International Journal of Civil and Structural Engineering Research ISSN 2348-7607 (Online) Vol. 6, Issue 2, pp: (227-239), Month: October 2018 - March 2019, Available at: www.researchpublish.com
Optimization Model for Prediction of Compressive Strength of Concrete Containing Fly Ash and Quarry Dust Based on Scheffe’s Simplex Theory Ephraim, M. E.1, ThankGod, O.2, Nule,S. J.3 1, 2 3
Lecturer, Civil Engineering Department, Rivers State University, Port Harcourt, Nigeria PG Student, Civil Engineering Department, Rivers State University, Port Harcourt, Nigeria Corresponding author:3nuson2002@yahoo.com
Abstract: This work involves the application of Scheffe’s optimization technique toobtain the mathematical model of response function for the optimization of compressive strength of a six- componentconcrete madewithcement, fly ash, sand, quarry dust, granite and water.A total of 84 standard 150x150x150mm cubes was cast, fromforty-two (42) mix ratios.The first twenty-one (21) were used to determine the coefficients of the model, while the remainingtwenty-one were used to validate the model.The MATLAB software developed gave optimum compressive strength of 43.01N/mm2after 28 days wet curing for a mix ratio of 0.91:0.094:0.868:0.138:2.18:0.40 (i.e. cement: fly ash:sand:quarry dust: granite: water).The output of the mathematical models compared favourably with the corresponding experimental results and the predictions from the response function were tested for adequacy using the statistical Fischer test and found to be adequate at 95% confidence level. The model derived in this study can be used to predict mix ratios for any desired compressivestrength ofa six-component concrete system within a 6,2 factor space. Keywords: Compressive Strength, Quarry Dust, Fly Ash, Mathematical model, Scheffe’s, Optimization, Concrete.
1. INTRODUCTION The problem of affordable housing and construction economy continue to remain a topic of discussion for researchers. Concrete is one of the most popular construction materials worldwide and itsuse has witnessed tremendous increase over the years.Concrete is a mixture of cement, fine aggregate and coarse aggregate and water and when sufficiently hardened is used in supporting various structural loads. The cost of production of concrete heavily impacts on construction cost. Most of the engineering characteristics of concrete depend on proportions of the constituent materials. The river sand which is commonly used as fine aggregate in the production of concrete, poses the problem of acute shortage in some areas, resulting inadditional cost of transportation from far-way sources. This emphasizes the need to optimize the use of river sand with a view to reducing the cost of concrete production.
2. AIMS AND OBJECTIVE OF STUDY Efforts have been made by various researchers to optimize the benefits of quarry dust and fly ash as alternative replacements for sand and cement in concrete production. Quarry dust is a by-product from the crushing process during production of granite aggregates.Quarry dust is known to increase the strength of concrete over concrete made with equal quantities of river sand. Fly ash is a pozzolanic material, obtained as by-product of burned coal from thermal power plants.Several studies have been conducted on the strength of concrete, containing quarry rock dust and fly ash. Ephraimand Rowland-Lato [1] concluded that total replacement of conventional granite and natural sand with 10mm washed gravel aggregate and quarry rock dust respectively is possible without compromising the compressive strength of concrete. Jamale and Kawade [2] studied the effect ofpartial replacement of cement with fly ash and sand with quarry duston the strength properties of grade 40 concrete.The authors
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