Behaviour of Three Dimensional Expanded Polystyrene (Eps) Sandwiched Concrete Panels Under Aggressive Environment

Abstract

The rising need for housing in developing countries has led to a demand for rapid construction materials and techniques. Additionally, the desire for better living comfort and low energy consumption has driven a shift from traditional masonry construction to rapid construction methods that offer advantages such as insulation, lightweight properties, and acoustic insulation. One such extensively used material is Expanded Polystyrene (EPS) Sandwiched Concrete Panels, known for their rapid construction capabilities, cost￾effectiveness, insulating properties, and lightweight load-bearing capacity. This study aims to evaluate the flexural performance of these panels under aggressive environmental conditions, including chloride exposure, acid exposure, sulfate exposure, and elevated temperatures. Additionally, the study employs Acoustic Emission (AE) non-destructive testing to monitor the panels. The EPS panels used in this study have dimensions of 1000 × 600 × 130 mm (Length × Width × Thickness), with welded wire mesh of size 50 × 50 mm serving as wythe reinforcement and truss-shaped shear connectors. In the first phase of this study, chloride exposure, which results in corrosion, is simulated using an impressed current technique for accelerated corrosion. The panels were corroded to different levels by varying the days of exposure of 5-, 10-, 15- and 20-days, the panels were then tested under a monotonically increasing flexural loading. The failure mode and behavior of the corrosion-damaged panels were investigated regarding flexural strength, stiffness, ductility, and composite action. The investigation showed decreases of 6.98%, 13.93%, 20.62%, and 60.45% in the ultimate flexural load-carrying capacity after 5, 10, 15, and 20 days of accelerated corrosion, respectively. The ductility, evaluated using the Ductility Factor (DF), showed a decrease of up to 85.01% in highly corroded panels. AE parameters, such as cumulative AE hits, amplitudes, and X-Y event plots, were used to detect faults, reliably indicating damage in the tested panels. The AE hits correlated with the decreasing flexural load-carrying capacity as corrosion increased, and X-Y event plots accurately located faults in all corroded panels. In the second phase of the study, significant exposure conditions involving acid and sulphate attacks were also established. The aggressive environment of acid attack was created by immersing the EPS panels in sulfuric acid (H2SO4) solution at pH=1 for varying 7, 14, 21, and 28 days. Similarly, a sulphate attack was simulated by immersing the panels in sodium sulphate (Na2SO4) solution for 90, 180, 270, and 360 days. The panels were tested for residual flexural strength post-exposure. Acid-exposed panels retained 99%, 82.28%, 74.42%, and 37.25% of the control panel's strength for EPS-A07, 14, 21, and 28 days, respectively. Sulfate￾exposed panels retained 91.64%, 88.89%, 77.19%, and 57.28% of their original strength for EPS-S90, 180, 270, and 360 days, respectively. The ductility of acid-exposed panels decreased, while sulfate-exposed panels showed a loss in stiffness after 180 days. AE monitoring during flexural testing revealed correlations between AE parameters (cumulative AE hits, amplitudes, Rise Angle (RA), and Average Frequency (AF)) and the mechanical properties of the panels. RA-AF plots analyzed during different loading stages indicated that shear cracks dominated from the initial loading phase as the panels degraded. In the third phase of the study, the performance of EPS panels exposed to elevated temperatures was evaluated by subjecting them to 50ºC, 100ºC, 150ºC, and 200ºC using hot plates. Post-exposure, the panels underwent four-point flexural loading tests to assess their mechanical properties. The study found that temperatures above 100ºC significantly affected the panels' yield load, stiffness, ultimate load, and composite action. Detailed analysis of AE parameters—hit counts, amplitudes, average frequency (AF), cumulative signal strength (CSS), and rise angle (RA)—provided precise indications of the panels' degradation. The AE data revealed patterns correlating with thermal exposure levels, identifying critical temperature thresholds compromising panel integrity. These findings underscore the importance of temperature management in applications involving EPS sandwiched concrete panels, offering insights for enhancing their durability and performance in environments subject to elevated temperatures. This study investigates EPS panels' flexural performance and durability under various environmental exposures—chloride, acid, sulfate, and elevated temperatures. The results indicate significant degradation in mechanical properties with increasing exposure, highlighting the need for careful evaluation and management of these panels in harsh conditions. These insights are crucial for improving the resilience and longevity of EPS panels in construction applications.