| 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
-
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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| 11. |
- Liu, Jun, et al.
(författare)
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Exploring the carbon capture and sequestration performance of biochar-artificial aggregate using a new method
- 2023
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 859
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Tidskriftsartikel (refereegranskat)abstract
- To achieve the ambitious goal of carbon neutrality, more carbon sequestration channels need to be developed. In this study, we tried to combine biochar with cold-bonded artificial lightweight coarse aggregate (ALCA) which is made from municipal solid household waste incineration bottom ash (MSWIBA).The strong carbon capture ability of biochar was used to attract external CO2 into the interior of ALCAs, which combined with CaO in MSWIBA to form CaCO3 to achieve the effect of chemical carbon sequestration. The total carbon sequestration and carbon sequestration rate of biochar-ALCAs were quantified by a self-designed CO2 concentration change test box, the physical and mechanical properties of biochar-ALCAs were investigated, as well as the changes before and after carbonization. The results showed that biochar and ALCAs had good synergistic carbon sequestration ability. The total carbon sequestration of biochar-ALCAs could reach 30.58–33.06 kg/ton. The carbon sequestration efficiency could reach 70.2 % and 84.9 % at 28 d/56 d in a low CO2 concentration environment (0.05 % VOL). In addition, the water absorption of biochar-ALCAs decreased by 4.3 %–13.9 %, the apparent density increased by 0.9 %–2.8 %, and the strength increased by 4.3 %–7.0 % after carbon sequestration, and the physical and mechanical properties were significantly improved. The purpose of this paper is to investigate the synergistic carbon sequestration of biochar in combination with ALCAs and to quantitatively assess its ability to solidify low concentrations of CO2 in the natural environment. A new test apparatus and test method were designed for this purpose. This paper may contribute for an important advance on the preparation of recyclable cement-type composites able to capture and solidify CO2 from the natural environment.
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| 12. |
- Liu, Jun, et al.
(författare)
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Influence of deicing salt on the surface properties of concrete specimens after 20 years
- 2021
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618. ; 295
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Tidskriftsartikel (refereegranskat)abstract
- The low temperature of ice and snow all year round in Sweden leads to the common use of deicing salt to melt the roads, but the splash of the deicing salt on the reinforced concrete (RC) on both sides of the roads brings about the deterioration of the durability of RC components. The chloride ions diffusion coefficient is an important parameter to evaluate the durability of RC. By adopting the rapid chloride migration method (RCM) and replacing chloride ions with iodide ions, the samples of concrete blocks exposed on the side of the highway for 20 years were taken. This is directly beneficial to study the influence of the type, content, and water-cement ratio of mineral additions on the diffusion and distribution of iodide ions in concrete and analyze the surface environmental effect depth of concrete. The influence of chloride ions on the pore structure and microscopic morphology of concrete also were studied by scanning electron microscope-energy dispersive spectrum and X-ray diffractometer. The results show that as the water-cement ratio increases, the surface environmental effect depth of concrete and the diffusion area of iodide ions gradually increase. Silica fume and ground granulated blast furnace slag (GGBF slag) have an impediment to the diffusion of iodide ions, especially with the high volume of the GGBF slag (about 50%), the diffusion of iodide ions is very low. In general, this research is helpful to provide some empirical ideas and suggestions for the manufacturing and durability design of concrete structures in marine environments or deicing salt road environments.
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| 13. |
- Liu, Jun, et al.
(författare)
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Investigation of using limestone calcined clay cement (LC3) in engineered cementitious composites: The effect of propylene fibers and the curing system
- 2021
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Ingår i: Journal of Materials Research and Technology. - : Elsevier BV. - 2238-7854. ; 15, s. 2117-2144
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Tidskriftsartikel (refereegranskat)abstract
- Limestone calcined clay cement (LC3) is a new type of low-carbon cement that can reduce energy consumption and carbon dioxide emissions while meeting the performance requirements of ordinary cement. In this study, polypropylene (PP) fibers were mixed into limestone calcined clay cement-based materials to make new low-carbon ECCs. In this study, a total of 24 sets of specimens were designed for 4 groups of curing ages and 6 types of mix ratios. The compressive load–displacement data were measured the compressive curve characteristics were analyzed then, a compressive constitutive model of the composites was deduced and obtained. Through XRD, SEM-EDS and MIP experiments, the reasons and laws of the compressive strength ranges of adding PP fibers and LC3 to engineered cementitious composites (LC3-PP-ECCs) are further explained from the perspective of the pore size, microstructures and hydration products. The results show that, after 28 days, the compressive strength values of LC3-PP-ECCs generally decreases with increasing PP fiber content and the combined effect of PP fibers and hydration products causes the compressive strength of LC3-ECCs with 0.5% PP fibers to drop sharply. In addition, the specimens showed better properties in terms of toughness, ductility and energy absorption. However, in the microstructures, the addition of PP fibers will cause more internal defects and flaws. This results of this study can provide some theoretical experience and technical support for the engineering application of LC3-ECCs.
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| 14. |
- Liu, Jun, et al.
(författare)
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Mechanics, hydration phase and pore development of embodied energy and carbon composites based on ultrahigh-volume low-carbon cement with limestone calcined clay
- 2022
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Ingår i: Case Studies in Construction Materials. - : Elsevier BV. - 2214-5095. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- Engineered cement-based composites exhibit excellent deformability, mechanical behavior, fresh performance and durability. However, the traditional cement-based composites incorporating high volume ordinary Portland cement would lead to high carbon footprint. In this study, a new and eco-efficient engineered cement-based composites was designed by incorporating Polypropylene fibers (PPF) and eco-friendly cement with limestone calcined clay (LC3-ECCs). The LC3-ECCs were analyzed and discussed in terms of mechanical properties, microscopic morphology, hydration products and porosity. The study found that the 28-days compressive behavior was above 44.2 MPa, and the flexural strength remained above 4.8 MPa. Because of the formation and gathering of highly polymerized compound products (C-S-H gel, C-A-S-H gel) in the matrix and plenty of ettringite, the bonding effect between PPF and LC3 cementitious matrix is better. Additionally, the LC3-ECCs with 1.5 % volume content of PP fiber showed less porosity beneficial to the mechanical behavior. This study suggests that low-carbon LC3 has the potential to be successfully utilized as the alternative to OPC and is suitable to design sustainable ECCs, and this low-carbon construction product can be also generally applied into some area with the abundant clay sources.
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| 15. |
- Liu, Jun, et al.
(författare)
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Novel recycling application of high volume municipal solid waste incineration bottom ash (MSWIBA) into sustainable concrete
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 838
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Tidskriftsartikel (refereegranskat)abstract
- Since municipal solid waste incineration bottom ash (MSWIBA) contains some heavy metals that are harmful to the groundwater and soil, this study proposes an effective and new approach to deal with high-volume MSWIBA. Selecting 70% MSWIBA, 10% ordinary Portland cement (OPC), 10% fly ash/ground granulated blast furnace slag (FA/GGBFS), and 1% volume of polypropylene (PP) fiber as the raw materials, this project designed and manufactured cold-bonded fiber aggregates (CBFAs) and applied them into sustainable concrete. It was found that the water absorption of CBFAs was between 12 and 14%, the bulk density was between 900 and 1100 kg/m3, and the compressive strength of single particle was greater than 1.8 MPa. And it was found that the mechanical strength and bulk density of CBFAs were positively correlated, while the mechanical strength and water absorption were negatively correlated. The leaching behaviors of CBFAs on Cu, Pb, Cd, and Cr were successfully suppressed to less than 1% of that originally from MSWIBA, which can be in line with the Chinese standards. Additionally, it is also found that the green concrete with adding GGBFS-CBFAs has higher overall fluidity and better mechanical properties than the concrete with FA-CBFAs. The mechanical properties of concrete were the best under the replacement rate of 60% of CFBAs, and the strength of green concrete added with GGBFS-CBFAs reached 96% of that of ordinary concrete. In this study, the rapid chloride ion penetration test, mercury intrusion and electron microscope tests found that the bonding effect between the CBFAs and the green concrete matrix was better, and the pore structure in the transition zone of the surrounding interface was refined. The proportion of transition pores in the pore structure was up to 59%. This shows that the concrete added with CBFAs has better resistance to chloride ion diffusion, and has some improvement on the durability. This research suggests that CBFAs including high volume MSWIBA has the potential to be successfully applied as the alternative to natural aggregates in sustainable concrete, and this can also advance waste recycling, and solidify high volume heavy metals in infrastructures.
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| 16. |
- Liu, Jun, et al.
(författare)
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Numerical model of the effect of water vapor environment on the chloride transport in concrete
- 2021
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Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618. ; 311
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Tidskriftsartikel (refereegranskat)abstract
- Chloride ions are known as one of the most crucial factors for rebar corrosion in reinforced concrete (RC) structures exposed to marine environments under drying-wetting cycles. In this condition, the chloride ion content in unsaturated concrete will change under the coupled effect of diffusion and capillary suction. This study simulates the atmosphere zone of the marine environment to explore the law of the chloride transmission behavior under the context of constant temperature and humidity. To analyze the effect of different drying-wetting ratios on the chloride ion profile in the concrete by conducting the dry-wet cycle tests. It is found that the most unfavorable drying-wetting ratios for RC structures in this study is 1:5.5. A finite element numerical model of chloride ion transmission based on Fick's Ⅱ law was established by COMSOL Multiphysics. It can be used to predict the range of concrete surface chloride ion concentration, and dynamic change of the distribution of chloride ion concentration inside the RC structures under different drying-wetting cycles over time. The comparison of experiment data and simulation results verify that the chloride diffusion prediction model has a good correlation.
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| 17. |
- Liu, Jun, et al.
(författare)
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Synthesis of geopolymer using municipal solid waste incineration fly ash and steel slag: Hydration properties and immobilization of heavy metals
- 2023
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Ingår i: Journal of Environmental Management. - 0301-4797 .- 1095-8630. ; 341
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a novel method for the disposal of municipal solid waste incineration fly ash (MSWIFA) was proposed. By applying geopolymer technology, steel slag (SS) and MSWIFA were used together as precursors to synthesize a cementitious material with sufficient strength that is useable in construction. The effects of the dosages of SS and alkaline activator on the properties of the geopolymer were investigated. Compressive testing was used to characterize the mechanical properties of the geopolymer. X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used for microscopic analysis. Leaching tests were performed to assess the immobilization effect of the geopolymer on heavy metals. The results showed that the compressive strength of the geopolymer reached 23.03 MPa at 56 d with 20% SS and 11% Na2O admixture. Highly polymerized hydration products, such as C-(A)-S-H gels and N-A-S-H gels, contributed to the compact microstructure, which provided mechanical strength and limited the migration and leaching of heavy metals in the geopolymer matrix. In terms of the results, this work is significant for the development of MSWIFA management.
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| 18. |
- Liu, Jun, et al.
(författare)
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The impact of cold-bonded artificial lightweight aggregates produced by municipal solid waste incineration bottom ash (MSWIBA) replace natural aggregates on the mechanical, microscopic and environmental properties, durability of sustainable concrete
- 2022
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Ingår i: Journal of Cleaner Production. - : Elsevier BV. - 0959-6526. ; 337
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Tidskriftsartikel (refereegranskat)abstract
- Currently, most of the municipal waste is incinerated and then transported to landfills for disposal, which takes up a lot of land resources and causes safety problems due to the hazardous materials such as heavy metals in MSWIBA. Therefore, a novel and green recycling approach is urgent. Here, MSWIBA is recycled by manufacturing artificial light coarse aggregates (ALCAs) and used as coarse aggregates to partially replace natural aggregates (NAs) to design green concrete. In this work, ALCAs made of MSWIBA replaced NAs with different percentages (0%, 25%, 50%, 75% and 100%) to manufacture artificial lightweight coarse aggregate concrete (ALCAC). The influence of specific gravity, compressive strength, splitting strength, carbonization performance and micro properties of ALCAC were studied. It was observed that with an increase in the replacement rate of ALCAs, the specific gravity of ALCAC decreased by up to 12.1%, and the mechanical properties also declined. However, the compressive strength can still reach more than 30 MPa, and the splitting strength can reach more than 3.3 MPa. In addition, an increase in the ALCA content also led to an increase in the ALCAC matrix pores, and CO2 was more likely to invade the concrete interior, which increased the depth of concrete carbonization. The hydration products of ALCAC make the interface zones (ITZs) rougher, and the bonding effect in the ITZ area is significantly better than that of NAC. Compared with fly ash (FA) light aggregate concrete, ALCAC has lower energy consumption and CO2 emissions. This study provides insight into the recycling of MSWIBA and application of ALCAs for sustainable RC structures.
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| 19. |
- Liu, Jun, et al.
(författare)
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Valorization of municipal solid waste incineration bottom ash (MSWIBA) into cold-bonded aggregates (CBAs): Feasibility and influence of curing methods
- 2022
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 843
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Tidskriftsartikel (refereegranskat)abstract
- The municipal solid waste incineration bottom ash (MSWIBA) contains amounts of hazardous elements or composition, and its disposal to landfills may pose a serious threat to the ground water and soil. To reduce the environmental impact of MSWIBA, a novelty application into the utilization of MSWIBA for the manufacture of cold-bonded aggregates (CBAs) was investigated in this study. This study explored the impacts of curing systems on the comprehensive properties of CBAs. Furthermore, the hydrating phases of the designed CBAs were studied by X-ray diffractometer, and the micro characteristics of CBAs was analyzed by Scanning Electron Microscopy. The results show that CBAs produced from the MSWIBA had good properties with density of 1.75–1.98 g/cm3, moisture content of 0.78–16.48 %, water absorption of 3.99–14.02 % and compressive behavior of 1.6–4.8 MPa. Moreover, the heating water curing environment can significantly improve the comprehensive properties of CBAs. Specifically, the compressive strength of the CBAs under the 80 °C curing condition was increased by 74 %–113 %, and the water absorption rate was reduced by 3.4 %–8 %, compared with other curing regimes. Additionally, the XRD analysis showed that there are spinel phases in the CBAs compounds, which is beneficial to solidify the hazardous metals. Also, low-carbon CBAs also greatly reduce the amount of Cu and Pb leaching, which meets the limit requirements in the Chinese standards. Overall, application of MSWIBA as admixture in CBAs is an effective approach to recycle waste and replace natural aggregates. Meanwhile, this work can provide an insight for the production of eco-friendly LWAs.
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