Abstract
This dissertation presents an experimental investigation into the potential use of South African natural zeolite and metakaolin as cement extenders. Improvement of Portland cement characteristics is a subject of research interest in the field of construction materials engineering. Natural zeolites are available in South Africa and are effectively being used in farming such as fish farming, cat litter and hen houses, etc. Kaolin clays are also available in South Africa and are used as industrial fillers for a variety of applications such as adhesives, rubber, paint and laundry soap bars.
The use of cement extenders reduces the amount of Portland cement required in concrete mixtures and therefore minimizes the environmental impact that may be caused by the production of cement. Extenders also improve the properties of concrete. The effectiveness of both South African zeolites and metakaolin on cementitious systems, has not been fully explored. The emphasis of this study was on the improvement of fresh properties, mechanical and durability properties of mortars made using natural zeolite and metakaolin as pozzolans or cement extenders. Natural zeolites were assessed at varying proportions of 10, 20 and 30%, while metakaolin was incorporated at proportions of 5, 10 and 15%. The mixes were prepared at water /cementitious ratios of 0.5 and 0.6, with the mixes designed such that the 28 - day compressive strengths of natural zeolite mixes were 25 to 40 MPa or 30 to 60 MPa for metakaolin mortar mixes. The tests carried out on mortars include flow, compressive strength, pozzolanic activity, drying shrinkage, resistance to sulphate attack and resistance to alkali - silica reaction. X - ray fluorescence, X - ray diffraction, scanning electron microscopy and thermo - gravimetric analysis were done for analytical study of mortar samples. In conclusion, both the natural zeolite and metakaolin showed effectiveness as pozzolans for improving the mechanical and durability properties of cementitious systems.