The effect of microsilica on the setting time of high-strength concrete

This paper is the result of laboratory work performed on the initial and final setting times of high-strength concrete with different percentages of microsilica. The penetration resistance method (ASTM C 403) has been used to determine the setting times of concrete. In this method, first the concrete is made and then the coarse grades of the four large aggregates are separated using a sieve. It is important to know the timing of concreting in the planning of its executive operations. In fact, this feature of concrete is effective in determining the allowable time of transport, casting, vibration and surface polishing of concrete. The results of the initial setting time test are also used to find the starting point for spontaneous shrinkage of concrete, which accounts for the largest amount of shrinkage in highly resistant concretes. The results of this study show that with increasing microsilica percentage, the initial and final bonding times of concrete increase.