Title: The Effect of the Charge Density of a Comb Polyphosphate Superplasticizer on the Structural Build-Up of Cement Paste
Author(s): Alexander Mezhov, Wolfram Schmidt, Hang Zhang, Charles E. Diesendruck
Publication: Symposium Paper
Appears on pages(s): 255-262
Keywords: admixture; superplasticizer; polyphosphate; structural build-up
Lately, there has been rising attention to superplasticizers (SP) based on polyphosphate esters. However, the influence of the molecular structure of the polyphosphate polymers on time-dependent properties such as structural build-up has not been examined yet intensively. To investigate this effect, three comb polyphosphate superplasticizers with different charge densities were synthesized by free radical polymerization. Our findings indicate that SP with the lowest and medium charge densities extend the induction period more strongly than the SP with the highest charge density. The reduction of the structural build-up rate is linearly dependent on the dosage and concentration of the functional group of polyphosphate SP in the cementitious system. This study proposes a mathematical equation expressing the relationship between the structural build-up rate during the induction period and the molecular structureof the polyphosphate SP.