Researchers in the Indian Institute of Technology (IIT) Madras, Chennai, India developed a method to use solar thermal energy to recycle concrete waste from construction and demolition sites. As reported by The Indian Express, they demonstrated a treatment process that uses solar thermal energy to recycle waste concrete from construction and demolition debris. The researchers also discovered that the quality of concrete produced using this method was superior in quality compared to the recycled concrete obtained through mechanical crushing.
The technology was demonstrated at the India One Solar Thermal Power Plant in Rajasthan, India, which is largely covered by the Thar desert and received significant sunlight throughout the year. The plant has 770 solar concentrators that are used to produce electricity using steam generated at high pressure. The researchers used the large reflectors of the solar concentrators to heat concrete rubble from demolition sites in cast iron receivers to a sustained temperature of 500 degrees Celsius (about 930 degrees Fahrenheit). After this, they mechanically scrubbed the material to yield coarse and fine recycled concrete aggregate (RCA).
“There are no significant by-products as mostly physical changes occur in the concrete. There could be some emission of water vapour but certainly nothing toxic,” said Dr. Ravindra Gettu, coauthor of a research paper published in the journal Materials and Structures. Gettu is a professor at the Department of Civil Engineering, IIT Madras. According to the Building Materials and Technology Promotion Council, the demand for concrete in India is approximately 380 million tons a year, which is mostly met by virgin aggregates as of now.