STUDY OF THE INFLUENCE OF AN INTERNAL EXPANSIVE AGENT AND OF A SHRINKAGE REDUCING AGENT ON FREE AND RESTRICTED VOLUME’S VARIATIONS OF CONCRETE

摘要

Durability of concrete is greatly affected by shrinkage cracking (antogenous and restrainedshrinkage) and therefore requires special attention. Restrained shrinkage of concretecauses tensile stresses and the formation of cracks that allow the penetration ofaggressive agents. The overall objective of the research is to study the free and restrainedvolume variations of a 25 MPa concrete containing a CaO based internal expansion agent(IEA) and a shrinkage reducing agent (SRA). The results show that free and restrainedexpansions increase with the IEA dosage. The addition of SRA has little effect on theexpansion kinetic by the IEA. The initial expansion (0 -7 days) decreases the totalshrinkage by 72% at 7 days and 43% at 224 days. The shrinkage-reducing agentdecreases the drying shrinkage by 40% at 7 days and by 30% at 224 days. These resultslead a better understanding of the effects of IEA and SRA on the volume variations ofconcrete, and in particular on the development of drying shrinkage.