Suitability of lime-pozzolan in stabilizing laterite soil for rural roads construction in Tanzania

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University of Dar es Salaam
Discovery of large quantity of locally available pozzolan in Arusha, Mbeya and Kilimanjaro regions, which possess good amount of reactive silica led to further study on their suitability in stabilizing late rite soil which is one of the marginal and problem soil materials used in road construction in Tanzania. Three types of late rite soils categorized by origin, location and particle size were investigated. These soils were in the range of sandy to clayey. Strength tests were conducted for these soils with varying amounts of lime and pozzolan, in different curing age from zero days to 28 days. Standard tests on physical properties for materials before and after stabilization of mixes were conducted mostly based on standards, specifications and test methodology of the Ministry of Works (Tanzania). Further, specialized chemical and mineralogy analyses using X-ray fluorescence (XRF) and X-ray diffraction (XRD) methods were carried out on soils to study minerals present and their contribution to lime-pozzolan reactions. Results show that, for the tested range, density and moisture content for Kifaru soil (sandy) were increasing with pozzolan while for Ngangu soil (mostly clay) the opposite was the case. There was an increase in strength for all soils with the increase of pozzolan and lime contents. Pozzolan contents were increased in ratios to lime content, i.e. 1:1, 2:3, 1:2, 2:5 and 1:3. Lime-pozzolan ratio of 1:3 was found to have the highest strength for all soils than other tested ratios; this implies that pozzolan from Oldonyo Sambu is very reactive. Chemical and Mineralogical tests on Ngangu soil revealed high content of hematite (Fe203) and kaolinite (Al2Si205(OH)4) with significant amount of quartz (Si02) and almost absence of base minerals.
Available in print form, East Africana Collection, Dr. Wilbert Chagula Library, Class mark (THS EAF TP 881.T34.N45)
Pozzuolanas, Lime, Rural roads, Design and construction
Ngalu, R. (2006) Suitability of lime-pozzolan in stabilizing laterite soil for rural roads construction in Tanzania, Master dissertation, University of Dar es Salaam. Dar es Salaam.