Structural Performance of Concrete with Waste Glass Enhanced with Wood Ash

Abstract

Environmental effects of river sand harvesting and the need to provide cheaper housing has necessitated for researchers to look for alternative materials to concrete ingredients. This can be achieved by partially or fully replacing some of these concrete components. Although several researches on effects of wood ash and waste crushed glass on concrete have been carried out, no research work on effect of blue gum ash on glass concrete has been done hence the necessity to carry out this research. In this research, blue gum ash was dosed in portland cement (power plus 42,5N) in the proportions of 0, 0.5, 0.75, 1.0, 1.25 and 1.5% by cement weight and crushed glass used to partially replace river sand in the proportions of 5,10,15,20 and 25% by river sand weight, in concrete mix of class 25. Physical and mechanical properties of the concrete materials, fresh and hardened properties and cost benefit effects of the blue gum ash glass concrete were studied in this research work. From consistency, setting times and chemical composition tests, it was found that blue gum ash can be dosed in cement up to a maximum of 1%, providing allowable consistency, initial and final setting time and blue gum ash cement with required chemical compositions. Good workability was notable for blue gum ash dosed in cement at 1% and glass used to replace fine aggregates at 10%. For compressive, flexural and tensile split tests, strengths of the various mixes were lower as compared to the control mix. Also, significant increase of up to 1% dosage of cement with blue gum ash at 10% replacement of fine aggregates with crushed glass was noted to achieve strengths of 27.8N/mm2 and 30.1N/mm2 at 7 days and 28 days respectively. The tensile split test increased with increase in the concrete curing age, and also increased with increase in blue gum ash content in the mix, up to 1% by cement weight attaining strengths of 2.18N/mm2 and 3N/mm2 for 7 and 28 days respectively. The mathematical relationship between the compressive strength (Fcu28) at 28 days and the corresponding split tensile strength (Ft28) at 28 days was quadratic. Also notable was the increase in flexural strength with increase in curing age and blue gum ash dosage in the mix. There was increase in water absorption with increase in blue gum ash content. In terms of cost, there was saving of up to 2.2% for concrete containing blue gum ash of 1.5% of cement by weight and 30% crushed glass of fine aggregates. All this was based on 1M3 concrete. In conclusion, it can be recommended that, cement can be dosed with blue gum ash at 1% and fine aggregates replaced with crushed glass at 10% for good workability and strength. This mix can be used for lightly loaded beams and lintels in buildings provided the engineers design mix for the members is class 25.