EFFECT OF BINARY POZZOLANIC ADMIXTURES OF SNAIL SHELL ASH AND PALM BUNCH ASH ON PROPERTIES OF CONCRETE

Abstract

Abstract: The presence of voids and pores in concrete is a menace to concrete structures. Besides the reduction of the strength of concrete, it exposes the concrete to capillary activities such as absorbtion of water, chemicals and gases which may be injurious to the life span of the concrete and may lead to corrosion in the case of reinforced concrete. Also, the possibility of shrinkage and cracks due to contraction and expansion of the concrete have been confirmed. Concrete tends to decay at a faster rate when exposed to humidity (swampy environment) and aggressive chemicals. Many methods have been used to prevent the permeation of these harmful liquids and gases into concrete. In this study binary pozzolanic admixtures (snail shall ash and palm bunch ash) were mixed with various dosages of cement to produce concrete mixtures. The main purpose is to determine the interaction of the admixture with the various cement dosages and relate it to the strength and permeability of concrete produced. Snail shell and palm bunch were calcined and characterized using X ray Diffraction ,XRD and their pozzolanicity obtained using Thermo gravimetric Analysis, TGA & Differential scanning calorimetry, DSC. Then the snail shell ash(SSA)and palm bunch ash (PBA) were used to produce concrete cubes and beams which were subsequently tested for water absorbtivity (permeability). The fine and coarse aggregates were sourced from Nyama River, Enugu State and Ishiagu, Ebonyi State respectively, Ordinary port land cement (Dangote brand) were used to produce the concrete cubes and beams samples. Concrete cubes were made with various dosages of binary admixture and cement of (95%, 90%, 85%, 80%, 75%, 70%, 50%) dosages. The permeability test shows that for 9% SSA and 1% PBA this is (10% binary admixture) and 90% cement, there was a reasonable reduction in the permeability of concrete which leads to a reduction in the depth of water penetration in the concrete cube to 6mm as against 9mm in control mix at a given length of time (30mins). At 50% PBA and 50% SSA, It was discovered that adding 50% of the binary admixture to 50% of cement 30mm produce concrete of reasonable permeability compared with control concrete mix produced with 100% cement which means that the binary pozzolanic admixture of PBA & SSA can serve as a partial replacement of cement up to 50% proportion. According to this study, the highest flexural strength of 6.556N/mm² was achieved at 5% of PBA,7.5% of SSA and 87.5% of cement . It was discovered that the replacement of cement with 15% PBA and 35% SSA, this is (50% binary admixture)   led to reduction of bulk density by 3%.   

Keywords – admixtures, ash, concrete, pozzolanic, permeability, pores, palmbunch, snailshell.