Sustainable Highway Pavements The Evaluation of Pavement Quality Concrete Produced with Rice Husk Ash Binder

This thesis investigates the use of rice husk ash (RHA) as a sustainable alternative to traditional portland cement in rigid highway pavements. The literature review highlights the significant environmental impact of cement production, the historical development and properties of concrete, and the potential benefits of using RHA, a by-product of rice milling, due to its high pozzolanic activity and availability.

The methodology involved preparing various concrete mixes, including control mixes and those with RHA replacements. Detailed tests were conducted to evaluate workability, compressive strength, tensile strength, curing time, and durability. The research adhered to the specifications set out in the Manual of Contract Documents for Highway Works (MCHW) and relevant British Standards. The preparation of materials included ensuring the quality and consistency of aggregates, cement, water, admixtures, and RHA. The concrete samples were tested for workability using slump tests, and mechanical properties were assessed through uniaxial compression and indirect tension tests.

Key results indicate that RHA concrete mixes exhibit comparable or superior compressive strength to traditional mixes, with improved tensile strength and enhanced durability against environmental stressors such as freeze-thaw cycles and chloride penetration. The workability and curing times of RHA mixes were also found to be favourable, with RHA improving the mix's overall performance. The study also noted that RHA concrete had a lower heat evolution peak during curing, reducing the risk of thermal cracking.

A field trial on the M180 motorway demonstrated the practical applicability of RHA concrete, showing satisfactory performance in real-world conditions. The concrete mix used in the field trial met the target strength requirements and exhibited good workability and durability. The findings suggest that RHA concrete not only meets structural and durability requirements but also significantly reduces the carbon footprint of pavement construction.

This research concludes that RHA is a viable and sustainable alternative for use in pavement quality concrete. Recommendations for future work include long-term performance monitoring, economic feasibility studies, optimisation of mix designs, and the development of standards and guidelines to facilitate the adoption of RHA in the construction industry.