Papers by Author: Min Hui Fang

Abstract: Concrete durability is one of the most important considerations in the design of new structures in aggressive environments. It generally depends on the quality of the concrete surface and the cracks of concrete. In this paper, the rebound numbers of concrete cast using controlled permeability formwork (CPF) and ordinary steel formwork were determined. And the early age shrinkages of concrete cured in dry environment of 20±2°C, 75±5% RH, in sealed condition with plastic film and in covered condition with CPF liner were measured. Testing results indicated that CPF could improve the concrete surface hardness and reduce the early age shrinkage of concrete. So CPF can enhance concrete durability and prolong its life-span.

Abstract: A series of water-soluble polycarboxylate-type superplasticizer (PCA) were synthesized by free-radical copolymerization of methyl acrylic acid and methoxy poly(ethylene glyco1) monoacrylate macromonomers in water solutions．Micelles were formed from the resultant PCA with predetermined hydrophobic and hydrophilic blocks in water. The hydrodynamic diameter and size distribution of micelles were determined by dynamic light scattering. The change of the concentration of the electrolyte results directly in the variation of the dispersing force of PCA in cement paste. The dispersing force degrades with increasing electrolyte concentration.

Abstract: Based on designed and manufactured test equipment of concrete early age shrinkage, the influence of shrinkage reduce agent (SRA) on early age autogenous shrinkage of concrete was researched. The test results show that early age autogenous shrinkage of concrete was reduced with SRA added and the shrinkage-reducing ratio increased with concrete strength grade heightened. SRA could also greatly reduce early age autogenous shrinkage of concrete added with pulverized ly ash or slag. Superplasticizer would increse early age autogenous shrinkage of concrete, and the shrinkage was larger than those without superplasticizer, even the SRA mixed into. Furthermore, early age curing should be enhanced for concrete with superplasticizer.