SA Affordable Housing March - April 2019 // Issue: 75 - Page 15

FEATURES About 1.6 million Chinese citizens die each year from respiratory illnesses linked to small particulate matter emissions, of which 27% of deaths are related to cement production. cement production can significantly lower cement factory power demand. Among her suggestions is the use of a single pinion kiln drive with an air clutch and a synchronous motor and roller presses and roller mills, in pre-grinding instead of ball mills. Taking this to the next level the Lawrence Berkeley National Laboratory is investigating electrifying cement kilns to reduce cement’s immense carbon footprint. While WWF China has pushed alternate fuels such as waste straw, used car tyres and municipal waste instead of coal for use in cement kilns. There are also a number of innovations in the sector which attempt to either replace concrete or use less of it for the same tasks in an attempt to reduce its environmental impact. The use of recycled materials in making concrete is currently finding increasing acceptance within the industry with aggregate now being extracted from various solid wastes including fiberglass, glass, granulated plastics, wood products and old tyres, among others. In that line Papercrete or fibercrete / fibrous concrete is made by using waste paper as an aggregate material therefore reducing the cement, which is marginally more carbon friendly. Foamcrete is a lighter, aerated, foam-based concrete that requires less energy to produce. Ceramicrete and glass fibre reinforced concrete are sold as being twice as strong as traditional concrete so builders use less of it, though the actual studies remain inconclusive and Grasscrete is a method of laying concrete in a chequered, cellular pattern www.saaffordablehousing.co.za that allows grass to grow between the concrete blocks therefore uses less concrete and improves drainage and storm run-off. Perhaps the most promising alternative is a substance known as Ferrock. Made from waste steel dust, it is normally discarded from industrial processes and silica from ground up glass, the iron within the steel dust reacts with CO 2 and rusts to form iron carbonate. This is fused into the matrix of Ferrock and, like concrete after it’s dried, it cannot be melted back into a liquid form but retains its hard, rock-like qualities. Initial testing at the University of Arizona suggests Ferrock may be as much as five times stronger than concrete and can withstand more compression before breaking. Whether it is cost effective, or able to scale to need is still in question, but the substance’s inventor David Stone (yes, that’s really his name) suggests that even if it is not the exact answer or the most cost-effective solution in the long term. “It’s a promising starting point for developing smarter technologies that address our insatiable hunger for development and the devastating result it’s having on our environment.” All the technologies are, however, are attempting to replace cement but no-one has come up with an affordable, commercial-scale alternative for sand yet, something Beiser says will be difficult to change. “We can however be smarter about our access to it and our usage of it,” he insists. MARCH - APRIL 2019 13