The soluble phosphates in phosphogypsum (PG) are generally considered to hinder its utilization without pretreatments. This paper investigated the positive effect of soluble phosphates on the strength development of anhydrite calcined from PG at 800 ºC for 1 hour. PG, washed PG with different soluble phosphate contents, washed PG added with washed water, and flue gas desulfurization gypsum (FGD) were used to prepare anhydrite. The hydration degree and strength development of anhydrite were measured. The effect mechanism was explored by XRD, FTIR, and SEM. Results showed the 28-day strength decreased from 35.9 MPa to almost no strength when the soluble P2O5 content decreased from 0.7480% to 0.0471%. Soluble phosphates in PG would affect the microstructure of anhydrite particles, promoting the strength development, however, they did not affect the strength of anhydrite calcined from FGD. It is concluded that the soluble phosphates in PG are beneficial for manufacturing anhydrite, which is a promising utilization.
{"title":"Effect of soluble phosphate on strength development of anhydrite calcined from phosphogypsum","authors":"Ying Hua, Zhichao Zhang, Lu Yuan, Jueshi Qian, Yanfei Yue, Zhen Li, Xingwen Jia","doi":"10.1016/j.cemconcomp.2025.105920","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2025.105920","url":null,"abstract":"The soluble phosphates in phosphogypsum (PG) are generally considered to hinder its utilization without pretreatments. This paper investigated the positive effect of soluble phosphates on the strength development of anhydrite calcined from PG at 800 ºC for 1 hour. PG, washed PG with different soluble phosphate contents, washed PG added with washed water, and flue gas desulfurization gypsum (FGD) were used to prepare anhydrite. The hydration degree and strength development of anhydrite were measured. The effect mechanism was explored by XRD, FTIR, and SEM. Results showed the 28-day strength decreased from 35.9 MPa to almost no strength when the soluble P<sub>2</sub>O<sub>5</sub> content decreased from 0.7480% to 0.0471%. Soluble phosphates in PG would affect the microstructure of anhydrite particles, promoting the strength development, however, they did not affect the strength of anhydrite calcined from FGD. It is concluded that the soluble phosphates in PG are beneficial for manufacturing anhydrite, which is a promising utilization.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"14 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142917111","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study explores the effect of polymer concentration on the dispersion of carbon nanotubes (CNTs) and the mechanical properties of cement-based materials via tests and molecular dynamics (MD) simulations. The results showed that all three polymers (ethylene-vinyl acetate (EVA), styrene-acrylate (SAE), and styrene-butadiene (SB) copolymers) significantly enhanced CNTs’ dispersion. The key factors driving this improvement are the coordination bond, H-bonds, π-π stacking, and van der Waals forces between the polymer and CNTs, which promote strong adsorption. This reduces the interaction energy generated among the CNTs. Additionally, the combined use of polymers and CNTs improves the mechanical properties of cement-based materials. First, the polymer films and CNTs formed a mesh structure inside the mortar, linking the hydration products, unhydrated cement particles, and aggregates. Secondly, the polymer films wrapped around the surface of the CNTs, which promoted the bond strength between the CNTs and calcium silicate hydrate. The synergistic effect between the polymers and CNTs is a promising approach for the development of advanced cementitious composites. The polymer promoted the dispersion of CNTs, whereas the CNTs compensated for the reduced compressive strength of the polymer-modified mortar and promoted hydration.
{"title":"Enhancing dispersion and mechanical properties of carbon nanotube-reinforced cement-based material using polymer emulsions","authors":"Shi-Wei Zhang, Ru Wang, Jiao-Long Zhang, Yong Yuan","doi":"10.1016/j.cemconcomp.2024.105910","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105910","url":null,"abstract":"This study explores the effect of polymer concentration on the dispersion of carbon nanotubes (CNTs) and the mechanical properties of cement-based materials via tests and molecular dynamics (MD) simulations. The results showed that all three polymers (ethylene-vinyl acetate (EVA), styrene-acrylate (SAE), and styrene-butadiene (SB) copolymers) significantly enhanced CNTs’ dispersion. The key factors driving this improvement are the coordination bond, H-bonds, π-π stacking, and van der Waals forces between the polymer and CNTs, which promote strong adsorption. This reduces the interaction energy generated among the CNTs. Additionally, the combined use of polymers and CNTs improves the mechanical properties of cement-based materials. First, the polymer films and CNTs formed a mesh structure inside the mortar, linking the hydration products, unhydrated cement particles, and aggregates. Secondly, the polymer films wrapped around the surface of the CNTs, which promoted the bond strength between the CNTs and calcium silicate hydrate. The synergistic effect between the polymers and CNTs is a promising approach for the development of advanced cementitious composites. The polymer promoted the dispersion of CNTs, whereas the CNTs compensated for the reduced compressive strength of the polymer-modified mortar and promoted hydration.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142924779","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-03DOI: 10.1016/j.cemconcomp.2025.105919
Peiyun She, Shuhang Ye, Yiming Yao, Deju Zhu, Cong Lu
Textile reinforced engineered cementitious composite (TR-ECC) is a cementitious composite reinforced with continuous textiles and short random fibers, characterized by high tensile strength and strain capacity due to the successive formation of multiple fine cracks. Various tensile failure modes of TR-ECC have been extensively observed in experimental studies, while clear classification of these failure modes and their underlying mechanisms are to be explored. In this study, the novel established numerical model explains the causes of different tensile failure modes of TR-ECC based on the physical interactions among fibers, textiles, and the matrix. In the model, the tensile behavior of TR-ECC was innovatively simulated through a displacement-controlled loading method, while the stress field in different components was analyzed considering five phases: textiles, short fibers, matrix, textile/matrix interface, and fiber/matrix interface. With the proposed model, two distinct tensile failure modes (modes I and II) were identified. Simulated TR-ECC stress-strain curves (OP-I and OP-II) of both failure modes were acquired with adjustments of several key micro-properties on the same base curve under the guidance of the proposed model. OP-I achieved a tensile strength exceeding 9.5 MPa and maintained a strain capacity above 2% due to secondary hardening after textile rupture, while OP-II exhibited stable multiple cracking with a lower peak strength of 7.2 MPa but a higher strain capacity exceeding 6%. These two specific optimization strategies were proposed based on the model to address different material performance requirements, providing a framework for performance-driven design of TR-ECC to ensure optimal mechanical performance and durability.
{"title":"Micromechanical Model and Performance-driven Design Strategy for Textile Reinforced Engineered Cementitious Composite (TR-ECC)","authors":"Peiyun She, Shuhang Ye, Yiming Yao, Deju Zhu, Cong Lu","doi":"10.1016/j.cemconcomp.2025.105919","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2025.105919","url":null,"abstract":"Textile reinforced engineered cementitious composite (TR-ECC) is a cementitious composite reinforced with continuous textiles and short random fibers, characterized by high tensile strength and strain capacity due to the successive formation of multiple fine cracks. Various tensile failure modes of TR-ECC have been extensively observed in experimental studies, while clear classification of these failure modes and their underlying mechanisms are to be explored. In this study, the novel established numerical model explains the causes of different tensile failure modes of TR-ECC based on the physical interactions among fibers, textiles, and the matrix. In the model, the tensile behavior of TR-ECC was innovatively simulated through a displacement-controlled loading method, while the stress field in different components was analyzed considering five phases: textiles, short fibers, matrix, textile/matrix interface, and fiber/matrix interface. With the proposed model, two distinct tensile failure modes (modes I and II) were identified. Simulated TR-ECC stress-strain curves (OP-I and OP-II) of both failure modes were acquired with adjustments of several key micro-properties on the same base curve under the guidance of the proposed model. OP-I achieved a tensile strength exceeding 9.5 MPa and maintained a strain capacity above 2% due to secondary hardening after textile rupture, while OP-II exhibited stable multiple cracking with a lower peak strength of 7.2 MPa but a higher strain capacity exceeding 6%. These two specific optimization strategies were proposed based on the model to address different material performance requirements, providing a framework for performance-driven design of TR-ECC to ensure optimal mechanical performance and durability.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142924778","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-02DOI: 10.1016/j.cemconcomp.2024.105905
Sharu Bhagavathi Kandy, Sebastian Remke, Thiyagarajan Ranganathan, Shubham Kiran Wani, Xiaodi Dai, Narayanan Neithalath, Aditya Kumar, Mathieu Bauchy, Edward Garboczi, Torben Gädt, Samanvaya Srivastava, Gaurav Sant
An inability to accurately control the rate and extent of solidification of cementitious suspensions is a major impediment to creating geometrically complex structural shapes via 3D printing. In this work, we have developed a thermoresponsive rapid stiffening system that will stiffen suspensions of minerals such as quartz, limestone, portlandite, and Ordinary Portland Cement (OPC) over a wide pH range. When exposed to trigger temperatures between 40 °C and 70 °C, the polymer binder system undergoes a thermally triggered free radical polymerization (FRP) reaction, leading to an ultrafast stiffening of the suspension at an average rate on the order of 1 kPa/s and achieving MPa-level strength in less than a minute. The cured composites exhibit flexural strength and strain capacity far greater than OPC-based composites (σf∼ 25 MPa, γf> 1 %). We successfully demonstrated 3D printing using these engineered slurries, showcasing their thermal response, thermal latency, and printability, thereby validating our design approach and its potential for diverse applications. These thermoresponsive slurries facilitate freestyle printing, non-horizontal printing, and the creation of complex geometries with high overhangs. This approach provides a means to surmount the significant limitations of extrusion-based 3D printing using particulate suspensions and open up new possibilities in integrating design and production.
{"title":"Design and function of thermoresponsive-ultrafast stiffening suspension formulations for 3D printing","authors":"Sharu Bhagavathi Kandy, Sebastian Remke, Thiyagarajan Ranganathan, Shubham Kiran Wani, Xiaodi Dai, Narayanan Neithalath, Aditya Kumar, Mathieu Bauchy, Edward Garboczi, Torben Gädt, Samanvaya Srivastava, Gaurav Sant","doi":"10.1016/j.cemconcomp.2024.105905","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105905","url":null,"abstract":"An inability to accurately control the rate and extent of solidification of cementitious suspensions is a major impediment to creating geometrically complex structural shapes via 3D printing. In this work, we have developed a thermoresponsive rapid stiffening system that will stiffen suspensions of minerals such as quartz, limestone, portlandite, and Ordinary Portland Cement (OPC) over a wide pH range. When exposed to trigger temperatures between 40 °C and 70 °C, the polymer binder system undergoes a thermally triggered free radical polymerization (FRP) reaction, leading to an ultrafast stiffening of the suspension at an average rate on the order of 1 kPa/s and achieving MPa-level strength in less than a minute. The cured composites exhibit flexural strength and strain capacity far greater than OPC-based composites (<mml:math altimg=\"si1.svg\"><mml:mrow><mml:msub><mml:mi>σ</mml:mi><mml:mi>f</mml:mi></mml:msub></mml:mrow></mml:math><mml:math altimg=\"si2.svg\"><mml:mrow><mml:mo>∼</mml:mo></mml:mrow></mml:math> 25 MPa, <mml:math altimg=\"si3.svg\"><mml:mrow><mml:msub><mml:mi>γ</mml:mi><mml:mi>f</mml:mi></mml:msub></mml:mrow></mml:math><mml:math altimg=\"si4.svg\"><mml:mrow><mml:mo linebreak=\"goodbreak\" linebreakstyle=\"after\">></mml:mo></mml:mrow></mml:math> 1 %). We successfully demonstrated 3D printing using these engineered slurries, showcasing their thermal response, thermal latency, and printability, thereby validating our design approach and its potential for diverse applications. These thermoresponsive slurries facilitate freestyle printing, non-horizontal printing, and the creation of complex geometries with high overhangs. This approach provides a means to surmount the significant limitations of extrusion-based 3D printing using particulate suspensions and open up new possibilities in integrating design and production.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"97 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2025-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142912361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-30DOI: 10.1016/j.cemconcomp.2024.105918
Heongwon Suh, Doheon Koo, Dong-Hee Son, Jin Park, Sooheon Kim, Baek-Il Bae, Chang-Sik Choi, Hongyun So, Sungchul Bae
This study addresses the limitations of conventional methods in incorporating nanomaterials, including prolonged dispersion times and handling challenges in construction field applications, by developing graphene oxide/functionalized carbon nanotube/nanosilica (GCS) sheets. The GCS sheet, as a portable sheet form of a nanomaterial composite, achieves high nanomaterial dispersibility with only 1 min of sonication. The dispersion efficiency of the GCS sheets was evaluated using UV–vis spectroscopy, zeta potential measurements, and transmission electron microscopy, and the impact on material properties was assessed using compressive strength tests. The hydration processes were investigated using X-ray diffraction and 29Si nuclear magnetic resonance, and the nanomaterial dispersion within the cement matrix was studied using synchrotron X-ray nanoimaging. The GCS sheet facilitated more effective nanosilica dispersion on the graphene oxide plane compared to the powder form, achieving optimal dispersion in 1 min. This resulted in enhanced compressive strength, increased polymerization of calcium silicate hydrates, and a more elongated pore structure owing to the reduced aggregation of the GCS composites.
{"title":"A Novel Strategy Utilizing Graphene Oxide/Functionalized Carbon Nanotube/Nanosilica Sheet for Nanomaterial Incorporation in Cement Paste","authors":"Heongwon Suh, Doheon Koo, Dong-Hee Son, Jin Park, Sooheon Kim, Baek-Il Bae, Chang-Sik Choi, Hongyun So, Sungchul Bae","doi":"10.1016/j.cemconcomp.2024.105918","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105918","url":null,"abstract":"This study addresses the limitations of conventional methods in incorporating nanomaterials, including prolonged dispersion times and handling challenges in construction field applications, by developing graphene oxide/functionalized carbon nanotube/nanosilica (GCS) sheets. The GCS sheet, as a portable sheet form of a nanomaterial composite, achieves high nanomaterial dispersibility with only 1 min of sonication. The dispersion efficiency of the GCS sheets was evaluated using UV–vis spectroscopy, zeta potential measurements, and transmission electron microscopy, and the impact on material properties was assessed using compressive strength tests. The hydration processes were investigated using X-ray diffraction and <sup>29</sup>Si nuclear magnetic resonance, and the nanomaterial dispersion within the cement matrix was studied using synchrotron X-ray nanoimaging. The GCS sheet facilitated more effective nanosilica dispersion on the graphene oxide plane compared to the powder form, achieving optimal dispersion in 1 min. This resulted in enhanced compressive strength, increased polymerization of calcium silicate hydrates, and a more elongated pore structure owing to the reduced aggregation of the GCS composites.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142902105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In order to effectively solve the problem of pollutant degradation in cement-based materials, the BiVO4 was introduced into the reconstruction of the water-encountered MgAl-LDHs layer after calcination utilizing the memory effect of MgAl-LDHs which successfully prepared the highly adsorbable visible light photocatalytic material, BiVO4/MgAl-LDHs. Its layered structure results in a large specific surface area with more active sites, promotes the growth and development of crystal nuclei, and thus accelerates cement hydration. Also, the nanofilling effect can optimize the microstructure and improve the mechanical properties of the cement paste. It is noteworthy that excessive BiVO4/MgAI-LDHs will weaken the aforementioned promotions due to the reduction in the number of active species and heterogeneous defects. In the self-cleaning performance test, the specimens prepared by the coating method showed better behavior, whose degradation outcome was close to that of BiVO4/MgAl-LDHs on methylene blue (MB) solution with a degradation rate of up to 89.2%, once again confirming that BiVO4/MgAl-LDHs possesses good chemical stability. The test for the durability of photocatalytic efficiency demonstrated that the specimens produced by the polyvinyl chloride (PVC) film loading method performed better. The above two performance tests illustrate that the number of BiVO4/MgAl-LDHs molecules on the paste surface plays a major role in the degradation of MB solution.
{"title":"Preparation of adsorbed bismuth-based visible light photocatalytic materials and their effects on the performance of cement-based materials","authors":"Yidong Xu, Yuquan Wang, Weijie Fan, Shi-Tong Li, Xiaoniu Yu","doi":"10.1016/j.cemconcomp.2024.105911","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105911","url":null,"abstract":"In order to effectively solve the problem of pollutant degradation in cement-based materials, the BiVO<sub>4</sub> was introduced into the reconstruction of the water-encountered MgAl-LDHs layer after calcination utilizing the memory effect of MgAl-LDHs which successfully prepared the highly adsorbable visible light photocatalytic material, BiVO<sub>4</sub>/MgAl-LDHs. Its layered structure results in a large specific surface area with more active sites, promotes the growth and development of crystal nuclei, and thus accelerates cement hydration. Also, the nanofilling effect can optimize the microstructure and improve the mechanical properties of the cement paste. It is noteworthy that excessive BiVO<sub>4</sub>/MgAI-LDHs will weaken the aforementioned promotions due to the reduction in the number of active species and heterogeneous defects. In the self-cleaning performance test, the specimens prepared by the coating method showed better behavior, whose degradation outcome was close to that of BiVO<sub>4</sub>/MgAl-LDHs on methylene blue (MB) solution with a degradation rate of up to 89.2%, once again confirming that BiVO<sub>4</sub>/MgAl-LDHs possesses good chemical stability. The test for the durability of photocatalytic efficiency demonstrated that the specimens produced by the polyvinyl chloride (PVC) film loading method performed better. The above two performance tests illustrate that the number of BiVO<sub>4</sub>/MgAl-LDHs molecules on the paste surface plays a major role in the degradation of MB solution.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"50 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-27DOI: 10.1016/j.cemconcomp.2024.105912
Hammad Ahmed Shah, Weina Meng
This study aims to enhance the utilization rate of recycled concrete aggregate (RCA) in structural concrete through the application of a novel carbonation treatment method to improve the microstructure of old adhered mortar in RCA and enhance its compatibility with the new concrete. Carbonation of RCA is a commonly used method to densify the microstructure of old adhered mortar, but it exhibits limitations due to the low available calcium content in RCA for reacting with CO2. To address this, a novel approach by coating the RCA with blast furnace slag before subjecting it to carbonation was proposed. This involves two key benefits: (1) it introduces external calcium, thereby increasing the CaCO3 content after carbonation and densifying the microstructure, and (2) it provides silica, facilitating a pozzolanic reaction that enhances bonding with new concrete. The effectiveness of pressurized and wet carbonation methods was evaluated and compared in the research. Following carbonation of the slag-coated RCA, the microstructure densification and improvement in interfacial properties between RCA and new cement paste were assessed through water absorption and slant shear test, respectively. The underlying mechanism was investigated by TGA, XRD, and SEM-EDS. The findings indicate that slag coating significantly enhances microstructure densification, reducing water absorption by up to 40% and increasing bond strength by up to 65% after carbonation. Pressurized carbonation enhances CO2 penetration and dissolution in RCA, increasing CaCO3 production and improving the microstructure. It also produces more needle-like aragonite, strengthening the bond between RCA and new concrete.
{"title":"Enhancement of recycled concrete aggregate through slag-coated carbonation","authors":"Hammad Ahmed Shah, Weina Meng","doi":"10.1016/j.cemconcomp.2024.105912","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105912","url":null,"abstract":"This study aims to enhance the utilization rate of recycled concrete aggregate (RCA) in structural concrete through the application of a novel carbonation treatment method to improve the microstructure of old adhered mortar in RCA and enhance its compatibility with the new concrete. Carbonation of RCA is a commonly used method to densify the microstructure of old adhered mortar, but it exhibits limitations due to the low available calcium content in RCA for reacting with CO<sub>2</sub>. To address this, a novel approach by coating the RCA with blast furnace slag before subjecting it to carbonation was proposed. This involves two key benefits: (1) it introduces external calcium, thereby increasing the CaCO<sub>3</sub> content after carbonation and densifying the microstructure, and (2) it provides silica, facilitating a pozzolanic reaction that enhances bonding with new concrete. The effectiveness of pressurized and wet carbonation methods was evaluated and compared in the research. Following carbonation of the slag-coated RCA, the microstructure densification and improvement in interfacial properties between RCA and new cement paste were assessed through water absorption and slant shear test, respectively. The underlying mechanism was investigated by TGA, XRD, and SEM-EDS. The findings indicate that slag coating significantly enhances microstructure densification, reducing water absorption by up to 40% and increasing bond strength by up to 65% after carbonation. Pressurized carbonation enhances CO<sub>2</sub> penetration and dissolution in RCA, increasing CaCO<sub>3</sub> production and improving the microstructure. It also produces more needle-like aragonite, strengthening the bond between RCA and new concrete.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"33 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The disposal of solid and radioactive waste poses significant risks to terrestrial and marine ecosystems. This study presents a sustainable solution by recycling silica-rich glass waste (RG) and fly ash (FA) to develop a functional nanocomposite concrete for radionuclide treatment. A Radionuclide removal Zeolite (RrZ) was hydrothermally synthesized from RG powder at low temperature and NaOH molar ratio. The RrZ was incorporated into a porous geopolymer composite concrete (PGCC) comprising 20% RrZ and 80% FA, with SiO₂/Na₂O = 1, liquid-to-solid ratio (L/S) = 0.33, paste-to-bone ratio (B/A) varying from 0.15–0.2, and porosity (P) from 14.95–25.45%. The results from SEM, TEM and BET indicated a highly porous structure of RrZ adsorbent with mesopores capable of achieving high adsorption efficiency (83.13–97.71% for Sr2⁺ and 55.31–91.01% for Cs⁺) within short time, adhering to the quasi-second-order kinetic models. Moreover, the XRD results identified key crystalline phase of analcime (NaAlSi₂O₆•H₂O), and no new phase formed after ion exchange with Sr2⁺ and Cs⁺, while the FTIR analysis revealed minimal chemical changes post-adsorption. Additionally, the porosity of 14.95% - 25.45% and water permeability of 1.876–11.956 mm/s were the key factors for PGCC design, while larger aggregates and lower B/A ratios helped to optimize the adsorption. The ANOVA analysis revealed that aggregate size was the most significant factor for single-cycle adsorption, followed by porosity and B/A ratio. This study demonstrates that PGCC effectively combines waste recycling with environmental remediation, offering a durable and efficient method for hazardous radionuclide removal from marine ecosystems.
{"title":"Performance and characterization of nano-engineered silica waste concrete composite for efficient marine radionuclides remediation","authors":"Jean-Baptiste Mawulé Dassekpo, Chonkei Iong, Dejing Chen, , Xiaoxiong Zha, Jianqiao Ye","doi":"10.1016/j.cemconcomp.2024.105914","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105914","url":null,"abstract":"The disposal of solid and radioactive waste poses significant risks to terrestrial and marine ecosystems. This study presents a sustainable solution by recycling silica-rich glass waste (RG) and fly ash (FA) to develop a functional nanocomposite concrete for radionuclide treatment. A Radionuclide removal Zeolite (RrZ) was hydrothermally synthesized from RG powder at low temperature and NaOH molar ratio. The RrZ was incorporated into a porous geopolymer composite concrete (PGCC) comprising 20% RrZ and 80% FA, with SiO₂/Na₂O = 1, liquid-to-solid ratio (L/S) = 0.33, paste-to-bone ratio (B/A) varying from 0.15–0.2, and porosity (P) from 14.95–25.45%. The results from SEM, TEM and BET indicated a highly porous structure of RrZ adsorbent with mesopores capable of achieving high adsorption efficiency (83.13–97.71% for Sr<sup>2</sup>⁺ and 55.31–91.01% for Cs⁺) within short time, adhering to the quasi-second-order kinetic models. Moreover, the XRD results identified key crystalline phase of analcime (NaAlSi₂O₆•H₂O), and no new phase formed after ion exchange with Sr<sup>2</sup>⁺ and Cs⁺, while the FTIR analysis revealed minimal chemical changes post-adsorption. Additionally, the porosity of 14.95% - 25.45% and water permeability of 1.876–11.956 mm/s were the key factors for PGCC design, while larger aggregates and lower B/A ratios helped to optimize the adsorption. The ANOVA analysis revealed that aggregate size was the most significant factor for single-cycle adsorption, followed by porosity and B/A ratio. This study demonstrates that PGCC effectively combines waste recycling with environmental remediation, offering a durable and efficient method for hazardous radionuclide removal from marine ecosystems.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"29 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142888272","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study investigated the tensile performance of pre-cracked ultra-high performance concrete (UHPC) subjected to sustained loading and various environmental conditions, including air, water, and a 3% NaCl solution. The findings indicated that prolonged tensile loading significantly reduced the tensile properties of UHPC, particularly at higher stress levels. Interestingly, the presence of water and NaCl solution facilitated recovery and, in some instances, even enhanced the mechanical properties of the cracked UHPC specimens beyond their original values. Microstructural analyses using SEM and EDS revealed that hydration products, predominantly C-S-H gel and CaCO3, improved the bonding between steel fibers and the UHPC matrix. These products effectively filled the cracks and refined the overall microstructure. The results underscored the significant influence of stress levels and environmental exposure on the performance of UHPC in service, highlighting the necessity of considering these factors in the design and application of UHPC to ensure long-term structural integrity and durability.
{"title":"Tensile performance of pre-cracked UHPC under the coupled actions of sustained loading and corrosive media","authors":"Yiming Yao, Gan Wu, Kaimeng Yang, Hongrui Zhang, Jianan Qi, Yuqing Hu, Jingquan Wang, Hongyu Zhou","doi":"10.1016/j.cemconcomp.2024.105915","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105915","url":null,"abstract":"This study investigated the tensile performance of pre-cracked ultra-high performance concrete (UHPC) subjected to sustained loading and various environmental conditions, including air, water, and a 3% NaCl solution. The findings indicated that prolonged tensile loading significantly reduced the tensile properties of UHPC, particularly at higher stress levels. Interestingly, the presence of water and NaCl solution facilitated recovery and, in some instances, even enhanced the mechanical properties of the cracked UHPC specimens beyond their original values. Microstructural analyses using SEM and EDS revealed that hydration products, predominantly C-S-H gel and CaCO<sub>3</sub>, improved the bonding between steel fibers and the UHPC matrix. These products effectively filled the cracks and refined the overall microstructure. The results underscored the significant influence of stress levels and environmental exposure on the performance of UHPC in service, highlighting the necessity of considering these factors in the design and application of UHPC to ensure long-term structural integrity and durability.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"83 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884325","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-25DOI: 10.1016/j.cemconcomp.2024.105917
Chuang Feng, Huanxun Liu, Ziyan Hang, Yu Su, Xiaodong Xia, George J. Weng
Thermal conductivity of cement composites is crucial for developing various sustainable engineering structures, creating an urgent need to elucidate the influencing factors and their associated mechanisms. Introducing various 0-, 1- and 2-dimensional carbon fillers into traditional cement composites with tailored thermal conductivity demonstrates great potential for practical engineering applications. However, limited studies have been done on the thermal conductivity of cement composites involving temperature- and pore size-dependent mechanisms. This work firstly attempts to develop a comprehensive micromechanical framework combining phonon thermal transport in carbon fillers and phonon boundary scattering in pores. The overall thermal conductivity of 0D-carbon black (CB), 1D-carbon nanotube (CNT) and 2D-graphene nanoplatelet (GNP) reinforced saturated/dry porous cement composites subject to temperature is predicted. The effects of porosity, saturation and the attributes of pores and the carbon fillers are considered. It is found that the order of the contribution of the carbon fillers to the improvement of the thermal conductivity is 2D-GNP>1D-CNT>0D-CB. The effective thermal conductivity of the porous cement composites tends to decrease as the temperature rises. Furthermore, as the aspect ratio of the carbon fillers increases, the thermal conductivity composites with 1D-CNTs and 2D-GNPs increases and decreases, respectively. The effective thermal conductivity of cement composites with random distribution of pore size is significantly higher than that with uniform distribution. The effective thermal conductivity of the saturated porous cement composites is less sensitive to the aspect ratio of the pores compared to their dry counterparts. This work provides guidelines for optimizing the thermal conductivity of porous cement composites for various potential engineering applications.
{"title":"Study on Thermal Conductivity of 0D/1D/2D Carbon Filler Reinforced Cement Composites with Phonon Physical Model","authors":"Chuang Feng, Huanxun Liu, Ziyan Hang, Yu Su, Xiaodong Xia, George J. Weng","doi":"10.1016/j.cemconcomp.2024.105917","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105917","url":null,"abstract":"Thermal conductivity of cement composites is crucial for developing various sustainable engineering structures, creating an urgent need to elucidate the influencing factors and their associated mechanisms. Introducing various 0-, 1- and 2-dimensional carbon fillers into traditional cement composites with tailored thermal conductivity demonstrates great potential for practical engineering applications. However, limited studies have been done on the thermal conductivity of cement composites involving temperature- and pore size-dependent mechanisms. This work firstly attempts to develop a comprehensive micromechanical framework combining phonon thermal transport in carbon fillers and phonon boundary scattering in pores. The overall thermal conductivity of 0D-carbon black (CB), 1D-carbon nanotube (CNT) and 2D-graphene nanoplatelet (GNP) reinforced saturated/dry porous cement composites subject to temperature is predicted. The effects of porosity, saturation and the attributes of pores and the carbon fillers are considered. It is found that the order of the contribution of the carbon fillers to the improvement of the thermal conductivity is 2D-GNP>1D-CNT>0D-CB. The effective thermal conductivity of the porous cement composites tends to decrease as the temperature rises. Furthermore, as the aspect ratio of the carbon fillers increases, the thermal conductivity composites with 1D-CNTs and 2D-GNPs increases and decreases, respectively. The effective thermal conductivity of cement composites with random distribution of pore size is significantly higher than that with uniform distribution. The effective thermal conductivity of the saturated porous cement composites is less sensitive to the aspect ratio of the pores compared to their dry counterparts. This work provides guidelines for optimizing the thermal conductivity of porous cement composites for various potential engineering applications.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"123 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142884365","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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