Effects of Microwave Curing on the Mechanical Properties of Ultra-high Performance Concrete and Affecting Mechanism
GAO Xiaojian1,2, LI Shuangxin1,2
1 School of Civil Engineering, Harbin Institute of Technology, Harbin 150001 2 The Key Laboratory of Structural Engineering Catastrophe and Control of the Ministry of Education, Harbin 150001
Abstract: Ultra-high performance concrete (UHPC) is, after high strength concrete and high performance concrete, the newly developed concrete, which possesses high strength and high durability, ect. It has a significant application potential in the construction of high rise, super high-rise buildings, large span structure and the civil projects under harsh corrosive environment. In the perspective of material preparation, ultra-high performance concrete (UHPC) was added with mineral admixture and was treated with microwave curing, more efficient curing method. The effect of mineral admixture and microwave curing method on the strength was studied, as well as the affecting mechanism through the microstructural characterization. The cement in UHPC has been partially replaced by blast furnace slag (BFS) in the weight percentages of 10%,30%,50%,70% and 90%. Three days delayed microwave curing regime was adapted. After the samples were tested for strength, some typical samples were selected to be examined with 29Si and 27Al NMR and XRD. It was found that, under the standard curing, the compressive strength reduced with the addition of BFS, but the microwave curing enhanced the development of strength through accelerating the hydration of BFS. The acceleration effects were more significant with the early age samples; moreover, it increased with the addition of BFS increasing. The microstructural characterization confirmed the acceleration of hydration by microwave curing, and showed that the formation of crystalline phases and C-S-H with short chains were increased, which both help overcoming the retarded effects by the addition of BFS.
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2019, Vol. 33 
