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Put to the test: Sripath’s PGXpand

PGXpand was developed for a variety of applications and conditions in Australia.

Sripath Technologies’ PGXpand® polymeric additive has been put to the test, with recent trials evaluating its performance in hot spray seal applications. Roads & Infrastructure learns the outcomes of these trials, as well as the implications for the road construction sector.

The bitumen additive market has grown exponentially throughout the past 20 years.

Developments in technology, as well as a renewed focus on improving the sustainability and performance of pavements, has accelerated the procurement of additives that improve performance of bitumen and asphalt mixes.

One such product is Sripath Technologies’ PGXpand.

PGXpand is a bitumen-friendly polymeric-additive, specially designed to increase the performance attributes of bitumen and asphalt mixes, especially when it comes to the overall durability in paving applications.

Ravi Rajagopalan, General Manager, Sripath Asia-Pac says the product has already been used across a variety of applications.

“In Australia, our customers are using PGXpand for hot asphalt mixes, hybrid PMBs, hot spray seal, and high stiffness applications,” Rajagopalan says.

Early testing

Recent trials on the Melba Highway in Dixons Creek, Victoria, put PGXpand to the test.

Deepak Madan, the company’s Chief Marketing & Business Development Officer, says the trials evaluated the potential for the product to be used Australia-wide.

“PGXpand has been tested, vetted and used worldwide since 2016. We have repeat customers in the USA, Canada, India, Australia, and the Middle East. Customers in New Zealand, South Africa, and Europe are in final stage of approval,” Madan says.

These trials also aimed to evaluate the performance of PGXpand with crumb rubber in hot spray seal applications. 

The trial, which was conducted in collaboration with the Victorian Department of Transport and Planning, was largely hailed as a success across a number of key criteria.

Conducted in March this year, this trial utilised a 500-metre stretch of road. The hot spray seal was used across two lanes on what is a frequently trafficked section, with up to 5000 vehicles using the connection daily. 

A two coat 14/7 spray seal was specified for this road which consists of two through lanes and shoulders. PGXpand plus crumb rubber was used in the first binder coat in the shoulder. 

This sprayed so well that the PGXpand and crumb rubber was added to the binder for the seven millimetre binder coat over the full pavement width

Rajagopalan says the trial aimed to show how PGXpand could be used in Australian conditions while applying local methods.

“They blend it at around 180-200 degrees centigrade and then it’s ready to be sprayed. First they spray the modified bitumen on the road and add the first layer of aggregate. Then, they spray another layer of modified bitumen and lay a finer aggregate on top to create the second layer,” Rajagopalan says.

“Department of Transport and Planning was looking for improved performance. Therefore, they wanted to try PGXpand.”

Class 170 bitumen was combined with 18 parts crumb rubber. This “recipe” was used for the main lane trial as part of the first layer, as well as the full width of the road in the second layer. The second coat also featured one per cent PGXpand.

For the first layer on the road shoulder, the recipe differed slightly, this time with 10 parts crumb rubber and 0.8 per cent PGXpand.

The bitumen in the tanker was maintained at a constant temperature of around 200 degrees Celsius. The final, polymer-modified bitumen was digested for 20 minutes and kept at a temperature of 180 to 185 degrees Celsius. Then finally, the spraying was done at a temperature between 175 to 180 degrees Celsius.

Steve Halligan, Director of Road Surfacing Solutions, says these trials can give the industry confidence that this product could be applied on more heavily trafficked sites. 

“When I was initially presented with the results and I looked at the increase in the softening point and changes in viscosity, I just thought ‘no way’. I thought that wasn’t how [similar additives] normally behave,” he says. 

“But I was wrong by a country mile.”

Halligan was present at the Department of Transport and Planning trial of PGXpand. He says that apart from beneficial attributes in the softening point and viscosity, the visual performance of the product also stood out.

“I could see that we were getting better spray performance than our earliest sprays. When the PGXpand wasn’t being used I could see a bit of tram tracking,” he says. “When we sprayed with PGXpand, any evidence of tram tracking was gone.”

Halligan believes the results of the trial show the potential for PGXpand to be used nationwide. 

“One of the biggest learnings from the trial is that the product can be applied anywhere in Australia where the product can be blended on site.”

Recent trials with the DTP successfully trialled the performance capabilities of PGXpand.
Recent trials with the DTP successfully trialled the performance capabilities of PGXpand.

Embracing a greener approach 

Sripath Technologies’ PGXpand is an environmentally sustainable product, resulting in lower GHG gas emissions and lower energy consumption. It boosts the high temperature performance, the paving grade and the softening point. It also delivers excellent rutting resistance.  

Kate Brough, Director Digital Marketing, says these are just some of the many products that make up the suite of Sripath Technologies’ sustainable products.

“Sripath strives to develop and market environmentally friendly products such as PGXpand, NuMIXER, and ReLIXER. These versatile and sustainable additives help lower the carbon footprint, reduce greenhouse gas emissions, and decrease energy consumption,” Brough says.

Through international research and development, these products are well suited for use in Australian applications.

“It’s also exciting to have the unique properties of PGXpand to deliver solutions for Australian issues,” Brough says. “It’s even more gratifying for us that people are now beginning to accept the material and understand its virtues, while thinking about it within the context of what they have to deal with on a day-in, day-out basis.”


 

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The results 

Rajagopalan witnessed the trial on behalf of Sripath. He says the support of Department of Transport and Planning was absolutely pivotal to the success of the trial.

“It was very satisfying to not only deliver the conceptual underpinnings of this trial, but also to have a customer run a trial that was nearly flawless,” he says.

RMIT (Royal Melbourne Institute of Technology) University was also a key supporter of both the development and the trials. 

Filippo Giustozzi, Associate Professor – Civil and Infrastructure Engineering, says development on such a product was sparked through demand from both industry and government.

“Department of Transport and Planning aimed to improve the high temperature performance of their standard products in use, which is sprayed seal that only includes crumb rubber. Past applications of this product have highlighted issues of flushing and softening of the seal, especially during the summer season. Therefore, DTP VIC asked for a new product that could modify the high temperature properties of their standard sprayed seal with crumb rubber but without compromising on the viscosity,” Giustozzi says.

“At the time RMIT University was currently conducting research activities on behalf of Sripath on a novel polymeric material – PGXpand – that has the ability to boost the high temperature performance without modifying the final viscosity of the binder.”

He says the performance of the product outweighed expectations.  

“The product performed in the field exactly as it did in the laboratory at RMIT University during the experimentations. The high temperature performance was improved without compromising on the final viscosity of the binder, which remained unchanged after the addition of one per cent PGXpand,” Giustozzi says.

“We also found that the adhesion between the aggregate and the binder was improved, hence suggesting greater durability of the sprayed seal compared to the standard DOT practice. The application in the field went smoothly and the operators did not have to adjust the sprayer and/or the spraying temperature after the addition of PGXpand.”

These benefits are also reflected in the versatility of the product. So much so, that operators don’t need to make any changes to their equipment and processes.

“Those small additions of the right polymer can significantly increase the service life of our sprayed seal roads. All without the need for new equipment or drastic operational changes,” Giustozzi says.

As part of the trial, PGXpand was successfully field blended into the bitumen along with the crumb rubber. Crews also found the PGXpand with PMB blend was easy to spray, as Rajagopalan explains.

“There were no issues, it went over very well and seamlessly,” he says.

“Professor Filippo looked at various percentages of crumb rubber and PGXpand and discovered during this investigative phase that PGXpand is actually able to enhance the adhesion of the binder to the rock.”

“I’m very optimistic and enthused as we can offer a hot spray option that can help to reduce temperatures and environmental impacts, while at the same time delivering a much higher performing roadway. It’s very exciting,” Rajagopalan says.

Following the success of the trials, Sripath Technologies is hoping to conduct further tests before seeing a wider rollout of products across Australia and New Zealand.

“We’re really excited, not just about the trial, but what it portends for us in various states. We’re now exploring New South Wales, Western Australia and Queensland,” Rajagopalan says. 

This article was originally published in the September edition of our magazine. To read the magazine, click here.

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