Determining the Water Demand of Fine Aggregates

Abstract

For the effective design of concrete and mortar compositions, it is important to know the quantitative and qualitative characteristics of their components, in particular, aggregates, including artificial aggregates. One of the essential characteristics affecting the quality of fine aggregates is water demand. Determining the water demand of sand in a solution using well-known methods depends on the composition of the solution and its liquid phase and cannot objectively characterize its quality. Water demand, defined as the amount of water held by the surface forces of water particles, is more suitable for assessing the quality of fine aggregates. The wetting power of grains is a determining factor in the water demand of dense sands, such as sands for heavy concretes. When developing a new method for determining the water demand of sand, our task was to use the positive aspects of two methods–drying and measuring electrical conductivity. The advantage of the proposed method is the continuous change and recording of dehydration parameters and the clear distinction between free and bound moisture at standard temperatures. The developed method consists in the continuous measurement of the electrical conductivity of pre-moistened sand during dehydration with a room temperature air flow, recording a characteristic point on a graph of conductivity over time, and determining the moisture content corresponding to the water demand of the sand using the weight method. We proved that the method is sufficiently accurate and reproducible when using sands with a wide range of grain compositions.