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Exploring the Durability of Recycled Aggregate Concrete

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Exploring the durability properties of Recycled Aggregate Concrete based on some recent researches in this area. Durability issues associated with Recycled Aggregates presented and mitigation measures suggested.

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Exploring the Durability of Recycled Aggregate Concrete

  1. 1. Ahmad Shah Kakar 2 0 1 7 C E T 2 5 3 2 IIT-Delhi 2019 Mid-term project presentation Submitted to Professor Shashank Bishnoi CVL871-Durability and Repair of Concrete Structures Exploring the Durability of Recycled Aggregate Concrete
  2. 2. IIT-Delhi 2019 Introduction Natural Aggregates The world demand for natural aggregates will be 51.7 metric tons in 2019, and it will rise 5.2 percent annually.* Construction & Demolition waste Construction and Demolition Wastes (CDWs) accounts for 25–30 % of the whole waste generated in the EU (1 billion tons each year).*** Recycled aggregates Aggregates made from recyclable products. Conservation of non-renewable raw materials Less volumes of materials sent to inert waste landfills.** * Freedonia group (2016) ** Eurovia (2011) *** Silva et al. (2014)
  3. 3. IIT-Delhi 2019 Stats from EU Adapted form: Silva et al. (2014) Households 9% Mining and quarrying activities 27% Manufacturing 11% Energy and water supply sectors 10% Construction and Demolition activities 34% Other Economic activities 9% Households Mining and quarrying activities Manufacturing Energy and water supply sectors Construction and Demolition activities Other Economic activities Waste generated by economic activity in the European Union.
  4. 4. IIT-Delhi 2019 Market Growth Source: FACT.mr Incremental opportunity in the RA market by region For the Asia Pacific region excluding Japan, highest compound annual growth rate (CAGR) is expected for the 2019- 2027 period.
  5. 5. IIT-Delhi 2019 Processing Figure adapted from Marinković et al. (2011) *Portland Cement Association (2018) Recycling of concrete is a relatively simple process. It involves breaking, removing, and crushing existing concrete into a material with a specified size and quality. ACI 555 (2001) provides guidelines on processing old concrete into recycled concrete aggregates. The quality of concrete with RCA is very dependent on the quality of the recycled material used. Reinforcing steel and other embedded items, if any, must be removed, and care must be taken to prevent contamination by other materials that can be troublesome, such as asphalt, soil and clay balls, chlorides, glass, gypsum board, sealants, paper, plaster, wood, and roofing materials.*
  6. 6. IIT-Delhi 2019 Permeability 48 50 52 55 6060 65 70 75 77 68 70 75 80 82 0 10 20 30 40 50 60 70 80 90 0 Percent RA 25 Percent RA 50 Percent RA 75 Percent RA 100 Percent RA DepthofPenetration(mm) Percentage Replacement of RA w/c=0.4 w/c=0.5 w/c=0.6 Adapted from: Adnan et al. (2008) Depth of Water Penetration for 28-d for Various Percentage Replacement of RA
  7. 7. IIT-Delhi 2019 Chloride ingress Adapted from: Guo et al. (2018) Relative charge passed against coarse RA content The passed charge of RAC increases with the increase of RA replacement ratio. Total charge passed increases with the increase of coarse RA content regardless of the quality of RA. This is consistent with its effect on impermeability. There is a 95% probability that the total passed charge of RAC with 100% coarse RA content is about 2.07 times greater than that of NAC. The effect of fine RA on chloride penetration is more obvious than that of coarse RA due to the higher amount of adhered mortar and clay content.
  8. 8. IIT-Delhi 2019 Carbonation Adapted from: Silva et al. (2015) Carbonation depth for concrete prepared with 100% coarse RA content can be up to 2.5 times greater than the corresponding Natural Aggregate Concrete (NAC).
  9. 9. IIT-Delhi 2019 ASR Adapted from: (Li et al. 2006; Shehata et al. 2010) • RAC containing reactive aggregates from parent concrete will have a potential risk of ASR. • The expansion hazard of recycled aggregates obtained from ASR-affected concrete is similar to parent concrete. • the processing procedures have a significant influence on the mechanical and durability of properties of recycled aggregate concrete. • Crushing method affect the expansion of RA. • Smaller size of coarse RA will exhibit more expansion • It is possible to mitigate the influence of ASR on recycled aggregate concrete by using supplementary cementitious material (SCM).
  10. 10. IIT-Delhi 2019 Freeze-thaw Adapted from: (Medina et al. 2013; Richardson et al. 2011) Relative freeze-thaw resistance versus RA content Numerous studies show that the freeze-thaw resistivity of RAC is similar to NAC. However there are studies which reported greater strength loss for RAC comparing to NAC due to freezing and thawing. The relative freeze-thaw parameter of RAC changes with a change in replacement percentage of RA content.
  11. 11. IIT-Delhi 2019 Conclusions Ahmad Shah Kakar • The Recycled aggregates (RA) can be an appropriate alternative to natural aggregates taking into consideration the rapid growth in demand for aggregates and the restrictive environmental regulations in many countries. • However, replacing entirely the natural aggregates (NA) with RA is not recommended as far as the structural application is concerned. • The processing procedure of RA plays a significant role in its mechanical and durability properties. • The porosity and water absorption of RAC mainly depends on the amount of adhered mortar. • As the w/c ratio and RA contents increase in a concrete mix, the performance decreases from durability viewpoint. • the performance becomes even poor with higher fine RA content in comparison with coarse RA content.
  12. 12. IIT-Delhi 2019 Recommendations Ahmad Shah Kakar • Permeability and lower resistance to chloride ingress and carbonation are the main flaws of RAC; it is possible to mitigate each of these issues by making changes in materials and mix proportions. • It is recommended to incorporate mineral admixtures for improving the durability performance of RAC. • It is important to take into consideration the strength of parent concrete while replacing natural aggregates by RA. • Higher strength of parent concrete will decrease the durability issues of RAC. • It is recommended to mitigate the influence of chloride ion penetration by using fly ash or some other mineral admixture. • It is advised to incorporate fly ash and air entrainment to minimize the effect of these deterioration processes.
  13. 13. IIT-Delhi 2019 References Ahmad Shah Kakar 1. Evangelista, Luís, and Jorge De Brito. “Durability of Crushed Fine Recycled Aggregate Concrete Assessed by Permeability-Related Properties.” Magazine of Concrete Research, 2018, pp. 1–9., doi:10.1680/jmacr.18.00093. 2. Faleschin, Flora, and M.A. Zanini. “Environmental Impacts of Recycled Aggregate Concrete.”Italian Concrete Days - Giornate Aicap 2016 Congresso CTE, 2016. 3. Henry, Michael, et al. “Balancing Durability and Environmental Impact in Concrete Combining Low-Grade Recycled Aggregates and Mineral Admixtures.” Resources, Conservation and Recycling, vol. 55, no. 11, 2011, pp. 1060–1069., doi:10.1016/j.resconrec.2011.05.020. 4. Johnson, Robert, and Medhat H. Shehata. “The Efficacy of Accelerated Test Methods to Evaluate Alkali Silica Reactivity of Recycled Concrete Aggregates.” Construction and Building Materials, vol. 112, 2016, pp. 518–528., doi:10.1016/j.conbuildmat.2016.02.155. 5. Kapoor, Kanish, et al. “Durability of Self-Compacting Concrete Made with Recycled Concrete Aggregates and Mineral Admixtures.” Construction and Building Materials, vol. 128, 2016, pp. 67–76., doi:10.1016/j.conbuildmat.2016.10.026. 6. Xiao, J.-Zh., et al. “On Relationships between the Mechanical Properties of Recycled Aggregate Concrete: An Overview.” Materials and Structures, vol. 39, no. 6, 2006, pp. 655–664., doi:10.1617/s11527-006-9093-0. 7. Xiao, Jianzhuang, et al. “Mechanical Properties of Recycled Aggregate Concrete under Uniaxial Loading.” Cement and Concrete Research, vol. 35, no. 6, 2005, pp. 1187–1194., doi:10.1016/j.cemconres.2004.09.020. 8. Xiao, Jianzhuang, et al. “Seismic Behavior of Semi-Precast Column with Recycled Aggregate Concrete.” Construction and Building Materials, vol. 35, 2012, pp. 988–1001., doi:10.1016/j.conbuildmat.2012.04.062.

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