ABSTRACT
The project compares the flexural and split tensile strength of concrete using granite dust as partial replacement for fine aggregate. The main aim of the present work was to
systematically study the effect of percentage replacement of granite dust by fine aggregate (sand) as 0%, 5%, 10%, 15% and 20% on the strength properties of concrete.30 specimen of flexural and split tensile concrete were cast each, and 0%, 5%, 10%, 15% and 20% of fine aggregate were replaced with granite dust. The specimen were cured after 24hrs of casting while two specimen of each percentage of flexural and split tensile were tested. Based on the result, there was decrease in the flexural strength with increase of sand replacement. The difference is small hence, granite dust can be used in structures in which design depend mainly on flexural strength at 10% replacement. The tensile strength decreased with percentage of increase in granite powder in the mix till 10% replacement and it reaches its optimum value at 20% replacement at 28days. Therefore, based on the size effect principle, it would follow that the flexural strengths would be higher than the splitting tensile strengths.
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INTRODUCTION
BACKGROUND OF THE STUDY
Concrete is the most widely used composite material today. The constituents of concrete are coarse aggregate, fine aggregate, binding material and water. Rapid increase in construction activities leads to acute shortage of conventional construction materials. The function of the fine aggregate is to assist in producing workability and uniformity in the mixture. It is conventional that sand is being used as fine aggregate in concrete. This is due to the ease of acquisition and its well-graded nature and that all sizes of grains are well distributed in a given sample. The application of river sand is mainly for all kinds of civil engineering construction. The annual sand demand for the construction industry in Nigeria and other developing countries is high and all is obtained from major rivers. The excessive excavation of river sand is becoming a serious environmental problem. Erosion and failure of river banks, lowering of river beds and damage of structures situated closer to the rivers, saline water intrusion into the land and coastal erosion are the major adverse effects due to intensive river sand mining. The demand for natural sand is also quite high in developing countries owing to rapid infrastructural growth which results to scarcity of natural sand. Therefore, construction industries of developing countries are in stress to identify alternative materials to replace the demand for natural sand.
In the future, the entire construction industry may come to a halt if there are no alternative sources of sand. Therefore, it is necessary to explore the possibilities for alternative sources to minimize river sand extraction. At present, the identified alternative sources are fibre glass as partial replacement, wood
ash, saw dust, recycled concrete and fly ash. They are not effective because of their quantity and they also have low workability. Granite dust has been proposed as an alternative to river sand. Quarries are operating in many parts of Nigeria to supply coarse aggregates for various types of construction, especially for concrete, road construction and foundations of buildings. The advantages of utilization of byproducts or aggregates obtained as waste materials are pronounced in the aspects of reduction in environmental load & waste management cost, reduction of production cost as well as augmenting the quality of concrete.
STATEMENT OF THE PROBLEM
The granite dust, the by-product, was never used before instead of river sand earlier because of the different quality. Various rock types produce different types or different qualities of quarry dusts due to the inclusion of their fresh minerals. Also, it has no uniformity and similarity to river sand. Although, now, it is used for road work. The industry people are afraid to use it for concrete or such strong constructions due to the higher percentages of minerals other than quartz. Therefore, detailed studies on granite dusts are needed to find out their suitability. The research focused on the use of granite dust as replacement for fine aggregates in concrete.
AIM AND OBJECTIVES OF STUDY
The main aim of the present work is to systematically study the effect of percentage replacement of fine aggregate (sand) by granite dust as 0%, 5%, 10%, 15% and 20% on the
strength properties of concrete.
OBJECTIVES OF THE STUDY
The specific objectives are as follows:
i. To investigate the spilt tensile and flexural strength of concrete made using quarry dust
as fine aggregate.
ii. To investigate changes in strength of concrete as fine aggregate (sand) is replaced with
granite dust in different percentages.
iii. To investigate the effect of granite dust on the workability of concrete in different
proportions.
SIGNIFICANCE OF THE STUDY
This research determines the strength of concrete produced with granite dust hence it will be easier for engineers to specify in which projects and in what proportions granite dust could be used. There is need for this research since granite dust has recently gained good attention to be used as an effective filler material instead of sand. Some construction companies tend to use it without the knowledge of its strength which results to risk of failure of structures.
LIMITATION OF THE STUDY
Granite dust is obtained from rocks with different chemical properties hence there may be no specific mechanical strength (flexural and split tensile strength) for concrete produced by different granite dust.
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