Estimation of water absorbed by expanding clay aggregates during structural lightweight concrete production

The estimation of water absorption in aggregates is still one of the major challenges related to the production of structural lightweight aggregate concrete (SLWAC). At present these predictions are only based on common practice and a more soundly based approach is required. Aggregate absorption is mainly affected by its microstructure, surface characteristics, percentage of broken particles, initial water content and characteristics of the surrounding mortar. These are the key parameters taken into account in this paper, where the absorption of different types of Iberian aggregates with varying initial water content is analysed in detail. Based on experimental tests, and by introducing new parameters which take into account the microstructure and water content of the aggregates, a new procedure for predicting absorption by aggregates in concrete is suggested. This procedure will make it possible to more accurately specify the amount of mixing water to be used in SLWAC production, and it is almost independent of the type of aggregate. Therefore, the proposed method should be easily extended to other types of aggregate. Finally, the proposed method was checked experimentally by producing several concrete mixtures, and the results were promising.