The disposal of industrial steel mill sludge in landfills has frequently received significant concern as the sludge has a very notable potential to contaminate soil surface and groundwater in the long run. Recently, the incorporation of industrial steel mill sludge into fired clay brick has become one of the promising alternative methods as it could produce a lightweight product while minimizing the environmental impact of the waste used. In this study, fired clay bricks as the most common building material were incorporated with 0%, 5%, 10% and 15% of steel mill sludge and fired at 1050°C (heating rate of 1°C/min). The manufactured bricks were subjected to physical and mechanical properties such as firing shrinkage, dry density, and compressive strength while the Toxicity Characteristic Leaching Procedure (TCLP) was conducted to analyze leaching behavior from the manufactured bricks. The results demonstrated that incorporation up to 15% of steel mill sludge reduces the properties up to 27.3% of firing shrinkage, 8.1% of dry density and 67.3% of compressive strength. The leaching behavior of Zn and Cu from steel mill sludge was reduced up to 100% from 7414 to 9.22 ppm (Zn) and 16436 to 4.654 ppm (Cu) after 15% of sludge incorporation. It was observed that high temperature during the firing process would improve the properties of bricks while immobilizing the heavy metals from the waste. Therefore, recycling steel mill sludge into construction building materials could not only alleviate the disposal problems but also promote alternative new raw materials in building industries.

In this globalized era, building materials play an essential role in the civil engineering field. Nowadays, with the increase in population, the demand for construction activities is also increasing. Polyethylene (PET) bottles are among the most widely used materials and cause an abundance of non-degradable waste, at about 0.94 million tonnes in Malaysia. One of the alternatives to reduce this waste's environmental impact is to incorporate it inside building materials such as brick and concrete. As PET bottles' recycling is highly promoted, the physical and mechanical properties of building materials made from PET bottles have also been reviewed. The data analysis shows that the compressive strength, flexural strength, split tensile strength and density of building materials decreases as the percentage of PET waste increases. However, other properties such as water absorption, initial absorption rate, and firing shrinkage increase proportionally with the PET waste. Besides, heavy metals in these building materials comply with the United States Environmental Protection Agency (USEPA) standards. It can be concluded that the percentage of PET waste incorporated into brick and concrete must be less than 5% and 2%, respectively, to produce suitable materials to provide alternatives in reducing and recycling PET waste.