Cost Analysis of partially replaced Ordinary Portland Cement (OPC) with Groundnut Shell Ash in a Concrete Mix

Afolayan J. O, Oriola F. O. P., Sani J. E.

The cost analysis of partially replaced cement with groundnut shell ash (GSA) was conducted to ascertain the percentage reduction in price of cement in concrete.  Researchers have revealed that agricultural wastes are viable replacement materials, especially for cement in concrete. GSA was used in this research and the percentage level of cement replacement adopted were 0%, 5%, 10%, 15%, 20%, 25% and 30%. Workability was measured in the fresh concrete by the Slump test and 100mm x 100mm x 100mm cube specimens were tested for compressive strength at 7, 14 21 and 28days using a concrete mix ratio of 1:2:4 and water cement ratio of 0.55. Results showed that workability reduced with increase in percentage of GSA replacement with an acceptable value of 15mm for 15% replacement, if mechanical vibrator is to be employed. Compressive strengths of 32.01 N/mm2 and 31.78N/mm2 were obtained at 5% and 10% of replacement of cement respectively. While the maximum strength of the specimen with 0% replacement was 34.22N/mm2. Compressive strength values of 32.01 N/mm2 and 31.78N/mm2 for the 5% and 10% cement replacement also satisfied the provisions for minimum structural grade concrete of 25N/mm2. This leads to economy of material and enhances the alternative usage of agricultural wastes. The use of 10% GSA replacement leads to a decrease in the cost of cement in concrete to a value of 10% of the total cost of cement required. The cost saving becomes significant when large volume of concrete is involved in construction.