Towards a circular economy in the construction industry – The advantages and challenges of concrete recycling under economic, technical and ecological considerations.

ESSAY TOPIC

WE WRITE ESSAYS FOR STUDENTS

Tell us about your assignment and we will find the best writer for your paper.

Write My Essay For Me

Towards a circular economy in the construction industry – The advantages and challenges of concrete recycling under economic, technical and ecological considerations.

GUIDELINES

o Language: English

o Style: Essay / Paper, please base your work on an appropriate number of scientific sources and include a bibliography

o Quoting style: your choice, please use one quoting style consistently

o Font: Times New Roman

o Font Size: 12

o Word count: approximately 2000

o Margins: 2 cm

o Line spacing: 1.5 cm

Concrete recycling
Concrete recycling is the use of rubble from demolished concrete structures. Recycling is cheaper and more ecological than trucking rubble to a landfill.[1] Crushed rubble can be used for road gravel, revetments, retaining walls, landscaping gravel, or raw material for new concrete. Large pieces can be used as bricks or slabs, or incorporated with new concrete into structures, a material called urbanite.
The demand of construction aggregate was projected to reach 48.3 billion metric tons by 2015; the highest consumption was to be in Asia and the Pacific.[4] Demolition to make space for new structures generates a large volume of waste. The most common way to dispose this waste is to dump it in a landfill, which can pollute the air and water. This, along with the resource use of this construction, has caused more and more countries to consider the importance of recycling of demolition waste.
Benefits include:
• Conserves natural resources compared gravel mining.[5] Recycling one ton of cement can save 1,360 gallons water, 900 kg of CO
• Reduces pollution from transport to landfills and dumps[6]
• Reduces costs of transporting materials and waste[5]
• Saves landfill space[6]
• Creates employment[5]
Process[edit]
Re-purposing urbanite (concrete rubble pieces) involves selecting and transporting the pieces, and using them as slabs or bricks. The pieces can be shaped, for example using a chisel; this can be labor-intensive.
Crushing involves removing trash, wood and paper; removing metals such as rebar, using magnets and other devices, to be recycled separately;[citation needed] sorting the aggregate by size; crushing it using a crushing machine; and removing other particulates by methods such as hand-picking and water flotation.[7]
Crushing at the construction site using portable crushers is cheaper and causes less pollution than transporting material to and from a quarry. Large road-portable plants can crush concrete and asphalt rubble at 600 tons per hour. These systems normally include a side discharge conveyor, a screening plant, and a return conveyor from the screen back to the crusher for re-crushing large chunks. Compact, self-contained crushers can crush up to 150 tons per hour and fit into tighter areas. Crusher attachments to construction equipment such as excavators can crush up to 100 tons per hour and make crushing of smaller volumes economical.
Uses[edit]
Large pieces of concrete rubble (urbanite) can be used in walls as building as stones,[9] as slabs in walkways,[10] or as riprap revetments[11] to reduce stream bank erosion.[12]
Small pieces are used as gravel for new construction projects. Sub-base gravel is laid as the lowest layer in a road, with fresh concrete or asphalt poured over it.[13] The US Federal Highway Administration may use such techniques to build new highways from the materials of old highways.[14] Concrete pavements can be broken in place and used as a base layer for an asphalt pavement through a process called rubblization.[15]
Crushed concrete free of contaminants can be used as raw material (sometimes mixed with natural aggregate) to make new concrete.
Well-graded and aesthetically pleasing materials can be used as landscaping stone and mulch.[13]
Wire gabions (cages), can be filled with crushed concrete and stacked as retaining walls or privacy walls (instead of fencing).
Precautions[edit]
There have been concerns about the recycling of painted concrete due to possible lead content. The Army Corps of Engineers’ Construction Engineering Research Laboratory (CERL) and others have studied the risks, and concluded that concrete with lead-based paint should be safely used as fill without an impervious cover as long as it is covered by soil.[16]
Some experiments showed that recycled concrete is less strong and durable than concrete from natural aggregate. This can be remedied by mixing in materials such as fly ash.

Introduction: The increasing volume of construction and demolition waste associated with economic growth is posing challenges to sustainable management of the built environment. One of the largest fraction of construction and demolition waste is end-of-life concrete. The most widely applied method for end-of-life concrete recovery is road base backfilling which is considered low-grade recovery. The high-grade recycling is wet process which is washing the end-of-life concrete into clean coarse aggregate for conceret manufacturing and it is costly. As a result, a series of projects have been launched to advance the technologies for high value-added concrete recycling. Source: (Resources, Conservation and Recycling, Volume 149, October 2019, Pages 649-663).
About 374 million tonnes of construction and demolition waste were generated in 2016 (Eurostat,2019) making it is the largest waste stream. Construction and demolition is defined as a priority area in the EU according to the Circular Economy Action Plan (EC 2015) for closing the loop, while the revised Waste Framework Directive (WFD 2008/98/EC, amended 2018/851) sets a mandatory target for its recovery of 70 per cent by 2020. Despite high recovery rates, however, C&DW is often downcycled. To make an economy truly circular, it is necessary to take additional measures by focusing on the whole life cycle of construction products in a way that preserves resources and closes the loop.
There is a range of economic, technical and ecological benefits in recycling concrete rather than dumping it or burying it in a landfill. These advantages include:
• Reduced tippage and related freight charges
• Cheaper source of aggregate than newly mined
• Reduction of landfill space required for concrete debris
• Using recycled material as gravel reduces the need for gravel mining
• Increasingly, high-grade aggregate for road construction is available only at greater distances, increasing the associated economic and environmental cost impacts associated with the longer haulage distances versus using recycled aggregate
Concrete Recycling helps the environment:
1. Sustainable Sites
2. Water efficiency
3. Energy and atmosphere
4. Material and resources
5. Indoor environmentally quality
• Sustainable sites, concrete recycling can be re-used for concrete parking garages on the lower floors of the buildings. This can help to reduce the footprint of the development. In this context, the building footprint includes the building, access roads and parking area.
• Using pervious concrete payments from concrete recycling will reduce the rate and quantity of stormwater runoff becuse they increase infiltration of stormwater. Pervious concrete contains coarse aggregate, little or no fine aggregate from concrete recycling process, and insufficient cement paste to fill the voids between the coarse aggregate. Permeable paving for walkways, driveways, and other outdoor hard surfaces: Broken concrete that is carefully laid creates a stable, porous traffic surface that rainwater can filter through. This technique reduces the amount of runoff water that must be managed by storm sewer systems and helps to replenish groundwater.
• Base for new asphalt paving: Through a process called rubblization, old concrete pavement can be broken in place and used as a base layer for asphalt pavement laid over it.
• Bed foundation material for trenches containing underground utility lines: Utility trenches are oven covered with gravel to assist drainage, and crushed concrete makes a good, inexpensive substitute for gravel.
• Aggregate for mixing new concrete: Crushed concrete can replace some of the virgin (new) aggregate used in ready-mix concrete.
• Controlling streambank erosion: Larger pieces of crushed concrete placed along vulnerable stream banks or gullies can help control erosion.
• Landscaping mulch: When properly crushed and well sorted, ground concrete can replace river rock or other gravels used as ground covers and mulch.
• Fill for wire gabions: Wire cages (gabions) filled with crushed gravel can make decorative and functional privacy screen walls or retaining walls.
• Material for building new oceanic reef habitats: Large pieces of concrete carefully positioned offshore can form the foundation for coral to build new reefs.
o Source: https://www.thebalancesmb.com/recycling-concrete-how-and-where-to-reuse-old-concrete-844944
• Recycled concrete can be used for landscape and exterior design which help to reduce the heat islands. Solar radiation includes the ultraviolet as well as the visible spectrum. Generally, light-colored surfaces have a high albedo, but this is not always the case. Surfaces with lower albedos absorb more solar radiation. The absorbed radiation is converted into heat and the surface gets hotter. Where paved surfaces are required, using materials with higher albedos will reduce the heat island effect—consequently saving energy by reducing the demand for air conditioning—and improve air quality. As the temperature of urban areas increases, so does the probability of smog and pollution.
• Recycling concrete can be really a profitable addition to an aggregates quarrying organization. A road-portable recycling system can work at demolition or construction sites. This eliminates or lowers the need for landfill transporting and carrying in aggregates from a remote quarry, offering three benefits:
o Cutting trucking cost
o Conserving time and speeding up the production, cutting labor and other expenses.
o Removing or lowering complaints from neighbors, companies and city governement reagrding to traffic congestion and dirt onto the roads and streets by the noisy trucks.
o A professional road-portable recycling system working on the construction sites can squash concrete at a production rate of approximately 600 tons per hour or more. The whole system includes a rubber crusher, screening plant, side discharge conveyor and a return conveyor from the screen to the crusher inlet. An experience crew can establish on-site in less than a dozen hours, compared with other systems which can take up two or three times as long. This recycling system helps to reduce the time for the investment projects.
o Source: https://landfill-site.com/concrete-recycling.html
• Concrete recycling can help to reduce the amount of waste going into landfill sites and can help to clean up illegal dumping in the environment. As landfill costs for construction, demolition and land clearing debris continue to rise and the landfills become more heavily regulated, it makes economic sense to seek alternative means of disposal of concrete from construction and demolition operations. Sending concrete to landfills is an expensive way to dispose. Transporting such heavy material can cost as much as $25 per mile for every ton of waste. Tipping fees at landfills can be $100 per ton or more. Avoiding that cost only begins to explain the benefits of concrete recycling.
• Recycling extends the useful life of quarries and other natural reserves. Mining rock to make aggregate uses a lot of water, energy and adversely affects the ecology of forested areas and riverbeds. And like other mined materials, the earth does not have an inexhaustible supply.
• Gravel or sand recycled from construction rubble can be used in most of the same ways as virgin aggregate. It makes a lighter concrete that’s cheaper to transport. Or the crushers can leave coarser pieces suitable for such uses as sub-bases for highway construction.
• Reef restoration projects can use larger pieces of concrete as a foundation for coral.
o Source: https://sustainingourworld.com/2019/03/14/recycling-concrete-processes-and-benefits/
• Decoration: Recycled concrete can be used for building patios, walkways look like flagstone, flower beds, fire pits, retaining walls and other outdoor structures. The spaces between concrete pieces can be filled with sand or gravel or can plant ground cover that will grow nicely between them.
• The process of concrete recycling involves breaking, removing and crushing concrete from an existing pavement into a material with a specified size and quality. There are several advances have been made for the recycling to be more economical for all types of concrete payments including:
o Development of quipment for breaking concrete payments.
o Development of methods to remove steel that minimizes hand labor.
o Use and application of crushing equipment that can accommodate steel reinforcement.
o Source: https://www.concretenetwork.com/concrete/demolition/recycling_concrete.htm
• The process of concrete recycling includes 3 phases: I) Transport; II) Recycling; and III) virgin material production. The first phase considers the transportation of the EOL concrete for treatment. It varies from different technology systems. For the off-site ones, it includes the transportation of the EOL concrete from the demolition site to the recycling plant. For the in-site recycling pathways, it refers to the transportation of the processing equipment. The recycling phase is about processing EOL concrete into diverse secondary products, which can be used as raw materials for concrete manufacturing, so save virgin materials, accordingly. In order to guarantee the compatibility across different technology systems, virgin material production processes are added in several systems, which are grouped in the phase of virgin material production. It is assumed that the transport costs for the secondary products are the same as for virgin materials to their next destination.
• Challenges in concrete recycling: Compared to making virgin aggregate, recycling concrete presents some extra problems. It often contains dirt, plastic, wood or other organic material. Reinforced concrete contains steel rebars. It is necessary to remove the contaminants before the rubble can be reused. Currently, the industry does not have advanced technology yet to help to remove contaninants from the concrete. Air seperators, water flotation, even picking contaminants out by hand are considered inefficient methods produce a lot of dust, which is a health hazard for workers. https://news.nd.edu/news/why-not-recycled-concrete/
o Another big barrier to using the recycled concrete has been the variability and uncertainty in the quality and properties of the recycled materials and how this variability affects the strength, stiffness and durability of reinforced concrete structures. Kurama’s team is trying to develop an understanding of how using recycled concrete affects the behavior of reinforced concrete structures so that buildings using large amounts of recycled material can be designed for safety and to serve their intended purpose without undesirable consequences in performance.
• Conclusion: End of life concrete is the predominant in Construction and demolition waste with a high potential for reuse and recycling. End of life concrete is usually down-cycled for road base or even used in landfills. It is important to shift from less preffered end of life concrete treatment and disposal way towards methods maximizing recourse efficiency. The most advantageous technological routes are recycling on-site and producing high-value secondary products. With respect to policy implications, relative policy recommendations are avoiding the transport of waste, enacting regulations and standards for secondary raw material and enhancing the publicity and promotions of technological innovations. As we use more and more concrete, we’re also recycling more and more of it. Without concrete recycling, construction projects cannot be sustainable. https://www.sciencedirect.com/science/article/pii/S0921344919302848