Utilizing Volcanic Ashes as Partial Replacement of Cement in Concrete Production

Abstract

Volcanic Ash (V.A) is one of Pozzolanas natural occurring material that has been tested for partial replacement of cement for production of concrete. With respect to reduction of cement consumption for sustainable construction (i.e. reducing gas emission), evaluation of the strength reduction is crucial as it has a severe impact on the structure under construction. Therefore, this paper examines the effects of replacing cement by using Tanzanian Volcanic Ash on the strength of concrete (i.e. concrete grade). The research aims to determine the optimal amount of V.A for production of high-grade concrete. The samples of V.A received from Holili, Kilimanjaro were prepared in five different proportions (0, 10, 20, 30 & 40 wt %) to make concrete cubes. Uniaxial compressive tests were used to examine the strength of concrete achieved after 7 and 28 days of curing. Results revealed the grade of concrete is significantly affected by adding more than 30 wt% of the V.A (i.e. optimal amount of V.A is 30%). For high-grade concrete, 20 wt% replacement provides less than 10% reduction in strength relative to reference concrete strength (i.e. 0% of V.A). This maintained the desired strength of concrete structure for construction. Hence, a partial replacement of cement can be allowed for 20 to 25 wt% of V.A.