DEVELOPMENT OF AN OPTIMISATION MODEL TO PREDICT THE COMPRESSIVE STRENGTH OF CONCRETE CONTAINING RICE HUSK ASH BASED ON SCHEFFE’S THEORY

Abstract

ABSTRACT The cost of cement as one of the ingredients for producing concrete has rapidly increased over the years. This has led to the search for it to be possibly replaced with some other materials that possess same, or better property than that of cement. Rice Husk Ash (RHA), being an agricultural waste has played significant role in concrete mix research. It has served as complementary material to some of the ingredients of concrete especially cement. In this study, it served as a fifth ingredient of concrete blend as it replaced 5%, 10%, 15%, 20% and 25% of cement. The other four ingredients were cement, sharp sand (fine aggregates), granite (coarse aggregate) and water. Scheffe’s theory was used for five mix ratios in a {5, 2} experimental design, which resulted in additional ten mix ratios. For the optimisation model to be verified and also tested, fifteen additional mix ratios were generated. The thirty mix ratios were subjected to laboratory experimentations to determine the 28 days compressive strengths. The results for the first fifteen compressive strengths were used for calibration of the model constant coefficients, while those from the second fifteen were used for the model verification using Scheffe’s simplex lattice design. The model compared favorably with the experimented data and the predictions from the model were tested with statistical Fischer test and found to be adequate at 95% confidence level. A mathematical regression model was derived from the experimented results, with which the compressive strengths were predicted; this ascertained the model to be adequate with an R2 value of 0. 902.The mathematical model developed in this study can be used to predict mix ratios for any desired compressive strength of RHA concrete within the factor space of the simplex used in the study. ABSTRACT The cost of cement as one of the ingredients for producing concrete has rapidly increased over the years. This has led to the search for it to be possibly replaced with some other materials that possess same, or better property than that of cement. Rice Husk Ash (RHA), being an agricultural waste has played significant role in concrete mix research. It has served as complementary material to some of the ingredients of concrete especially cement. In this study, it served as a fifth ingredient of concrete blend as it replaced 5%, 10%, 15%, 20% and 25% of cement. The other four ingredients were cement, sharp sand (fine aggregates), granite (coarse aggregate) and water. Scheffe’s theory was used for five mix ratios in a {5, 2} experimental design, which resulted in additional ten mix ratios. For the optimisation model to be verified and also tested, fifteen additional mix ratios were generated. The thirty mix ratios were subjected to laboratory experimentations to determine the 28 days compressive strengths. The results for the first fifteen compressive strengths were used for calibration of the model constant coefficients, while those from the second fifteen were used for the model verification using Scheffe’s simplex lattice design. The model compared favorably with the experimented data and the predictions from the model were tested with statistical Fischer test and found to be adequate at 95% confidence level. A mathematical regression model was derived from the experimented results, with which the compressive strengths were predicted; this ascertained the model to be adequate with an R2 value of 0. 902.The mathematical model developed in this study can be used to predict mix ratios for any desired compressive strength of RHA concrete within the factor space of the simplex used in the study. ABSTRACT The cost of cement as one of the ingredients for producing concrete has rapidly increased over the years. This has led to the search for it to be possibly replaced with some other materials that possess same, or better property than that of cement. Rice Husk Ash (RHA), being an agricultural waste has played significant role in concrete mix research. It has served as complementary material to some of the ingredients of concrete especially cement. In this study, it served as a fifth ingredient of concrete blend as it replaced 5%, 10%, 15%, 20% and 25% of cement. The other four ingredients were cement, sharp sand (fine aggregates), granite (coarse aggregate) and water. Scheffe’s theory was used for five mix ratios in a {5, 2} experimental design, which resulted in additional ten mix ratios. For the optimisation model to be verified and also tested, fifteen additional mix ratios were generated. The thirty mix ratios were subjected to laboratory experimentations to determine the 28 days compressive strengths. The results for the first fifteen compressive strengths were used for calibration of the model constant coefficients, while those from the second fifteen were used for the model verification using Scheffe’s simplex lattice design. The model compared favorably with the experimented data and the predictions from the model were tested with statistical Fischer test and found to be adequate at 95% confidence level. A mathematical regression model was derived from the experimented results, with which the compressive strengths were predicted; this ascertained the model to be adequate with an R2 value of 0. 902.The mathematical model developed in this study can be used to predict mix ratios for any desired compressive strength of RHA concrete within the factor space of the simplex used in the study. ABSTRACT The cost of cement as one of the ingredients for producing concrete has rapidly increased over the years. This has led to the search for it to be possibly replaced with some other materials that possess same, or better property than that of cement. Rice Husk Ash (RHA), being an agricultural waste has played significant role in concrete mix research. It has served as complementary material to some of the ingredients of concrete especially cement. In this study, it served as a fifth ingredient of concrete blend as it replaced 5%, 10%, 15%, 20% and 25% of cement. The other four ingredients were cement, sharp sand (fine aggregates), granite (coarse aggregate) and water. Scheffe’s theory was used for five mix ratios in a {5, 2} experimental design, which resulted in additional ten mix ratios. For the optimisation model to be verified and also tested, fifteen additional mix ratios were generated. The thirty mix ratios were subjected to laboratory experimentations to determine the 28 days compressive strengths. The results for the first fifteen compressive strengths were used for calibration of the model constant coefficients, while those from the second fifteen were used for the model verification using Scheffe’s simplex lattice design. The model compared favorably with the experimented data and the predictions from the model were tested with statistical Fischer test and found to be adequate at 95% confidence level. A mathematical regression model was derived from the experimented results, with which the compressive strengths were predicted; this ascertained the model to be adequate with an R2 value of 0. 902.The mathematical model developed in this study can be used to predict mix ratios for any desired compressive strength of RHA concrete within the factor space of the simplex used in the study. ABSTRACT The cost of cement as one of the ingredients for producing concrete has rapidly increased over the years. This has led to the search for it to be possibly replaced with some other materials that possess same, or better property than that of cement. Rice Husk Ash (RHA), being an agricultural waste has played significant role in concrete mix research. It has served as complementary material to some of the ingredients of concrete especially cement. In this study, it served as a fifth ingredient of concrete blend as it replaced 5%, 10%, 15%, 20% and 25% of cement. The other four ingredients were cement, sharp sand (fine aggregates), granite (coarse aggregate) and water. Scheffe’s theory was used for five mix ratios in a {5, 2} experimental design, which resulted in additional ten mix ratios. For the optimisation model to be verified and also tested, fifteen additional mix ratios were generated. The thirty mix ratios were subjected to laboratory experimentations to determine the 28 days compressive strengths. The results for the first fifteen compressive strengths were used for calibration of the model constant coefficients, while those from the second fifteen were used for the model verification using Scheffe’s simplex lattice design. The model compared favorably with the experimented data and the predictions from the model were tested with statistical Fischer test and found to be adequate at 95% confidence level. A mathematical regression model was derived from the experimented results, with which the compressive strengths were predicted; this ascertained the model to be adequate with an R2 value of 0. 902.The mathematical model developed in this study can be used to predict mix ratios for any desired compressive strength of RHA concrete within the factor space of the simplex used in the study.