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.


