Construction and demolition waste are increasing in large amount and now it is employed as a replacement of coarse aggregate in concrete, use of these type of waste do offer strength in concrete or it will go down in the reverse manner?
Hi, it is true that many researches are conducted on that but results suggested recycle aggregate is very effective on low strength concrete. For Low cost building, it is easily achieved up to 34 MPa. But due to its( Recycle aggregate) low impact and crushing strength and used materials there are lots of uncertainty. But recycle waste are definitely abundant materials and there should be a effective use. Obviously low strength concrete can be a solution.
It all depends on what type of aggregate was added, it depends whether it was concrete or granulate obtained from crushing bricks, blocks or stone.
Usually using aggregates saves 80% of imported stones. Doha - Al-Raya: The General Authority for Qatar Standards and Metrology discussed with the government and private agencies the quality of the rubble after recycling and the possibility of its application in some building and road projects.
When concrete structures are demolished or restored, concrete recycling is becoming an increasingly popular way to take advantage of rubble. It was customary in the past to transport concrete to landfills for disposal, but recycling bears a number of benefits that make it a more attractive option in our times with more environmental awareness and environmental laws and a desire to reduce construction costs
Recent statistics indicate that the growing demand for total construction may reach 48.3 billion metric tons by 2015 as consumption reaches its highest levels in Asia and the Pacific. The increasing demand for concrete means the construction of more new buildings after the demolition of old buildings, which leads to the generation of a large amount of construction and demolition waste as a result of economic growth. However, the most common way to dispose of this waste is to dispose of it in landfills. Without proper maintenance, landfills can cause many environmental problems such as air and water pollution. This, coupled with the shortage of resources caused by growth in the construction sector, has led to an increase in the number of countries that have begun to consider the importance of recycling construction and demolition waste.
That will depend on how the design composition is. But usually resulting in minimal strength overall.
Depends on what you are using. If you are using Recycled concrete aggregate (RCA) it gives acceptable strength. and if you are using Recycled Aggregate (which contains C&D waste, bricks tiles etc.) it gives low strength. for more guidelines you can refer to IS 383:2016.
Strength of concrete using Construction Demolished waste ( may be called as recycled aggregates) depends on type of aggregates , size, shape , cement content and water cement ratio. Normally , achievement of compressive strength up to 40 MPa is possible. However, sorting of suitable aggregates form the demolished waste is important. Bond strength between aggregates in concrete is important. Due to rough surface improvement in bond strength may be observed but failure in previously adhered mortar which may have low strength , may affect strength results. Maintaining homogeneous mix by proper mix design and proper compaction of green concrete will help to improve strength of concrete made from recycled aggregates.
For demolition residues to be added to concrete, laboratory tests must be carried out, specific to materials, strength and others. It is not a managerial decision, but a technical one.
Hi Bala
Replacement of coarse aggregate with the recycled coarse aggregates in concrete reduces the concrete performance generally due to the old attached mortar with the recycled aggregates. To overcome the inferior performance of recycled aggregate concrete, various techniques have been adopted by the researchers to remove or strengthen the old adhered mortar. To remove the adhered mortar of recycled aggregates, techniques such as mechanical grinding, heat grinding, pre-soaking in water and pre-soaking in acid have been explored. Similarly, treatment of recycled aggregates through polymer emulsion, pozzolan slurry, calcium carbonate bio deposition, sodium silicate solution and carbonation can strengthen the adhered mortar. However, every treatment method has pros and cons with respect to cost, practicality and its environmental impacts.
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