Dispersing Effect of Core Cross-linked Star Polycarboxylate Superplasticizers on the Cement Paste

Jinlong Zhang,Xiaolong Chen,Furen Huang,Kaihong Zhong,Haijun Xu

doi:10.1051/e3sconf/202128301048

Abstract

Researches on topological modification of polycarboxylate superplasticizers to improve the water-reducing or slump-retainning properties have been a hot topic in rencent years. Herein, a core crosslinked star polycarboxylate superplasticizers (SPCE) were synthesized by crosslinking the comb polycarboxylate superplasticizers (CPCE) in aqueous solution. Crosslinkers and spacing monomers were added into the polymerization to promote the formation of hydrophobic core. A larger molecular weight with 75% of yields of the SPCE were observed by gel permeation chromatography (GPC). The dispersing effect of SPCE on the cement paste was then investigated by varying the dosage of crosslinkers and spacing monomers. It was found that the dispersing ability of SPCE became weakened compared to the CPCE. More of the crosslinkers led to smaller flow spread, as revealed by cement paste experiments. Introduction of the spacing monomers contributed to the formation of SPCE. However, the dispersing ability was also weakened. Best conversion efficiency and water-reducing ability was obtained when the molar ratio of crosslinker and spacing monomer to CPCE was set as 3:5:1.

Highlights

Polycarboxylate superplasticizers (PCE), which featured by the properties of low dosage, high water-reducing, and excellent slump-retainning et al, have been proved to be indispensible materials in concrete.[1, 2] The steric hindrance of the long side chains and the electrostatic repulsion of carboxyl groups of PAA made PCE a better admixtures in concrete than lignosulfonate and naphthalene typed superplasticizers.factors such as the shortage of natural sands, quality fluctuation of the concrete original materials and long-distance delivery, have put forward much higher request on the adaptability and slumpretainning ability of PCE
The comb polycarboxylate superplasticizers (CPCE) was used as the chain transfer agents to trigger the crosslinking reaction to give SPCE (Fig.1)
The linkers ethylene glycol dimethacrylate (EGD) caught CPCEs to form a hydrophobic core, and the butyl methacrylate (BMA) being as the spacing monomers were used to reduce the rigidity of EGD

Summary

Introduction

Polycarboxylate superplasticizers (PCE), which featured by the properties of low dosage, high water-reducing, and excellent slump-retainning et al, have been proved to be indispensible materials in concrete.[1, 2] The steric hindrance of the long side chains and the electrostatic repulsion of carboxyl groups of PAA made PCE a better admixtures in concrete than lignosulfonate and naphthalene typed superplasticizers. Factors such as the shortage of natural sands, quality fluctuation of the concrete original materials and long-distance delivery, have put forward much higher request on the adaptability and slumpretainning ability of PCE. The flow of cement paste could be maintained for 4h with only 13.7% loss, and the hydration of cement could be effectively delayed. [5]

Methods

Results

Conclusion