Low cost pozzolana based cement from industrial and agricultural waste materials
Muthengia, J. W.
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This thesis reports the results of a study aimed at making low cost cement from some agricultural and industrial wastes. The utilization of these wastes would avail an economical and environmentally friendlier waste disposal methods and cheap cementing material. The cement made was based on the materials whose pozzolanic reaction was investigated. The materials tested for pozzolanicity included rice husks ash (RHA) from wastes of rice milling factories, spent bleaching earth (SBE) from oil processing factories and broken bricks (BB) from clay products manufacturers. Natural pozzolana (Ptuff) used for making East African Portland Pozzolana cement was tested for comparative purposes. Heat content of rice husks (RH) and spent bleaching earth (SBE) was found to be adequate for activation of silica and alumina in the pozzolanic materials. Only a little kerosene was necessary for ignition. Acetylene lime sludge (ALS) from acetylene manufacturing industry and commercial hydrated lime (CHL) were used for the pozzolana-hydrated lime reaction. Pozzolanic activity of the materials with commercial hydrated lime (CHL) in different ratios was investigated on the pozzolanic materials separately. A blended calcined mix and a calcined blended raw mix of the materials was similarly tested. The results showed that the test materials were active pozzolanas. A 1:2 ratio of the pozzolanic material: CHL gave the best results. The 1:2 ratio now using ALS was also investigated on the materials. ALS showed a superior performance than CHL with all the pozzolanic materials under test. Calcined blended raw mix exhibited a better performance than the blended calcined mix. The test materials were then singly interground in different proportions with laboratory made ordinary Portland cement (OPC) as per the Kenya Standard (KS) 02 1263 of 1993  for cement tests. The resulting mixtures were then assessed using the same standard. The results showed that up to 25 percent replacement of the cement with the pozzolanic materials under test met the standard requirements. Calcined blended raw mix was interground with ALS and OPC from Bamburi Cement Factory in different percentages. The resulting products were subjected to the Kenya Standard . Up to 45 percent replacement of the OPC with the material under test met the standard requirements, while higher percent replacements failed. A rough financial estimate suggested a running cost saving of up to 20 percent per tonne of PPC.