When structures made of concrete are demolished or renovated, recycled concrete is an increasingly common method for using debris. Concrete has been routinely transported to landfills for disposal, but recycling has a number of benefits that make it a more attractive option in this greater age of environmental awareness, more environmental legislation, and a desire to reduce construction costs.
Concrete aggregates collected from dismantling sites are inserted through the crusher. The destruction facility accepts only uncontaminated concrete, which must be free of garbage, wood, paper and other such materials. Metals such as rebar are acceptable, as they can be removed with magnets and other sorting devices and melted for recycling elsewhere. The remaining aggregate pieces are sorted by size. Larger pieces can be through the destroyer again. After the crush has occurred, other particulates are filtered out through various methods including hand picking and water flotation.
Destroying at the actual construction site using a portable crusher reduces the construction cost and the resulting pollution when compared to transporting materials to and from the mine. Large plants on portable roads can destroy concrete and asphalt debris with 600 tons per hour or more. This system usually consists of debris crusher, side exhaust conveyor, filtering mill, and back conveyor from the screen to the inlet of the crusher for reprocessing of large materials. Compact-complete mini-crusher is also available which can handle up to 150 tons per hour and enter into more tight areas. With the emergence of attachment crusher - which is connected to various construction equipment, such as excavators - the trend of recycling in place with the volume of smaller materials growing rapidly. This Appendix covers a volume of 100 tons/hour and less.
Video Concrete recycling
Use of recycled concrete
Smaller pieces of concrete are used as pebbles for new construction projects. Sub-base gravel is placed as the lowest layer on the road, with fresh concrete or asphalt poured over it. The US Federal Street Administration may use such techniques to build new highways from old road materials. Crushed recycled concrete can also be used as a dry aggregate for new concrete if free of contaminants. Also, concrete sidewalks can be damaged in place and used as a base layer for asphalt pavement through a process called rubblization.
Larger pieces of crushed concrete can be used as a riprap revetment, which is a "very effective and popular method for controlling streambank erosion."
With proper quality control at the demolition facility, well-valued and aesthetically pleasing materials may be provided in lieu of landscaping or mulching stones.
Bronjong (cage) wire, can be filled with crushed concrete and stacked together to provide an economical retaining wall. The bronjong pile is also used to build privacy screen walls (instead of fences).
Maps Concrete recycling
Use of recycled rough aggregates in concrete
The latest statistics show that increased aggregate demand for construction could reach 48.3 billion metric tons by 2015 with the highest consumption being in Asia and the Pacific. The high demand for concrete means more and more new buildings will be built after the demolition of old buildings, resulting in large volumes of C & amp; D (waste disposal & waste disposal) as a product of economic growth. However, the most common way to dispose of this waste is to dispose of it in landfills. Without proper care, landfills can cause many environmental problems like air pollution and water contamination. This, along with the resource shortages caused by growth in this construction, has led to more and more countries beginning to consider the importance of recycling C & amp;
In general, the reuse and recycling of construction waste is concentrated in the preparation of recycled aggregates for concrete. By adding part of the recycled aggregate, instead of the crude natural aggregate into the mixture, it produces recycled concrete, which can save energy and materials for the production of concrete.
Strength and Durability of recycled aggregates
According to "The Effects of Rough Recycling", the experimental results show that "the recycled aggregate absorption value is 7.5% higher than the aggregate WSDOT specification in 3.7% maximum.This is because the paste on the gravel will affect the absorption of water therefore , the recycled aggregate meets the absorption specifications. Also, adding different parts of the recycled aggregate to the mixture will have different levels of influence on specific gravity, strength characteristics, compressive strength, elastic modulus and bending strength.They mix 0%, 35% 50% and 65% of the recycled aggregate into the mixture and found that as the percentage of the recycled aggregate added increased, the specific gravity, characteristic strength, compressive strength, modulus elasticity and decreased bending strength, can not indicate that the recycled aggregate is not good to be used only by comparing this data with natural aggregate properties. If we use 65% of aggregates t recycled or above, any physical properties will greatly decrease. However, if we limit the portion of the recycled aggregate added to the concrete, it will not affect much of each property. Based on research and trials, "the maximum replacement of recycled aggregate that can be used in concrete is 35%". Some experiments show that recycled aggregates do not have good endurance such as natural crude aggregates but we can increase their endurance by mixing with special materials such as fly ash to produce high strength and durable concrete.
Benefits
There are various benefits in recycling concrete rather than disposing of it or burying it in landfills.
- Keeping the concrete debris from the landfill saves the landfill space.
- Using recycled concrete can save natural resources by reducing the need for gravel, water, coal, oil and gas mining.
- Using recycled concrete as the base material for highways reduces the pollution involved in trucking materials.
- Recycling of concrete can create more job opportunities.
- Recycling concrete drags down the cost of buying raw materials and transporting waste to landfill sites.
- Recycling a ton of cement can save 1,360 gallons of water, 900Ã, Â ° CO 2
Contamination of lead paint
There are concerns about recycling of painted concrete because of the possibility of lead content. The Army Corps of Engineers' Construction Engineering Research Laboratory (CERL) and others have done research to see if lead-based paint in crushed concrete actually poses a hazard. It was concluded that concrete with lead-based paint would be used as a clean contents with no resistant cover but with some type of ground cover.
References
External links
- Construction Material Recycling Association
- Information About Benefits of Concrete Recycling
- Oder Betomeroglu's ERO Concrete Recycling Robot
- Strength and Durability Evaluation of Recycled Aggregate Concrete
- Aggregate usage of construction waste and recycling of recyclables in concrete
Source of the article : Wikipedia
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