Thermal and autogenous shrinkages of very early strength latex-modified concrete

A study evaluated the factors influencing thermal and autogenous shrinkages of very early strength latex-modified concrete (VES-LMC) with respect to latex content (latex solids-cement ratio, by weight); water-cement ratio; retarder content (retarder solids-cement ratio, by weight); and antifoamer content (antifoamer-latex solids ratio, by weight). Examined were three levels of latex content (0%, 5%, 15%) at a constant slump, three levels of water-cement ratio (0.34, 0.38, 0.42) at a constant latex content of 15%, three levels of retarder content (0.0%. 0.3%, 0.6%), and three levels of antifoamer content (0.0%, 0.5% and 1.0%) at a constant latex content and water-cement ratio. Results were that total shrinkage was governed by thermal deformation at very early age because of the high heat of hydration of VES cement After 5 h, total shrinkage was governed by the autogenous shrinkage process. The absolute magnitude of thermal expansion was 130 micro strains while the autogenous shrinkage was 120 micro strains. The autogenous shrinkage increased as latex content increased. VES-LM concrete with a high latex content and low water-cement ratio caused autogenous shrinkage. The total and autogenous shrinkages of VES-LMC were not affected or only slightly affected by the water-cement ratio or the antifoamer content. Excessive retarder induced expansion at very early age, which increased the absolute shrinkage. Thus, attention should be paid whenever retarder is added in response to weather conditions. Furthermore, immediate and proper wet curing is necessary when adding more retarder because of greater susceptibility to plastic shrinkage.