FLY-ASH

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                                                          ABSTRACT

This study presents the investigations of effect of fly-ash on concrete containing slag. Cement is a costly material and is used extensively for construction works all over the world. Replacing a certain fraction of cement by fly-ash contributes to the strength of concrete due to its pozzolanic reactivity. However, since pozzolanic reaction is slow, the initial strength is low. 

fig-1.

This pozzolanic reaction also makes the structure of concrete denser, resulting in decrease in water and gas permeability. Slag is generated during iron and steel production. The addition of slag reduces the rate of heat evolution and increases the resistance to chemical attack. It is made use of in hot regions due to less effect on early strength of concrete. The percentage of slag used also depends upon the aggregate. If the aggregate is highly reactive it would require more of the slag to mitigate ASR or alkali-silicate reaction. The project aims at studying the influence of these two important industrial wastes on the compressive strength of concrete. The methodology adopted for the test is the standard one taken up from Indian Standard code of concrete testing and for metal leaching a modified version of soil test is used. 

The test results obtained after 7 day and 28 day are then analyzed on the basis of their compressive strengths and leaching characteristics. The optimum value of slag and fly-ash is found which gives largest compressive strength. The more leaching takes place, more the porous structure is formed. Thus leaching values form an important part of the project. Slag and fly-ash available are low cost or zero cost materials and therefore can be used economizing the cost of project. Apart from economy it also saves the environmental cost of 

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