Influence of Pre-Saturation of Recycled Aggregates on Concrete Workability and Strength

What is it about?

This paper presents an experimental study to evaluate the influence of the water addition and pre-saturation of recycled aggregates (RA) on rheological and mechanicals properties of concrete. Quantities of water absorbed and their variations in times were measured according to the European standard (EN 1097-6). Two methods were evaluated: pre-saturate the aggregates and add them to other parameters making concrete or add water absorbed quantity to the mixing water. Replacement rate of natural aggregates (NA) 0%, 50% and 100% were studied. The results obtained showed that the gravels class 3/8 have a greater absorption capacity than the gravels class 8/16. Adding absorbed water during mixing have caused concretes segregations and an excess volume of water was observed at the surface of the concrete. The pre-saturation of aggregates 24 hours before mixing and introducing them as a component in concrete was the best method. The initially saturated aggregates did not consume concretes mixture water. Workability by slump test and mechanical strengths developed with pre-saturated aggregates (100 % RA) and (50% RA - 50% NA) were measured on concretes, and then were compared to those of the reference concretes made with 100 % of natural aggregates. A direct relationship between workability and mechanical strengths of concretes made with unsaturated recycled aggregates was established.

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