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Due to inadequate crude oil supply and a rising demand for petroleum asphalt in roadconstruction, the asphalt sector faces a continuing shortage. Continous research was conducted on renewable materials such as bio-oils derived via pyrolysis from local palm oil industries. Bio-oil is currently a viable option due to its renewability, environmental friendliness, and variety of sources. Despite numerous studies indicating that biooils enhance the properties of bitumen, the research on the effects of PKS biooil on bitumen properties is minimal and needed further investigations. The application of 2,4-diphenylmethane diisocyanate (MDI) in this study is established to enhance the properties of bio-oil modified bitumen. The objectives of this study are to analyse the relationship between the percentage andratio of PKS bio-oil and 2,4-diphenylmethane diisocyanate (MDI) of the modified bitumen, its physical and chemical effects and the optimization of bio-asphalt mixture after the 2,4diphenylmethane diisocyanate (MDI) has been blended with PKS bio-oil and bitumen. PKS bio-oil and MDI were applied into the bitumen as additive and replacement of bitumen at 3%, 5% and 7% with two different ratios; 1.0:0.6 and 1.0:1.0. The functional groups of the bitumen are identified using Fourier Transform Infrared (FTIR) analysis. The result generated from FTIR analysis showed that the modified bitumen samples were slightly different when compared to the conventional bitumen regarding the functional group. Response surface methodology (RSM)was implemented to determine the statistical analysis and optimum amount of PKS bio-oil and MDI content in the bitumen, through central composite design.

The presence of heavy metals affects the properties of soil due to a decrease in the dielectric constant, which increases the risk of contamination. Current conventional treatments are costly, slower, and environmentally unsustainable. Therefore, soil biocementation improvement using enzymatically induced calcium carbonate precipitation has gained attention due to its cost-effectiveness, sustainability, and environmental friendliness. This study investigates the effect of this technique on the retention and immobilization of heavy metal-contaminated mine waste sourced from Lohan Dam, Sabah, Malaysia, under different curing periods (1 and 3 days), degrees of compactions (70 and 80% of the maximum dry density), and curing temperatures (5 °C, 15 °C, and 25 °C) but at constant 1.0M cementation solution using inductively coupled plasma-optical emission spectrometry, acid washing test, and scanning electron microscopy. Results indicate that the treatment effect is immediate and able to increase the retention of heavy metals in the order of Ni> Cu > Pb, with the highest retention observed at 25 °C and higher retention at lower degrees of compaction. SEM images confirm the formation of calcite in soil particles. In conclusion, the optimum treatment conditions for a 1.0 M EICP cementation solution are 25 °C, 70% MDD, and 1-day curing.

It is not uncommon for mining activity to generate wastes associated with negative engineering impacts include susceptibility to runoff due to the absence of vegetation, erosion, and sinkhole. Due to their high degree of permeability, movement of heavy metal contaminants in waste soils and aquifers occurs actively along with the hydrogeological parameters, and research on using biocementation methods such as enzyme induced calcite precipitation (EICP) to reduce the hydraulic conductivity is therefore beneficial. Mine waste soil collected from a copper mine in Lohan Dam, Sabah is characterized physically, morphologically, and chemically then treated with EICP under different operational parameters include curing duration (1,3,7 days), curing temperatures (5, 10, and 25 oC ), and relative density (70 and 80 %). The hydraulic conductivity was then tested using a constant head permeability test and the calcium carbonate content (%) is determined using the HCL washing method. Properties of the Lohan Dam wastes are found to be predominantly coarse grain soil of low plasticity, high specific gravity, high permeability, acidic in nature, and low organic content. Morphologically, they are composed of powdered and hardened particles with dark brown color with high amount of irregular-shaped particles. Mineralogical, Lohan Dam soil wastes contain a high level of heavy metals beyond the safety level of the Department of Environmental Malaysia. EICP treatment had to change the degree of permeability from ‘high and medium’ to ‘low’ with a 94-97% reduction in hydraulic conductivity corresponding to the amount of calcium carbonate content produced ranging 6.94-9.63%. In conclusion, relative density shows the marginal effect, curing duration, and temperature shows a more significant impact on the treatment effectiveness.