EXPERIMENTAL INVESTIGATION OF COMBINED EFFECTS OF TEFF STRAW ASH AND BAMBOO LEAF ASH AS PARTIAL REPLACEMENT OF CEMENT IN PROPERTIES OF THE CONCRETE

Abstract

Concrete is one of the most widely used materials in today's infrastructure around the world. Cement is an essential concrete material that takes up 10%–15% of the volume of the concrete. Its production is an environmentally unfriendly process due to release of CO2 gas to the atmosphere. In addition to this, it is the most expensive material when compared to the other components of concrete. However, scholars’ tray to replace cement by, alternative, cheap natural pozzolanic cementing materials in such a situation. Teff straw ash (TSA) and bamboo leaf ash (BLA) are cheap agricultural by-products and possess pozzolanic properties. Bamboo leaves are as waste on the ground in Ethiopia during the manufacture of bamboo buildings and furniture. Ethiopia accounts for 67 percent of African bamboo and cover over one million hectare. The teff plant accounts for 24 percent of grain area, producing 5000 kilograms of straw per hectare. The primary goal of this study was to conduct an experimental study of the combined effect of the partial replacement of cement with teff straw ash and bamboo leaf ash in concrete production. The study examined the chemical composition and physical properties of Teff straw ash and bamboo leaf ash, the workability of fresh concrete, the mechanical properties and durability of concrete, and also the microstructural analysis of hardened concrete. The chemical composition of bamboo leaf ash and teff straw ash was examined, and the summation of SiO2, Al2O3, and Fe2O3 bamboo leave ash was 76.21% and classified as class F. But for teff straw ash the summation of SiO2, Al2O3, and Fe2O3 was 68.73%, and classified as class C pozzolana. The consistency and setting times) increase as the TSA and BLA replacement amounts increase, but workability decreases as replacement increases. The compressive strength of concrete for B-2 (5% teff straw ash and 5% bamboo leaf ash) and B 3 (5% teff straw ash 10% bamboo leaf ash) shows improvement on the 28th day. 5% bamboo leaf ash and 5% teff straw ash replacement improves the concrete strength by 2.29% and 10% bamboo leaf ash and 5% teff straw ash replacement improves the concrete strength by 0.73%, respectively over the control mix. The water absorption and sulfate attack have significant improvement for the combined replacement of teff straw ash up to 5% and bamboo leaf ash up to 10%. Microstructure tests such as X-ray diffraction (XRD), Fourier Transform Infrared Spectrometry (FT-IR) and Scanning Electron microscopy (SEM) analysis shows improved performance for replacement of teff straw ash up to 5% and bamboo leaf ash up to 10%. Therefore, the optimum amount of replacement is 5% teff straw ash and 10% bamboo leaf ash by weight of cement, which gives comparable properties to the control mix