PROJECTS UNDERTAKEN

AN INVESTIGATION INTO DURABILITY, WEATHERING AND SOME STRENGTH PROPERTIES OF NATURAL CORAL BUIDING STONES.

BY: PAUL OCHIENG ODERA

SUPERVISOR: S.K MUTUA

Abstract

Natural coral stone is used as a building material for coastal settlements throughout the Indian Ocean, Arabian/ Persian Gulf and the Red Sea. It remains a favored building material along the coastal region because of its functional and decorative characteristics despite the lack of standards and specifications for the building stones. In this study, two different samples of coral stones have been obtained from the South Coast (SC) and the North Coast quarries (NC) of the Kenya’s coastal region. An investigation into their durability, weathering and strength (compressive and tensile) properties have been done through laboratory tests that have been carried out in accordance with the Kenya standard for tests on natural building stones obtained from the Kenya Bureau of Standards (KEBS) headquarters, Nairobi-Kenya.

The weathering test has been done in cycles using the gypsum (CaSO₄.2H₂O) salt attack on the stones and the results have been reported in terms of the percentage increase in absorption and percentage increase in volume of the samples. The attack has been found to be more pronounced in the SC samples than the NC samples. Similarly the durability test has been carried out as sodium sulphate soundness (SSS) test for 5 cycles and the results has been reported in a percentage change in mass. The NC samples have been found to be sounder than SC samples since the latter samples experienced larger mass reduction than former samples because of the more effect of sodium sulphate (NaSO₄.10H₂O) crystallization on the SC samples than the NC samples.

The strength tests have been performed in both dry and saturated conditions and from the test results, the dry condition compressive, flexural and tensile strengths have been found to be higher than saturated condition strengths. Eventually, the NC samples gave higher strengths in both condition and have been found to stronger than SC samples. These values have been found to compare favorably with the specified values of the most commonly used natural building stone in the region-Limestone and tuff. The coral stone has therefore been recommended for use as supplementary low cost building material in the coastal region.

Dedication

This project is dedicated to my mother Rosa A. Odera. Your inspiration, support, guidance, encouragement and prayers have been very important as I pursued this course.

Thank you.

Acknowledgement

I am grateful to the Almighty God for His steadfast love, grace and mercy that have enabled me to reach this far and to carry out this study.

I would like to sincerely appreciate my project supervisor Mr. S.K Mutua. His able guidance, financial support and indispensable advice has enabled me reach this far.

Furthermore, I would like to give thanks to my brother Patroba A. Odera for his incredible financial and moral support. The sacrifice shown is highly appreciated. I also appreciate the help his wife Wilkyster has given me. I am also grateful to my fiancée Vivian for her undying encouragement and support. You helped me reach this far.

Finally, I wish to thank my friend Nick Amito, Mr. J. Kitu of Ministry of Roads’ Materials Laboratory and all the laboratory technicians in the University Nairobi’s concrete laboratory for their necessary support, and all those who have helped me in finalizing this project.

Thank you.