed concretes (1 to 2 in. slump) where the availability of curing water during the 24 -hr. period in which the test cylinders were in the molds was increased by two means, ft) saturating the aggregate prior to use, and (2) ponding the top of the cylinder im- mediately after casting. For the 0.42 water -cement ra- tio concrete the increase in strength due to these tech- niques was nil at one day and about 750 psi at 28 days. For the 0.29 water-cement ratio concrete the increase was about 400 psi at one day and 850 psi at 28 days. Fig. 4 shows data for vibrated concretes (zero slump) made with saturated aggregate with either damp burlap covering or ponding during the 24 -hr. period in the molds. At one day, there was little influence of the ponding, the increases ranging from zero at 0.42 water- cement ratio to about 150 psi at 0.29 water-cement ratio. At 28 days, there was no increase at 0, 42 and about 1000 psi increase at 0.29 water -cement ratio. These increases at the low water -cement ratio become significant as early as three days, as can be seen in Fig. 4, The influence of depth of section on the efficiency of the ponding technique has not yet been evaluated. Burlap in direct contact with the surface and kept satu- rated would approximate the ponding treatment. For concrete made with lightweight aggregates i ', tests indicate that ponding was of no benefit. Light- weight aggregates absorb considerable water during mixing which apparently can transfer to the paste dur- ing hydration. Temperature Since the reaction between water and cement is a chemical reaction, increasing the temperature during curing might be expected to increase the rate of strength gain. To illustrate the influence of temperature on A5-2 EARLY HIGH-STRENGTH CONCRETE FOR PRESTRESSING strength development, Fig. 5 shows the one -day strengths of concretes mixed and cured at different tempera- tures^ as percentages of the 73°F strengths. These concretes were cast in uninsulated steel molds and were stored at the temperatures indicated. Temperatures be- low 73°F resulted in lower one -day strengths, and tem- peratures above 73° F resulted in higher one -day strengths, than that developed at 73°F. Although later - age strengths are somewhat reduced by initial curing at elevated temperatures, no retrogression in strength oc- curs with age ( \ Acceleration of strength gain at the early ages by providing elevated temperatures can be accomplished in a number of ways. The use of saturated steam at at- mospheric pressure serves up to the boiling point of water. From that point, saturated steam under pressure can be used to provide still higher temperatures. For the prestressed concrete industry, saturated steam at at- mospheric pressure appears most adaptable for the size f thape, and manner in which the majority of units must be made. Ponding of exposed top surfaces or covering with burlap kept saturated could be employed to ad- vantage to reduce the possibility of drying and to pro- vide additional curing water to counter the effect of lelf-dessication. Saturated steam must be provided to prevent drying out during the curing process. This type of curing normally employs temperatures in the range of 140 to 165° F. Temperatures higher than this may, in some cases, result in somewhat lower strengths at the end of the curing cycle. This range appears to be the optimum for most concretes. The cycle usually con- sists of a 3 to 6 -hour preset, or waiting, period im- mediately after fabrication at normal temperature, fol- lowed by about a 16 -hour period of heating with satu- rated steam at the temperature within the range selected as optimum for the materials being used, and subsequent gradual cooling over about a 3 -hour period to avoid ex- cessive drying. The optimum temperature is .dependent to some extent on mix proportions, type of cement, and type of aggregate. In a recent series of tests, concretes were prepared at 0.4 and 0.5 water-cement ratios by weight, cement contents approximately 9^ and 7^ sacks of Type I Portland cement, respectively, and subjected to saturated steam at 140°F for 16 hours after a 4 -hour preset period at 73°F. The one -day strength of these concretes was 4080 and 2940 psi, respectively, in con- trast to the respective 73°F one -day strengths of 1590 and 950 psi. This comparison demonstrates the strength increases that can be obtained by the use of saturated - steam curing at atmospheric pressure. The reaction between cement and water liberates heat. In the production of prestressed concrete elements mixes of low water-cement ratio and high cement con- tent are necessarily employed. Because ofthe high con- centration of cement in these mixes, a considerable amount of heat is liberated. This heat, if retained , can raise the concrete temperature by a substantial amount and thereby increase early strength develop- ment. Figure 6 shows the increase in concrete tempera- ture normally to be expected if the heat generated were fully retained. These theoretical calculations were based on heat-of-hydration studies of neat-cement pastes using the conduction-calorimeter technique ( 4 ) and are for a A\ gal. per sk. mix containing 8i sk. of Type I or Type III Portland cement per cu. yd. For example, using a typical Type I cement in this concrete mix at 70° F, and retaining all of the heat generated, a rise of almost 60° F in concrete temperature to about 130° F at 24 hours should be noted. Actually, the temperature would rise somewhat above 130° F f since the additional heat increases the rate of hydration and more and more heat would be generated as the concrete temperature rose, as seen by the 105°F data for both types of cement. Complete retention of the heat generated within the first 24 hours could raise the temperature ofthe concrete well over what might be considered optimum. However, almost perfect insulation would be extremely costly and is not likely to be used. Insulation of the blanket or bat type, such as spun glass, rock wool, balsam wool, and others, is reusable and can retain sufficient heat to pro- vide significant increases in the early strengths. Insu- lation used in combination with some artificial heat at the start to promote heat generation appears to offer possible economies in the production of prestressed units. The effectiveness of various insulating materials is being evaluated in a current series of tests in our labo- ratory. As an example, concrete cylinders were fabri- cated by external vibration in steel molds, using a dry mix at a water-cement ratio of 0.36 by weight and both Type I and Type HI Portland cements. The tops of the cylinders were sealed with a thin sheet of plastic to pre- vent loss of moisture. The group of molds was then completely wrapped in a one -inch-thick blanket of spun glass fibers. After one day, some of the cylinders were removed for immediate testing or for 2 days of ad- ditional curing in the moistroom at 73 F, The re- mainder were kept wrapped for an additional two days. The results of these strength tests are shown in Fig. 7. The one -day strength was increased from 2200 psi to 2700 psi for the Type 1 cement, an increase of about 25%. For the Type III cement, the increase was about 28%. The temperature of the concrete at the end of the first day was about 90° F for the Type I cement and about 100 F for the Type III cement. The initial temperature of both concretes was about 75°F. Actually, for complete A5-3 WORLD CONFERENCE ON PRESTRESSED CONCRETE retention of heat, these temperatures at one day should have been somewhat higher. Under these test con- ditions, this particular mode of insulation retained about 40% of the heat generated. Nevertheless, the increase in the one -day strength was 23°}o for the Type I cement and 28% for the Type III cement --economically sig- nificant increases considering that the insulation can be reused a number of times. Maintaining insulation for 3 days resulted in further increases in strength. The cost of more efficient insulation, which would retain a greater proportion of the heat generated, would have to be balanced against the cost of supplying additional heat by means of saturated steam or other means. A combination of these two techniques appears to be the most desirable course, particularly since some insulating enclosure must be provided even when additional heat Is supplied. More efficient, reusable insulation would re- sult in savings in the amounts of additional heat which would need to be provided. INFLUENCE OF TYPE OF CEMENT The rate of strength development of concrete can be varied by using different types of Portland cement. Of the different types in general use (ASTM Types I, n, III, and their counterpart air -entraining cements), ASTM Type III (high -early -strength portland cement) develops strength more rapidly than the other types. Concrete made with this type of cement gains strength more rap- idly at early ages than concrete made with Type I or Type II cement. However, under continuous moist cur- ing the strengths are about the same at ages later than about 3 months. Figure 8 shows some typical strength data of concretes made with Type I and Type III portland cements. The net water -cement ratio of these concretes was 0.35 by weight, the cement content 6i sk. per cu. yd. These were zero -slump concretes compacted by ex- ternal vibration. Curing was at 73°F t in steel molds for the first day and thereafter in the moistroom. The con- cretes made with the Type III cement were considerably stronger than those made with the Type I cement; the strength ratios of Type 111 to Type I were 1.86, 1.50, and 1.23 for 1, 3, and 7 days, respectively. The use of Type III cement coupled with the blanket insulation pre- viously described and saturated-steam curing at elevated temperature would produce concretes having a one -day strength well in excess of 5000 psi. THE INFLUENCE OF ACCELERATORS The hydration of cement can be accelerated by the addition of relatively small amounts of inorganic mater- ials. Of these materials, calcium chloride is the most commonly used accelerator. Calcium chloride in amounts ranging from one to two percent by weight of the cement provides significant increases in early strength development In common with other means of accelerating strengtn gain at the early ages, at28days and later the strengths of concretes with and without calcium chloride are approximately equal. Figure 9 shows the effect of V]o of calcium chlor- ide on the strength of a 0.35 water-cement ratio mix made with Type I portland cement. There is a consider- able increase in the one -day strengths, these increases decreasing with age, as indicated by the ratios at the ages of one, three, and seven days. However, a serious problem has arisen with regard to the use of calcium chloride in prestressed concrete. The presence of chloride ions in the concrete may pro- duce conditions favorable for corrosion of the steel. Lo- calized and severe corrosion under these conditions may occur in the steel, particularly at voids in the interface between the steel and the concrete, causing steel failure. A comprehensive study of this corrosion problem is now under way in our laboratories. Available evidence indi- cates only that when chloride ions are present, localized corrosion and consequent failure of steel under stress may take place. At present, the use of calcium chloride for prestressed concrete is not recommended, particularly for pretensioned prestressed applications. In post -ten- sioned work, either grouting of the steel after tension- ing or the presence of a bond -breaking shield might in- troduce a sufficient barrier to chloride ions. This possi- bility is being investigated. INFLUENCE OF COMPACTION It was stated earlier in this report that the strength of the concrete was controlled primarily by the water-cem- ent ratio, provided the concrete was fully compacted. Actually, strength is related to the voids-cement ratio, the voids being the sum of the volumes of water and air in the concrete, the volume of air being an index of the efficiency of compaction. The air in this case is not the air which we intentionally entrain in the paste by means of air -entraining cements or air -entraining admixtures, but is entrapped air resulting from the use of dry, harsh mixes. Any technique of compaction is suitable, provided full compaction can be attained. If full compaction is attained, the water-cement ratio will then be as good a criterion of strength as voids-cement ratio, since the amount of entrapped air voids would be small and exert little influence on the magnitude of the voids-cement ratio. Figure 10 shows the one-day and three -day strengths A5~4 EARLY HIGH-STRENGTH CONCRETE FOR PRESTRESSING of concretes of four different water -cement ratios! for both hand -placed and vibrated concretes. Essentially similar strengths were produced by the two placing tech- niques. However, the hand -placed concretes had slumps in the range of one to two inches and were easily com- pacted by rodding. In a recent series of tests of zero- slump concrete by both hand-placing and vibration, the strength ratios of vibrated to hand -placed concrete ranged from 1.00 to 1.09 for about a 5% average increase in strength of the vibrated concretes. This indicates that with the dry, harsh mixes, hand-roddingof the specimens did not achieve complete compaction, even though ex- treme care was taken. In stiff, low water-cement ratio mixes, mechanical compaction must be resorted to in order to compact these mixes efficiently and economically. Figure 2 showed the economy which could be effected by the use of vi- bration in compacting these concretes. Three general types of vibration may be employed: internal, form, or surface vibration. Internal and form vibration are more generally applicable to the production of prestressed con- crete units. Of these two methods, internal vibration is to be preferred since the power is transmitted directly to the concrete and the portability of the equipment permits more flexible use during vibration. Opinions vary as to the influence of frequency of vi- bration and amplitude of vibration on strength. A recent series of tests were made in our laboratory using a vi- brating table to supply external vibration during casting of test cylinders. Aside from the time of vibration nec- essary, there appeared to be little choice as to frequen- cy or amplitude provided that the concrete was fully compacted. Some typical test results are shown in Fig. 11. Frequencies ranging from 3600 to 11,000 vibrations per minute used in combination with different amplitude settings showed no consistent influence on the strengths of these zero -slump concretes. However, frequency and amplitude influenced considerably the duration of vibra- tion necessary to achieve adequate compaction. At a particular frequency, a larger amplitude of vibration re- duced the required time and, at a given amplitude, a higher frequency reduced the time for compaction. Ob- viously, from the standpoint of economy, the particular combination of frequency and amplitude which achieves full compaction in the shortest time would be desirable. To take advantage of this situation would necessitate cottly variable frequency, variable amplitude vibrating equipment. Equipment generally available, at least for internal vibration, is of the fixed -frequency type, with little opportunity for amplitude change. The choice of vibration equipment for a particular application cannot readily be determined by theoretical analyses. The in- fluence of factors such as frequency, amplitude, mix characteristics, and size and shape of member is diffi- cult to evaluate. The type of equipment required is gen- erally determined by trial. A means for producing low water-cement ratio con- crete is available in the patented vacuum-treatment pro- cess. This method of extracting water from plastic mix- es is limited to the use of relatively thin sections. INFLUENCE OF AGGREGATE CHARACTERISTICS Since aggregate comprises a large fraction of the volume of concrete, the characteristics of the aggregate significantly influence the properties of the concrete. Of immediate interest is the influence of these character- istics on strength. Grading and maximum size of aggregate affect strength only indirectly by their influence on the water requirements for a particular level of consistency. For the same water-cement ratios, different gradations of the same aggregate will produce essentially the same strengths. A grading which requires more water for a particular level of workability will, however, result nec- essarily in a higher cement content in a mix of fixed water-cement ratio. A decrease in the maximum size of aggregate also results in higher water requirement with its consequent influence on cement content. Generally, once a mix is selected, control is governed by the con- sistency of the concrete produced. Variations which oc- cur in grading would then be reflected in different a- mounts of water necessary to attain the desired consis- tency. This would result in changes in water -cement ratio and concomitant changes in strength. These vari- ations in strength, if not reduced by closer control of uniformity of grading, would require a redesign of the mix in order to insure the production of satisfactory min- imum strengths. This would result in more costly con- crete. Separation of the aggregate into a number of size fractions and recombining when batching would increase the uniformity of concrete produced. On sizable jobs, sufficient savings would result from increased uniformity of concrete to more than offset the cost of processing the aggregates. More emphasis should be placed on uniform- ity of grading of the fine aggregate, since variations in grading of the fine aggregate influence workability to a greater degree than variations in grading of the coarse aggregate. Particle shape exerts an influence mainly on the a- mount of paste necessary to achieve workability. Flat and elongated particles require a greater paste content than rounded or cubical particles for the same workabil- ity. Significant savings in concrete costs can be effected by reducing flat and elongated pieces to a minimum. A5-5 WORLD CONFERENCE ON PRESTRESSED CONCRETE In the case of aggregate manufactured by crushing, par- ticles more nearly cubical aie to be preferred over an- gular panicles, the shape being generally dependent on the type of crusher being used. Different types of aggregates may, at equal water- cement ratios, produce concretes of different strength. Some of this difference may result indirectly from the effect of certain aggregate characteristics such as surface texture on the amount of cement paste in the mix. Smooth surfaces require less paste for lubrication than rough sur- faces. The main differences in strength attributable to aggregate type are thought to be due to the degree of bond developed between the paste and aggregate (both porosity and surface texture being important) and to the strength and elastic properties of the aggregate particles themselves. The interplay of characteristics such as po- rosity, surface texture, strength, elastic properties, and other variables makes it difficult to predict behavior. Bond of the paste to aggregate particles generally in- creases with roughness, although many other aggregate characteristics also influence bond. Increase in bond due to surface roughness, or for any other reason, will increase the flexural strength of the concrete. However, differences in surface texture have relatively little in- fluence on compressive strength. Lightweight Aggregates Lightweight aggregate, generally produced by arti- ficial means, is assuming increasing importance in pre- stressed concrete work, and, for that matter. In most phases of concrete construction. These aggregates are obtained by expanding, calcining, or sintering materials such as blast-furnace slag, shale, slate, clay, diatom ite, and others. Differences in the elastic properties of light- weight aggregate can cause more change in strength and elasticity of the concrete than those of the heavier nat- ural aggregates such as gravels and crushed stones. Al- though, like normal-weight concrete, water-cement ra- tio is the main controlling influence in strength develop- ment, an important factor is the strength of the particles of lightweight aggregate. One of the reasons for the apparent wide differences in strengths produced by different lightweight aggregates lies in the large and not readily determinable absorption characteristics of these materials. For this reason, mixes are usually compared on an equal cement -content basis, rather than on an equal water -cement ratio basis. This may account for a large pan of the strength differences attributed to the aggregate, per se. Lightweight -aggre- gate concretes differ considerably in the amount of water required to attain proper workability, due to grading, shape, and surface texture of the aggregate used. Those aggregates which, for the reasons noted, require exces- sive amounts of water to produce proper workability will therefore lequire excessive amounts of cement in order to provide adequate strength. The use of natural sand to replace a portion of the fines or the use of air entrain - ment will result in reduced water requirements. The natural sand will raise the unit weight of the concrete and decrease the advantages accruing to lower weight. Concrete made with lightweight aggregate has gen- erally been said to have an upper limit of compressive strength of about 5000 psi. Advances in the technology of manufacture of such aggregates, closer control of uni- formity of grading, and a greater appreciation of pro- portioning and mixing techniques have served to raise this limit considerably. Early high -strength concrete can be produced with most lightweight aggregates in a man- ner similar to the heavier natural gravels and crushed stones. Some work by our laboratories in this regard will appear this year in the Journal of the American Concrete Institute (2), INFLUENCE OF CONTROL OF UNIFORMITY When representative samples of a concrete are sub- jected to strength tests, the results of these tests show a certain dispersion about an arithmetic mean. This is not a peculiarity of concrete alone, but is a common occur- rence with other building materials. These differences in strength of presumably representative test cylinders made from supposedly like batches of concrete may re- sult from either random or systematic variation of nu- merous factors. A few, for example, are variations in batching and mixing, curing of cylinders, sampling of concrete, compaction, and capping and testing tech- niques. The degree to which effective control measures are adhered to in minimizing variations determines the magnitude of the spread or dispersion of test results about the arithmetic mean. In order to assure that more than a certain small percentage of the concrete being pro- duced does not go below a specified minimum design strength, the average strength must of necessity be high- er than this minimum. The difference between this av- erage strength and the minimum is influenced by the degree of control of all phases of concrete making, sam- pling, curing, and testing. The less effective the control exercised, the higher the average strength required to ensure attaining the proper percentage of tests higher than the minimum design strength designated. When produc- ing early high-strength concrete for prestressing, design- ing for a considerably higher strength than required in order to offset poor control is particularly uneconomical. The level of control required for prestressed con- crete work should be higher than that for most other con - A5-6 EARLY HIGH-STRENGTH CONCRETE FOR PRE-STRESSING crcte construction. A CI Committee 214^ recommends for most concrete construction that the control of con- crete-making operations be such that not more than one test in ten fall below the designated minimum strength. For prestressed concrete work a higher degree of control appears desirable, possibly as a goal one test out of one hundred. In order to attain this goal as economically as possible and not need to over-design the concrete drasti- cally to attain the requirement of one in one hundred, strict attention must be paid to all phases of the opera- tion to reduce variations to a minimum. The lower the coefficient of variation of test results, regardless of the probability level adopted, the lower the average strength required to assure attaining the necessary minimum strength of concrete. For example, considering the cri- terion of one test out of one hundred falling below a des- ignated minimum strength, with a coefficient of varia- tion of 10% (considered excellent for general field con- struction), the average concrete strength necessary would be about 31% higher than this minimum. For a coeffi- cient of variation of 5%, the average concrete strength necessary would be only 14% higher than the minimum strength. The savings in concrete cost would help off- set any additional costs incident to closer control of op- erations. OTHER PROPERTIES OF EARLY HIGH-STRENGTH CONCRETE In the design of prestressed concrete units, physical properties of concrete aside from strength are also of im- portance. Properties such as modulus of elasticity, creep, drying shrinkage, bond to steel, and durability under various conditions of exposure must also be considered. Considerable information relative to these properties is available for concretes of all types used in varied struc- tural applications. Most of this information has been obtained for concrete strengths ranging up to 5000 or 6000 psi. The increasing emphasis on early high -strength concrete is pointing up the need for more data concerning these properties. Data obtained in some of our recently completed laboratory studies and current studies afford additional background for the discussion to follow. Modulus of Ela sticity The modulus of elasticity of concrete depends upon the modulus of the cement paste, the modulus of the ag- gregate, and the relative amounts of these two compo- nents. The modulus of elasticity of the paste component increases as the degree of hydration increases. Changes in modulus for a given concrete occur because of changes in the modulus of elasticity of the paste as curing con- tinues. As the modulus of the paste increases, the con- crete strength also increases, and for any given concrete mixture and curing condition there then exists a general empirical relationship between strength and modulus of elasticity. For the same cement and aggregate, this em- pirical relationship between strength and modulus is in- fluenced by the relative amounts of paste and aggre- gate^. The moduli of elasticity of pastes range up to 2. 5 to 3. 5 x 10" psi, while those for aggregates are gen- erally considerably higher, except for most of the light- weight aggregates. Therefore, the greater the volume of paste per unit of aggregate, the lower the modulus of elasticity should be at comparable degrees of hydration or strength. Data supporting this are shown in Fig. 12. Here we see the influence of the volumetric ratio of paste to aggregate on the modulus of elasticity for dif- ferent levels of compressive strength. This merely em- phasizes the fact that strength, by itself, is not a good indicator of modulus of elasticity of different concrete mixtures over the whole range of strengths possible to produce with the same materials used in different pro- portions. What is important is how the strength was ob- tained for any given set of materials. Was it by longer curing, by a change in mix proportions, or by a change in water-cement ratio? However, for any particular mix strength serves as a good indicator of the modulus of elasticity, the modulus increasing with strength. Tht modulus does not increase as rapidly as strength and ap- pears to approach some limiting value in the high -strength region. The modulus of elasticity of concretes made with lightweight aggregates is not influenced materially by the volumetric concentration of aggregate since the mod- ulus of the aggregate is generally of the same order of magnitude as that of the paste(2). The modulus of e- lasticity of concretes made with lightweight aggregate is considerably lower than that for concretes made with sand and gravel or crushed stone as aggregates. Depend- ing upon the aggregate, the percentages may range from about 40 to 85% at 28 days, and at 6 months or later about 40 to 65%. Drying Shrinkage In prestressed -concrete construction, drying shrinkage should be kept to the minimum possible in order to avoid excessive loss of prestress. Shrinkage of concrete is in- fluenced by many factors, most important of which are the amount of water per unit volume of the concrete, the elastic pro pen ies of the aggregate, and paste content and characteristics. The size and shape of the member and the type of exposure are factors, but changes in these factors axe generally not possible. A5-7 WORLD CONFERENCE ON PRESTRESSED CONCRETE In concretes having cement contents in the range of 4 to 6sk, per cu. yd. , the amount of water per unit vol- ume is essentially constant for a particular level of con- sistency. In mixes richer than about 6 sk. per cu, yd. f the amount of water required for the same consistency and workability increases markedly. Rich mixes are gen- erally required for early high-strength concrete. The water content of these mixes can be reduced provided mechanical means of compaction are available. This reduction in water content will result in lower drying shrinkage. This is a particularly effective means of counteracting the inherently higher shrinkage of light- weight-aggregate concretes. Using the largest maximum size of aggregate that will satisfy placing conditions will result in a lower unit water content and will accordingly, for a particular wat- er -cement ratio, provide more aggregate per unit vol- ume. Aggregate provides considerable restraint to shrink- age of the paste. The more aggregate per unit volume the more restraint to shrinkage. The elastic properties of the aggregate play an important role in drying shrink- age. Those aggregates having a low modulus of elastic- ity provide less restraint than those of higher modulus; witness the relatively large drying shrinkage of most lightweight -aggregate concretes. Selection of the larg- est possible maximum size of aggregate having a rela- tively high modulus of elasticity will result in reduction in drying shrinkage. High-strength zero-slump concretes generally will show somewhat lower drying shrinkage than the usual structural -grade concrete of plastic consistency. In rec- ent tests(2), concretes made with a natural sand and gravel at a consistency of about 1\ in. slump (2000 to 3500 psi at 7 days) showed an average drying shrinkage at one year of about 680 millionths. For the same ag- gregate in zero -slump concretes compacted by vibra- tion (6000 to 8000 psi at 7 days) the average drying shrinkage was about 550 millionths. For these two class- es of concrete, but made with a typical expanded -shale ligl eight aggregate, the respective drying shrinkage averages were 900 and 600 millionths. reep The < reep of concrete under sustained load results in a loss in prepress, as does the shortening due to drying shrinkage. Considering this point alone, creep should be kept to a minimum. Creep does serve a useful func Uon, howe , in relieving localized overloads by redis- tribution and equalization of stress. Most available data indicate that creep of concrete laveitely proportional to its strength. Creep has been related to many other variables such as age, curing, and type of cement. These may be indirect relationships. The physical characteristics of the aggregate are of im- portance and operate in a manner similar to their effect on drying shrinkage. The moisture content of the con- crete is an important factor; concrete which is drying exhibits greater creep than wet concrete. Many of these means of reducing creep cannot al- ways be utilized. From a practical standpoint, using certain available materials for producing concrete, what are the creep characteristics of high -strength concrete made from these materials? Recent tests^ 2 ^ of concretes made with natural sand and gravel and with an expanded- shale lightweight aggregate show that the ultimate creep coefficient (millionths per psi) as a function of com- pressive strength was not linear over the range of strength! from 2000 to 10,000 psi. The relationship departed from linearity at about 5000 to 6000 psi, the higher- strength concretes showing less of a reduction in ultimate creep coefficient with increase in strength than those below 6000 psi. For 7-day loading, at 8000 psi, the ul- timate creep coefficient for the sand and gravel con- crete was about 0.40 millionths per psi, at 6000 psi it was about 0.55, at 4000 psi 0.80, and at 2000 psi 1.40 millionths per psi. The values for the expanded -shale lightweight -aggregate concretes were about the same at strengths below 5000 to 6000 psi. At the higher strength levels, these concretes showed greater ultimate creep coefficients than the sand and gravel concrete. Most other lightweight aggregates included in this study showed greater creep coefficients at all strength levels than the sand and gravel concrete, while a few showed slightly less creep. Bond of Concrete to Steel Bond of concrete to steel increases with increase in compressive strength of the concrete. The relationship is curvilinear, bond strength increasing less rapidly as the compressive strength of the concrete is increased. The bond strengths developed by high-strength concretes are far above the maximum allowable average bond stress recommended by ACI-ASCE Joint Com mittee *23 ( I. in some recent tests^ 2 ) of vibrated zero -slump concretes in the strength range of 7000 to 10,000 psi, bond strengths of top horizontal bari> in pull-out speci- mens exceeded 1400 psi. Actually, the yield strength uf the steel was developed in most of these tests, indi- cating higher bond strengths than this figure. This was for the sand and gravel concretes and one of the light- weight-aggregate concretes (expanded shale). At the 3000 to 4500 -psi level, bond strengths developed for top horizontal bars ranged from 520 to 900 psi. Included in A< EARLY HIGH-STRENGTH CONCRETE FOR PRESTRESSING this Latter strength range were seven different light- weight-aggregate concretes and one sand and gravel con- crete. Durability In many applications, prestressed concrete will be subjected to severe exposure conditions. Bridge decks, for example, will be exposed to the use of salts for pur- poses of ice removal. Portions of structures may be ex- posed to freezing and thawing while in a saturated state. These severe service conditions must be met by provid- ing concrete with a high degree of resistance to such ex- posure. Water in concrete, like any other water, undergoes about a 9% increase in volume when frozen. This freez- ing in concrete is a gradual process as the temperature drops because of rate of he at transfer, difference in freez- ing point of water in the pores of various sizes, and the progressive increase in concentration of dissolved alkalies in the remaining unfrozen paste liquid. Freezing creates an excess volume of water which must reach some relief zone, such as an unsaturated region or an air void, or disruptive hydraulic pressures will be created. Factors which determine the potential destructiveness of this freezing are the amount of water freezing, the permea- bility of the paste, the tensile strength of the concrete, the rate of freezing, characteristics of the aggregate, and -- most important of all --the amount and distribu- tion of air voids in the paste. Based on extensive laboratory data and field service records, we know that the only practical and efficient means of securing a high level of resistance to freezing and thawing is by entraining air in the required amount and proper distribution of air void sizes. In mixes of plastic consistency, the proper amount of air is based on a requirement of 9± 1% of air in the mortar fraction of the iniXV*', For concretes made with aggregate of max- imum size l{ in. , the mortar content is approximately 50 to 55rfo by volume. On a concrete basis, the air con- tent would be4^ to 5%. For other maximum sizes of ag- gregate, the required air content would be calculated in the same manner. Control of air is then based on the determinations of the air content of the concrete as a whole. For the same air -entraining cement or the same a- mount of air -entraining admixture per unit of cement, decreasing the slump within the range of slumps normal- ly used results in decreased volumes of air entrained. Some laboratory tests made using both a tilting -drum mixer and an open -tub type mixer and a typical Type LA Portland cement showed air contents of about 4^Jo at a slump of 3 in. , while at a slump of 4 to £ in. the air content was slightly over 3% Internal vibration of rela- tively long duration lowered the air content to about 3fy and 27o. respectively. While these are considerable re- ductions on a volume basis, the resistance to freezing and thawing is primarily dependent on the size and dis- tribution of the air voids, not on the gross amount. Vi- bration removes the large voids, which account for a greater proportion of the volume of the air, and leaves the average size and spacing of the small, but efficient, voids relatively unchanged. Curing air -entrained concretes at elevated temper- atures does not appear to reduce the beneficial influ- ence of the entrained air on durability. Recent labora- tory tests comparing air -entrained concretes made and cured at 70°F and at 105°F indicated comparable resis- tance to freezing and thawing, even though at the ele- vated temperature of mixing the volume of air entrained was reduced slightly. In fact, for those concretes whose curing period prior to test included an air-drying period, the 105°F air-entrained concretes were somewhat more durable than the 73°F concretes. Entrained air increases the durability of concretes made with any of the types of portland cements or port- land blast-furnace slag cements. In some recent tests of resistance to scaling(9) resulting from the use of salts for ice -removal purposes, ihe use of entrained air in con- cretes made with either Type I, 11, or [II portland ce- ment produced concretes of comparable and greatly im- proved resistance to scaling. These particular air -en- trained concretes were made by adding an air -entraining admixture at the mixer. Similar results would have been obtained by the use of the respective a 11 -entraining ce- ment types. Aggregates of good quality are a necessary compo- nent of durable concrete. Unsound aggregate particles such as chert, soft sandstone, clay lumps, and some high- ly absorptive limestones may, when saturated and incor- porated in even an air-entrained paste, cause disruptic of the concrete during freezing. Some of these aggre - gates may be beneficiated by drying prior to use or by removal of the offending particles by methods such as heavy-media separation or an elastic -rebound processing technique. SUMMARY Early high-strength concrete can be produced by any one of a number of techniques or combinations of tech- niques. The selection of method will depend upon the availability of specific materials, mixing equipmer-r, and compacting equipment The following means for obtaining concrete of high quality and having early high A5-9 WORLD CONFERENCE ON PRESTRESSED CONCRETE strength for prestressing are suggested, together with oth- er considerations; 1. 2. 3. 4. 5. 6. The use of low water -cement ratio, rich mixes of plastic consistency, or the use of low water-cement ratio, rich, dry mixes placed by mechanical means of compaction such as vibration, to permit the use of more aggregate per unit volume. The use of high -early -strength port land cement (Type III). The use of saturated steam at atmospheric pressure at temperatures below the boiling point of water, together with the use of effective insulation to re- tain heat generated by cement hydration. Careful control of aggregate gradation, weighing of materials, and mixing, compacting, and curing of concrete. The use of entrained air to assure adequate resis- tance to exposures involving freezing and thawing and the use of de-icing chemicals. The use of water curing during the early hours of hydration, either by ponding the surface or by the use of saturated aggregates. When dry or saturated lightweight aggregates are used, the provision of additional curing water does not appear necessary since aggregates of this type hold greater amounts of water available for this purpose. the Journal of the American Concrete Institute. Pre- sented at the ACI Convention in Dallas, Feb. , 1957. 4. Verbeck, George J. , and Foster, Cecil W. : "The Long-Time Study of Cement Performance with Special Reference to Heats of Hydration, " Proc, ASTM, Vol. 50, 1950. Reprinted as PCA Bulletin 32. 5. "Recommended Practice for Evaluation of Compres- sion Test Results of Field Concrete (ACI 214-57), " Jour- nal of the American Concrete Institute, Proc, Vol. 54, July, 1957. 6. ACI-ASCE Joint Committee 323 , "Recommended Practice for Prestressed Concrete, " December, 1956. 7. Klieger, Paul: "The Long -Time Study of Cement Performance in Concrete, Chapter 10 - Progress Report on Strength and Elastic Properties of Concrete, " to be published in the Journal of the American Concrete in- stitute. 8. Klieger, Paul: "Effect of Entrained Air on Strength and Durability of Concretes Made With Various Maxi- mum Sizes of Aggregate, "Highway Research Board Pro- ceedings, December 1951. Reprinted as PCA Bulletin 40. 9. Klieger, Paul: "Curing Requirements for Scale Re- sistance of Concrete, " Highway Research Board Bulletin 128, 1956. Reprinted as PCA Bulletin 82. SELECTED BIBLIOGRAPHY 7. Although calcium chloride will increase the early strength development of concrete, in view of the possibility of serious corrosion of the prestressmg steel its use in prestressed concrete is not now rec om mended. REFERENCES 1. Powers, T.C. : "A Discussion of Cement Hydration in Relation to the Curing of Concrete," Highway Re- search Board Proceedings Vol. 27. 1947. Reprinted as PCA Bulletin 25. 2. Shideler, Joseph J. • "Lightweight Aggregate Con- crete for Structural Applications, "to be published in the October 1957 Journal of the American Concrete Institute Presented at the ACI Convention in Dallas, Feb. , 1957. 3. Klieger, Paul: The Effect of Mixing and Curing Temperature on Concrete Strength, " to be published in Banks, R, R. • "High Strength Concrete Required for Pre- stressing, " Commonwealth Engr. 41, (2) 48-51 (Sept. 1953); Abstract in Eng. Ind. (1953). Banks, K. R. : "High Strength Concrete for Prestressing, ■ Constructional Review^, (3) 17-25 (1953); Abstract in B. S. A. 26 (9) 1145 (Sept. 1953). Banks, K. R. ■ "High Strength Concrete for Prestressing, " Symposium on Prestressed Concrete, Sydney, June 30 - July 2, 1953, Cement and Concrete At§0< of Australia, pages 40-47; discussion, pages 48-54. Blanks, R. F. : "Concrete for Prestressing," First U.S. Conferew e on Prestressed Concrete (see B.S.A. 1538) 136-49 (1951); Abstract in B. S.A. 24 (12) 1671 (Dec 1951), Carlson, R. W. : "Drying Shrinkage of Concrete as Af- fected by Many Factors, M Proc ASTM, Vol. 38, Pan II. 1938. A5-I0 EARLY HIGH-STRENGTH CONCRETE FOR PRESTRESSING Collins, A.R. : "The Principles of Making High -Strength Concrete," Engineering 169 (4382) 80-1 (Jan. 20, 1950). Davis, R. E. and Troxell, G. E, : "Properties of Concrete and Their Influence on Prestress Design, " Journal of the American Concrete Institute, January, 1954, (Proc. Vol. 50). Kennedy, H. L. : "High Strength Concrete," First U.S. Conference on Prestressed Concrete (see B. S. A, 1538) 126-35 (1951); Abstract in B.S.A, 24 (12) 1670 (Dec. 1951). Menzel, Carl A.: "An Investigation of Bond, Anchor- age, and Related Factors in Reinforced Concrete Beams, " Portland Cement Association, Research Department Bul- letin No. 42. > A5-I1 WORLD CONFERENCE ON PRESTRESSED CONCRETE e> CO UJ en </> UJ Gl o VIBRATED HAND- PLACED FULL COMPACTION WATER -CEMENT RATIO Fig. 1 Influence of W/C on Strength NET W/C, GAL/SK 3.5 4.0 4.5 ! 1 1 1 V 1 r d l3 >- EXTERNAL VIBRATION - 4900 VPM D 12 - ©(20% SAND, BY WT.) ^ \ i V* o 2 ,0 UJ 9 8 UJ 7 5 UJ O 6 tie (37%) i 1 1 1 1 i (27%) 028 030 032 34 0.36 38 040 42 NET W/C - by wt. Fig. 2 Influence of Method of Compaction on Cement Requirements 9 o o 2 e fi 7 - -~- £ en 4 UJ 07 5 CO UJ £ a o NET W/C, GAL/SK 3 5 4.0 4.5 1 T T T r PONDED _^-> BURLAP 280 PONDED TYPE I CEMENT BURLAP — DRY AGGREGATE SATURATED AGGREGATE i 1 * ID 028 030 032 34 036 038 040 042 NET W/C, BY WT Fig. 3 Influence of Moisture Availability on Strength Development (Hand-Placed Concretes) o ° 9 o 9 C 8 7 (D UJ 4 > CO (/) 3 UJ or CL 9 o NET W/C t GAL/SK 3 5 4.0 4 5 1 1 T T T PONDED BURLAP PONDED BURLAP 28 D 3D I D AGGREGATE SATURATED 1 TYPE I CEMENT i i i. i. 028 030 032 034 Q36 0.38 040 Q42 NET W/C, BY WT Fig, 4 Influence of Moisture Availability on Strength Development (Vibrated Concretes) A5-I2 EARLY HIGH-STRENGTH CONCRETE FOR PRE-STRESSING T T T 180 \L • 160 140 I 120 O Z 100k X h 80h & 60 S 40 U 2j 20 ONE* DAY TESTS TYPE I CEMENT I 30 40 50 60 70 80 90 100 IK) 120 MIXING a CURING TEMPERATURE -°F Fig. 5 Influence of Mixing and Curing Tem- perature on Early Strength Development 2 4 8 10 12 14 16 AGE IN HOURS 8 20 22 24 8 o o o IP I I INSULATION I" THICK SPUN GLASS BLANKET y UJ E > UJ O TYPE m CEMENT [INSULATE Jl DAY THEN (MOIST AT- \73 # F Fig. 6 Influence of Heat Generated Dur- ing Hydration on Concrete Temperature (Calculated Assuming Full Retention of Heat Generated) TYPE I CEMENT INSULATE Q OAT THEN MOIST AT Z3 # F r a 8 8 en 7 a. i 6 NET W/C - 36 TYPE 1-64 SK/CU YD TYPE HI- 6 9 SK/CU YO DRY, VIBRATED 6 * 12 -IN CYLINDERS 4 UJ 3 co 2 UJ o I r&2— (1.23) 73° F a 100% RH . NET W/C - 35 ZERO SLUMP VIBRATED i. i x AGE - DAYS 2 3 4 5 6 AGE - DAYS Fig. 7 Influence of Heat Insulation on Strength Development Fig. 8 Influence of Cement Type on Strength A5-I3 WORLD CONFERENCE ON PRESTRESSED CONCRETE o o o 8 m 7 I I 6 h- O Z 5 UJ 4 ^CJ *— < Lie) - r, "(146) *° G<* &z_ CO UJ > 3 h CO co UJ cc CL . (196} o o I - u 73° F 6 100% RH. TYPE I CEMENT NET W/C- 35 ZERO SLUMP VIBRATED 1 1 1 i X 1 1 Fig. Deve l 234567 AGE - DAYS 9 Influence of CaCl^ on Strength lopment o o o to CL I 7 - 6 - 5 - 4 - 3 - O 2 - UJ cr CO UJ I - ^ 2 - NET W/C, GAL/SK 3.5 40 45 i O z UJ T CO 3 UJ > CO 2 CO LU £ O , . TYPE I CEMENT • I -2 INCH SLUMP. HAND PLACED • SLUMP, VIBRATED 1 X 1 1 028 030 0.32 0.34 036 038 040 042 NET W/C , BY WT. Fig. 10 Hand-Placed vs. Vibration O V)-' 8 - 7 - OUJ T T T T 10,000 9,000 8,000 " * 7.000 2 02O j. TYPE I CEMENT " NATURAL SAND AND _, GRA,VEL 030 40 050 RATIO OF PASTE TO AGGREGATE -By vol 4900 7200 II 000 FREQ.vPtt E E F F G 6 AMP E '- LARGE F -- MEDIUM G = SMALL Fig. 11 Influence of Frequency 8, Fig. 12 Influence of Compressive Amplitude of Vibration on Strength Strength and Mix Proportions on (External Vibration) Modulus of Elasticity 060 A5-J4 >


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Free personalized radio that
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Peter Hollens
Selected Discography
Track List: Peter Hollens
Track List: What's My Name? / Only Girl (A Cappella) (Radio Single)
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I wish that his songs with Skydoesminec r a f t were on here, Adam actually should have his songs on here to. Love you Peter.
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Following Renault's tie-up with Caterham to produce Alpine sports cars, Renault's sub-branding bifurcation is taking more sensible shape. When the French brand announced the revival of the Gordini brand in 2010, the plan was that Gordini cars would "slot in above the current Renaultsport offerings." That plan was quickly shot dead, Gordini models starting with a Clio and Twingo that featured extra performance bits, moving onto the base Twingo as a paint-job trim level, then seemingly slapped on
2012 Renault Twingo R.S. and Twingo Gordini R.S.
Renault announces facelifted F1-inspired Twingo R.S.
- Jonathon Ramsey
- Feb 16, 2012
There are two additional performance versions of the Renault Twingo joining the base model introduced earlier this year: the Twingo R.S. and Twingo Gordini R.S. They are set apart from the donor hatch by a lower bumper element meant to mimic the nose of an F1 car (Mercedes-Benz once did something similar with its sporty cars). The rear bumper is also reshaped, getting a diffuser and "aerodynamic extensions," and the tailgate is topped by a spoiler.
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Statement by the HSH Prince Albert II, Sovereign Prince of Monaco, on the occasion of the first session of UNEA.
On 22nd March 2016, the Former UNEP Executive Director Achim Steiner joined youth in Mathare, an informal settlement on the outskirts of Nairobi, to kick off the final of the Solar Soccer Cup at the Philips Community Lighting Centre. Philips Lighting Africa CEO Tamer Abolghar was in attendance as well to introduce the final match of the tournament.
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Guy's return was listed on the league's transaction report on Monday. Seattle has received a roster exemption, but Guy cannot play until he is added to the active 53-man roster.
Guy has been active for just two games this season for the Seahawks. He was selected in the sixth round out of Kentucky.
Seattle also cut wide receiver Lavasier Tuinei from the practice squad and signed defensive end Monte Taylor.


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Police Seek Tips After 20-Year-Old Man Found Fatally Shot In SouthfieldPolice are asking for the public's help in solving the murder of a young Eastpointe man over the weekend.
19-Year-Old Ypsilanti Twp. Man Found Fatally Shot In Front YardA murder investigation is underway after a 19-year-old man was found dead outside a Washtenaw County home.
Chilling Video Shows Chaos Inside Courthouse As Inmate Steals Gun, Kills 2 Bailiffs"I'm not trying to die, and I don't want too," the letter reads. "I'm just trying to get free and I'll die trying."
Man Shot Dead Outside Of Home On Detroit's West SideNeighbors told police they heard multiple gunshots before a gray car sped away from the scene.
$2,500 Reward Offered For Tips In West Side Detroit KillingDionycio Coach, 27, was gunned down in his car by an unknown assailant.
1 Dead, 1 Injured In Detroit Gas Station ShootingDetroit police are searching for suspects in the killing on W. Warren Sunday night.
22-Year-Old Man Found Fatally Shot On Front Lawn Of Detroit HomeThere have been no arrests after a body was found in the area of 7 Mile and Lahser, early in the morning.
Police: Estranged Husband Wanted In Fatal Shooting Of 2 WomenPolice say two women have been fatally shot in Detroit, possibly by the estranged husband of one of the victims.
Heritage Park In Farmington Hills Evacuated After ShootingThe park was closed into the afternoon for a police investigation.
Metro Detroit Native Among Police Officers Killed In Dallas ShootingsOne of the police officers killed in Thursday night's sniper-style shootings in Dallas, Texas, is from Redford Township.
Detroit Dad Convicted Of Manslaughter In Young Son's Shooting DeathThe child was shot by and older sister as they played with a shotgun at their father's home.
11-Year-Old Detroit Girl Testifies She Fatally Shot Brother With Dad's GunThe girl was granted immunity from prosecution in exchange for her testimony.


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Minnesota Golden GophersSun, February 10, 2013 - 1:00 PMWilliams Arena in Minneapolis, MN
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Mexico finds smuggling tunnel near US border
PHOENIX (AP) – U.S. officials say Mexican authorities have found a sophisticated smuggling tunnel equipped with electricity and ventilation not far from the Nogales port of entry into Arizona.
Santa Cruz County Sheriff Tony Estrada in Nogales, Ariz., says the Mexican military discovered the tunnel this week in downtown Nogales, Sonora, just across the border.
He says the tunnel originated in a two-story home in Mexico and stretched about 100 meters. Estrada says the tunnel was elaborately built with electricity and ventilation.
U.S. Border Patrol spokesman Victor Brabble says the tunnel did not cross into the U.S.
Similar tunnels have been used for years by criminals for smuggling people and drugs across the border.
More than 70 such passages have been found since October 2008, most concentrated along the border in California and Arizona.
(Copyright 2012 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.)
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jobs near Denver, CO
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OTR Truck Driver .50 cents a mile
Mile Hi Specialty Foods - Denver, CO
OTR Truck Driver must comply with all DOT, State, local regulations and company policies.• Perform pre-trip inspections and report problems.• Obtain paperwork...
HVAC Field Service Technician
Daikin Applied - Denver, CO
The technician will posses a working knowledge of all commercial air conditioning systems and components, as well as boilers, electric/electronic and pneumatic...
DEDICATED LANE - CDL Truck Driver Needed in Colorado!
C.R. England - Denver, CO
Dedicated, Intermodal, Regional, National, Solo, Team Driving, Driver trainer, Instructors. Experienced CDL-A drivers with a safe and clean record are offered...
Restaurant Manager
Village Inn - Denver, CO
You will provide direction, training and coaching to team members while understanding and demonstrating Village Inn standards, policies and procedures, Vision...
Material Handler
FedEx Express - Denver, CO
Performs clerical functions which may require a knowledge of general business and office procedures including maintaining follow-up files, answering phones,...
CNA's, PCP's and HHA's
Accessible Home Health Care of Denver - Aurora, CO
Required license or certification:. Colorado Drivers License. Must have a current Colorado driver's license, and reliable transportation with vehicle insurance....
Company Driver - Class A CDL
Doug Andrus Distributing LLC - Denver, CO
Doug Andrus requires that you be 21 years of age, have a valid Class A CDL and a clean MVR and a Certificate of Graduation from a driving school....
Handler (Non-DOT)
FedEx Express - Denver, CO
Completes systematic transactions such as:. Cleans company vehicles, repair and paint drop boxes to ensure compliance with corporate appearance standards....
HVAC Service Technician
ProCraft Mechanical, Inc - Broomfield, CO
Valid driver's license with clean driving; EPA Refrigerant certification; Knowledge of HVAC systems to service and repair roof top units, split systems, pumps,...
Truck Driver
XPO Logistics Less-Than-Truckload - Henderson, CO
Possess and maintain a valid Class A Commercial driver's license. Maintain a current Class A CDL with Hazardous Materials, Doubles/Triples and Tanker Vehicle ...


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permeability testing Equipment in Ohio
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Model MA-10 - Blaine Air Permeabilityby Gilson Company, Inc. based in Lewis Center, OHIO (USA)
Blaine apparatus measures the specific surface area of fine materials in square centimeters per gram of test sample. A quantity of air is drawn through a bed of definite porosity. The pore volume in the bed is a function of the size of particles, and determines the rate of air flow.


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- Swimmer Ryan Lochte reveals one of his worst dates - US Weekly
- Get the latest on Dr. Dre's arrest - TMZ
- Despite rumors, Eddie Murphy's daughter is not pregnant - Gossip Cop
- The Vampire Diaries star Michael Trevino steps out for a good cause - Just Jared Jr
- Are Blac Chyna and Kylie Jenner on good terms? - Radar
- Blue Ivy is just as stylish as her mom Beyonce! - Lainey Gossip
- This Narcos star confirms he's not coming back for another season of the show - The Hollywood Reporter
03 March 2009 at 11:41 AM
Malin Akerman is Silk Spectre
Posted in Malin Akerman is Silk Spectre
About this photo set: Malin Akerman premieres her new comic-book flick, Watchmen, at Grauman's Chinese Theatre on Monday (March 2) in Hollywood. The 30-year-old former model wore… Read More Here
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text:
plural noun
Sexual intercourse.
Example sentences
- He ordered them to break off their sexual relations.
- I did not have sexual relations with that woman.
- That same day, the eldest villager takes up sexual relations with his wife again, and his example is quickly followed by the other men of the village.
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Chat with Heather Dinich
Welcome to SportsNation! On Tuesday, ESPN.com's ACC blogger Heather Dinich stops by talk some college football.
Dinich covered ACC and Big Ten football for five seasons before joining ESPN.com in November 2007. She's an Indiana grad but somehow her favorite day of the week is Saturday.
Send your questions now and join Dinich Tuesday at 1 p.m. ET!
More Heather Dinich: Search | Chats | Blog
Heather Dinich (1:00 PM)
Hey guys, I'm here, let's go.
The one and only Dirk! (Lane Stadium)
How awesome would it be to be able to bring the Coastal division race back to the commonwealth next weekend!? As much as I would like to see UVA lose this weekend, I really do hope that it can come down to a game between VT and UVA.
Heather Dinich (1:01 PM)
I think it would be great for the division race and the ACC. It definitely adds to the excitement when two rivals are playing for a title. I'm sticking with my earlier prediction, though ... not gonna happen.
John (Virginia)
What's more likely: UNC beating VT or UVA beating FSU?
Heather Dinich (1:02 PM)
Great question. Check the blog for this week's upset watch and you'll get your answer.
Kevin (Blacksburg)
I think UVA is better than people give them credit for... would you like to see them beat VT for the ACC coastal or do you think that would be "bad" for the conference?
Heather Dinich (1:03 PM)
Personally, I honestly don't care who is in the ACC title game. It's my job to cover it regardless, but from an objective standpoint, it would obviously be best for the ACC if two top 10 teams were in the title game.
Justin (Charlotte, NC)
Heather, Do you think Ga Tech should be given their 2009 ACC Championship title back?
Heather Dinich (1:04 PM)
No, because they played an ineligible athlete. Every other team suffers the same consequence.
lemm (Charlotte, NC)
HD, what were the 3 things to give NC State Hope? None of us could watch the video.
Heather Dinich (1:06 PM)
It should be working now, but interceptions/turnover ratio and Clemson's set up for a let down were two of them. Oh, and the fact that NC State is still playing for a bowl.
John (Chicago)
It looks like Clemson has struggled a bit the last 8 quarters against Tech and Wake. Is this just the ebbs and flows a long season or have defenses figured out their offense?
Heather Dinich (1:06 PM)
Just talked to Dalton Freeman before the chat and his answer was turnovers.
Adam (Atlanta)
We've all been getting angry about this officiating (especially us Noles) this season. Is it an over-reaction or is it time to try to push for change within the ACC?
Heather Dinich (1:08 PM)
I emailed the ACC's coordinator of officials yesterday and am waiting on some numbers from him. Every year, he gives me the stats - missed calls, overturned calls, length of reviews, etc. Let's wait until we have the data before rushing to judgement. It might feel worse than it has been for some fan bases, and I will be the first to admit they have a tough job and know far more than I do, so it's not often I question their calls.
Mike (Raleigh)
Does it matter who wins the ACC title? Shouldn't we be more concerned with winning the Orange Bowl?
Heather Dinich (1:09 PM)
Who do you want to represent the ACC in the Orange Bowl? The ACC winner is your only choice.
Adam (Virginia)
HD do you thing this will be a air or ground game for Uva this week?
Heather Dinich (1:10 PM)
They've got to start with what they've been doing best lately, and that's running the ball. If FSU makes them one-dimensional, Rocco better be ready. Ideally, I'm sure they'll try to mix it up. Lazor has been doing a great job with that.
sean (chantilly, va)
do you expect a close game thursday night if renner is back to normal? the hokies looked good when they needed to against gt but duke was a scare. do you think vt can be consistent the rest of the year and look like a top 10 team?
Heather Dinich (1:11 PM)
I talked to Logan Thomas a bit about that this week, but yeah, I think they can. It's not easy to play at Wallace Wade. I think VT has hit its stride.
Danny A. Walters (the Philippines)
Is there any scenario at this point that could put an ACC team in a BCS bowl with an at-large bid?
Heather Dinich (1:13 PM)
It's not impossible, but here's the thing you have to remember: The loser of the ACC title game will have at least two losses. That's not an attractive option when better records are out there.
Joey Wells (Greensboro, NC)
Heather, when officials look at the film do they look for missed calls or just controversial ones? I don't know about every team, but I see Bjorn Werner and Brandon Jenkins held 8-10 times a game and it is rarely called, are the officials looking at those plays as well as reviews and strange calls?
Heather Dinich (1:13 PM)
They review everything, Joey, not just the controversial calls. Each week the officials are sent a cut-up to learn from from the leauge office.
Pete (Houston)
You wrote of how FSU is where they need to be unranked, they're currently at the bottom of the BCS rankings, do you believe given how they're playing now that they're better than say Southern Miss or Michigan or some of the teams directly above them?
Heather Dinich (1:15 PM)
I wrote that before the rankings came out and based on how they looked in that game. I have Florida State ranked at No. 24 ahead of Notre Dame this week.
Ryan (Clemson)
Do you think Chad Morris will Leave Clemson in the near future for a HC job or other OC job?
Heather Dinich (1:16 PM)
I think Clemson will put enough cash in front of him that it will be worth his while to stay, if they haven't done so already.
Nolegrad91 (Florida)
Hi Heather, have there been any changes with the assignments for the bloggers as I noticed bloggers writing for different conferences. Are you still going to be the ACC Blogger?
Heather Dinich (1:17 PM)
Haha yeah, hate to break it to you but you guys are stuck with me. Whenever there's a big story it's not unusual for everyone to pitch in. No biggie.
Garrett (Charleston, SC)
If you were in Dabo's shoes would you play Watkins this week or not? Clemson has already clinched the Atlantic and even with a loss, all their season goals are well within reach and regardless of how Watkins is feeling, there's at least a small chance of reinjuring the shoulder. On the other hand, we don't want to underestimate NC state or give up the momentum of the season that Clemson has going.
Heather Dinich (1:18 PM)
I would play him, yes, as long as there wasn't any potentially severe damage, and from what I understand, it's not serious.
Pete (Houston)
A win is a win though isn't it? No matter how "ugly" it is? Bottom line is FSU was still the better team against Miami was it not?
Heather Dinich (1:19 PM)
It was, yes. Miami's three turnovers and nine penalties? FSU got it done with defense and special teams, but it got it done.
Andre (Monticello, FL)
Hi Heather, this week UVA comes to Tallahassee and next week end the season with VA Tech at home. I know in both games they will be heavy underdogs. Could we expect an upset in either one of these matchups or better yet both games. I know it is a long shot stranger things have happen. Keep up the good work.
Heather Dinich (1:21 PM)
Thanks, Andre. I think you nailed it -- it's a long shot, but stranger things have happened (I think). Virginia is playing well, they're focused, and Mike London is doing a great job. They will be up against more talented teams, though, and will have to win with smart, disciplined football and excellent coaching.
Jim (Cincinnati)
Who goes for more yards in lane this thursday: D. Wilson or G. Bernard?
Heather Dinich (1:22 PM)
Andrew (Columbus, OH)
What do you predict Florida State to do in 2012? Record?
Heather Dinich (1:23 PM)
Well, heading into this season, when everyone was talking national title for FSU, I said 2012 will be their year. I don't think you can leave Clemson out of that conversation this time around, but we'll see how both teams finish the season. Not over yet.
GT0823 (Flandersonville, ND)
Heather, you report on ACC football every day. How can you not grasp the fact Thomas WAS NOT ruled ineligible by the NCAA prior to the ACCCG?
Heather Dinich (1:24 PM)
I get that, but the point is, he should have been!
Elliott (Charlottesville)
I never seem to get an answer in these chats...If UVa and VT both win this week, could you see Gameday in Charlottesville for the first time for the showdown on the 26th?
Heather Dinich (1:24 PM)
I'm ignoring you because I have zero input on where the crew goes, no idea. Not in those meetings.
Harris (Abington, VA)
Heather, was is just me or did the Penn State media obsession take away from the pivotal VT-GT match-up last Thursday?
Heather Dinich (1:25 PM)
That story took over everything, Harris, nationwide, news outlets everywhere.
Josh (Tallahassee)
How did Nigel Bradham not make your player of the week list?
Heather Dinich (1:25 PM)
That list comes from the league office. I only do helmet stickers.
James L. (DC)
Is UVA's success more a result of underrated talent or excellent coaching?
Heather Dinich (1:26 PM)
I think the coaching has had a TON to do with it. UVa has used several freshmen from a highly touted recruiting class, but the staff has also done a great job of getting guys in the right positions. Plus, it's the second season in the same systems, which helps.
Wes (DC)
The vegas line opened Florida State minus 17.5 against UVA. While I admit my bias as a UVA fan, I still think this margin is a bit large considering the body of work both teams have put forward to this point. Do you think this is a good approximation of the difference between these two teams?
Heather Dinich (1:29 PM)
To me it's kind of the same situation as the Clemson-Wake Forest game was. Going into it, I thought Wake Forest was either going to pull a stunner in a close game, or get beaten pretty soundly. I picked the wrong one. I think UVa is going to have tough time against FSU's defense.
A. Harris (Raleigh, NC)
So what are the chances of VT beating Clemson in a rematch? Assuming VT makes it to Charlotte.
Heather Dinich (1:30 PM)
I think the chances are great. First, you've got the fact that VT is used to being there. They know what it takes. I know, Clemson was there in 2009, but this is routine for Virginia Tech. Also, you've got the motivation from a lousy performance in the regular season, and the fact that Clemson's defense hasn't been championship caliber yet. Lots of reasons for VT fans to be optimistic ... if they get there.
Bubbles (Arlington VA)
Hi Heather, VT fan here, and as much as I hate to admit it I gotta say I'm impressed with what London and UVA have done this season. Though it's highly unlikely that UVA runs the gauntlet of FSU/VT to win the Coastal, and then Clemson in title game if it came to it, how soon do you see UVA challenging for the ACC title? I'll concede that they'd be in that position this season if they somehow beat FSU in Tallahassee.
Heather Dinich (1:31 PM)
If Virignia is a contender NOW, I don't see any reason to doubt them again next year.
Bubbles (Arlington VA)
Regarding bowl scenarios, I'm going to leap to the conclusion (though not taking it for granted) that VT & Clemson will meet again in Charlotte for ACC title. I know it's irrational to NOT want to win that game (I am a VT fan), but the thought of another VT/Cinci Orange Bowl makes me want to vomit, whereas a loss to Clemson would match up VT against an SEC team likely in the Chic-Fil-A Bowl. Please talk some sense into me. Of course, all of this is moot if WVU becomes the Big East representative, then I'd relish the opportunity of a VT/WVU matchup in the Orange Bowl.
Heather Dinich (1:33 PM)
Haha well it depends ... are you a bigger fan of the game itself or the Hokies? If you root for the better game, it would probably be the Chick-fil-A Bowl. If you're rooting for the Hokies, you want them to win another Orange Bowl.
Diamond (Atlanta)
Is Clemson a one hit wonder?
Heather Dinich (1:34 PM)
I don't think so, and I say that because they have 42 freshmen on their roster. Theoretically, this should be just the beginning.
Matt (Houston)
Don't forget that VT has won re-matches in the ACCCG before (Boston College)
Heather Dinich (1:35 PM)
This is also true, thanks, Matt.
Uncle Mike (NYC)
Heather, any chance A. Golden sit the 08 recruiting class for the last two games in order to some of the young guys some experience going into next year?
Heather Dinich (1:35 PM)
No, and he shouldn't. Those guys haven't lived up to the expectations, but they still have a chance to go out on a good note.
Sal Lizard (at the mall)
How do you feel about Wake Forest's chances next year...Will they contend again or regress like last season?
Heather Dinich (1:36 PM)
They're still a young team, I think they can build upon this year and expectations will be higher next season for them. At least respectable. I think they were picked to finish last in the division this year.
tyler (blacksburg)
also looking ahead to next year you mentioned FSU and clemson being title contenders...how can VT be left out of that....im gonna guess that 10 of 12 starters on defense will be back, whitley gone and hosley going to the draft although hes only having an average season, and LT3 only getting better and david wilson who is a monster....replacing the o-line will probably be the biggest task...
Heather Dinich (1:37 PM)
I think Virginia Tech is always in the mix. With their string of 10-win seasons and national rankings, it's easy to take for granted that they'll be in the conversation.
Jason (Nashville)
I thought the article that you referenced in lunchtime links a day or so ago that hoped for ACC officiating to fade once again into the background rather than "being the story" was a well said. Certainly seems like there are plenty of gripes lately. More than just your average fan biased arguments. Thoughts?
Heather Dinich (1:38 PM)
Yeah, he wrote that well. I would say that most reporters stay away from officiating comments, but this year they've been impossible for everyone to ignore.
Billy (Chapel Hill)
Logan Thomas has progressed quite a bit as a QB since the beginning of the season. Will there be a lot of regression next year since Virginia Tech has to break in a new class of receivers?
Heather Dinich (1:40 PM)
I don't think he will regress, he should be better, but the departures on the offensive line might be more of a concern. Don't have the depth chart in front of me.
Nathaniel (Bristol, TN)
Not to mention a new class of OL, Billy.
Heather Dinich (1:40 PM)
That's what I thought.
Robert Paulson (?)
Do you think that suspending linebacker Jeremiah "AttackU" for only the first half is a fair enough punishment?
Heather Dinich (1:41 PM)
From what I understand, Johnson gave him the same punishment the ACC would have. I think it would have been excessive to exceed that.
Megan (Georgia)
Do you think GT starts Tevin Washington next year? He has experience, but there appears to be a ceiling on his capabilities. Perhaps it would be better to use Vad Lee.
Heather Dinich (1:43 PM)
I would guess Paul Johnson will allow Lee the chance this offseason, but typically, it is hard to replace somebody with starting experience. Washington was pushed this past offseason, though, so I would expect a good competition again.
CPJfan (the ACCylum)
Which ACC team has the most freshmen on the 2-deep?
Heather Dinich (1:44 PM)
I'd have to look it up, but my guess would be Virginia, Clemson, Maryland or FSU.
Greg ( . Y .)
Does the Chik Fil A bowl have to take the loser of the ACCCG?
Heather Dinich (1:47 PM)
No. ACC media guide in front of me says "If the Chick-fil-A Bowl does not take the available ACC team with the best conference record, it must take a team within one win in the conference record. It can select a team with a difference of two wins in its conference record if that team is ranked more than five spaces higher in the final BCS standings than the team available wiht the best ACC record."
Patrick (Tallahassee, Florida )
Do you think Florida State will beat Florida?
Heather Dinich (1:48 PM)
Yes. Another state championship for the Noles.
Greg ( . Y .)
UVA leads the conference with 22 true freshmen
Heather Dinich (1:48 PM)
Thanks for looking it up, Greg. We'll have to take your word for it right this second. :)
Jake (Tallahassee)
How many bowl games do you expect the ACC to win?
Heather Dinich (1:49 PM)
Not more than it loses. I'll believe it when I see it.
Billie (Virginia)
Do you thing GA Tech will beat Georgia?
Heather Dinich (1:51 PM)
Earlier in the season I did, but now I'm not so convinced.
Skeeter (Athens)
HD - You are insane if you think Tech has a snowball's chance of beating the Dawgs. Georgia's D will stuff that HS triple option crap!
Heather Dinich (1:52 PM)
Didn't that same offense beat Georgia a few years ago?
Daniel (Raleigh, NC)
What will we see first - Flying cars or Miami in the ACC title game?
Heather Dinich (1:53 PM)
Vrrrrooooom. Woosh.
Jessica (Charleston)
Who's your pick for Clemson/South Carolina?
Heather Dinich (1:54 PM)
I'm sticking with the Tigers in that game. This is a different team and they'll be taking that game much more seriously than they did last year. And 2009.
steve (accylum)
which new coach do you see exiting first to better position or due to record?
Heather Dinich (1:55 PM)
I think UNC's interim coach Everett Withers is the first and only one out this year, but again, that's just a guess.
David (Gaithersburg)
UVA is young, but they have not played any where near 22 TRUE freshman this year. They also have a lot of seniors on defense and will lost most of their DL.
Heather Dinich (1:56 PM)
No, when I talk about the 42 freshmen for Clemson I'm talking true and redshirt.
Steve (Destin, FL)
I'm doubting very seriously that UVA has 22 frosh on the 2-deep. That was the original question...
Heather Dinich (1:56 PM)
Ok, the two-deep, sorry, was thinking total that have played this year. I know UVA is up there.
Drew (Savannah)
Tajh Boyd will more than likely have 3,500 yards passing and over 30 TD passes at the end of the season. Heisman hopeful for 2012?
Heather Dinich (1:57 PM)
Yes, along with Sammy Watkins and David Wilson.
Allen (Boston)
will BC win the rest of their games?
Heather Dinich (1:58 PM)
Both are on the road. One is ranked. I don't see it.
steve (accylum)
Do you think firing of Friedgen was worst coaching change in recent acc history. or is that a wait and see?
Heather Dinich (2:00 PM)
Interesting question I'd like to give more thought to, but my initial reaction is that Randy Edsall should be given some more time to state his case. Let him recruit, get the guys he wants in his system, etc. With that being said, there's really no excuse for Maryland's implosion this year. They could have been better.
Heather Dinich (2:00 PM)
Ok guys, my time is up here. Thanks for joining me today, see you next week.hd
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Engine Performance problem
1988 Toyota Pickup 4 cyl Two Wheel Drive Automatic 175000 miles
At speeds aproaching thirty five mph or under heavy loads the engine hesitates. It idles fine, new plugs and wires, new fuel filter, new transmission filter and fluid. I wonder if the EGR valve could be sticking or have clogged injectors. What should I check first?
Thursday, November 11th, 2010 AT 10:54 AM


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Make Way for Ducklings Hardcover – Jan 1 1941
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From Amazon
It's not easy for duck parents to find a safe place to bring up their ducklings, but during a rest stop in Boston's Public Garden, Mr. and Mrs. Mallard think they just might have found the perfect spot--no foxes or turtles in sight, plenty of peanuts from pleasant passers-by, and the benevolent instincts of a kindly police officer to boot. Young readers will love the mother duck's proud, loving protection of her wee webbed ones, and those with fond memories of Boston will enjoy familiar locales, from Beacon Hill to Louisburg Square, and over the Charles River--often from a duck's-eye view. Robert McCloskey, creator of Blueberries for Sal, never fails to elicit happy story-time giggles from youngsters, and his soft, brown-toned, Caldecott-winning illustrations make this gentle world come alive. (Ages 3 to 8) --Karin Snelson
"This delightful picture book captures the humor and beauty of one special duckling family. McClosky's illustrations are brilliant and filled with humor. The details of the ducklings, along with the popular sights of Boston, come across wonderfully. The image of the entire family proudly walking in line is a classic." - The Barnes & Noble Review. "The quaint story of the mallard family's search for the perfect place to hatch ducklings. For more than fifty years kids have been entertained by this warm and wonderful story." - Children's Literature --This text refers to the Paperback edition.See all Product Description
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Top Customer Reviews
The story follows Mr. & Mrs. Mallard, a realistically portrayed duck couple. No animals in funny clothes here. The two settle on a small metropolitan island to lay their eggs. Once hatched it's up to Mrs. Mallard and her troop to walk to their new home in the central park with the help of their local police force.
In the sixty some odd years since its publication, "Make Way For Ducklings" has remained exactly the same. The closest it comes to dating itself (aside from the stately cars and "lending library") is that Mr. Mallard abandons his family to fly ahead to the save island. That's one way of looking at it. Another way is to point out that Mrs. Mallard is a capable mother who knows exactly how to lead her small brood. The book is fun, diverting, and illustrated beautifully. It does not pretend to be anything it isn't. It is the classic above all other classics. And it is McCloskey's greatest invention.
by Robert McCloskey
The Viking Press
Imagine yourself as a mother duck, flying over Boston looking for a place to rest and lay your eggs, but you are very very particular about where you land. Considering that Boston is a busy place, would you want to raise a family there? This is what this story is all about. Make
Way for Ducklings by Robert McCloskey is a Realistic Fiction and Fantasy book for young and old readers. It takes place in the air when Mr. and Mrs. Mallard are looking for a place to land. Mr. Mallard finds very nice spots but Mrs. Mallard is not satisfied. She says she doesn't want to raise a family where there might be foxes in the woods or turtles in the pond. They fly on for awhile until they reach Boston. The Mallards are very tired and fly down for the night on a small island near the park. In the morning they hunt for food in the bottom of the river but don't have a lot of luck. Soon their luck turns good when a boat carrying a load of people has the people throw peanuts to them to fill their empty stomachs. Mr. Mallard and Mrs. Mallard decided that they would like to nest there, until a boy riding a bike zips by Mr. Mallard and almost runs him over. Now will the Mallards decide to stay or will they leave forever?
There are 3 main characters (or 11 counting all the ducklings) Mrs. Mallard, Mr. Mallard, their ducklings, and Michael the policeman. Mrs. Mallard is a mother duck, that thinks a lot about her kids' future, which I think makes a great mother. She is very independent and proud
about things she accomplishes and does. She loves her family and her husband very much and hopes for a pleasant future. She also loves her human friend, Michael, who is loving to the Mallard family. Mr. Mallard is the father duck.Read more ›
The book describes how a mother and father duck look for a safe spot to hatch their ducklings. They fly all around the woods, the pond, Beacon Hill, the State House, Louisburg Square, and finally, finding a nice cozy spot to hatch the eggs, the Public Garden. They make friends with the police man, Michael.
I think the book would be my choice to share with other children because it teaches the concept of making the right choice...such as you wouldn't want to live in a place that's dirty and smoky... for example around Beacon Hill and The State House. Also, they make friends with the Policeman, Michael, and other characters in the book. This book has been a classic for almost 45 years now, and I'm sure it will continue to be one for many years to come.
Most recent customer reviews
I had recently been on a visit to Boston and had seen the statues of the ducks in the park. I wanted to read about them and found this book very informative and passed it on to my... Read morePublished on Jan. 28 2014 by Shirley Corris
I grew up with books such as this "Make Way for Ducklings" and find them very nostalgic. They are not found anymore on bookstore shelves, so I was very happy to find this... Read morePublished on Dec 18 2013 by livewell2
Purchased this book before our trip to Boston with our 3 year old twins, and it was the perfect complement to our trip. Read morePublished on Sept. 20 2013 by Shiri sol Ohayon
What can I say that everyone else hasn't already? This is probably one of the finest children's books ever written. Read morePublished on May 2 2004 by Homeschooling Single Mom
This is a nice tale of a family of ducks finding their place in the world. We have the hard back version and the "book on tape" and both of my children like it. Read morePublished on Dec 7 2003 by britneyxyz
I am a student at West Virginia State College and taking a Childrens lit. class. Make way for ducklings is a delightful book and i strongly reccommend it to children of all ages. Read morePublished on July 9 2003 by Kim
Talk about the wonders of your own neighborhood. Robert McCloskey has taken a tale of Mr. and Mrs. Mallard and brought it to Boston, Massachusetts, and within its pages are not... Read morePublished on March 8 2003 by Gregory Nyman
This story will bring a smile to your face and tears of joy to your heart as you rejoice with this American family!
Dasia says, "This lovely family of ducks is great! Read more


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* EsotericHappyEnding: David loses his fiance (though they weren't marrying for love anyway), and his dinosaur skeleton (whether it's irreparable is unclear). However, he gets Susan, who he is at least very fond of at this point, and his museum does get the funding it requires.
* VindicatedByHistory: The film was a flop in its first release, to the point where Katharine Hepburn had to buy out her contract to RKO and Howard Hawks was fired from ''Film/GungaDin''. Nowadays, it's regarded as a classic.


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Welcome | The Department of Anthropology | University of Illinois
As anthropologists, we explore the human condition across time and space. Whether through the study of unburied artifacts, the human genome, grammatical categories or religious ritual, our mission is a holistic enterprise facing a fragmented world.
In Memoriam: Nancy Abelmann (April 24, 1959 - January 6, 2016)
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You might be barking up the wrong tree here. From their site:


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Fixed-Price - Intermediate ($$) - Est. Budget: $55 - PostedSkills: Drawing Brand Marketing Logo Design
I'm starting a gaming channel on youtube and need some channel art and a profile picture. I have a few I just need some retouchings or to be based off of. Heres my channel if you're interested -- https://www.youtube.com/channel/UCVXxwk-ywHpDe5rYs0Za51Q --- If we work well together, I may need more art in the future for the video thumbnails, I'd like it to be done soon.