A unified calculation method for temperatures of recycled aggregate concrete members exposed to fire: tests and numerical study

Abstract

The utilisation of recycled aggregate in reinforced concrete structures can effectively reduce demolition waste and overcome the deficiency of natural aggregate. Because the thermal conductivity of recycled aggregate concrete differs from natural concrete, its temperature developments should be studied particularly to accurately predict the fire resistance of those members exposed to fire. However, few studies have been performed on the heat transfers of recycled aggregate concrete (RAC) members, especially for fine recycled aggregate concrete members. Therefore, an experimental and numerical study was conducted on the heat transfer in coarse and fine RAC members. Eighteen recycled aggregate concrete specimens were tested, among which the influences of aggregate replacement ratios (0, 50%, and 100%), aggregate types (coarse recycled aggregate, fine recycled aggregate) and dimensions of heat transfer (one-dimensional (1-D), two-dimensional (2-D)) were carefully investigated. Finite element models of concrete members were then developed using the program COMSOL Multiphysics and verified against the test results. Parametric studies were conducted to identify their influences on temperature distributions and developments. Finally, a unified simplified method was proposed for the cross-section temperatures of those coarse and fine RAC concrete members featuring 1-D and 2-D heat transferring (e.g. slabs, walls, beams and columns).