| 1. |
- Fan, Xu, et al.
(författare)
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Effects of different supplementary cementitious materials on the performance and environment of eco-friendly mortar prepared from waste incineration bottom ash
- 2022
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618. ; 356
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Tidskriftsartikel (refereegranskat)abstract
- Municipal solid waste incineration bottom ash (MSWIBA) is a by-product produced by municipal waste incineration treatment. In this study, MSWIBA particle size distribution, chemical composition and particle shape were investigated and confirmed its value for reuse in the construction field and its good research potential. MSWIBA was used as fine aggregates, while coal fly ash (FA) and ground granulated blast furnace slag (GGBFS) were used as auxiliary cementitious materials to replace part of cement to manufacture the eco-friendly mortar (EFM). The effect of FA/GGBFS on the mechanical and microscopic properties of EFM with different material ratios was mainly investigated. And the analysis of the environmental friendliness and economy of this EFM was made. The results show that the combination of FA and GGBFS at the same time reduces the early mechanical properties of the mortar. However, the strength developed rapidly after 7 days, with an increase of more than 6 times the rate before 7 days. Compared with GGBFS, FA is more helpful in improving the mechanical properties of the EFM. After 28 days of full hydration, the hydration products within the EFM are numerous and well bonded to each other. Not only do these hydration products increase the mechanical strength of EFM, but they also successfully solidify the hazardous components in MSWIBA and reduce their negative environmental effects. In addition, the use of MSWIBA instead of sand for mortar preparation reduces energy consumption and CO2 emissions, and it reduces the cost by more than 50 %. This indicates that MSWIBA may perform well in the future development of the civil infrastructures. As well as recycling waste resources, it makes a valuable contribution to the development of green and sustainable building materials.
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| 2. |
- Fan, Xu, et al.
(författare)
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New applications of municipal solid waste incineration bottom ash (MSWIBA) and calcined clay in construction: Preparation and use of an eco-friendly artificial aggregate
- 2023
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Ingår i: Construction and Building Materials. - 0950-0618. ; 387
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to prepare MSWIBA as eco-friendly artificial aggregates (EFAAs) by cold bond granulation technique using a low carbon limestone calcined clay cement (LC3). The water absorption rate of EFAAs is between 14.42 and 21.82%, and the maximum compressive strength can reach 2.5 MPa. Calcined clay particles can effectively adsorb heavy metal ions after absorbing water, and EFAAs can reduce the leaching value of toxic elements in MSWIBA by more than half on average. Compared to standard OPC cementitious materials, LC3 composites only need 50% of the energy and discharge 43% of the CO2, producing a more environmentally friendly artificial aggregate. In addition, the 28-day compressive strength of concrete was higher than 30 MPa on average after applying EFAAs to concrete. The good application capability shown by EFAAs, as well as their low energy consumption and low carbon environmental characteristics, promote the better application of MSWIBA in buildings.
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| 3. |
- Jin, Hesong, et al.
(författare)
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An experimental study on the influence of continuous ambient humidity conditions on relative humidity changes, chloride diffusion and microstructure in concrete
- 2022
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Ingår i: Journal of Building Engineering. - : Elsevier BV. - 2352-7102. ; 59
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Tidskriftsartikel (refereegranskat)abstract
- Most engineering structures are exposed to various harsh environments, such as temperature fluctuations and humidity cycles, simultaneously. Additionally, moisture transfer and corrosive ion transport in concrete are driven by humidity gradients. Therefore, studying Chloride transport in concrete under constant humidity conditions is a meaningful research project. In this work, a new experimental setup was designed, and the Chloride diffusion behavior of concrete under a continuous humidity environment and NaCl immersion was investigated. Meanwhile, to accurately evaluate the internal humidity of concrete, humidity sensors were applied to the concrete. Additionally, the impacts of the water-binder ratio (w/b) and ambient humidity on the humidity diffusion coefficient, free Chloride content and bound Chloride content in concrete were evaluated. The microstructure was characterized by scanning electron microscopy, X-ray diffraction and mercury intrusion porosimetry. The results show that the content of free Chloride increases with an increasing w/b ratio. The humidity diffusion coefficient of concrete during water absorption (continuous high humidity environment) is significantly higher than that during water loss (continuous dry environment). Furthermore, under the drying condition, the Chloride content and the humidity diffusion coefficient on the concrete surface gradually increased, while during the wetting procedure, the Chloride content inside the concrete increased, and the humidity diffusion coefficient gradually decreased. However, the bound Chloride content inside the concrete is not affected by the humidity level in the environment. In the wetting environment, the calcium hydroxide in the matrix is gradually consumed, and the Chloride diffuses to the matrix to form more Friedel's salt and calcium carbonate. Moreover, lowering the w/b ratio or increasing the ambient humidity can enhance the formation of more hydrated compounds (C–S–H gel), which can reduce the total porosity and can also improve the ability of concrete to resist Chloride diffusion. Overall, this study provides a better understanding of and insight into the design and maintenance of seaside RC infrastructures.
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| 4. |
- Jin, Hesong, et al.
(författare)
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Effects of limestone calcined clay, fly ash and seawater on early hydrating behavior, mechanical properties, microscopic performance and sustainability of eco-friendly cement-based pastes
- 2024
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Ingår i: Journal of Thermal Analysis and Calorimetry. - 1388-6150 .- 1588-2926. ; 149:5, s. 2087-2107
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Tidskriftsartikel (refereegranskat)abstract
- In some remote areas or islands, the availability of freshwater for infrastructures has encountered a huge shortage, which has prompted more researchers to explore the possibility of applying seawater to design green concrete or composites. This study investigated the mechanical and microstructural properties of cement-based pastes (CBPs) mixed with fly ash (FA) and limestone calcined clay (LC2) and seawater at different curing ages. The early-age hydration, exothermic evolution, hydration phase, unconfined compressive strength (UCS), pore distribution, microstructure and sustainability of CBPs were investigated. It was observed that seawater has an accelerating effect on OPC hydration and can significantly enhance the early UCS. Combining with seawater, the pozzolanic activity of LC2/FA can result in generating more C–S–H gels. Therefore, the combination of LC2 or FA with seawater can obtain better the mechanical properties of CBPs. Besides, the micro characteristics of CBPs are observed by X-ray diffraction, thermogravimetric analysis, mercury-pressure porosimetry and scanning electron microscopy technologies, and it is revealed that seawater and SCMs play significant role in the micro morphology of CBPs due to silicate, semicarbonate, calcium aluminate, C–S–H gels. This also leads to a denser and more complex microstructure, which lowers the total porosity, obviously leads to transferring macropores into gel pores and enhances the UCS. Additionally, CBPs with FA or LC2 or seawater show about 1/6–1/5 lower embodied energy (EE), 1/6–1/5 lower embodied carbon (EC) and 1/6–1/4 lower cost than the typical CBPs with freshwater, CBPs with SCMs and seawater are even more perfect in terms of EE, EC and cost per unit UCS. Overall, this work assesses the feasibility of adding LC2/FA and seawater to CBPs, and also can provide a better insight into the applications of seawater cementitious composites for marine infrastructures.
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| 5. |
- Jin, Hesong, et al.
(författare)
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Experimental study on chloride ion diffusion behavior and microstructure in concrete under alternating ambient humidity conditions
- 2023
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Ingår i: Construction and Building Materials. - 0950-0618. ; 401
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Tidskriftsartikel (refereegranskat)abstract
- The migration of chloride in concrete in atmospheric zones is mainly influenced by climatic conditions, e.g., various dry-wet cycles in marine tidal zones, and ambient humidity is one of the most important influences. Ambient humidity also determines the moisture content in concrete, which is necessary for the diffusion or transport of chloride in concrete and can enhance the migration of chloride in micropores, thus affecting the distribution of chloride in concrete. In this study, the effects of chloride diffusion and its mechanism, and the evolution of moisture in concrete under alternating drying-wetting cycles, were investigated using an environmental moisture simulation chamber. Chloride diffusion tests were also performed to evaluate the effects of different dry-wet ratios and numbers of drying-wetting cycles on the chloride diffusion depth, chloride content and saturation in concrete. The microstructure of concrete was studied and analyzed using XRD, SEM and MIP technology. The findings showed that the saturation of concrete decreased rapidly with increasing number of wet-dry cycles and finally stabilized. Under different alternating moisture conditions, the saturation of concrete was greater, especially when the wetting time was longer. Additionally, in areas near the surface of concrete (depths of 2 mm-6 mm), the chloride content was proportional to the number of wet-dry cycles. In the interior of concrete (depth > 6 mm), when the number of drying-wetting cycles was larger, the chloride concentration was smaller. However, as the number of wet-dry cycles increased, this led to the decalcification of C-S-H gels, which resulted in the reduction in the number of C-S-H reticular gels with good crystallinity. A pore analysis showed that the cumulative pore size and the maximum probability pore size of concrete gradually increased with increasing number of wet-dry cycles, the deterioration of pore structure was more obvious, and the compactness of concrete gradually decreased, which accelerated the migration of chloride in the matrix. Overall, this study can provide reliable and valuable test data for the development and design of high-performance concrete for applications in atmospheric marine tidal zones.
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| 6. |
- Jin, Hesong, et al.
(författare)
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Iodide and chloride ions diffusivity, pore characterization and microstructures of concrete incorporating ground granulated blast furnace slag
- 2022
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Ingår i: Journal of Materials Research and Technology. - : Elsevier BV. - 2238-7854. ; 16, s. 302-321
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Tidskriftsartikel (refereegranskat)abstract
- Innovative approaches are under research to study the resistance of chloride ion penetration in concrete containing chloride ions, to minimize the impact of chloride ion penetration test errors in coastal reinforced concrete (RC), which is helpful to the design of coastal RC structures. In this study, the diffusion depth, free ion concentration and diffusion coefficient of chloride, iodide ions with different curing ages and GGBFS content were measured by the Rapid Chloride Migration Test (RCM) and Rapid Iodide Migration tests (RIM). The SEM-EDS and MIP were used to analyze the microstructures, pore size distribution and the hydrated products. The results show that the performance of GGBFS concrete against the diffusion of corrosive ions is affected by the curing age and the content of GGBFS. With the increase of GGBFS content, especially concrete with 60% GGBFS, the influence of chloride, iodide ion penetrating into concrete gradually becomes smaller. The long-age curing system is more conducive to the concrete resistance to the migration and diffusion of chloride, iodine ions. Compared with the ordinary concrete, the total porosity of concrete mixed with GGBFS is lower, the internal microstructures have fewer cracks and defects, the density is better, and the diffusion coefficient of chloride and iodide ions is also lower. In addition, using the concept of corrosive ion adjustment coefficient (conversion coefficient of diffusion between chloride ion and iodide ion) and applying the data regression analysis (DRA), it is found that there is a good quadratic parabolic function relationship between the GGBFS content and the ions adjustment coefficient.
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| 7. |
- Li, Zhenlin, et al.
(författare)
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Research on the durability and Sustainability of an artificial lightweight aggregate concrete made from municipal solid waste incinerator bottom ash (MSWIBA)
- 2023
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618. ; 365
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Tidskriftsartikel (refereegranskat)abstract
- This study chooses to use three common cementing materials, Portland cement (OPC), ground granulated blast furnace slag (GGBFS) and fly ash (FA), as the binder for the production of three artificial lightweight coarse aggregates (ALCAs) through cold bonding with municipal solid waste incineration bottom ash (MSWIBA) in which MSWIBA accounts for 70% of the total content by volume. In this study, three ALCAs were used to replace 0%, 30%, 60%, and 100% of natural aggregates used in the production of concrete. Through capillary water absorption and rapid migration of chloride ions, the effect of the replacement amount of ALCAs on the durability of concrete was explored. Additionally, in accordance with the Material Sustainability Index (MSI), a statistical analysis of the CO2 emissions, energy consumption and cost of the concrete made of the three ALCAs was carried out. Studies have shown that ALCAs can improve the Interfacial Transition Zone (ITZ) and pore structure of concrete, thereby improving the ability of concrete to resist chloride ion penetration. In addition, the use of ALCAs can reduce the cost of concrete. Among the ALCAs used in this study, those which use GGBFS and FA as adhesives (without OPC) can improve the durability of concrete the most and reduce CO2 emissions.
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| 8. |
- Liao, Chenyue, et al.
(författare)
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Numerical and experimental analysis of chloride and iodide transports in concrete under natural diffusion
- 2023
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Ingår i: Construction and Building Materials. - 0950-0618. ; 392
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the natural diffusion laws of chloride ions and iodide ions in concrete and proposes their correlations during the process of diffusion. By measuring the free ion concentration at different exposure times and diffusion depths, time-varying laws related to the ion diffusion coefficient D and surface ion concentration Cs were proposed. The linear proportional relationship between two kinds of ions is explored and fills the relevant research gaps. Natural diffusion models of ions are established via the finite element software COMSOL and the adjustment parameters K and λ are innovatively proposed. Thus, this enables the effective conversion of the ion resistance permeability coefficients measured by the RCM and RIM methods, especially for the concrete containing chloride. The results of numerical calculation and experimental measurement have a strong correlation. Furthermore, a two-dimensional concrete model with different aggregates is used to simulate the ion diffusion characteristics. It is confirmed that the increase in aggregate volume ratio and tortuosity inhibited ion diffusion, and the ion concentration in the local area was greatly reduced.
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| 9. |
- Liu, Jun, et al.
(författare)
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Alkali-activated binders based on incinerator bottom ash combined with limestone-calcined clay or fly ash
- 2022
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618. ; 320
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates the feasibility of improving the properties of alkali-activated bottom ash (AABA) binders by incorporating limestone-calcined clay (LC2) or fly ash (FA) with the aim of treating and utilising bottom ash in a large-scale as a potential resource for construction materials. Experimental results revealed that increasing the substitution with LC2 or FA in the AABA binders increased both the compressive strength and the immobilization capacity of heavy metal when compared to the pure AABA binders. Given a Na2O content of 5%, the compressive strength of the AABA binder with 30% bottom ash substituted by FA was almost 200% higher than that of the pure AABA binder. However, further increase in the Na2O dosage did not necessarily lead to higher compressive strength, which was found to be controlled by the volume fraction of air voids and large pores. When greater Na2O dosages were employed, i.e., 6 % and 7 %, LC2 was found to be more useful in improving the properties of AABA binders than FA. Furthermore, the substitution of bottom ash with FA resulted in the formation of N-A-S-H gels, whereas the substitution with LC2 led to the formation of more C-A-S-H gels. Finally, the immobilization capacity appeared to be influenced by many factors, such as hydration products, capillary pores and different types of heavy metals.
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| 10. |
- Liu, Jun, et al.
(författare)
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Electrically driven ionic transport in the RCM and RIM: Investigations based on experiments and numerical simulations
- 2022
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618. ; 331
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Tidskriftsartikel (refereegranskat)abstract
- In this work, the rapid chloride migration test (RCM) and the rapid iodide migration test (RIM) were utilized to investigate ionic transport in concrete with the aid of an externally applied electric field. Unlike most existing work, this study establishes computational models of ionic transport in chloride-contaminated and chloride-free concrete. The model is validated by the consistency between the numerical and experimental chloride profiles. It is found that the chloride migration depth in the RCM test is obviously affected, and the results for chloride-contaminated concrete are 50% larger compared with those for chloride-free concrete. However, the difference between the two kinds of concretes is only 5% when measured using the RIM test. Thus, the results of the RIM test are more accurate and provide a better choice for applications to characterization of chloride-contaminated concrete.
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