Recycled Concrete Aggregate in Construction Part III

Using recycled concrete aggregates (RCA) for pavements is crucial to achieving sustainability. Implementing RCA for new pavement can minimize carbon footprint, conserve natural resources, reduce harmful emissions, and lower life cycle costs. Compared to natural aggregate (NA), RCA pavement has fewer comprehensive studies and sustainability assessments.

1. use of RECYCLED CONCRETE AGGREGATE IN CONSTRUCTION CIVIL ENGINEERING DEPARTMENT ADITYA RANJAN PATRA ( TRANSPORTATION ENGINEERING)

2. Contents Introduction SOURCES OF RCA Process of RCA VARIOUS TEST CONDUCTED ON AGREEGATE Application of RCA Advantages & disadvantages of RCA Conclusion references

3. INTRODUCTION: To achieve sustainable issue in construction area, researchers and companies focus on using waste concrete as a new construction material. It is called recycled aggregate which can be produced by concrete crusher. The aggregates are categorized by size as coarse and fine aggregate. Recycled concrete aggregate is an popular replacement for natural stone aggregate. R ecycled concrete aggregate has a proportional mortar which attached to aggregate, it gives a higher porosity and a lower strength than the normal concrete.

4. SOURCEs OF AGGREGATE : The enormous quantities of demolished concrete are available at various construction sites. Many old buildings, concrete pavement, bridges and other structures have overcome their age and limit of use due to structural deterioration beyond repair and need to be demolished. The structures, even adequate to use are under demolition because they are not serving the needs in present scenario. Structures are turned into debris resulting from natural disasters like earthquake, cyclone and floods etc.

5. PROCESS : For the production of the RC without impurity in the required gradation, a production plant has to be used. Leftover concrete is taken to a recycling facility where it is broken into small pieces using grinder machines. This can either be stationary or mobile with same set-up. Crushing Pre-sizing Sorting Screening

6. VARIOUS TEST CONDUCTED ON AGREEGATE Shape and size - The size of fine aggregates is defined as  4.75mm or smaller . That is, aggregates which can be passed through a number 4 sieve, with a mesh size of 4.75mm. Fine aggregates include things such as sand, silt and clay. Crushing - Aggregate crushing value is defined as the percentage by weight of the crushed (or finer) material obtained when the test aggregates are subjected to a specified load under standardized conditions. Abrasion - Abrasion Test is the measure of aggregate toughness and abrasion resistance such as crushing, degradation and disintegration. The percentage wear of the sample aggregates due to rubbing with steel balls is determined and is known as Los Angeles Abrasion Value.

7. Cont.. Impact - Test  of the ability of a material to withstand sudden load. Aggregate Impact Value = (B/A) X 100 where A = weight in g of saturated surface - dry sample, B = weight in g of fraction passing through 2.36 mm IS Sieve. Water absorption - Aggregates having more absorption are more porous in nature and are generally considered unsuitable, unless found to be acceptable based on strength, impact and hardness tests. Specific gravity - Specific Gravity is defined as the ratio of Weight of Aggregate to the Weight of equal Volume of water. The specific gravity of an aggregate is considered to be a measure of strength or quality of the material. Aggregates having low specific gravity are generally weaker than those with high specific gravity.

8. Application of recycled concrete aggregate

9. Road - It is the aggregate used for road construction. It is size of 40 mm, 50mm, 60 mm or as per design requirement. Drainage - It also improves drainage, preventing water from pooling beneath the concrete. Ground improvement - Recycled aggregates from crushed concrete have a higher percentage of water absorption than natural aggregates due to the mortar adhered to the aggregates' surface, which increases the void ratio of the recycled aggregate. Others - They are commonly used as a base for roads, parking lots, and driveways, as well as backfill material and shoulder stone. This product is typically used for site stabilization, bottom layer road base, and backfill.

10. PARTICULARS VALUES Natural Aggregate Recycled Coarse Aggregate 1 Specific Gravity 2.4-3.0 2.35-2.58 2 Water Absorption 0.29%-0.3% 0.3%-0.32% 3 Bulk Density 1678.2 KN/m3 1469.8 KN/m3 4 Crushing Values 18.4% 36.3% Impact Values 17.65% 35.2% Specific gravity – The specific gravity of aggregate used for construction 2.5-3.0 with an average value 2.68. which considered as the indication of strength. Water absorption – water absorption shall not be more than 0.6 per unit by weight. Bulk density – it is indicator of compaction. Calculated dry weight with respect to its volume. Bulk density of aggregate that is commonly used in normal weight concrete in between 1200-1750 kg/ cubm . Crushing and impact value – As per IS2386 the crushing & impact value should not exceed than 30% for wearing surfaces and 45% for other than wearing surfaces.

11. Advantages: Save environment Save energy Reduce cost Reduce the demand of natural aggregate. Disadvantages: Lack of specification and guidelines. Less quality as it is a waste material. Benefits: Using recycled material as gravel reduces the need for gravel mining. Using recycled concrete as the base material for roadways reduces the pollution involved in trucking material.

12. Conclusions: The physical properties of recycled aggregates make them ideally suited for road base and sub-base. This is because of their physical properties which means less cement is require making them suited for sub-base use. This is in addition to the cost benefits accrued by developers in the process. Recycle & reuse is an appropriate solution to problems of dumping hundred of thousands of tons of demolition wastes. However more research and initiation of project for application of recycled concrete aggregate is started for modifying design codes, Specifications & procedure for use of recycled concrete aggregate.

13. R EFERENCES: Parekh D. N. and Dr. Modhera C. D., “Assessment of recycled aggregate concrete”, Volume II, Issue 1, pp. 1-9, March 2011. Jitender Sharma, Sandeep Singla, “Study of Recycled Concrete Aggregates”, Volume 13, pp. 123-125, July 2014. RIMT-IET, Mandi Gobindgarh , PTU, India. Animesh Awasthi, Gourav Soni , Ram Bharosh , “Study of Recycled Aggregate Concrete as Partial Replacement for Cement”, Volume 4, Issue 2, pp. 239-245, 2018. https://www.slideshare.net/neelanjan06/recycled-aggregate-concrete https://www.researchgate.net/publication/222515274_Recycled_concrete_aggregates https://www.sciencedirect.com/science/article/pii/S2352710221000528