Effects of Incorporating Steel Fibers and Municipal Waste on the Compressive Strength of Concrete

In this study, we assessed the impact of substituting natural fine aggregates with municipal solid waste incineration bottom ash (MSWI-BA) in steel fiber (SF)-reinforced concrete on its compressive properties post high-temperature exposure. The concrete specimens incorporating MSWI-BA as the fine aggregate and SFs for reinforcement underwent uniaxial compression tests after exposure to high temperatures. Through the tests, we investigated the impact of high-temperature exposure on mechanical properties, such as mass loss rate, stress-strain full curve, compressive strength, peak strain, elastic modulus, and so on, over different thermostatic durations. The analysis revealed that with the increasing exposure temperature and durations, the mass loss rate gradually increased; compressive strength initially increased and then decreased; peak strain significantly increased; stress-strain curve flattened, and elasticity modulus monotonically decreased. Different thermostatic durations led to distinct critical temperatures for the compressive strength (700°C for 1.0 and 1.5 h, and 500°C for 2 h). The concrete specimens exhibited an increasing compressive strength below the critical temperature, followed by a rapid decrease upon exceeding it. Based on the strain equivalence hypothesis and Weibull distribution theory, we derived expressions for the total damage variables and a uniaxial compression constitutive model, which accurately reflected the changing macro mechanical properties of concrete under various exposure temperatures and thermostatic durations. The concrete matrix microscopic morphology continuously deteriorated beyond 500°C, resulting in a loss of compressive strength. This degradation in the concrete microstructure serves as the fundamental cause for the decline in its macroscopic mechanical properties. © 2024 Tech Science Press. All rights reserved.