Effect of Different Mix Ratios of Rice Husk Ash Blended Cement Concrete on the Resistance to Sulphate Attack on Concrete
1Nura Hassan; 1Mohammed Ya’u; 1Jibrin Umar
1. Department of Civil Engineering Technology
Federal Polytechnic Damaturu
Concrete is the most widely used construction material in the world, because of its availability and versatility. The increasing demand for the durable concrete that is environmentally friendly is growing by day. Rice husk ash proved to be one of the supplementary cementing materials that supplement cement and produce a durable concrete that is environmentally friendly. Sulphate attack on concrete makes the concrete to suffer from deterioration and becomes less durable. This paper investigates the effect of different mix ratios of rice husk ash blended cement on the resistance to sulphate attack on concrete. One hundred and eighty (180)of rice husk blended concrete cubes of grades 25, 30 and 35, with the nominal mix ratios of 1:2:4; and 1:1:2 were cast and cured for 28 days. Later on, the cubes were immersed into water with 0%, 2.5%, 5%, and 10%, concentrations of sulphuric acid (aggressive media). Twenty per cent(20%) replacement was used throughout the research work. The zero per cent (0%) concentration wasused as a control, so as to establish a basis for comparison of the effect of the aggressive media on the rice husk blended cement. Three cubes from each of the concentrations of the acid-water were tested for compressive strength at 3, 7, 14, 21 and 28 days of acid curing for each of the grades. It was observed that the richer the mix ratio of the cement-rice-husk-ash blending the better the resistance to sulphateattack. The statistical analysis of the data indicated that, the F-values of the compressive strengths of the concrete at 95% confidence limit are 6.48, 5.91, 5.59, 5.23 and 4.88 for 3, 7, 14, 21 and 28 days of aggressive media curing respectively, these values are greater than 4.26. This indicated there is significant difference in resisting sulphate attack by different grades of concrete, that is, the richer the grade of concrete, the more resistance it offers to sulphate attack significantly.It was also observed that, the higher the concentration of the acid and the longer the period of curing in aggressive media, the higher the attack on the concrete.
Key Words: Concrete, Rice- husk- ash, Durability, Aggressive-media, Grades of concrete