Determining physical - chemical properties of Zambian soils used as plaster paste - Luapula.

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Mulenga, Brian Chileshe
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The University of Zambia
Soil plaster pastes have been used around the world by local rural populations for centuries to give a finishing touch to their houses, and depending on the soil used, some chemical contamination cannot be ruled out. Some soils may contain heavy metals and other parameters depending on where it is located and the type of environment. The purpose of this study is to determine the physical and chemical properties in the abundant Zambian coloured soils found in Luapula Province, Mwansabombwe area in Kawambwa District that are used for plastering houses mainly by rural communities. Similar types of soil are found in many other areas around the country. The presence of heavy metals and other parameters could affect the soil colour if binders are added in order to improve these plaster pastes. Analysis of the soil samples was as follows: The pH meter with combined electrode and saturated potassium chloride (KCl) was used to analyze for pH; while for all heavy metals i.e. copper, iron, manganese and chromium, a laboratory protocol of sample digestion analysis for ore and soil was used. Organic content was analyzed by the Walkley Black method involving the reduction of potassium dichromate by the organic carbon compound. Barium sulfate precipitation was used for sulfates and chlorides in titration. Traces of heavy metals found averaged as follows: Copper in all the six samples was 20%, Iron in all the six samples was 0.5395 %% , Chromium in all the six samples was 0.002% , Manganese in all the six samples was 16.17 % respectively. While Organic matter in all the six samples was 18.47 ppm, Chlorides in all the six samples was 11.76 ppm, Sulfates in all the six samples was 10.26 ppm, pH in all the six samples was 5.62 Traces of heavy metals: manganese, iron copper and chromium including parameters: pH, organic matter, sulfates and the chlorides were found in the soil samples. Signifying that, an addition of a binder may trigger a reaction that may alter the original natural colour of the soil. If soil colour is lost then, the desired results of improving the soil paste for use in the construction industry as a plastering material is defeated.
Thesis of Master of Engineering in Construction Management.