جستجوی مقالات مرتبط با کلیدواژه « Microsilica » در نشریات گروه « فناوری اطلاعات »

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.

In this paper, the effect of microsilica on the short-term mechanical properties of high-strength concrete is discussed. Nowadays, due to the fact that the use of microsilica in high-strength concrete has become very common, it is very important to know the effect of this material on different characteristics of concrete. The relationship between resistance, the sequential elastic modulus and the return elastic modulus is one of the cases discussed in this study.Another effect has been the length of the wet storage period on the long-term strength of these concretes. In the laboratory work performed in this study, the ratio of water to cement materials and the total amount of cement materials are 0.35 and 500 kg / m3, respectively. The percentage of microsilica substitutes for cement was 0, 6, 8, 10 and 15%. The 28-day strength of the concrete in question was between 58 and 70 megapascals. To study the effect of storage conditions on the long-term resistance of these types of concretes, the 400-day resistance of the samples kept in saturated conditions until the test was compared with the samples stored in these conditions for 7 days.The result is that long-term processing has little effect on the long-term strength of microsilica concrete. This is not true of microsilica-free concrete. Research on the relationship between resistance and modulus of elasticity and modulus of return elasticity also shows that the model proposed by the ACI 318 regulations does well in these high-strength concretes similar to this research predicts.