Abstract
Three polycarboxylates with different comb structures (i.e., the same degree of polymerization in side chains but different main chains) were synthesized via radical polymerization reaction at room temperature. The effect of polycarboxylates on the surface tension and the flowability in cement pastes was determined. The best product was selected to study its effects on the hydration heat evolution, compressive strength, autogenous shrinkage, and drying shrinkage of cement pastes with different kinds and contents of supplementary cementitious materials. The results showed that with the increase of molar ratio between AA and TPEG to 6 : 1, we could synthesis the best product. When the water‐binder ratio was 0.4, with the increase of polycarboxylates, the cement hydration heat evolution had been slowed down, and the more the dosage was, the more obvious the effect was. Adding supplementary cementitious materials to cement under the same experimental conditions also played a mitigation role in slowing down the hydration heat. When the water‐binder ratio was 0.3, supplementary cementitious materials could increase the strength of cement by 24.5% in maximum; its autogenous shrinkage and drying shrinkage could be decreased, respectively, by 60.1% and 21.9% in the lowest.
Highlights
Polycarboxylate contained many functional groups including -COOH, -SO3H, -NH2, -OH, and other groups. ese groups could be adsorbed on the hydration products of cement and its surface particles
Synthesis of polycarboxylate was commonly used in the heating method. e temperature was between 60 and 90°C or even higher. e product had relatively low solid content, so that in the synthesis and the transport process, the cost was increased inadvertently. us synthesizing polycarboxylate at room temperature had become a trend in the development of the industry
We found that the incorporation of supplementary cementitious materials could reduce the hydration heat release rate and total release heat of cement pastes under the same experimental conditions
Summary
Polycarboxylate contained many functional groups including -COOH, -SO3H, -NH2, -OH, and other groups. ese groups could be adsorbed on the hydration products of cement and its surface particles. Supplementary cementitious materials (SCMs) had become an essential component in the process of preparation of concrete nowadays, including slag, fly ash, silica fume, metakaolin, and other commonly used materials. Chemical composition and particle size distribution of PI 42.5 Portland cement, slag, fly ash, and metakaolin are available in Table 1 and Figure 1. The solution containing 120 g of TPEG, 80 ml of pure water, 10 g of PEG-200 was fully stirred in a 250 ml four-neck round bottom flask. After that, another solution which contained 0.1 g of dibutyltin dilaurate, 1.2 g of toluene sulphonic acid, and a certain quantity of 30% hydrogen peroxide was added. After adding some NaOH and adjusting the PH value to 6-7, we obtained three kinds of polycarboxylates called PCE-1, PCE-2, and PCE-3
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