Performance of dry mix pressure compacted concrete incorporating expanded polystyrene as wall panel / Siti Nurul Ain Ali

Dry mix concrete (DMC) is vital to enhance speedy concrete production but to ensure a sustainable environment, replacing the aggregates with lightweight crushed expanded polystyrene (EPS) waste materials is recommended. However, entrained air in the EPS with zero force is a significant concern that can produce an inferiority of strength in the DMC. Since the incorporation of EPS in DMC reduced workability and cohesiveness, leading to weak bonding between the composite mix, the method of compaction with pressure was employed for DMC. This research aimed to analyse the statistical data and optimise the design mixture of dry mix concrete with EPS (EPS-DMC) according to the maximum strength and appropriate density. Then, the EPS-DMC was assessed for its morphology characterisation, mechanical properties and thermal conductivity (k-value) by the hot box method. Besides that, another objective was to determine the ultimate load of EPS-DMC as a lightweight slender wall panel. This study was investigated three variables, including the three mix proportions of cement with sand (c:s) of 1:3, 1:3.5, and 1:4; the partial EPS replacement by volume at 0%, 35%, 40%, 45%, 50%, and 55%; and the different levels of pressure compaction at 500 psi, 600 psi, and 700 psi. Using Analysis of Variance (ANOVA), the design model by three factors interaction was found to fit with the response of compressive strength and density, which this model was significant. The optimum concrete design mixture of 1:3 with 45% EPS replacement (3EP45) at 700 psi was confirmed from the optimisation of the design mixture simulated via the Response Surface Method. The optimum design mixture of EPS-DMC was adopted for the wall panel for testing under compression uniformly distributed load (UDL) and eccentric load by experimental work and FEA by Abaqus software. The FEA results exhibited the ultimate load, displacement and stress-strain similar to the experimental work. The findings show that the EPS-DMC maximum compressive strength achieved in 3EP45 is 17.97 N/mm2, with a density of 1797 kg/m3. It discovered that EPS-DMC increased its strength by up to 45% of EPS replacement and decreased its performance by 50% of EPS. The modulus of elasticity, flexural strength and pulse velocity of EPS-DMC were all found to agree with the compressive strength. The EPS affected the microscale structure at the interfacial transition zone (ITZ) since the accumulated water around the crushed EPS enhanced cement hydration. Meanwhile, the micro-pores formed outside the aggregate in control DMC specimen due to less water for cement hydration, where the air pockets were trapped. For the thermal conductivity, the k-value reduced from 1.53 W/m°C to 0.47 W/m°C in the range of 0% to 50% EPS replacement and the k-value appropriate function is directly proportional to the density property. The ultimate load subjected to UDL and eccentric loadings were 872 kN and 587 kN, respectively. The stress value of the double-stack wall panel was significantly lower than the single-stack wall panel, as it was affected by a reduction of the stress resistance to fracture at a high slenderness ratio. However, the panel without reinforcement exhibited better post-peak behaviour than the panel with reinforcement. The lack of cohesiveness of the DMC was responsible for the weak stress in the centre section where the reinforcement was embedded. Finally, this research concluded that the EPS-DMC has the potential to be used as a wall panel, where it can withstand the applied load. The new EPS-DMC design was realised via the use of pressure compaction execution ideal for lightweight structural concrete produced with concrete consolidation, strength, and performance credibility.