Sustainable Resurfacing

We are always looking for ways that we can carry out our work in a more environmentally friendly way and sourcing a viable sustainable surfacing product is one result that would make an incredible difference. After many months of hard work and we are delighted to be planning surfacing trials for a new form of more sustainable concrete made with cement that includes the residue of rice husks.

Works agent Fraser Hyndman has just started a PhD that could reinvent the supply chain for cement manufacture and create a cheaper, more workable, more sustainable concrete product for road surfacing.

He is taking forward work already started with Dr A Ahmed at Leeds Beckett University looking at using the ash from burned rice husk as a replacement for PFA or GGBFS (ground granulated blast furnace slag) as a pozzolan in cement to help with its hydration.

This spring, what has so far been cubes and beams manufactured with the rice husk mix at the university will transfer to live surfacing field trials at the A-one+ Ainley Top depot near Huddersfield.

“We didn’t have the qualitative analysis to allow us to do trials on strategic road network,” Hyndman says.  “So instead we are going to lay the mix at a depot where the surface takes a lot of battering. We’ll monitor it over six months to five years and that will give us the data we need.

“The material has great qualities in use,” Hyndman says. “When you mix concrete with the rice husk ash, the concrete doesn’t bleed, it holds its shape well in slipform and retains air bubbles which means it is water reducing so you don’t need additives to get desirable properties for pavement material.”

The rice husk product’s properties are similar then to those of PFA and GGBFS. But Hyndman was driven to find alternatives to improve cement’s reputation as a sustainable material. “PFA and GGBFS are both byproducts of heavy industry – coal fired power plants and steel production, but both those industry’s are in decline. The Concrete Society has estimated that there may only be 12 years supply left.

“I have always taken a keen interest in research and when you can see a problem coming it is a professional responsibility to consider sustainable solutions,” says the 29 year old who is a qualified design civil engineer.

“I came across the option of using rice husk ash which has a high amorphous silica and have been working with the university to trial it as a pozzolan. This opens the door to creating a new supply chain in emerging parts of the world that would help them create a commercial business in deprived rural areas.  People in rice growing areas already burn the rice husk to produce steam for power. The roads industry’s use of the ash waste product would achieve not only environmental sustainability but also economic and social sustainability.”

Hyndman believes that design teams have become divorced from the detail of road resurfacing material because of the employment of end use specification over the last 30 years. “The design team has become distant from the material spec so understanding of the ingredients gets lost and the default is to use proprietary product. We need to get people thinking out of the box to come up with new options that open up new markets and supply chains.”

The benefits can be commercial too. “The rice husk ash is cheap and 25% less dense than alternatives so transport costs are reduced.”

Hyndman recognises that there will be resistance to change from people and players used to established routines. “Innovation is a disruptive process, it’s often met with hostility. But if contractors like A-one+ can grasp the issue with both hands, we can lead the way.”

That is certainly something that we are trying to achieve on both our Highways England Asset Support Contracts, in Area 12 and Area 4.

This innovative research has been featured in the February issue of Highways Magazine and we look forward to bring you the results of the trial soon.