COMPRESSIVE AND FLEXURAL BEHAVIOR OF POZZOLAN FROM PUMICE-CEMENT MORTAR

Abstract

The need to find alternative cementitious material in concrete works is inevitable because of high cost of cement. Pumice ash is a possible material that could be used as partial or total replacement for cement provided the compressive and flexural properties of the concrete from it meet the ACI/ASTM specifications. This paper present the chemical composition of pumice ash and the mechanical properties of pozzolan from pumice ash. It showed how the partial replacement of cement with pumice powder (ash) affects the compressive and flexural properties of the pozzolanas from pumice-cement mortar. 50g of pumice was collected to make five samples for the chemical analysis. The samples were crushed and grounded to powdered form. Chemical analysis of the pumice ash sample was carried out using the X-ray florescence (XRF Spectra IQ) technique. For the mechanical properties of the mortar from pumice powder, three samples of cubes and three samples of beams were made from pumice ash mortar at 5 %, 10 % and 15 % replacement of cement. The compressive and flexural strengths of the cubes and beam samples were determined in accordance with ASTM C 109 and C 348 respectively. The results showed that combination of Silicon Oxide, Aluminum Oxide and Iron Oxide of the pumice ash is 78.86 % which is greater than 70 %, the minimum requirement of a good pozzolan manufacturing of blended cement should meet. It was observed that the compressive and the flexural strengths of the mortar increased with age but decreased with increase in percentage of pumice ash in the mortar. At 28 days, the compressive stress of 0, 5, 10 and 15 % replacement were 58.4, 35.2, 31.2 and 30.0 N/mm2. Similarly, the flexural strengths of 0, 5, 10 and 15 % replacement were 9.71, 6.90, 6.55 and 6.20 N/mm2 at 28 days. The mortar mix can be classified as type M (ASTM C 109) which is applicable in construction of moderate loading walls and structures.