Chennai: A study by Indian Institute of Technology Madras (IIT Madras) researchers to produce recycled concrete aggregate (RCA) by construction debris using solar thermal energy have established that it would help reduce the carbon footprint and aid in sustainable development besides saving electricity used in the process.
The study was undertaken in three stages— the use of concentrated solar energy in the thermomechanical beneficiation of concrete waste, the production of high-quality RCA from the waste, and assessing the performance of the RCA in concrete to establish the fact that waste can be recycled.
Prof. Ravindra Gettu who co-authored the study said they wanted to develop the proof-of-concept that solar radiation could be used in the thermomechanical beneficiation of concrete waste to produce good quality recyclable material for new concrete and the evidence is compelling.
"This study presents strong evidence for the use of concentrated solar energy for recycling waste concrete, with promise for large-scale waste concrete recycling. This would reduce the energy footprint of Construction and Demolition waste processing significantly, and lead to savings in raw material and electricity, towards circular economy,” he said.
According to the study, the properties of the aggregates produced were found to be comparable with those of RCA produced in an electric furnace, with the total yield of recycled products being (90% of the feed concrete). Preliminary results on concrete made with the RCA indicate its suitability for typical concrete applications.
The waste concrete from demolition was heated using solar radiation to produce recycled concrete aggregate (RCA) that was higher in quality when compared to those obtained from mechanical crushing. The findings of this story were published recently in the reputed, peer-reviewed journal Materials and Structures. The paper was co-authored by Rohit Prajapati, Surender Singh, and BK Jayasimha Rathod.
The concrete saga
Concrete is the most common material used in construction universally with an annual production estimated to be 10–30 billion tonnes. The global consumption of construction aggregates, including that needed for making concrete, is projected to reach 63 billion tonnes in 2024, according to studies.
Practically all aggregate demand is currently met by extensive quarrying and mining, leading to the depletion of primary mineral resources. Moreover, there is a severe shortage of fine aggregate in many countries due to bans on the mining of river sand to avoid serious environmental damage.
On the other hand, construction activities generate considerable waste, estimated to be about 3 billion tonnes per annum. Some developed countries recycle up to 90% of the construction and demolition (C&D) waste whereas others still resort to the dumping of large quantities in landfills.
A rational way is to provide an alternative supply of aggregates is through recycling of C&D waste, which would curtail mining for aggregates and free up space used as landfills. The present study attempts to mitigate the limitations of conventional thermomechanical techniques with regard to harmful emissions through the utilization of concentrated solar energy.
