Construction and demolition waste generation has exceedingly increased around the World to about 40% annually. Out of which, concrete constitutes to about 80% of the total waste. Therefore, it is necessary to recycle concrete waste to recycled aggregate and recycled aggregate concrete. Sustainable development is focused through usage reduction of natural raw materials and consumption of recycled goods.
Recycling of slurry water is necessary to avoid ground water contamination which poses a great hazard in the ground water table. The solution to it is in recycling the concrete and the slurry water. The benefits to it are that it reduces the production of greenhouse gas emissions and other pollutants by reducing the need to extract raw materials and ship new materials to long distances.
Concrete and its ingredients:
Concrete is a mixture of cement, water, and aggregate material. Cement is made by heating a mixture of limestone and clay containing oxides of calcium, aluminium, silicon and other metals in a kiln and then pulverizing the resulting clinker. The fine aggregate particles are usually sand. Coarse aggregate is generally gravel or crushed stone. When cement is mixed with water, a chemical reaction called hydration occurs, which produces glue that binds the aggregates together to make concreteConcrete Washout:
After concrete is poured at a construction site, the chutes of ready mixed concrete trucks and hoppers of concrete pump trucks must be washed out to remove the remaining concrete before it hardens. Equipment such as wheelbarrows and hand tools also need to be washed down. At the end of each work day, the drums of concrete trucks must be washed out. This is customarily done at the ready mixed concrete batching plants, which are usually off-site facilities, however large or rural construction projects may have on-site batch plants.Wet concrete recycling:
Builders often order more ready mixed concrete than they actually need, so it is common for concrete trucks to have wet concrete remaining in their drum after a delivery. This unused concrete can be returned to the ready mixed plant and either (1) used to pour precast concrete products (e.g., highway barriers, retaining wall blocks, riprap), (2) used to pave the ready mixed plant’s yard, (3) washed into a reclaimer, or (4) dumped on an impervious surface and allowed to harden, so it can be crushed and recycled as aggregate. Unused wet concrete should not be dumped on bare ground to harden at construction sites because this can contribute to ground water and surface water contamination. Schwing Stetter recycling plants helps in conserving the environment by not contaminating the ground water through recycling of slurry water and reusing it in making concrete. To explain further on one such product:
Schwing Stetter’s RA 12 can recycle the concrete at a washing capacity for normal concrete at 12m3 per hour. The major benefits to RA 12 are easy operation, fully automatic, no wastage of aggregates or raw materials, short vehicle downtimes during cleaning, no disposal costs, exceptionally resistant to wear, variable installation possibilities and low operating costs.
Typical system for recycling wash water/ aggregate recovery is that the surplus concrete is fed into the washing drum with the help of vibrators in the hopper. Depending on the system, upto two trucks can be unloaded simultaneously. The boom pump delivers water to concrete transit mixer for washing. Concrete transit mixer washes out concrete discharges into the charging hopper and flows into the drum. The drum rotates to separate the aggregate and slurry water by reverse flow method. The slurry water gets collected into the slurry tank. The aggregates gets collected through vibrating sieve. The agitator stir the slurry tank in regular interval to avoid deposition. The rinsing pump delivers water to drum through vibrating sieve and charging hopper. Batching pump delivers slurry water to concrete batching plant for concrete production.
Our happy customers are quite a many: Leighton, Larsen and Toubro at their Dhirubhai Ambani International Convention centre were able to reuse the remaining concrete from 4 lakhs m3 from the construction site. For every 50 numbers of transit mixers washed per day through RA 12, a total of 10 lakhs can be saved yearly.
Schwing Stetter are the best in the next generation - recycling plant. RA 12 offers easy to use, low noise equipment wherein it separates aggregates and slurry from the concrete to be reused. The major benefits of concrete recycling are keeping concrete debris out of landfills saves landfill space, recycled gravel reduces the need for gravel mining and using the recycled concrete as the base material for roadways reduces the pollution involved in construction, satisfying legal authorities guidelines of not allowing waste water containing cement slurry should be allowed to be flushed into municipal drains, minimum payback period of capital investments made on RA 12 system.
