Research On The Influence Of Compound Admixture On Main Performance Of Crushed Sand Concrete

Crushed sand has the similar physical properties with natural sand and is of economic value, thus could be a fine substitute of natural sand. It is rich in China, so the way by which natural sand is substituted by crushed sand in concrete can well solve the problem of the shortage of natural sand resources, and also produce apparent economic and social benefits. Centered on the existing problems occurring in the practical use of crushed sand concrete, this paper proposes effective solutions, that is, to mix appropriate volume of compound admixtures so as to totally improve the performance of crushed sand concrete, and provide wide use of crushed sand concrete with theoretical basis.Firstly, optimize contrast experiments were done. According to the performance of fresh concrete and mechanical properties shown in the experiments, combined with economic value, the rational compound volume of admixtures was decided. Secondly, by contrast experiments, the influence of compound admixture on main performance of crushed sand concrete was analyzed, and the microstructure of the concrete was explained by means of SEM. Lastly, the values of long-term dry shrinkage of crushed sand concrete were observed and predicted by using RBF neural network model.Research shows that, the influence of compound admixture on the performance of crushed sand concrete is represented at several aspects as follows: at the aspect of fresh concrete, compound admixture can obviously improve the workability of crushed sand concrete, and meanwhile save the amount of cement; at the aspect of long-term properties, compound admixture would enlarge the early dry shrinkage of crushed sand concrete, so the concrete curing should be early enhanced; at the aspect of durability, compound admixture can produce large amount of little closed air bubbles, and thus noticeably enhance the anti-freeze-thaw durability and anti- penetration of crushed sand concrete, but would not exert great impact over the carbonation and the steel corrosion in the crushed sand concrete.Research also shows that, RBF neural network model, which is used in the prediction of lone-term dry shrinkage, achieves remarkable results with high precision.