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20 pages, 6198 KiB

Open AccessArticle

Carbonation of Recycled Concrete Aggregates for New Concrete and Concrete Fines to Make Cement-Free Hollow Blocks

by Jef Bergmans, Hadi Kazemi Kamyab, Debabrata Ghosh, Peter Van Mierloo, Hilde Carens and Peter Nielsen

Sustainability 2024, 16(8), 3494; https://doi.org/10.3390/su16083494 - 22 Apr 2024

Viewed by 330

Abstract

Mineral carbonation provides a way to increase the recycling of concrete waste in added-value products, and contributes to the principles of the circular economy. At present, most concrete waste is still downcycled. The high water absorption of recycled concrete aggregates, among other factors, [...] Read more.

Mineral carbonation provides a way to increase the recycling of concrete waste in added-value products, and contributes to the principles of the circular economy. At present, most concrete waste is still downcycled. The high water absorption of recycled concrete aggregates, among other factors, impedes their recycling in the concrete industry. The quality of coarse recycled concrete aggregates (RCA) can, however, be enhanced by carbonation. Even when starting with high-grade RCA obtained from a selective demolition process, the carbonation process can decrease the water absorption of the RCA to as low as 3.0%. Concrete with a 50% replacement rate of carbonated RCA can be produced without a significant compressive strength reduction. The research further shows that carbonation can be performed at atmospheric pressure and low CO₂ concentrations (e.g., 10%). The recycled concrete fines (RCF, 0–4 mm) in combination with 25% stainless steel slag were used to make zero-cement hollow blocks (39 × 19 × 9 cm) by carbonation curing without using any hydraulic binder. The hollow blocks have a compressive strength of 15.4 MPa at the lab scale. Both technologies were demonstrated on a pilot scale. In both processes, CO₂ is immobilized in the resulting construction product. The developed production processes use less primary raw materials and cause less greenhouse-gas emissions than the production of traditional concrete products. Full article

(This article belongs to the Special Issue Sustainable Mineral-Based Materials in Construction)

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19 pages, 8385 KiB

Open AccessArticle

Explorative Study into Alkali-Activated Repair Mortars Using Blast Furnace Slag and Glass Waste

by Ivana Krajnović, Anastasija Komkova, Bryan Barragán, Gérard Tardy, Léo Bos and Stijn Matthys

Sustainability 2024, 16(2), 764; https://doi.org/10.3390/su16020764 - 16 Jan 2024

Viewed by 665

Abstract

The repair of concrete structures is increasing in prevalence. Conventional repair mortars are expensive materials rich in Portland cement (PC) and other organic and inorganic components that question their economic efficiency and carbon footprint. Alkali-activated materials (AAMs) are an eco-friendly alternative to PC [...] Read more.

The repair of concrete structures is increasing in prevalence. Conventional repair mortars are expensive materials rich in Portland cement (PC) and other organic and inorganic components that question their economic efficiency and carbon footprint. Alkali-activated materials (AAMs) are an eco-friendly alternative to PC that possess properties desirable for repair mortars. The article presents the mix design, mechanical, bond, and shrinkage properties of alkali-activated binary mortars intended for structural concrete repair. Mix optimisation based on mechanical properties of repair mortar and utilisation of glass waste (GW) is presented together with total and restrained shrinkage, pull-off bond tests, and life cycle assessment (LCA) for selected configurations. Results demonstrate good compressive and flexural strength, exceeding 45 N/mm² and 7 N/mm², an excellent pull-off bond strength (1.8–2.3 N/mm²) of the alkali-activated mortar to the concrete substrate, in spite of extensive shrinkage, with an order of magnitude of a couple of thousands of microstrains, which is also reported. Shrinkage appears to increase with the increase of the applied GW in the mixture. LCA revealed that alkali-activated mortars have up to 54% lower CO₂ eq. emissions compared to PC-based repair mortar. Full article

(This article belongs to the Special Issue Sustainable Mineral-Based Materials in Construction)

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15 pages, 2631 KiB

Open AccessEditor’s ChoiceArticle

Utilization of Waste Brick Powder as a Partial Replacement of Portland Cement in Mortars

by Zhuomin Zou, Samuel Provoost and Elke Gruyaert

Sustainability 2024, 16(2), 624; https://doi.org/10.3390/su16020624 - 11 Jan 2024

Viewed by 652

Abstract

Partially substituting Portland cement (PC) with waste brick powder (WBP) is an effective method to reduce environmental pollution. In this paper, the effects of a WBP with low pozzolanic activity on the fresh and hardened properties of blended cement with 0–40% WBP or [...] Read more.

Partially substituting Portland cement (PC) with waste brick powder (WBP) is an effective method to reduce environmental pollution. In this paper, the effects of a WBP with low pozzolanic activity on the fresh and hardened properties of blended cement with 0–40% WBP or 50% of WBP+GGBFS (by mass) were studied. Sodium sulphate (SS) (1.5 and 2.5%, related to powder mass) was used to activate the blended cement with 40% WBP or 50% WBP+GGBFS at 20 °C. Results show that the performance of blended cement is decreased with the increase in WBP content since the WBP with low pozzolanic activity mainly contributes to the dilution effect. Binary cement with 10% WBP shows a similar carbonation depth and chloride migration coefficient to PC. Ternary cement with 10% WBP and 40% GGBFS exhibits a slightly lower strength at 90 days and a lower chloride migration coefficient than PC. The SS solution increases the compressive strength at 2 days and decreases the compressive strength at 28 and 90 days. Moreover, the SS solution results in a lower carbonation depth and chloride migration coefficient, except for ternary cement with 10% WBP and 40% GGBFS, which shows a higher carbonation depth at 42 and 68 days. This paper provides a reference for the application of WBP to produce green mortars. Full article

(This article belongs to the Special Issue Sustainable Mineral-Based Materials in Construction)

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23 pages, 9286 KiB

Open AccessArticle

Numerical Study of Potential Delayed Ettringite Formation in Cemented Nuclear Wasteforms

by Abubaker Danfour, Janez Perko, Suresh Seetharam, Quoc Tri Phung, Diederik Jacques and Özlem Cizer

Sustainability 2024, 16(1), 389; https://doi.org/10.3390/su16010389 - 31 Dec 2023

Viewed by 730

Abstract

This paper presents a numerical study to investigate delayed ettringite formation (DEF) that may pose a long-term durability risk by altering the microstructure with consequent swelling leading to cracking. A chemo–thermal model is used to predict the evolution and distribution of temperature and [...] Read more.

This paper presents a numerical study to investigate delayed ettringite formation (DEF) that may pose a long-term durability risk by altering the microstructure with consequent swelling leading to cracking. A chemo–thermal model is used to predict the evolution and distribution of temperature and hydration phases in a wide range of blended cements. In particular, the influence of nuclear waste loading, waste package size, and the addition of supplementary cementitious materials (SCMs) on DEF is systematically and numerically investigated. The analyses show that higher amounts of ordinary Portland cement (OPC) and waste loadings result in higher hydration temperatures and consequently increased DEF potential by enhancing sulfoaluminate dissolution and hydrogarnet precipitation. Partial replacement of OPC with SCMs reduced hydration heat and mitigated DEF risks. The analysis indicated that the DEF evolution may be different for waste packages of different sizes due to a shift from sulfate-controlling to aluminate-controlling reactions at high temperatures. Interestingly, higher temperatures did not necessarily induce higher DEF potential due to the excessive precipitation of aluminates in the form of hydrogarnet. This research enriches our understanding of DEF’s complex behavior, providing valuable insights for engineering applications beyond civil engineering, such as nuclear waste conditioning. Full article

(This article belongs to the Special Issue Sustainable Mineral-Based Materials in Construction)

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18 pages, 7477 KiB

Open AccessArticle

Physical-Mechanical Behavior of CDW and Tire Flake Integration in Building Block Manufacturing

by Mauricio Arreola-Sanchez, Wilfrido Martinez-Molina, Hugo Luis Chavez-Garcia, Marco Antonio Navarrete-Seras, Jorge Alberto Borrego-Perez, Judith Alejandara Velazquez-Perez, Rosalia Ruiz-Ruiz, Adrian Ixcoatl Cervantes-Servin, Adriana Pelagio-Chávez and Elia Mercedes Alonso-Guzman

Sustainability 2023, 15(21), 15418; https://doi.org/10.3390/su152115418 - 30 Oct 2023

Viewed by 898

Abstract

Among the construction products manufactured with Portland cement (PC) are (in addition to hydraulic concrete) construction blocks. These elements are used as masonry materials for the elaboration of walls in all types of construction. For the elaboration of these elements, large amounts of [...] Read more.

Among the construction products manufactured with Portland cement (PC) are (in addition to hydraulic concrete) construction blocks. These elements are used as masonry materials for the elaboration of walls in all types of construction. For the elaboration of these elements, large amounts of geomaterials such as sand are utilized. The aim of this investigation was to reduce the consumption of geomaterials using block manufacturing that incorporates construction and demolition waste as a substitute for gravel and tire flakes as a substitute for sand. These blocks were characterized by their resistance in a compression test, flexion, modulus of elasticity, electrical resistivity, moisture absorption, and MEB microscopy, as well as an analysis of the unit price for different mixtures. The results show that the addition of tire flakes severely decreased the blocks’ physical-mechanical performance and increased the production costs, while the incorporation of 50% construction and demolition waste achieved a performance very close to that of the control blocks and presented improvements in the modulus of elasticity, although the costs could be higher than those for the control blocks. Full article

(This article belongs to the Special Issue Sustainable Mineral-Based Materials in Construction)

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14 pages, 2389 KiB

Open AccessArticle

Use of Sulfur Waste in the Production of Metakaolin-Based Geopolymers

by Mazen Alshaaer, Abdulaziz O. S. Alanazi and Ibrahim M. I. Absa

Sustainability 2023, 15(18), 13608; https://doi.org/10.3390/su151813608 - 12 Sep 2023

Viewed by 715

Abstract

This preliminary study introduces the incorporation and chemical stabilization of sulfur waste into a geopolymer matrix and explores the concept of material production for further environmental and engineering solutions. In this study, a novel synthesis procedure for sulfur-based geopolymers was introduced, and the [...] Read more.

This preliminary study introduces the incorporation and chemical stabilization of sulfur waste into a geopolymer matrix and explores the concept of material production for further environmental and engineering solutions. In this study, a novel synthesis procedure for sulfur-based geopolymers was introduced, and the role of sulfur in geopolymers and its optimal content to obtain a stable structure were explored. Geopolymers were synthesized by dissolving sulfur in an alkaline activator in different proportions. The alkaline solution was then mixed with metakaolin to synthesize the geopolymer matrix. Adding sulfur in amounts from 0 wt.% to 5 wt.%, compared with metakaolin, led to an increase in the compressive strength of the geopolymers from 22.5 MPa to 29.9 MPa. When sulfur was between 5 wt.% and 15 wt.%, a decrease in the compressive strength was observed to 15.7 MPa, which can be explained by defects and voids in the geopolymer’s microstructure due to the solubility of excess sulfur. Because of the incorporation of sulfur into the geopolymers, a compact and dense microstructure was formed, as reported in the SEM analysis. An XRD analysis showed that, besides quartz and analcime, a new phase, A_l2·H₁₀·O₁₇·S₃, was also formed as a result of sulfur dissolution in the alkaline activator of the geopolymers. Full article

(This article belongs to the Special Issue Sustainable Mineral-Based Materials in Construction)

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17 pages, 2155 KiB

Open AccessArticle

Experimental and Estimated Evaluation of Drying Shrinkage of Concrete Made with Fine Recycled Aggregates

by Maria E. Sosa and Claudio J. Zega

Sustainability 2023, 15(9), 7666; https://doi.org/10.3390/su15097666 - 07 May 2023

Cited by 2 | Viewed by 1303

Abstract

Using fine recycled concrete aggregates (FRCA) in concrete manufacturing points towards achieving sustainability in recycled aggregate valorisation. The higher absorption and amount of hardened cement paste of FRCA may impair concrete performance. One of the most influenced properties is drying shrinkage; this is [...] Read more.

Using fine recycled concrete aggregates (FRCA) in concrete manufacturing points towards achieving sustainability in recycled aggregate valorisation. The higher absorption and amount of hardened cement paste of FRCA may impair concrete performance. One of the most influenced properties is drying shrinkage; this is because of the extra cement paste content and higher porosity and deformability of FRCA when compared to natural sand. Thus, the influence of FRCA on shrinkage appears to depend on the quality of FRCA and how its absorption is considered during mix design. In this study, the influence of FRCA mineralogy and quality on drying shrinkage is evaluated, also considering the compensation of FRCA absorption rates. In addition, the feasibility of different models to predict the ultimate shrinkage is also analysed. The quality of FRCA and the compensation of water absorption cause different effects on concrete according to the property evaluated. The storage of water inside the FRCA particles causes no influence (or even a beneficial influence) on the shrinkage of concretes. Models used to estimate the drying shrinkage show they are still reliable with the use of FRCA. Full article

(This article belongs to the Special Issue Sustainable Mineral-Based Materials in Construction)

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Review

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21 pages, 1811 KiB

Open AccessReview

Current Knowledge and Pending Research on Sulfate Resistance of Recycled Aggregate Concrete

by Lautaro R. Santillán, Claudio J. Zega and Edgardo F. Irassar

Sustainability 2024, 16(3), 1310; https://doi.org/10.3390/su16031310 - 04 Feb 2024

Viewed by 824

Abstract

The building sector’s sustainability requires construction and demolition waste (CDW) to contribute to the circular economy. Among the CDW, recycled concrete aggregates (RA) have been mainly studied to replace natural aggregates. Still, the approval of their use in regulations and standards is slower. [...] Read more.

The building sector’s sustainability requires construction and demolition waste (CDW) to contribute to the circular economy. Among the CDW, recycled concrete aggregates (RA) have been mainly studied to replace natural aggregates. Still, the approval of their use in regulations and standards is slower. Some barriers to the adoption of RA are related to the durability of recycled aggregate concrete (RAC). However, their physical and mechanical properties have been extensively studied. The durability risks associated with sulfate attacks have been solved for conventional concrete. However, sulfate attack on recycled concrete still raises numerous unsolved questions. In this literature review, the experience of sulfate attack on RAC is compiled and analyzed using a compressive framework highlighting the most relevant aspects of the new matrix in RAC and the old matrix of RA to support its relevance to the damaging sulfate process. Suggestions for further research are presented to understand the full extent of this issue and contribute to incorporating and extending recycled aggregates into existing regulations. Full article

(This article belongs to the Special Issue Sustainable Mineral-Based Materials in Construction)

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