Commodity Concrete Shrinkage Performance Of The Pilot Study

Merchandise concrete with merit of accomplished quickly, good quality, spared manpower, low expend, state-of-art technology and civilized scene, has became the indispensable part in the civil architecture field. However, owing to the larger liquidity, the larger ratio of cement and fine aggregate in mixing proportion and the smaller ratio of coarse aggregate, merchandise concrete has larger shrinkage and emerges cracks easily. According to statistics, non-load cracks occupy more than 70 percent in all concrete structure cracks. So, how to find out the shrinkage reasons of merchandise concrete and control shrinkage cracks still to be solved problem.Through measured 24 groups 99 lumps of merchandise concrete shrinkage specimens' shrinkage strain in series 180 days, this paper analyzed and worked out the shrinkage strain-time computing formula of merchandise concrete under standard condition. Shrinkage strain-time multi-coefficient computing formula of merchandise concrete under nonstandard conditions was gave out by using multi-coefficient superposition method, at the same time, each influence coefficients were offered basing this experiment dates and referencing shrinkage text material of home and abroad.Besides, the comparing and analyzing were proceeded both computing formula given by this paper and ACI formula, Trost formula, the Building Research Council of China formula and Wang Tie-meng formula, though which prove that the formula given by this paper was true of merchandise concrete.When merchandise concrete specimens placed steel bar shrank, concrete was tensioned and steel bar was pressed. Utilizing the equilibria of pull and press and the dispersion between placed and unplaced steel bar specimens, this paper put forward the shrinkage stress-time computing formula and elastic modulus-time computing formula of merchandise concrete that offered the reference for controlling merchandise concrete cracks.At last, based on the research and analyses, this paper gave the measures of compensating and controlling the merchandise concrete shrinkage.This research subject is the sixth passel subject of code for design of concrete structure.