Partial Replacement of Coarse Aggregate with Demolished Waste

Published on 02 Jul 2021. Written by Vinay Raj

The use of building materials has been changing every year. Materials like molded earth brick stones, Timber, Steel, Aluminium, PVC which are less in cost and locally available have replaced the traditional and high-cost materials. However, all these materials have been developed to meet specific requirements of climate, availability of skilled labour and specific raw materials to affect the desired economy.

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Due to rapid industrialization, demolishing the old structures and constructing the new structures in the place of old structures has become a common practice especially in metropolitan areas. And only some part of demolished concrete is recycled or reused. Due to these strict environmental laws and less availability of the land for dumping in urban areas, the problem of disposing of the demolished waste is problematic. Even the quarrying of the raw materials is becoming difficult due to narrowing of the resources.

Demolished waste from structures primarily consists of concrete, steel, and foreign matter such as hardware’s, woods, plastics, etc. From this waste, the concrete can be used by removing the impurities and crushing it into the desired aggregate size. This can be done by using mechanical devices such as impact crushers, jaw crushers, hammer crushers, etc.

Water absorption of coarse aggregate and fine recycled aggregates must be determined in the laboratory before any concrete mix design using recycled aggregates. If the water content in concrete is increased then it shows the effect on durability and strength of concrete. For this reason, it is not recommended to use recycled fine aggregate in the construction.

The processes used for processing of demolition waste are

• Thermal
• Dry
• Wet

These processes can be used alone or in the combination of two processes. The major difference between the recycled concrete and traditional made concrete is recycled concrete water absorption rate is more than traditional concrete.

Requirements:

Cement, Coarse and Fine aggregate.

Knowledge of Mix design.

Need of a Concrete technology laboratory with apparatus to have testing apparatus such as slump cone, CTM, etc.

Project Implementation:

1. Make mix design for any mix (ex. M25, refer IS 10262).
2. Find the quantities of fine and coarse aggregate, water and cement.
3. Replace the quantity of coarse aggregate with Demolished waste.
4. Make specimen of 100mm and test it on 7^th day, 14^th day and 28^th
5. Iterate the percentage of the demolished waste until you get optimum compressive strength.
6. Compare the compressive strength between natural aggregate concrete and recycled aggregate concrete.
7. Choose and report the optimum usage value of demolished waste in the concrete mix.

Advantages:

• Economical for poor areas unable to afford hauling costs for coarse aggregates from other locales.
• Reduce the amount that is being paid for landfilling.
• Saving the environment as we are reusing the waste.
• Provide a cost-saving.

Software Requirements:

• A graph drafting software such as MS Excel, Origin Pro, Minitab, etc. can be used to plot the graphs for different percentage of demolished waste.

Conclusion:

This project helps you in knowing the procedure of mix design, advantages and disadvantages of using the demolished waste in the concrete mix.

Kit required to develop Partial Replacement of Coarse Aggregate with Demolished Waste:

• Cement
• Fine and Coarse aggregate

Technologies you will learn by working on Partial Replacement of Coarse Aggregate with Demolished Waste:

• Cement
• Aggregate
• Demolished waste

Any Questions?