Papers by Author: Kuang Liang Qian

Abstract: The first 3d early shrinkage of recycled concrete from initial setting time with different replacement rates of recycled aggregate was investigated by self-made equipment. The differences between the unimproved recycled concrete and the improved one are observed, in the latter, new mixing method was utilized，that is, R-aggregates is coated with slag and nanoCaCO3, and relevant mechanism is analyzed. The results illustrate that early shrinkage of recycled concrete outweighs natural concrete, but there is not a definite link between the replacement rate of recycled aggregate and the early shrinkage. The treatment can effectively reduce the shrinkage of recycled concrete in 10h, but can not have a sustaining effort. Prewet treatment will generate water loss channels accelerating evaporation speed of water in concrete to accelerate shrinkage of concrete. The treatment can block water loss channel by coating, and slag and nanoCaCO3 can change pore structure and humidity in concrete to reduce the first10h early shrinkage.

Abstract: Some long-term properties such as anti-carbonation properties, shrinkage, penetrability of chloride ion of fly ash concrete with nano-CaCO3 middle slurry were studied. Test results showed that the properties of anti-carbonation and impenetrability for chloride of fly ash concrete increased by adding nano-CaCO3 middle slurry because the tiny hole was filled by nano-CaCO3 and the density of concrete increased. But at the same time, the shrinkage of fly ash concrete with and without nano-CaCO3 was the same. Results of SEM also implied the hydration degree of fly ash could be increased by nano-CaCO3.

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.