Designing and optimizing of concrete mix proportion using statistical mixture design methodology

Kharazi, Media (2013) Designing and optimizing of concrete mix proportion using statistical mixture design methodology. Masters thesis, Memorial University of Newfoundland.

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Abstract

The primary objective of this thesis is to investigate and explore the feasibility of using statistical mixture experimental design and analysis methods in the optimization of concrete mix proportion and the subsequent prediction of concrete properties. Designing a concrete mixture proportion, which contains several components, such as cement and water content, coarse and fine aggregates, and various additives, to meet several performance criteria, can be a difficult and time-consuming task. -- A statistical mixture design approach, which provides a structured design matrix, provides a cost-effective means of concrete performance optimization. In this study, a statistical mixture approach based on an IV -optimal design was applied to investigate the effect of five mixture components (cement, water, coarse aggregates, fine aggregates, and admixture) on key performance criteria, which included the slump, 3-7-28- 56- and 91 - day compressive strengths, 3- 7- 28- and 56-day modulus of rupture and the modulus of elasticity. In total, 20 statistically designed concrete mixtures were cast to establish the prediction models for the several performance criteria. The models were developed for mixtures with 3 72 to 443 kg/m³ blended hydraulic cement, 155 to 164 kg/m³ water, 1066 to 1127 kg/m³ coarse aggregates, 671 to 736 kg/m³ fine aggregates, and 3.3 to 4.4 liters of high range water reducing agent. The accuracy of the prediction models were validated by confirmation tests for predicted concrete performance. The desirability function methodology was used for simultaneous optimization of multiple responses and determining the optimum binder combinations. -- The current research presents a procedure for the successful application of statistical mixture design methodology in concrete mix proportion. The procedure explained in the thesis can be used as a guideline for designing concrete mix proportion for different field application. -- As a secondary objective, the results of five mixtures with blended cement from part one, were compared with mixtures of similar proportions but made using ordinary Portland cement. The goal was to compare the differences in compressive strength, flexural strength, and modulus of elasticity gam with time. The results showed that the compressive and flexural strength of blended cement concrete were lower than ordinary Portland cement concrete at early ages. However, the blended cement concrete reached higher strength than conventional concrete after 28-day and onward. The type of cement had no significant effect on the modulus of elasticity.

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