Some other admixtures, especially air-entraining admixture, can increase the slump of a mix. Flowable fill includes mixtures of Portland cement and filler material, and can contain mineral admixtures. The most common admixtures are retarders and accelerators. Raising the water content or adding chemical admixtures increases concrete workability. Cement accelerators are available as admixtures for the use in concrete, mortar, rendering and screeds. Mineral admixtures use recycled materials as concrete ingredients. Other ingredients such as chemical admixtures, pozzolans, and pigments also may be added. Admixtures may be used to control setting time, slump and workability. Calcium nitrate is used in set accelerating concrete admixtures. Lime mortar can be improved in strength and performance by admixtures of vegetable juices. Modern admixtures and water reducers can modify that time span to some degree. Iron, manganese, cobalt and nickel may occur as admixtures, but only in small amounts. Admixtures are defined as additions "made as the concrete mix is being prepared". The performance of a concrete mix can be altered by use of admixtures. Honey from goldenrods often is dark and strong because of admixtures of other nectars.