EXPERIMENTAL AND PROBABILISTIC ASSESSMENT OF CONCRETE INCORPORATING EXPANDED POLYSTYRENE (EPS) WASTE AT ELEVATED TEMPERATURES

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Department of Engineering

ABSTRACT
This study is to investigate the effects of Expanded Polystyrene (EPS) as a partial replacement for coarse aggregates at 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, and 50% at elevated temperatures of Room Temperature (280C), 200?, 400?, 600?, and 800? for the duration of 2 hrs each. Compressive strength and flexural strength were carried out on concrete cubes of size 150mm × 150mm × 150mm and concrete beams of size 150mm × 150mm × 750mm respectively. The experimental results shows that the increase in EPS content as well as the increase in temperature causes decrease in the strength of concrete at room temperature, while inclusion of EPS from 5% to 15% increased the resistance of concrete to heat better than the control at a maximum temperature of 4000C. This implied that the trapped air within the closed cells of EPS reduces the flow of heat, thereby reducing loss of moisture from the concrete but the optimum performance of EPS in concrete lies at 10% EPS content at a temperature of 4000C, where the target Compressive strength of 25N/mm2 was still achievable. Maximum flexural strength was achieved at 2000C at 25% EPS content. The mathematical model relating compressive strength of concrete cubes with Expanded Polystyrene was predicted using least regression analysis from the experimental data obtained and it was found to have coefficient of correlation values (R2) of 0.984, 0.934, 0.856, 0.947 and 0.952 respectively for 280C, 2000C, 4000C, 6000C and 8000C. These were incorporated in the Probabilistic assessment of a designed simply supported reinforced concrete beam exposed to elevated temperatures. Flexural limit state function was developed and evaluated using First Order Reliability Method (FORM) which was implemented through a developed program using MATLAB. From the reliability analysis, safety index is higher at load ratio (dead load to live load) of 1.0 ( = 7.8kN/m), while for a reinforced concrete beams to be considered safe in bending considering 8000C, the maximum EPS content must be 20% coarse aggregate replacement which gives a safety index of 3.98 as above the targeted safety of 3.8 as recommended in JCSS (2001).