Influence of Various Factors on the Water Demand of Hard Coal Fly Ashes, Cements and Hard Coal Fly Ashes/Cement Mixtures

Project Number 234

For an optimised usage of the possitive effects of fly ash on the consistency and the reological properties of concretes, a precise knowledge of the water demand of the concrete raw materials, particularly of the fine-grained materials like sand, cement and fly ash is required. Hereby, the water demand of the material mix is essential for the intended consistency of the concrete, which however cannot be linear derived from the water demand of the single initial concrete components.

The water demand of fly ash is investigated on building sites as well as in monitoring and research labs. To determine the water demand not only a single procedure is to applied. Thus, differences in the determination of the water demand of one fly ash quality from different sources will always be analysed material-specifically.

The examinations are carried out in the framwork of a joint project of VGB PowerTech and BVK (German Association of Power Plant By-products). First of all, the factors of influence on the examinations procedures are practically determined to specify the grain gross density and the water demand of fly ashes and cements.

The aim of the examinations is the definition of a suitable examination procedure for a common evaluation of the water demand of fly ashes and cements as the substantial representatives of fine-grained concrete raw materials.