What is Recycled Concrete Aggregate

Recycled concrete as aggregate is nothing but aggregates produced from the previously used construction material such as masonry or concrete. Recycled aggregates consist of hard, graduated fragments of inert materials, which include sand, crushed stone, rock dust, gravel, slag or powder.

Need of Using Recycled Concrete as Aggregate

Concrete is the most common material used for construction around the world. Approximately million tons of concrete debris is dumped as construction waste per year.

These demolished materials are often dumped on land and are not reused for any purpose. This effects the environment and fertility of the land.

Using recycled concrete as aggregate would lead to environmental and economic benefits. Apart from these, recycled aggregate has several benefits since they are durable like natural aggregate.

To use recycled concrete as aggregate for concrete contaminants like reinforcing, steel foundation, materials soil etc are removed from the concrete debris. It can be done by screening, air-separation, demolition using electromagnets.

Then the debris is crushed either manually or mechanically. It in done in specified size and quality usually around 20 millimeters to 50 millimeters.

Based on various research it is generally accepted that around 30% of natural crushed coarse aggregate can be replaced with coarse recycled aggregate. It is done without significantly affecting any of the properties of the concrete.

However it is advised to perform the various concrete tests by replacing some part of natural aggregate. This is done to determine the perfect proportions of concrete.

Important Sources of Collecting Concrete Waste for Recycling

• Best source for collection is waste generated due to construction or demolition of the structure.
• Natural calamities like earthquake causes demolition of old buildings, structure etc, which could again prove to be important source.
• Tested Specimens (concrete cubes) which are further of no use can be collected from big testing laboratory.
• Waste concrete generated in the ready mix concrete plant and precast concrete fabrication units.
• Worn out rail ballast.

Process of Recycling Concrete Aggregate

It is mainly done by two methods :

1. Mechanical Method.

2. Air-heating and Grinding Method.

Uses of Recycled Concrete Aggregate

Recycled Concrete Aggregate has a wide variety of uses in the field of the construction Industry. The uses are grouped into two categories :

• Unprocessed Recycled Aggregate
• Processed Recycled Aggregate

Unprocessed recycled aggregates are used for bulk fills, backfill material, riverbank protection, base fill for drainage structures, aggregate for road construction etc.

The processed recycled aggregates are being utilized for various structural works in bridges pavements, used as an aggregate in lean concrete, bituminous concrete, used in the construction of shoulders, median barriers, sidewalks, curbs and gutters etc.

Merits :

• Wide market for supply.
• Providing more job opportunities.
• Creates minimal environmental impact.
• Resulted aggregate is light weight than original aggregate.
• More Sustainable.

Demerits :

• Less strength than original aggregate.
• No proper guidelines and specifications for process.
• Supply is currently inefficient.