Influence of shrinkage reducing admixtures on distinct SCC mix compositions

Shrinkage cracking is a major problem in view of the durability of cement-based materials. One way to mitigate shrinkage, and thus reduce or avoid shrinkage cracking, consists in adding a shrinkage-reducing admixture (SRA) during mixing. SRAs are known for their capability to reduce shrinkage but the current state of knowledge on SRAs lacks in regard to: (i) their influence on other concrete properties and (ii) the influence of the concrete composition on the SRA performance. The present research evaluates the influence of two SRAs produced by different companies on two distinct self-compacting concrete (SCC) mix compositions. Each mix composition was studied for 0%, 1%, 2% and 5% of the SRA-to-powder weight ratio. Tests were carried out in order to evaluate the influence and the performance of the SRA type and its content on concrete fresh properties, hardening and shrinkage evolution. After 330 days the E-modulus, compressive strength, resistivity and chloride diffusion tests were evaluated in the same specimens that had been previously used for shrinkage measurement. Results showed that both SRAs induced similar effects and that mix composition plays an important role in the SRA performance.