This study tried to compare the flexural strength of concrete made with riversand and quarry dust as fine aggregate.River sand was collected from Osogbo, Osun State, replaced at 0-100% at intervals of 10% with quarry dust gotten from Wasimi, Osun State, Nigeria.Abstract Common river sand is expensive due to the excessive cost of transportation from natural sources. Also, large-scale depletion of these sources creates environmental problems. As environmental transportation and other constraints make the availability and use of river sand less attractive, a substitute or replacement product for concrete industry needs to be found. River sand is most commonly used fine aggregate in the production of concrete poses the problem of acute shortage in many areas. Whose continued use has started posing serious problems with respect to its availability, cost, and environmental impact. In such a situation the Quarry rock dust can be an economic alternative to the river sand. Results show the compressive strength (CS) of concrete for 7days curing as; 19.28, 19.65, 20.38, 20.90. 21.32, 22.66, 20.60, 19.23, 18.16, 17.54, and 16.06 KN/mm2 respectively for a percentage replacement ratio of sand: quarry dust of; 100:0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, 100:0 respectively. 14 days curing period results in; 21.08, 21.27, 22.19, 22.80, 23.18, 24.51, 22.31, 21.32, 20.03, 19.32, and 17.20 KN/mm2 with a replacement ratio of 100:0, 90:10, 80:20, 70:30, 60:40, 50:50, 40:60, 30:70, 20:80, 10:90, and 0:100 respectively. At 21 days curing period, the study shows the average compressive strength (CS) of concrete as; 22.31, 22.98, 23.21, 23.81, 24.47, 25.17, 23.02, 21.82, 20.95, 20.22, 18.27 KN/mm2 for 100:0, 90:10, 80:20, 70:30, 40:60, 50:50, 40:60, 30:70, 20:80, 10:90, 0:100 replacement of sand by quarry dust. 28 days curing period yields compressive strength of 24.51, 24.95, 25.31, 25.83, 26.34, 27.11, 24.82, 23.62, 22.77, 22.16, and 20.24 KN/mm2 for replacement percentage; 100:0, 90:10, 80:20, 70:30, 60:40, 30:70, 20:80, 10:90, and 0:100, sand to quarry dust. This study notes and concludes that, the maximum average compressive strength of concrete was attained at ratio 50:50 at 7, 14, 21, and 28 days curing periods respectively.



1.1   Background to the study

Currently Nigeria is under-going infrastructural development in all spheres of civil engineering. Concrete is an important component in almost all infrastructures such as building, bridges, highways etc. Concrete is essentially a mixture of coarse and fine aggregates, cement and water, that is required for the environmental development of the Nation. Its workability allows it to be easily used in many shapes and forms. Concrete is basically of three types: the light weight with density weighing less than 19,200.00 kg/m3, normal weight concrete which is most common with density of about 24,000.00 kg/m3 and heavy weight concrete with density above 28,000.00 kg/m3. Concrete is achieved when the paste (water and cement mixture) binds the aggregates into a rocklike mass known as concrete. According to Barritt, concrete is that pourable mix of cement, water, sand and gravel that hardens into super strong building material. Concrete is a man-made material used in the building and construction industry and consists of aggregates which are bonded together by cement and water (cement paste). The major constituent of concrete besides the cement is the aggregate. 

Various types of aggregates that may be used include sand, crushed-stone, gravel, granite, slag, ashes, burned shale, and burned clay. Fine aggregates refer to the size of aggregate used in making concrete slabs and in providing smooth surfaces. Coarse aggregates are used for massive structures or sections of concrete. The most commonly used fine aggregate is sand derived from river banks. River sand has been the most popular choice of fine aggregate component of concrete in the past, overuse of the material has led to environmental concerns, such as; depletion of river sand deposits resulting in flooding and an increase in price of the material. Developing country like Nigeria is facing shortage of good quality natural sand, natural sand deposits are being used up and causing serious threat to the environment as well as the society. The rapid extraction of sand from the river bed causes problem like deepening of the river bed, loss of vegetation on the bank of rivers, depletion of aquatic life as well as climate change and reduction in agricultural production due to lowering of soil nutrients etc.

On the other hand, quarry dust is a by-product which is formed in the processing of granite stones through rock blasting to produce coarse aggregate of different sizes. Quarry dust has been proposed as an alternative to river sand that gives additional benefit to concrete. Other studies have found that quarry dust is known to increase both fresh and hardened properties of concrete over concrete made with equal quantities of river sand. The fresh and hardened properties of concrete continue to increase with age for all percentage of quarry dust content. The utilization of quarry dust as fine aggregate would turn this waste material that causes disposal problem into valuable resource. In concrete production it could be used as a partial or full replacement of natural sand; besides, the utilization of quarry dust, which itself is a waste material, may reduce the cost of concrete production in the long run.  Hence, the purpose of this investigation is to compare the compressive strength of concrete made with sand as fine aggregate and substituted with quarry dust at intervals of 10% replacement.

1.2     Problem statement

Concrete plays the key role in construction and a large quantum of concrete is being utilized in every construction practice. River sand, which is one of the constituents used in the production of concrete, has become very expensive and also becoming scarce due to the depletion of river beds.

Due to size specification, the material selected to substitute this purpose is Quarry

Dust since it is a fine waste material and its utilization as sand replacement could perhaps increase the Strength of concrete to enhance the properties of concrete at the same time resulting in a cheaper concrete mix.