OJCE  Vol.4 No.3 , September 2014
Effects of Sand Quality on Compressive Strength of Concrete: A Case of Nairobi County and Its Environs, Kenya
ABSTRACT
Failure of concrete structures leading to collapse of buildings has initiated various researches on the quality of construction materials. Collapse of buildings resulting to injuries, loss of lives and investments has been largely attributed to use of poor quality concrete ingredients. Information on the effect of silt and clay content and organic impurities present in building sand being supplied in Nairobi County and its environs as well as their effect to the compressive strength of concrete was lacking. The objective of this research was to establish level of silt, clay and organic impurities present in building sand and its effect on compressive strength of concrete. This paper presents the findings on the quality of building sand as sourced from eight supply points in Nairobi County and its environs and the effects of these sand impurities to the compressive strength of concrete. 27 sand samples were tested for silt and clay contents and organic impurities in accordance with BS 882 and ASTM C40 respectively after which 13 sand samples with varying level of impurities were selected for casting of concrete cubes. 150 mm × 150 mm × 150 mm concrete cubes were cast using concrete mix of 1:1.5:3:0.57 (cement:sand:coarse aggregates:water) and were tested for compressive strength at the age of 7, 14 and 28 days. The investigation used cement, coarse aggregates (crushed stones) and water of similar characteristics while sand used had varying levels of impurities and particle shapes and texture. The results of the investigations showed that 86.2% of the sand samples tested exceeded the allowable limit of silt and clay content while 77% exceeded the organic content limit. The level of silt and clay content ranged from 42% to 3.3% for while organic impurities ranged from 0.029 to 0.738 photometric ohms for the unwashed sand samples. With regard to compressive strength, 38% of the concrete cubes made from sand with varying sand impurities failed to meet the design strength of 25 Mpa at the age of 28 days. A combined regression equation of with R2 = 0.444 was generated predicting compressive strength varying levels of silt and clay impurities (SCI), and organic impurities (ORG) in sand. This implies that 44% of concrete’s compressive strength is contributed by combination of silt and clay content and organic impurities in sand. Other factors such as particle shapes, texture, workability and mode of sand formation also play a key role in determination of concrete strength. It is concluded that sand found in Nairobi County and its environs contain silt and clay content and organic impurities that exceed the allowable limits and these impurities result in significant reduction in concrete’s compressive strength. It is recommended that the concrete design mix should always consider the strength reduction due to presence of these impurities to ensure that target strength of the resultant concrete is achieved. Formulation of policies governing monitoring of quality of building sand in Kenya and other developed countries is recommended.

Cite this paper
Ngugi, H. , Mutuku, R. and Gariy, Z. (2014) Effects of Sand Quality on Compressive Strength of Concrete: A Case of Nairobi County and Its Environs, Kenya. Open Journal of Civil Engineering, 4, 255-273. doi: 10.4236/ojce.2014.43022.
References
[1]   Orchard, D.F. (1979) Concrete Technology, Propertiess of Material. 4th Edition, Volume 1. Applied Science Publishers Ltd., London, 139-150.

[2]   Machuki, O.V. (2012) Causes of Collapse of Buildings in Mombasa County. A Case of Mombasa City—Kenya. Published on Department of Extra Mural Studies. University of Nairobi, Nairobi, Kenya.
http://ems.uonbi.ac.ke

[3]   Ayodeji, O. (2011) An Examination of the Causes and Effects of Building Collapse in Nigeria. Journal of Design and Built Environment, 9, 37-47.
http://e-journal.um.edu.my/filebank/published_article/3294/Vol%209-3.pdf

[4]   Ayuba, P., Olagunju, R. and Akande, O. (2011) Failure and Collapse of Buildings in Nigeria: Roles of Professionals and Other Participants in the Building Industry. Interdisciplinary Journal of Contemporary Research in Business, 4, 1267-1272.

[5]   Dimuna, K.O. (2010) Incessant Incidents of Building Collapse in Nigeria: A Challenge to Stakeholders. Global Journal of Researches in Engineering, 10, 75-84.

[6]   Dahiru, D., Salau, S. and Usman, J. (2014) A Study of Underpinning Methods Used in the Construction Industry in Nigeria. The International Journal of Engineering and Science (IJES), 3, 05-13.
http://www.theijes.com/papers/v3-i2/Version-3/B03203005013.pdf

[7]   Oloyede, S., Omoogun, C. and Akinjare, O. (2010) Tackling Causes of Frequent Building Collapse in Nigeria. Journal of Sustainable Development, 3, 127-132.
http://dx.doi.org/10.5539/jsd.v3n3p127

[8]   Savitha, A. (2012) Importance of Quality Assurance of Materials for Construction Work. Building Materials Research and Testing Division, 1-5.

[9]   Olanitori, L.M. (2006) Mitigating the Effect of Clay Content of Sand on Concrete Strength. 31st Conference on Our World in Concrete & Structures, Singapore, 16-17 August 2006.

[10]   Olanitori, L.M. and Olotuah, A.O. (2005) The Effect of Clayey Impurities in Sand on the Crushing Strength of Concrete (A Case Study of Sand in Akure Metropolis, Ondo State, Nigeria). 30th Conference on Our World in Concrete and Structures, Singapore, 23-24 August 2005.

[11]   BS 882 (1992) Specification for Aggregates from Naturanl Sources for Concrete. British Standard.

[12]   ASTM C117 (1995) Standard Test Method for Materials Finer than 75-um (No.200) Seive in Mineral Aggregates by Washing. American Society for Testing Materials, West Conshohocken.

[13]   Construction Standard CS3 (2013) Aggregates for Concrete, Technology, Ed., The Government of the Hong Kong Special Administrative Region, Hong Kong.

[14]   Harrison, D.J. and Bloodworth, A.J. (1994) Construction Materials, Industrial Minerals Laboratory Manual. Technical Report WG/94/12, Nottingham.

[15]   Anosike, N.M. (2011) Parameters for Good Site Concrete Production Managment Practice in Nigeria. Ph.D. Thesis, Deparment of Building Technology, College of Science & Technology, Covenant University, Ota.

[16]   IS 383 (1970) Specification of Course and Fine Aggregates from Natural Sources for Concrete. Bureau of Indian Standards, India.

[17]   ASTM C40 (2004) Standard Test Method for Organic Impurities in Fine Aggregates for Concrete. ASTM International, West Conshohocken.

[18]   BS 1881-120 (1983) Testing Concrete Method for Determination of Compressice Strength of Concrete Cores. British Standards Institute, London.

[19]   ASTM D854 (2014) Standard Test Method for Specific Gravity of Soil Solids by Water Pycnometer. ASTM International, West Conshohocken.

[20]   ASTM C39 (1990) Standard Method of Test for Compressive Strength of Concrete Specimens. ASTM International, West Conshohocken.

 
 
Top