Performance of non-fired bricks from recycled waste

Abstract

Nowadays the issue on environment preservation and sustainability has lead into a new finding on the new materials that had been generated by product from the industrial sector. A research work had been carried out at Faculty of Civil Engineering, Universiti Teknologi Malaysia regarding the production of Eco Green Brick (EGB), a by product from recycled waste into the production of bricks which is known as EGB Brick. Materials used were hydrated lime, Gypsum, POFA (Palm Oil Fuel Ash), PFA (Pulverized Fuel Ash), Bottom-Ash, sand, water and SP (Super- Plasticizer). In this EGB Brick, cement was totally eliminated (cement free) and replaced by another material that has cementitious properties such as hydrated lime and PFA (class F). The objective of this project is to investigate the optimum mix design with different amounts of bottom ash as a replacement of fine aggregates (sand) by various mix designs to develop a mixture with higher strength properties. The aim primarily is on achieving a proper mix design and a mixing method that will provide a 28-day compressive strength of at least 12 MPa. Two curing regimes were used in this experimental work, air curing and water curing. Experiments have been conducted by replacing 20%, 40%, 50%, 60% and 80% of sand by Bottom-Ash and finding optimum percentage of another material that replaced cement as a binder. The method used to find the water binder ratio was by trial and error with 1:3 ratio of cement to sand. Then, the mixes were cured by air at 7 and 90 days for the first batch. Next, a number of mixes were designed and tested for density and compressive strength. Later, the best strength development among the test result was selected. The density of brick was around 1800 kg/m³ with average strength of 12 N/mm². Other tests conducted on the EGB Bricks are strength development, water absorption, efflorescence, UPV and sulphate resistance. The test results showed that as the PFA:POFA ratio increase, the compressive strength of EGB will also increase. However, as bottom ash ratio increase, the density will decrease. The mix proportions using 50:50 (PFA:POFA) ratio and 60:40 hydrated lime to gypsum ratio were considered as the optimum mix design. The EGB has shown to have high resistance when exposed to efflorescence and sulphate solution.