MATHEMATICAL MODELLING OF STRENGTH OF CONCRETE MADE WITH RIVER SAND AND QUARRY DUST AS FINE AGGREGATE USING DIFFERENT OPTIMIZATION PRINCIPLES.

SOURCE:

Faculty: Engineering
Department: Civil

CONTRIBUTORS:

Chijioke C.
Aginam, C. H.
Nwaiwu, C. M. O.

ABSTRACT:

River sand has for years been the only fine aggregate used in the production of concrete. This has led to the destruction of our natural habitat and also led to astronomical increases in the price of river sand in recent years. Hence the need to find an alternative material that can be used in the replacement of river sand as fine aggregate in the production of concrete and still give all the required properties needed in concrete works. This research work used mathematical models to evaluate the suitability of using quarry dust as an alternative to river sand in the production of concrete. The values obtained were compared with the one produced with river sand as fine aggregate and were found to be adequate. The experimental work revealed that quarry dust can actually be used to replace river sand in the production of concrete. Quarry dust is a waste product generated from the quarry industry and its environmental effect is not friendly, hence its use in the production of concrete will go a long way in eliminating this waste. For this material (quarry dust) to be utilized effectively as a component in concrete production, it must depend on the mix proportioning of the various component materials. This research work used Scheffes four dimensional factor space having ten points to develop the possible mix combination of cement, river sand/quarry dust and coarse aggregate. A total of 30 experimental points were generated by the use of MINITAB 17 (CCD Matrix), and regression models were developed using these values. Four mathematical models were developed, each for predicting the compressive and flexural strengths of concrete produced with river sand as fine aggregate and that produced with quarry dust as fine aggregate using Surface Response method (Minitab 17) respectively. The models values obtained were in good agreement with the corresponding experimental values. The predicted values were tested with student T-test, F-test, random error of replicate and Normal probability Plot and analysis of variance, they were found to be adequate at 95% confidence level. Computer programs were written in Visual-Basic 6 based for Osadebe and Ibearugbulem regression model , and can be used to predict all possible combinations of mix proportion of cement, river sand/quarry dust, water and coarse aggregate if a desired compressive strength is given and vice versa. All the samples were cured for 28 days. From the data obtained, the optimum compressive strength of concrete made with river sand is 53.09N/mm2 at a mix ratio of 1:1.5:5 at water/cement ratio of 0.5 and for concrete made with quarry dust the maximum compressive strength is 37.86N/mm2 at a mix ratio of 1:1.5:3 at water/cement ratio of 0.50. The optimum flexural strength of concrete made with river sand is 5.53N/mm2 at a mix ratio of 1:1.99:5 at water/cement ratio of 0.5 and for concrete made with quarry dust the maximum flexural strength is 2.67N/mm2 at a mix ratio of 1:1.67:3 at water/cement ratio of 0.5. Hence from the results and analysis carried out, quarry dust can effectively be used as a replacement to river sand.