Effect of square hollow section on the strength of foamed concrete beam with processed spent bleaching earth as partial replacement of cement

Hollow beam is introduced to reduce the cost of the construction project by reducing the use of materials and formworks. Processed Spent Bleaching Earth (PSBE) is the SBE that has been treated and can be used as a partial replacement for cement in the foamed concrete due to its pozzolanic effect. Density of foamed concrete was designed to get 1600 kg/m³ density. The objective of the study is to determine the maximum load of the flexural beam, the deflection of the flexural beam, and the mode of failure of the flexural beam by using 4 point bending test. Four types of beams were prepared which namely controlled FC beam as known as solid beam (Beam 1) without the hollow section, hollow beam (Beam 2) with the opening size of (50mm x 50mm), hollow beam (Beam 3) with the opening size of (60mm x 60mm), and hollow beam (Beam 4) with the opening size of (70mm x 70mm). All the beams were casted with 30% of PSBE as a partial cement replacement. Each type of the beams were prepared for 3 units of beams (150mm x 200mm x 1500mm) to find the average value of maximum load and deflection. The 4 units of Linear Variable Displacement Transducer (LVDT) were used to measure the deflection of the beams. The crack pattern of beams were observed throughout the experiment and the cracking were then analysed accordingly. From the experimental result, in most of the size of hollow section, Beam 2 produced greater maximum load with 3.94 kN, flexural strength with 0.79 N/mm2 and deflection with 0.30mm. The result showed that the flexural strength of the beams decreased to certain degree of percentage of 12.7%, 37.3% and 51.1% for Beam 2, Beam 3 and Beam 4 respectively. Also, result for deflection showed that Beam 2, Beam 3 and Beam 4 deflected less compared to Beam 1 with decrement of 9.09%, 17.27%, and 25.76% respectively. The flexural strength of the beams depends on the second moment of inertia while second moment of inertia depends on the surface area of the beams. The maximum loading of beam with hollow section decreased due to the increasing dimension of hollow section. Since the beams were un-reinforced, therefore, they failed without any appearance of tiny crack. The vertical crack was called ultimate crack. Hence, the flexural strength and deflection of square hollow section decreased as the size of hollow increased