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  • 1.
    Oliva Rivera, Alexander
    et al.
    University of Borås, RISE Research Institutes of Sweden, Infrastructure and Concrete, Technology, Material Design , Brinellgatan 4, 50115 Borås , Sweden.
    Malaga, Katarina
    Högskolan i Borås, Akademin för textil, teknik och ekonomi. University of Borås, RISE Research Institutes of Sweden, Infrastructure and Concrete Technology , Brinellgatan 4, 50115 Borås , Sweden.
    Mueller, Urs
    Luleå University of Technology, Schwenk Sverige AB , Hyllie Stationstorg 31, 21532 Malmö , Sweden.
    Accelerated Carbonation of Binders Containing SCM at High CO2 Concentration2023Ingår i: Nordic Concrete Research, E-ISSN 2545-2819, Vol. 69, nr 2, s. 1-10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Accelerated carbonation of recycled concrete aggregates (RCA) could be an efficient way to reduce the carbon footprint. High CO2-concentration under optimal relative humidity could accelerate the CO2 binding capacity of the hydrated cement paste in the RCA. The latter is the topic of this paper. The study looks into the forced carbonation of crushed cement pastes as a basis to understand the CO2 uptake in relation to various binders containing supplementary cementitious materials (SCM) such as fly ash (FA) and ground granulated blast furnace slag (GGBS). Samples include three cement pastes: ordinary Portland cement, substitution rate of 30 % FA and 50 % GGBS respectively at a water/binder ratio of 0.45. All binders were graded to 0/2, 2/4 and 4/8 mm fraction sizes and preconditioned before exposed to CO2 concentration of 10 % under controlled temperature at 20 °C and 65 % RH. All tested binders presented a high CO2 uptake within the first hours of exposure with clear differences concerning the fraction sizes and the composition. The phase content before and after carbonation was observed by X-ray diffraction and the portlandite and calcite were quantified by thermogravimetric analyses and their derivative curves for fraction size 4/8 mm.

     

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  • 2.
    Oliva Rivera, Alexander
    et al.
    Department of Infrastructure and Concrete Technology, RISE Research Institutes of Sweden, Gothenburg, Sweden.
    Suchorzewski, Jan
    Department of Infrastructure and Concrete Technology, RISE Research Institutes of Sweden, Gothenburg, Sweden.
    Malaga, Katarina
    Högskolan i Borås, Akademin för textil, teknik och ekonomi. Department of Infrastructure and Concrete Technology, RISE Research Institutes of Sweden, Gothenburg, Sweden.
    Potential of CO2-Storage in Recycled Concrete Aggregates by Accelerated Carbonation2023Ingår i: SynerCrete 2023: International RILEM Conference on Synergising Expertise towards Sustainability and Robustness of Cement-based Materials and Concrete Structures / [ed] Agnieszka Jędrzejewska, Fragkoulis Kanavaris, Miguel Azenha, Farid Benboudjema, Dirk Schlicke, Springer, 2023, Vol. 44, s. 604-615Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    To reduce the carbon footprint of cementitious materials and resource extraction intensity of concrete industry (natural gravel or crushed rock), usage of recycled concrete aggregate (RCA) in concrete and as a CO2-sink by accelerated carbonation is widely investigated. Implementation of this technology will not only reduce the climate impact, but also improve the performance of the RCA creating a truly circular material. At first, some locally available recycled concrete was crushed in different fractions and characterized. To quantify the adhered mortar/aggregate content ratio on the as-received RCA, an image analysis method (IAM) was introduced. The analysis revealed that the adhered mortar accounts for around 40% of the RCA independently on the fraction. The results of IAM of as-received RCA were used to evaluate its remaining potential of CO2-storage. The effect of accelerated carbonation on the quality of RCA was evaluated by means of water absorption. The carbonation was determined by means of thermogravimetric analyses (TGA) and its derivative curve (DTG) resulting in similar CO2-storage for coarse fractions 4/8 mm and 8/16 mm under the accelerated carbonation conditions.

  • 3.
    Sadagopan, Madumita
    et al.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Malaga, Katarina
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Lundin, Magnus
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Nagy, Agnes
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Effects of Slag Addition and Mechanical Pre-Processing on the Properties of Recycled Concrete in Terms of Compressive Strength and Workability2021Ingår i: Nordic Concrete Research, ISSN 0800-6377, Vol. 64, nr 1, s. 11-29Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 4.
    Sadagopan, Madumita
    et al.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Malaga, Katarina
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Nagy, Agnes
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Improving Recycled Aggregate Quality by Mechanical Pre-Processing2020Ingår i: Materials, Vol. 13, nr 19Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 5.
    Sadagopan, Madumita
    et al.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Malaga, Katarina
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Nagy, Agnes
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Modified pycnometer method to measure the water absorption of crushed concrete aggregates2020Ingår i: Journal of Sustainable Cement-Based Materials, ISSN 2165-0373, E-ISSN 2165-0381Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 6.
    Sadagopan, Madumita
    et al.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Malaga, Katarina
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Nagy, Agnes
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    A modified pycnometer method to determine the water absorption of combined crushed concrete aggregate fractions2019Ingår i: International Conference on Sustainable Materials, Systems and Structures (SMSS2019): Novel Methods for Characterization of Materials and Structures / [ed] Gabrijel I, Grosse C, Skazlić M, 2019, s. 286-292Konferensbidrag (Refereegranskat)
    Abstract [en]

    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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  • 7.
    Sadagopan, Madumita
    et al.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Nagy, Agnes
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Malaga, Katarina
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    RE:Concrete- Study on Concrete Recycling in Sweden2017Ingår i: Nordic Concrete Research: Proceedings of XXIIIth Nordic Concrete Research Symposium Aalborg, Denmark 2017 / [ed] Marianne Tange Hasholt, Oslo, 2017Konferensbidrag (Refereegranskat)
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  • 8.
    Sadagopan, Madumita
    et al.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Nagy, Agnes
    Malaga, Katarina
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    RE:Concrete- Study on Recycling of Concrete in Sweden2017Ingår i: Nordic Concrete Research, ISSN 0800-6377, nr 56, s. 83-99Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Sweden’s concrete waste is recycled for use in low-utility purposes such as in the construction of sub-bases in roads but hardly as aggregates in new concrete. To analyse the potential for high-utility recycling, a literature study was conducted on the regulatory instruments, building standards, production and properties of recycled concrete aggregates and the recycled aggregate concrete for Sweden and European countries. Results urge statistics to quantify recycled concrete; regulations like source sorting of waste and selective demolition could potentially optimize recycled aggregate production. Also, the compressive strength of recycled concrete aggregate’s parent concrete influences the properties of the new concrete.

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1 - 8 av 8
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