Study On The Performance Of Plastic Concrete For Cut-off Wall

Because of good impermeability and the ability of adapting to the foundation deformation, plastic concrete is used widely in water conservancy projects as the impervious material, however, with the development of water conservancy projects and the trend of low carbon & environment protection, ordinary plastic concrete no longer meets the requirements of engineering. This paper from the angle of material composition to improve plastic concrete basic properties, in order to make plastic concrete meet the engineering strength requirement,meanwhile the elastic modulus as low as possible. The utilizing of industrial waste, take the environment protection into consideration. Combined with expected objective, analysis of the effect of different materials on concrete performance, ultimately selected rubber powder,silica fume and fly ash mixed with ordinary plastic concrete. At the same time, researched the working performance, mechanical properties and impermeability of mixed plastic concrete,on the basis of mathematical theory and related software the data were analyzed. The main research contents and conclusions are as follows:(1) Research on working performance of plastic concrete shows: rubber powder, silica fume and fly ash quantity change on plastic concrete mixture performance have different degrees of influence, which affected mixture’s slump more than expansion, mixture’s cohesive and water retentiveness were good and containing more sand. For three admixtures,the fluidity most affected is rubber powder, followed by fly ash, silica fume. Concrete fluidity decreased with the increasing content of rubber powder and silica fume, with the increasing content of fly ash, the fluidity increased first and then decreased.(2) Research of concrete compressive strength in different age shows: mixed rubber powder, silica fume and fly ash concrete strength development was more obvious after 7d,rubber powder and fly ash on 7d strength reduce degree was greater than 28 d, silica fume on7 d strength increase degree was the same as 28d; More than 10% silica fume or admixture with lower replace percentage, the strength of plastic concrete was higher than the reference value; Besides, the relationship between 7d and 28 d cube compressive strength and 28 d cube compressive strength and axial compressive strength was obtained.(3) Research of concrete elastic modulus shows: selected the 25%~75% ultimate failureload as the elastic stage of stress-strain curves for calculation of elastic modulus; Compared with the reference value, regardless of mixing three kinds of admixture, fly ash or rubber powder and fly ash can reduce plastic concrete elastic modulus and the average decline was32.53%; Rubber powder and fly ash can decrease elastic modulus, silica fume can increase elastic modulus, and the increase of the elastic modulus of silica fume was 0.5 times of the increase of the strength; Mixed three kinds of admixture can effectively reduce the ratio of elastic modulus and strength; In addition, the relationship between the elastic modulus and the cube compressive strength was obtained.(4) Research of concrete impermeability shows: Mixed three kinds of admixture can effectively improve plastic concrete impermeability, and more than half of mix ratio the relative permeability coefficient drop was more than 80%, rubber powder can decrease impermeability, silica fume can increase impermeability, and fly ash has double effects;Rubber powder and fly ash dosage should not be recommended more than 10% cement dosage; By using range analysis and variance analysis, the primary and secondary sequence and significance of influence factors were determined, silica fume was the most important factor with significant impact. Besides, the higher the strength, the lower the relative permeability coefficient was obtained.(5) On basis of mechanics performance, utilized multivariate nonlinear analysis to establish calculation models of strength and elastic modulus; To control costs as the main constrains, established dynamic multi-objective optimal planning problem and the MATLAB was used to solve it, designed graphical user interface to show final results; Comprehensive analyzed concrete mechanical properties, impermeability and cost, made a definition of comprehensive index to judge the best mix ratio of concrete, when rubber powder, silica fume and fly ash to replace the percentage of cement followed by 5%, 10% and 15%, the mix ratio was best meet all the concrete performance.