Synthesis and characterization of a novel early‐strength polycarboxylate superplasticizer and its performances in cementitious system

Abstract

A novel early-strength type polycarboxylate superplasticizer (PCE) was synthesized by a new design of molecule structure such as introducing long polyoxyethlene side chains, functional monomer (2-acrylamide-2-methylpropanesulfonic acid), and optimizing monomer composition. In this study, with introducing the sulfonate groups into PCE structure, its dispersion capacity and the absorbed amount are increased firstly and then decreased, but the retardation hydration effect is weakened gradually. The molecular weight, adsorbed amount, and dispersion capacity of PCEs firstly increased and then decreased with increasing the AA/TPEG monomer molar ratio, and the same trend as the compressive strength harden concrete with PCEs at the age of 1, 3, and 28 days. The early-strength type PCE exhibits good dispersive capacity and weak retardation hydration effect in cementitious system, and the early age strength of concrete with addition of early-strength type PCE develops quickly. This study indicates that reasonable design of PCE molecule structure and synthesis method can obtain a novel early-strength type PCE which makes a good balance between workability and fast development of early age strength in cementitious system.

Effects of crosslinked polycarboxylate superplasticizers with crosslinking agent containing ester and amide groups on the properties of cementitious systems

“…When the polymer content was continually increased, the dispersion effect of SP‐E was better than that of SP‐N, while the increasing trend for the fluidity of cement pastes containing SP‐N tended to decelerate with an increase of the superplasticizer dosages. The data in Figure 4 showed that the fluidity of cement slurries with the two superplasticizers increased to a maximum value at 60 min, which might have been due to the gradual increase in the adsorption capacity of superplasticizers on the surface of cement particles，as reported in the literature that the dispersion property of superplasticizers was based on the adsorption process 5,8,19 . Moreover, the ester or amide groups in the two crosslinking agents underwent hydrolysis and released anchoring groups to stimulate better adsorption of the polymers onto the cement particles, thus enhancing the dispersion between cement particles and in turn increasing the fluidity of cement slurries 14 .…”

“…The data in Figure 4 showed that the fluidity of cement slurries with the two superplasticizers increased to a maximum value at 60 min, which might have been due to the gradual increase in the adsorption capacity of superplasticizers on the surface of cement particles，as reported in the literature that the dispersion property of superplasticizers was based on the adsorption process. 5,8,19 Moreover, the ester or amide groups in the two crosslinking agents underwent hydrolysis and released anchoring groups to stimulate better adsorption of the polymers onto the cement particles, thus enhancing the dispersion between cement particles and in turn increasing the fluidity of cement slurries. 14 In addition, the adsorption capacity of SP-E on the surface of cement particles is higher than that of SP-N, and it is evident that SP-E provides a stronger dispersion effect than SP-N.…”

“…A polyelectrolyte is usually used as the backbone chain of a superplasticizer while polyoxyethylene ether groups are employed as the sidechains. [4][5][6][7][8][9] The generation of electrostatic interactions depends on the mutual attraction between cations and anions. 10,11 A large number of Ca 2+ ions and other cations will be formed when cement is mixed with water.…”

“…Polycarboxylate superplasticizers are designed based on making a delicate trade‐off between molecular structures and properties. A polyelectrolyte is usually used as the backbone chain of a superplasticizer while polyoxyethylene ether groups are employed as the side‐chains 4–9 . The generation of electrostatic interactions depends on the mutual attraction between cations and anions 10,11 .…”

Study on the dispersion performance and mechanism of polycarboxylate superplasticizer by the long side‐chain dicarboxyl terminated

“…At present, larger molecular weight polyoxyethylene ether macromonomers (M w greater than 3000 Da) are mainly used for the synthesis of early-strength PCE. 25,26 Compared with ordinary PCEs, these early-strength PCEs have long side chains, and short main chains. The hydrophilic side chains can allow more water to surround cement particles, thus ensuring the normal hydration of cement and improving the early strength of concrete.…”