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An experimental investigation of the thermal spalling of polypropylene-fibered reactive powder concrete exposed to elevated temperatures

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Science Bulletin 2015年第23期60卷 2022-2053页

作者： Yang Ju Li Wang Hongbin Liu kaipei tian State Key Laboratory of Coal Resources and Safe Mining China University of Mining and Technology State Key Laboratory for Geomechanics and Deep Underground Engineering China University of Mining and Technology Lawrence Berkeley National Laboratory School of Mechanics and Civil Engineering China University of Mining and Technology Institute of Construction Materials University of Stuttgart

Polypropylene fibers are embedded to prevent reactive powder concrete （RPC） from spalling failure under high temperatures. This paper probes the influence of embedded fibers at various volumetric dosages on the thermomechanical properties of polypropylene-fibered reactive powder concrete （PPRPC） exposed to high tem- peratures up to 350 ℃ and on the spalling performance and characteristics up to 600 ℃. The thermomechanical prop- erties include the characteristic temperature for spalling, and residual strengths, such as the compressive strength, split tensile strength, and flexural tensile strength. A high- definition charge-coupled device camera and scanning electron microscope technology were employed to capture the spalling processes and to detect the microstructural changes in the materials with various fiber dosages. To understand and characterize the mechanism by which polypropylene fibers influence the thermal spalling of RPC, a numerical model to determine the moisture migration and vapor pressure transmission during spalling was developed in this paper. It showed that there was an optimal volu- metric dosage of fibers to prevent PPRPC from explosive spalling. The relationships between the mechanical char- acteristics of PPRPC and the fiber dosages were derived based on experimental data.

关键词： Polypropylene reactive powder concrete(PPRPC) · Thermal spalling · Vapor pressuremechanism · Polypropylene fibers ·Elevated temperatures

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An investigation on micro pore structures and the vapor pressure mechanism of explosive spalling of RPC exposed to high temperature

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Science China(Technological Sciences) 2013年第2期56卷 458-470页

作者： JU Yang LIU HongBin tian kaipei LIU JinHui WANG Li GE ZhiShun State Key Laboratory of Coal Resources and Safe Mining China University of Mining and Technology Beijing Key Laboratory of Fracture and Damage Mechanics of Rocks and Concrete China University of Mining and Technology School of Mechanics and Civil Engineering China University of Mining and Technology

Reactive powder concrete （RPC） is vulnerable to explosive spalling when exposed to high temperature. The characteristics of micro pore structure and vapor pressure of RPC are closely related to the thermal spalling. Applying mercury intrusion po- rosimetry （MIP） and scanning electron microscopy （SEM） techniques, the authors probed the characteristics of micro pore structures of plain RPC200 when heated from 20-350~C. The pore characteristics such as specific pore volume, threshold pore size and most probable pore size varying with temperatures were investigated. A vapor pressure kit was developed to measure the vapor pressure and its variation inside RPC200 at various temperatures. A thin-wall spherical pore model was proposed to ana- lyze the thermo-mechanical mechanism of spalling, by which the stresses varying with the vapor pressure q（T） and the character- istic size of wall （K） at any point of interest were determined. It is shown that the pore characteristics including specific pore volume, average pore size, threshold pore size and most probable pore size rise significantly with the increasing temperature. 200~C appears to be the threshold temperature above which the threshold pore size and the most probable pore size climb up dramatically. The increase in the specific pore volume results from the growth both in quantity and in volume of the transition pores and the capillary pores. The appearance of the explosive spalling in RPC200 is mainly attributed to being unable to form pathways in favor of releasing water steam in RPC and to thin-wall sphere domain where the vapor pressure governs the the rapid accumulation of high vapor pressures as well. The spalling is bounded through the pore model.

关键词： reactive powder concrete (RPC) high temperature spalling pore structure vapor pressure microstructures mercuryintrusion porosimetry (MIP)

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