| 1. |
- Kadawo, Abdinasir, et al.
(författare)
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Combination of LCA and circularity index for assessment of environmental impact of recycled aggregate concrete
- 2023
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Ingår i: Journal of Sustainable Cement-Based Materials. - : Informa UK Limited. - 2165-0373 .- 2165-0381. ; 12:1
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Tidskriftsartikel (refereegranskat)abstract
- Multidisciplinary approach is used to evaluate concrete with recycled concrete aggregates (RCA) from technical, environmental impacts and product circularity perspectives. Two RCA replacements investigated, RAC50: fine aggregates; RAC100: both coarse, fine aggregates. Reference, recycled concretes have same cement content, similar workability and compressive strength requirement, proven experimentally. RCA is sourced from pre-fab element discards of a Swedish plant, the logistical alternatives requiring environmental impact analysis. Alternatives are RCA crushing at plant and crushing at a different location including transportation. LCA shows transportation is second largest contributor after cement in all impact categories. RAC alternatives show lower total impact than reference concrete due to RCA replacement. A circularity index for concrete based on economic value of recirculated aggregates; supplements LCA for sustainability reporting. Circularity index results: RAC100 > RAC50 > RC. Combining circularity index with LCA helps optimize recycling process with regard to amount of recycled material and logistics respectively.
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| 4. |
- Sadagopan, Madumita, 1987-, et al.
(författare)
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A modified pycnometer method to determine the water absorption of combined crushed concrete aggregate fractions
- 2019
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Ingår i: International Conference on Sustainable Materials, Systems and Structures (SMSS2019). - 9782351582176 ; , s. 286-292
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Konferensbidrag (refereegranskat)abstract
- Crushed Concrete Aggregates (CCA) as fine and coarse aggregates in new concrete helps achieve closed-loop recycling. Assessment of workability, mechanical properties and durability of concrete demands knowledge of the water absorbed by the CCA. The EN 1097-6standard method is difficult to execute due to the presence of entrapped air and CCAsedimentation while performing water absorption experiment for fine CCA. Additionally, the assessment of Saturated Surface Dry (SSD) state seems operator specific and nonreproducible;moreover, giving water absorption measurement only at 24 hours. However, findings from this paper show measurements at 15 minutes is influential for concrete workability. The modified pycnometer method analyses the water absorption of a combined fraction consisting of coarse and fine CCA as proportioned in a given concrete recipe. Furthermore, sedimentation and entrapped air are prevented by pre-soaking the CCA in a solution of distilled water and poly-carboxylate based superplasticizer before commencing the experiment. Ultimately, the combined fraction is drained to SSD condition by vacuum filtration, which is easy to handle by professional operators. In this way, the water absorption development is measured from starting point to 24 hours for the combined fraction to determine the appropriate water amount to saturate CCA during concrete mixing.
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| 5. |
- Sadagopan, Madumita, 1987-, et al.
(författare)
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Effects of Slag Addition and Mechanical Pre-Processing on the Properties of Recycled Concrete in Terms of Compressive Strength and Workability
- 2021
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Ingår i: Nordic Concrete Research. - : Walter de Gruyter GmbH. - 0800-6377 .- 2545-2819. ; 64:1, s. 11-29
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Tidskriftsartikel (refereegranskat)abstract
- Concrete waste as crushed concrete aggregates (CCA) in structural concrete prolongs the technical life of the reference concrete accomplishing closed loop recycling. CCA concrete reaches the reference concrete compressive strength and workability by the densification of CCA and cement paste. Our previous study demonstrates CCA densification by mechanical pre-processing, aggregate quality improvements discerned by increased packing density giving reference concrete strength and workability. This study addresses paste densification with blast furnace slag (GGBS) to replace 30 (wt.%) of Portland cement at reference concrete w/b ratio 0.5 and a lower w/b 0.42. Two CCA replacements are investigated: fine aggregates, CCA50; overall aggregate replacement, CCA100. Compressive strength results show that both CCA50, CCA100 mixes achieve reference values at w/b 0.42, only CCA100 achieves reference value at w/b 0.5 as a climate-optimized concrete. The CCA50 mix-w/b 0.5 reaches reference strength when paste densification by GGBS is combined with CCA densification from mechanical pre-processing of aggregates. The 7-day strength of CCA100 with GGBS increases by 11% by mixing with pre-soaked GGBS. Statistical analysis of CCA100 strength results shows significant improvements with GGBS compared to mechanical pre-processing. Significant improvements are possible in CCA50 mix for a combination of mechanical pre-processed aggregates and GGBS replacement.
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| 6. |
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| 7. |
- Sadagopan, Madumita, 1987-, et al.
(författare)
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Improving recycled aggregate quality by mechanical pre-processing
- 2020
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 13:19
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Tidskriftsartikel (refereegranskat)abstract
- Concrete with crushed concrete aggregates (CCA) shows lesser compressive strength than reference concrete with natural aggregates. The goal of this study is to improve the strength of structural concrete with 53% and 100% CCA replacements without increasing the cement content. Thus, improvements in CCA quality are induced by combining mechanical and pre-soaking pre-processing techniques. Mechanical pre-processing by rotating drum is separately pursued on fine and coarse CCA for 10 and 15 min respectively. Results show, adhered mortar content and CCA water absorption reduces as pre-processing duration increases. Pre-processing influences CCA particle grading, flakiness index, shape index, void-content, unit-weight and density, jointly seen as packing density, which increases with pre-processing duration. Water amount to pre-soak CCA before concrete mixing is stable despite grading modifications, due to reduced water absorption resulting from mechanical pre-processing. Compressive strength and workability for pre-processed CCA50 and CCA100 concrete are comparable to reference concrete and show similar trends of improvement with packing density. Packing density markedly shows the quality improvements induced by pre-processing on CCA, maybe considered as one of the quality assessment indexes for CCA. Packing density should be investigated for other recipes to see the stability of the trend with workability and compressive strength. © 2020 by the authors.
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| 8. |
- Sadagopan, Madumita, 1987-
(författare)
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Life Cycle Assessment: Concrete Hollow Core Slab
- 2013
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Rapport (populärvet., debatt m.m.)abstract
- A report about the environmental impacts involved in the use of recycled concrete waste as aggregates in new concrete. The environmental impacts were assessed based on a simple LCA using a prefabricated concrete producing company in Sweden as a case study. The results of the LCA revealed that major environmental impacts arised from the crushing and extraction processes as these were diesel fuel intensive. Comparatively, the use of recycled concrete as aggregates in new concrete saw a reduction in the environmental impacts as the need for extraction had reduced with the introduction of recycled aggregates.
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| 9. |
- Sadagopan, Madumita, 1987-, et al.
(författare)
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Modified pycnometer method to measure the water absorption of crushed concrete aggregates
- 2020
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Ingår i: Journal of Sustainable Cement-Based Materials. - : Taylor and Francis Ltd.. - 2165-0373 .- 2165-0381. ; 9:5, s. 259-269
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Tidskriftsartikel (refereegranskat)abstract
- The water absorption of crushed concrete aggregates (CCA) has a major influence on concrete workability. In order to determine the water absorption of CCA, a more porous material than natural aggregates, modifications to the standard pycnometer method are proposed as: (1) Water absorption is measured on a combined fraction CCA consisting of fine and coarse aggregates proportioned according to concrete recipe. (2) The CCA is pre-processed to mitigate sedimentation. (3) Saturated surface dry condition of aggregate is assessed by vacuum filtration and ocular technique. Water absorption development is measured at 0 min, 15 min, and 24 h. About 90% of the 24-h water absorption occurs in 15 min, value which is introduced in the concrete recipe; slump flow and compressive strength are determined. The modified pycnometer method shortens test duration, is operator insensitive and gives reliable water absorption result for CCA leading to concrete workability fitting industrial application. © 2020, © 2020 The Author(s).
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