Effect of the structure of macromonomer in polycarboxylate superplasticizer on viscosity and workability of concrete

Reducing the water-to-cement (w/c) ratio was the most direct way to decrease the dosage of cement while ensuring compressive strength of concrete. However, the concrete system tend to be more stickiness at low w/c ratio. Four types of polycarboxylate superplasticizers (PCEs) were synthesized using HPEG, IPEG, EPEG, or VPEG as macromonomers. The impact of PCEs on the viscosity and workability of cement and concrete was investigated. The mechanism behind the macroscopic properties exhibited by these four PCEs was explored through surface tension analysis, GPC analysis, NMR analysis, and adsorption capacity evaluation. The results indicated that, at high w/c ratio (>= 0.35), concrete mixed with four types of PCEs demonstrated almost the same flow velocity and viscosity, at low w/c ratio (<= 0.3), the V-funnel time of concrete which mixed with 67EPC3.5 reached 8.5 s, showed the fastest flow velocity and lowest viscosity, due to the structure of 67EPC3.5 containing the highest content of combined units of AAA which resulted in rapid adsorption rate and maximum adsorption quantity, and the viscosity effect was independent of surface tension. Concrete mixed with 67IPC3.5 displayed the superior workability at any w/c ratio primarily because the structure of 67IPC3.5 contained the highest content of polyoxyethylene ether which effectively reduced surface tension.