The Experimental Study On The Material Of Plastic Concrete Cut-off Wall

Plastic concrete takes the advantages of lower initial elastic modulus, greater ultimate strain, stronger impermeability, similar deformation modulus to that of the surrounding soil and tending to ensure the safety of the cut-off wall. In resent years, more and more attention was paid to plastic concrete, which was used as impermeable barrier material in the contaminated sites to prevent pollutants spread as first-aid treatment. In order to comprehend the properties of plastic concrete further, research the material ratio systematically, and understand the regularity for change of the permeability in the load and the impact of pollutants on the properties, the impact of different material ratio on slump value, compression strength, shear strength, modulus of elasticity and permeability coefficient of plastic concrete was studied, the permeability of plastic concrete under load was analysed,and he compatibility of plastic and heavy metal pollutants was disscussed. Main achievements are as follows:The experiments on the material ratio showed that change of the material content had influence on the performance of the plastic concrete. The slump value was increased, the modulus of elasticity was reduced and the impermeability was improved by decreasing the content of cement and increasing the content of bentonite. The compression strength and the impermeability was raised, but the slump value was reduced by increasing the sand ratio. The workability of the mixture was improved and the permeability coefficient and the modulus of elasticity were decreased by adding air-entraining water-reducing agent properly. The optimum ratio was determined by the ratio experiments. The mixture slump value was 18cm, the compression strength for 28 days was 6.01MPa, the cohesive strength was 1.88MPa, the modulus of elasticity was 11163MPa, and the permeability coefficient was 4.13×10^-8cm/s. All the parameters could meet the engineering requirement.The permeability test showed that confining pressure and water pressure being kept unchanged, the permeability coefficient of plastic concrete lowed slightly when the load ratio （the ratio between load and maximum load） was under 30%. When the load ratio increased to 30%⁶0%, the permeability coefficient dropped markedly, belonging to elastic phase. When the load ratio was higher than 60%, the permeability coefficient began to increase, belonging to plastic phase. When the load ratio reached up to 80%, macro-cracks appeared in the plastic concrete, and the permeability coefficient increased markedly.The experiment on compatibility showed that the plastic concrete and the heavy metal of Cr, Pb, and Cu were compatible. The plastic concrete was exposed to the heavy metal for 28 days, and the modulus of elasticity decreased for a little, but the strength and the permeability did not affected. The compression strength increased but the impermeability decreased when the plastic concrete was conserved by standing water, which should be paid attention in the engineering.