This study aims to reduce the elastic modulus of plastic concrete but keep its high impermeability performance by partially replacing bentonite with talc, while maintaining the strength of the concrete. To this end, bentonite based plastic concrete with two types of water cement ratios were prepared, with different dosages of talc as the replacement of bentonite, which are 0, 5%, 10%, 15% and 20% of the binding material. The effect of talc dosage on the properties of the plastic concrete was studied by testing the working performance of the concrete mixture, compressive strength, elastic modulus and impermeability of the bentonite based plastic concrete, as well as the microscopic morphology observation. The results showed that with the increase in talc dosage, the slump, expansion and compressive strength of the bentonite based plastic concrete mixtures all increased and then decreased, while the permeability coefficient of the concrete decreased first and then increased, and these parameters showed the extreme values when the talc dosage was 10%. However, the elastic modulus of the bentonite based plastic concrete mixtures showed a very slight decrement when the talc dosage was 5%, while decreased significantly as the increase of the talc dosage. Using talc to partially replace bentonite reduced pores in the concrete matrix which in turn made the concrete structure denser, and the concrete matrix with talc dosage of 10% was denser than that of 20%. The bentonite based plastic concrete with talc dosage of 10% showed the optimum comprehensive effect with improved working performance of the concrete mixture, enhanced compressive strength and impermeability as well as decreased elastic modulus of the plastic concrete.