Modelling the Effect of Maize Fuel Ash (MFA) and Plantain Leaf Ash (PLA) on the Heat of Hydration of Concrete

Abstract

This study modeled the effects of maize fuel Ash (MFA) and plantain leaf Ash (PLA) on the heat of hydration of concrete. The chemical composition tests of the MFA and PLA carried out showed their suitability as pozzolanas based on ASTM C618 (2008). OPC/MFA concrete cubes (0%, 10%, 20% and 30% MFA) and OPC/PLA concrete cubes (0%, 10%, 20% and 30% PLA) were made, cured at various ages, de-moulded and tested for compressive strength. The 28-day compressive strength of the OPC concrete was 22.54N/mm² . The OPC/MFA concrete compressive strength of 19.38N/mm² was the maximum value at 28 – day testing with M FA content of 10%. OPC/PLA concrete gave the maximum compressive strength of 19.31 M/mm² also at 28th day testing with 10% PLA fresh MFA and PLA concretes water – cement ratios of 0.5 were tested for heats of evolution in terms of temperature rise under semi-adiabatic conditions and the results recorded. The compressive strength of concrete produced when maize fuel ash (MFA) is used to replace cement at the replacement level of 10-30% and at the hydration period of 7-28 days ranges from 5.38 – 19.32N/mm² as against 11.34 – 22.54N/mm² for the control test. Similarly, the compressive strengths of concrete produced when plantain leaf ash (PLA) is used to replace cement at the source replacement level and hydration period ranges from 5.37 – 19.31N/mm² as against 11.35 – 53N/mm² for the control test. Regression analyses were done on the compressive strengths and heat of hydration results to generate mathematical models. The study revealed that both MFA and PLA were effective supplementary cementing materials, controlling the heat of hydration particularly between the first and second days after casting. The compressive strength analysis indicated that the amount of MFA and curing time significantly influenced strength with higher MFA amounts leading to decreased strength and longer curing times increasing strength. The analysis of heat release showed a negative impact of MFA/PLA on heat release with longer curing times exacerbating this effect. The ANOVA for the heat of hydration for MFA/PLA concrete showed that the regression models were statistically significant (p-value < 0.05).