{'fraction_non_alphanumeric': 0.02077922077922078, 'fraction_numerical': 0.007792207792207792, 'mean_word_length': 4.94980694980695, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 1, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Development of Precision Statement for Determining Air Void Characteristics of Fresh Concrete with Use of Air Void Analyzer

The presence of an adequate air void system is widely regarded as one of the key elements to producing durable, long-lasting concrete. Until recently, the air void system was monitored in the fresh state by a measure of the total air, and an indication of the air void characteristics, namely, the spacing factor and specific surface, was not possible until the concrete hardened. With the development of the air void analyzer (AVA), it is now possible to measure the spacing factor and specific surface of the air voids while the concrete is still in the plastic state. Currently, 14 states own an AVA unit, and numerous other states have investigated implementing the device. As a result of widespread use of this technology, the AASHTO Technology Implementation Group, led by the Kansas Department of Transportation, is working toward possible standardization of this test method. One of the crucial components of this effort is development of a precision statement for the test protocol. In response, a round-robin study consisting of 19 devices and operators was held in February 2006 to gather the necessary data. Through this study, the single operator coefficient of variation (COV) was determined to be 15%. The multiple operator COV was determined to be 19%. The statistical analysis that was performed and the interaction of the devices based on average spacing factor and specific surface are discussed.