Abstract

The highway pavement is the biggest structural asset a government can construct and maintain. Concrete rigid pavements are used to carry traffic in large volumes across countries safely and efficiently. The performance of the concrete pavement is vital for ensuring a successful economy. Pavement quality concrete mixes have high levels of portland cement which contributes to a large proportion of CO² emissions in the UK and across the globe. Currently the UK specifies ground granulated blast furnace slag (GGBS) and pulverised fuel ash (PFA) to reduce the quantity of portland cement used in pavement construction. GGBS and PFA come from heavy industry; which are industries that should not be relied upon to improve the sustainability of construction materials. This report shows that cement in pavement quality concrete can be replaced with rice husk ash without causing adverse effects to the mechanical properties required for highways. Rice husk ash comes from the food production industry and is vital for the growing global population. It is seen that this is a socially responsible objective to use a pozzolan in highway pavement construction that is sourced from an environmentally friendly industry. The report investigates the resultant compressive and tensile strength of rice husk ash mixes and compares them to existing pavement quality mixes already used and specified. The report found that sieving rice husk ash and not grinding it gives the best performance. Due to the low density of rice husk ash the investigation found that replacing cement by volume rather than weight provided the best results. The investigation found that CEM II / A-LL 32,5N mixed with 20% rice husk ash meets the required specification for pavement quality concrete and mitigates using the comparative CEM I 52,5N mix. The investigation also notes that rice husk ash is observed to be more reactive with CEM II / A-LL 32,5N rather than CEM I 52,5N and suits early strength gains required for pavement construction. The report concludes that rice husk ash is a sustainable material that reduces the embodied CO² of pavement quality concrete, which is well suited for building motorways to UK highway specifications and has the potential to improve the lives of people living in communities in rice growing countries across the globe.

Keywords:Rice husk ash; Pavement quality concrete; Pavement; Compressive strength