Performance of expansive concrete under the influences of mix proportions, restraining conditions and curing conditions

Although concrete is widely accepted for its high compressive strength, its tensile strength is comparably low which may result in cracking of the concrete, especially when it is under the influence of restraint. Cracks in concrete is highly undesirable and usually cracks due to restrained shrinkage of concrete are inevitable. Since expansive additive (EA) can be utilized to mitigate cracking due to shrinkage, the current study is performed to vary the mix proportions and curing conditions to generate required expansion. As induced expansion can mitigate the shrinkage cracking, expansion must be thoroughly studied and estimated for efficient application. A systematic experimental program was carried out for measurements of setting time, slump loss, expansion, shrinkage, and compressive strength using various series of mix proportions. Several parametric studies were done to clarify the influences of EA content, binder content, restraining condition, curing method, and curing temperature. The behavior and performance of expansive concrete were aimed to be evaluated to determine required amount of expansive agent.Test results revealed that increasing expansive additive content, binder content, and curing temperature expansion enhanced expansion at an early age. The expansion was observed to be reduced with an increasing level of restraint. Moist curing and water curing methods enhanced the formation of expansive products when compared to sealed curing. As early expansion defines the rate and amount of compensation of shrinkage developed in concrete, higher initial expansion was found to reduce shrinkage at 45 days. Moreover, this study also presents an experimental study compressive strength of expansive concrete under free and restrained conditions. The experimental findings indicate that the tested expansive additive slightly reduced the compressive strength of expansive concrete, however, the effects were reduced by restraining. Based on the experimentally measured results and previous studies, equations for predicting maximum free expansion and time-dependent free expansion at any time during the curing age were proposed. The equations focus on analyzing the expansion mechanism under the effects of expansive additive, binder content, w/b ratio, curing temperature and curing type. The equations were verified with expansive concrete mixtures having different types of fly ash and expansive additive under various mix proportions and curing conditions.