Recycled aggregates use set to growby Stian Overdahl on Jan 21, 2013
The use of recycled concrete aggregate is set to grow in Abu Dhabi, with specification of RCA for major infrastructure projects
The use of recycled concrete aggregates (RCA) is set to soar in Abu Dhabi, after having been specified in a number of major projects, including in the Etihad Rail project in Abu Dhabi.
Produced by the Al Dafra waste plant, use of RCAs all but came to a halt, and the plant was forced to shut down, with a stockpile of 1.6 million tonnes of material ready to be crushed.
But it roared to life again, when Al Jaber engineering ordered 750,000 tonnes of aggregate for use on the Etihad Rail project. This was followed by further orders, and according to Tim Harwood, executive general manager of Leighton Services, which manages the plant, the total orders of RCA for Etihad Rail total 1.2 million tonnes.
Demand is set to grow, and next year in Abu Dhabi, 40% of the aggregates used in the construction of new roads will be recycled, something that will be written into the specification, though the exact details will vary between projects.
Tim Harwood says that contractors can use RCA in projects in order to meet their Estidama requirements.
“One of the main barriers [for greater use of recycled materials] to overcome is ensuring that recycled materials are actually specified for use in contracts.
“Fortunately, there is a long track record of the use of recycled materials internationally, so you are not starting from scratch when you can adopt specifications that work elsewhere in the world.
In Abu Dhabi, the government has issued decrees approving specifications for recycled products and these have been adopted by various departments and municipalities across the Emirate.”
The specification for road construction follows a trial use of RCA in a road built for the development of the Baniyas Sports Club, where Al Jaber was the contractor and AECOM was the consultant.
Before work began, the RCA was tested to ensure it met the Abu Dhabi Municipality’s specifications, when it was found that the RCA from Al Dafra had a sulfate content of between 0.97 and 1.37%, higher than the 0.5% maximum allowance.
According to Ramin Yazdani, of the material quality section, internal roads and infrastructure division, at ADM, this final specification was adjusted to allow for the higher sulfate levels, in line with practices overseas.
The higher sulfate levels can be explained by the decades-old concrete – produced from concrete rubble taken from demolished buildings – absorbing sulfates through exposure to groundwater or airborne salts, and it may also be the case that the concrete had higher sulfate levels when it was originally poured.
Article continues on next page ...