Civil Engineering June 2022 | Vol 30 No 5

24 June 2022 Civil Engineering A lthough RMC has been used ex- tensively over the centuries, very little was known about the prop- erties of the material. Pioneering research work by Dr Rod Rankine, when employed by Cement & Concrete SA’s forerunner, the Portland Cement Institute, and released in his doctoral thesis in 2000, has led to a much greater understanding of the mechanical properties of RMC. Pretoria-based consulting engineering firm ARQ has been involved in the design of several RMC dams in Southern Africa and has reported that the performance of these dams during floods bears testimony to the durability and effectiveness of RMC for the construction of major dams. RMC is a composite material, derived from placing uncut stone randomly in a bed of mortar. It is often used in mass gravity and arch buttress dam construc- tion. The 30 m high multiple-arch buttress Mndwaka Dam in the Eastern Cape is a typical relatively recent example. The impressive dam, which won an Infrastructure Commendation in the 2017 Fulton Awards for excellence in the use of concrete, was built to supply the basic water needs of about 40 000 people living in 63 villages on the Eastern Cape’s Wild Coast. Situated in a particularly remote loca- tion close to Hole in the Wall, between Elliotdale and Coffee Bay, construction of the 30 000 m 3 dam – the largest of its kind yet built in Southern Africa – called for careful planning in terms of design, construction and materials procurement. Economic rubble masonry concrete dams can save costs and create jobs John Roxburgh Senior Lecturer Cement & Concrete SA School of Concrete Technology john.roxburgh@cemcon-sa.org.za Rubble masonry concrete (RMC) is a building material has been used throughout the world for thousands of years – as far back as AD 122 when Hadrian’s Wall was built in Britain, and 1679 when Cape Town’s Castle of Good Hope was constructed. Construction of the Mndwaka Dam provided abundant employment for residents of isolated Wild Coast villages