SAMI Bitumen Technologies’ SAMIflex emulsion binder is giving contractors the ability to undertake spray sealing operations in cooler periods in a safe and environmentally friendly way.
In 2015, the Bureau of Infrastructure, Transport and Regional Economics recorded Australia’s total road length at 873,573 kilometres, putting it in the top 10 for longest road networks in the world.
The task of maintaining this nearly 880,000 kilometres of road network is significant.
The ability to further build and maintain this vast road network even during the downtime of the cooler months is an advantage that could provide numerous cost and efficiency benefits.
For SAMI Bitumen Technologies’ Technical Services Manager, Iulian Man, one such untapped process in Australia is the use of emulsions in spray sealing, a practice he says is prevalent around the world.
“However, the interest is growing because emulsions offer many benefits over using hot binders,” Mr. Man adds.
Hot polymer modified binders are required to be cut back with kerosene when pavement surface temperatures fall below 25 degrees Celsius, whereas polymer modified emulsions can be sprayed when surface temperatures are as low as 10 degrees Celsius.
“This allows spray seals to be constructed in winter months on newly constructed bases and councils can complete reseals on low trafficked roads,” Mr. Man says.
He explains that the risks associated with cutting back hot binders include the increased propensity of the seal to flush with the onset of warmer weather.
“This is also an issue when constructing a primer seal or new seal in winter on a foam bitumen treated granular base course,” he says. “The high percentage of kerosene used to cut back the seal binder can soften the bitumen in the base, allowing embedment of the sealing aggregate under traffic leading to bleeding of the seal.”
Asphalt overlays can also be placed over the emulsion seals after construction compared with hot binders which have been cut back.
“For many councils, this provides them with an opportunity to carry out reseals at the end of their financial year should surplus funds and spray sealing resources become available,” Mr. Man asserts.
To assist councils and contractors to reap the benefits of emulsion spray seals almost year-round, SAMI Bitumen Technologies has developed a unique range of polymer-modified high residue emulsions – SAMIflex.
“These emulsions have high viscosities and are rapid setting to ensure good aggregate retention,” Mr. Man says. “They are also sprayed with a conventional sprayer at 90 degrees Celsius to avoid any risks of tram lining.”
SAMIflex minimises the water content and subsequent “run off” that is normally associated with conventional emulsions for spray sealing.
Mr. Man says the other advantages of using SAMIflex is that the aggregates don’t have to be dry and if they are clean, they don’t need to be precoated.
“With SAMIflex emulsions, the distance between the sprayer and aggregate spreading is not critical to achieve wetting of the cold aggregate as is the case with the freshly sprayed hot modified binder,” he says.
For Chris Shearer, Senior Spray Sealing Supervisor for New South Wales Roads and Maritime Services (RMS) Southern Region, the cooler months are when productivity can slow and where SAMI Bitumen’s SAMIflex has proved an effective pavement treatment.
Mr. Shearer and his team service the South Coast region of New South Wales, including the areas from Cooma through to Mount Kosciuszko, providing regular maintenance resealing works to the region.
“We were dealing with SAMI for a number of other products previously and the RMS decided to use emulsion, so it made sense to go with SAMI,” Mr. Shearer explains.
He adds that he and his crew have used SAMIflex in the past couple of years with great results.
“Most of what we’ve used it on is regular maintenance reseal works and it tends to work really well on the badly cracked areas because it fills the cracks so well.”
Mr. Shearer says being able to undertake spray seal operations earlier in the construction season poses a number of advantages for his team.
“We only tend to use it in spray sealing for flexible pavements, but we’ve been able to use it in the cooler months, which is better than hot bitumen because it’s such an earlier start period.
“If wet weather stops us from working later on in the season, we’ve already got a head start.”
Likewise, Mr. Shearer says the product’s flexibility makes it a suitable solution to undertake spray sealing in the extremes of summer.
“In the middle of summer it’s even quicker again – it’s that flexibility that’s probably the biggest advantage of the product.”
For Mr. Shearer, it’s not just the time efficiencies of the product that have proved beneficial to his team’s spray sealing operations, it’s the environmental and safety advantages too.
“You’re only heating the material to 90 degrees instead of 190 so that’s a huge safety benefit,” he says.
Similarily, its ease of use is what has really resonated, not just with Mr. Shearer, but his spray seal operators too.
“You’re not using cutters to mix with it and it fills the voids better,” he says.
“At first, some of the guys were struggling to get a hang of it, but now they’re really seeing the benefits.
“It’s an easy to use product that we can use on any gravel shoulder where we couldn’t with other bitumen products.”