Parameters influence on compressive strength of fly ash green concrete with fibers using a modern response surface method

Abstract

In last years, recycling has become a strategic factor in global politics, a vital component and a cost factor for economic development and the progress of society as a whole, generating a number of major global concerns. Exceeding twice the sum of all materials used in construction, annual concrete consumption around the world amounts to approximately 10 trillion tones being by far the most used building material and the partial or total replacement of a component of its mass with recyclable waste has a major positive impact on the world economy and implicitly on the environment. This study aims to determine the influence of fly ash and glass fiber on the compressive strength of cement concrete by using a modern Response Surface Methodology (RSM). The association of these two materials has unpredictable effects on the properties of concrete. The fly ash replaced a quantity of 10% from the cement dosage. The glass fibers were used in dosages between 0.25% and 1.75% from the concrete mass. The length of glass fiber varied between 10 mm and 35 mm. A number of 13 mixes of concrete were experimentally tested. Analysis of variance (ANOVA) gave the non-linear response surface and Pareto chars showed the importance order of variables. From statistical analysis it was concluded that an improvement of compressive strength is obtained for a concrete with 10% fly ash as replacement of cement, reinforced with disperse glass fiber with dosages between 0.4% and 1% and length of fibers bigger than 25 mm.