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TOPIC – INVESTIGATION OF THE USE OF QUARRY DUST AS A SUBSTITUTE OF RIVER SAND IN CONCRETE MIXES

Introduction

CIVIL AND STRUCTURAL ENGINEERING PROJECT REPORT – River sand has been widely used in Eldoret as a construction material for the manufacture of concrete. Quarry dust as a waste product from crusher operations, is considered by most construction sites as non-marketable and non- environmentally friendly material.

The overall economy of the concrete greatly depends on the cement content of the particular mix. Different researchers have established that the replacement of natural sand with crushed stone sand can result in savings in cement.

Replacement of a portion of natural sand with Quarry dust in the production of concrete is recommended only if the gradation of the resulting fine aggregate mixture conforms to the specified standards. In concrete, fine and coarse aggregates constitute about 80% of the total volume (Prabin, 2005). It is, therefore, important to obtain the right type and good quality aggregates at site.

The aggregates form the main matrix of the concrete mixes. Most of the aggregates used in Eldoret as fine aggregates are river sand. Fine aggregates used for concrete should conform to the requirements for the prescribed grading zone as per BS: 882 – 1982. The stone particles comprising the sand should be hard and sound.

Aggregate characteristics of shape, texture, and grading influence workability, finishability, bleeding, pumpability, and segregation of fresh concrete and affect strength, stiffness, shrinkage, creep, density, permeability, and durability of hardened concrete.

Construction and durability problems have been reported due to poor mixture proportioning and variation on grading [Lafrenz, 1997]. Fine aggregates should also not be covered with deleterious materials like clay lumps and should be clean.

They should not contain organic or chemically reactive impurities. Natural or river sand may not conform to all the above requirements and may have to be improved in quality by washing, grading and blending.

STUDY AREA

Eldoret town lacks the available deposits of river sand hence relying on deposits from Kisumu, Pokot and River Nzoia. This makes the market value of river sand to be higher compared to that of Quarry dust. The uses of quarry dust are also relatively few in the Eldoret region. There is also a perception that since quarry dust is a waste product it is inferior to sand but this may not be the case.

Experimental Significance

River sand is becoming a very scarce material. The sand mining from our rivers have become objectionably excessive. It has now reached a stage where it is killing all our rivers day by day. Hence sand mining has to be discouraged so as to save the rivers of our country from total death. Environmental pressure, costs and a shortage of river sand has made it necessary for an alternative in this type of deposit in developing countries to be used.

In this work, an attempt has been made to study the effects of using quarry dust as a substitute for river sand, its strengths, its weaknesses and the overall effectiveness when the river sand is replaced with Quarry dust in construction activities. In the context of the depletion of natural sand, what the study suggests will certainly give an impetus to the construction scenario of not only Eldoret town but our country in general. This study, incorporating the extended use of quarry dust, is directed towards exploring the possibility of making effective use of the discarded quarry dust in concrete.

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