To promote the application of carbonated recycled concrete powder (CRP), it is vital to thoroughly understand the performance of recycled concrete powder (RP) during the carbonation process. This paper presents an experimental study on the multiscale microstructure evolution of CRP and its chemical reactivity development during gas-solid carbonation. The phase transformation, nanostructure and reactivity evolution were investigated using thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), 29Si nuclear magnetic resonance (NMR) and zeta potential test. Scanning electron microscope and energy-dispersive spectroscopy (SEM-EDS), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) were employed to study the microstructural characteristics. Results indicate that portlandite, ettringite, and unhydrated clinker were carbonated into CaCO3 and alumina gel within 1d, while the C-S-H subsequently underwent decalcification, yielding silica gel and nano CaCO3. Regarding microstructure, calcium redistributes during carbonation, and silica phase undergoes polymerization from a nanoscale point of view. The CaCO3 derived from portlandite firstly formed and refine the pores, followed by the outward distribution of later-generated silica gel and nano calcium carbonate from C-S-H due to space limitations within the particle. The initially formed CaCO3 can chemically absorb Ca2+ in cement paste to facilitate the nucleation and growth of C-S-H, while the highly reactive silica gel obtained in later stage can further promote the formation of C-S-H. This study provides theoretical and technological support to improve the efficiency of carbonation processes and advance their engineering applications.
{"title":"Multiscale microstructure and reactivity evolution of recycled concrete fines under gas-solid carbonation","authors":"Xiaowei Ouyang, Xiaofeng Li, Jiaming Li, Yuwei Ma, Mingzhong Zhang, Zongjin Li, Jiyang Fu","doi":"10.1016/j.cemconcomp.2024.105903","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105903","url":null,"abstract":"To promote the application of carbonated recycled concrete powder (CRP), it is vital to thoroughly understand the performance of recycled concrete powder (RP) during the carbonation process. This paper presents an experimental study on the multiscale microstructure evolution of CRP and its chemical reactivity development during gas-solid carbonation. The phase transformation, nanostructure and reactivity evolution were investigated using thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), <sup>29</sup>Si nuclear magnetic resonance (NMR) and zeta potential test. Scanning electron microscope and energy-dispersive spectroscopy (SEM-EDS), transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET) were employed to study the microstructural characteristics. Results indicate that portlandite, ettringite, and unhydrated clinker were carbonated into CaCO<sub>3</sub> and alumina gel within 1d, while the C-S-H subsequently underwent decalcification, yielding silica gel and nano CaCO<sub>3</sub>. Regarding microstructure, calcium redistributes during carbonation, and silica phase undergoes polymerization from a nanoscale point of view. The CaCO<sub>3</sub> derived from portlandite firstly formed and refine the pores, followed by the outward distribution of later-generated silica gel and nano calcium carbonate from C-S-H due to space limitations within the particle. The initially formed CaCO<sub>3</sub> can chemically absorb Ca<sup>2+</sup> in cement paste to facilitate the nucleation and growth of C-S-H, while the highly reactive silica gel obtained in later stage can further promote the formation of C-S-H. This study provides theoretical and technological support to improve the efficiency of carbonation processes and advance their engineering applications.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"13 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142841565","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}
Assessing the permeability of concrete is crucial as it governs the transport of aggressive agents, such as chlorides and carbon dioxide, which are key factors in the degradation mechanisms. Moreover, concrete’s permeability constitutes an essential input parameter for durability models. Concrete’s permeability can be measured directly (by experimental methods) or indirectly by fitting a transport model to saturation degree profiles. In this paper, we introduce a novel indirect method for estimating the permeability by monitoring the saturation degree profiles with embedded resistivity sensors. These embedded resistivity sensors are used for the evaluation of the saturation degree profiles over time during two experiments: drying and imbibition with tap water. Firstly, measured resistivity profiles are converted to saturation degree profiles, using a calibration curve established on concrete cores of the same formulation. Concrete’s permeability is then estimated by fitting a hydric transport model to the experimental saturation degree profiles. Permeability values estimated using the embedded sensor are compared to those obtained by two reference methods: assessing the mass loss of a non-monitored specimen subjected to drying and saturation degree profiles obtained by gammadensimetry measurements. The permeability values obtained with the monitoring method are consistent for drying and imbibition experiments and fall within the range of values found in the literature. This is very promising for the continuous monitoring of concrete by embedded resistivity sensors.
{"title":"Monitoring of drying and imbibition of concrete using embedded resistivity sensors for the estimation of permeability","authors":"Marie-Ange Eid, Nicolas Reuge, Géraldine Villain, Stéphanie Bonnet, Sérgio Palma Lopes","doi":"10.1016/j.cemconcomp.2024.105900","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105900","url":null,"abstract":"Assessing the permeability of concrete is crucial as it governs the transport of aggressive agents, such as chlorides and carbon dioxide, which are key factors in the degradation mechanisms. Moreover, concrete’s permeability constitutes an essential input parameter for durability models. Concrete’s permeability can be measured directly (by experimental methods) or indirectly by fitting a transport model to saturation degree profiles. In this paper, we introduce a novel indirect method for estimating the permeability by monitoring the saturation degree profiles with embedded resistivity sensors. These embedded resistivity sensors are used for the evaluation of the saturation degree profiles over time during two experiments: drying and imbibition with tap water. Firstly, measured resistivity profiles are converted to saturation degree profiles, using a calibration curve established on concrete cores of the same formulation. Concrete’s permeability is then estimated by fitting a hydric transport model to the experimental saturation degree profiles. Permeability values estimated using the embedded sensor are compared to those obtained by two reference methods: assessing the mass loss of a non-monitored specimen subjected to drying and saturation degree profiles obtained by gammadensimetry measurements. The permeability values obtained with the monitoring method are consistent for drying and imbibition experiments and fall within the range of values found in the literature. This is very promising for the continuous monitoring of concrete by embedded resistivity sensors.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142841566","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 : 2024-12-17DOI: 10.1016/j.cemconcomp.2024.105896
Rashed Alarrak, Alexander S. Brand
This research investigated the mechanical performance of Functionally Graded Fiber-Reinforced Concrete (FG-FRC) produced via extrusion with a targeted fiber injection. Flexural toughness was assessed using a modified ASTM C1609, and fracture properties were analyzed through implementation of the two-parameter fracture model. The study introduced an innovative targeted fiber injection technique using a conveyor system, tailored for the integration of high-stiffness steel fibers into the mortar prior to extrusion. This method permits the use of fibers in more extrusion systems, since the fibers cannot jam in the pump. The research utilized digital image correlation to observe the full displacement field, allowing for an in-depth examination of crack propagation and strain localization. Additionally, X-ray computed tomography was employed to analyze fiber dosage and distribution within the FG-FRC layers. Results indicated that the targeted fiber injection method facilitated effective fiber distribution within FG-FRC layers, leading to enhanced mechanical performance through fiber dosage’s optimization.
本研究调查了通过定向纤维注入挤压法生产的功能级配纤维增强混凝土（FG-FRC）的机械性能。采用修改后的 ASTM C1609 评估了挠曲韧性，并通过实施双参数断裂模型分析了断裂性能。研究采用了一种创新的定向纤维注射技术，该技术使用输送系统，专门用于在挤压之前将高刚度钢纤维整合到砂浆中。这种方法允许在更多的挤压系统中使用纤维，因为纤维不会卡在泵中。该研究利用数字图像相关技术观察整个位移场，从而深入研究裂纹扩展和应变定位。此外，还采用了 X 射线计算机断层扫描技术来分析 FG-FRC 层内的纤维用量和分布情况。结果表明，有针对性的纤维注入方法促进了纤维在 FG-FRC 层内的有效分布，通过优化纤维用量提高了机械性能。
{"title":"Mechanical Performance of Extruded Functionally Graded Fiber-Reinforced Mortar with Targeted Fiber Injection","authors":"Rashed Alarrak, Alexander S. Brand","doi":"10.1016/j.cemconcomp.2024.105896","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105896","url":null,"abstract":"This research investigated the mechanical performance of Functionally Graded Fiber-Reinforced Concrete (FG-FRC) produced <em>via</em> extrusion with a targeted fiber injection. Flexural toughness was assessed using a modified ASTM C1609, and fracture properties were analyzed through implementation of the two-parameter fracture model. The study introduced an innovative targeted fiber injection technique using a conveyor system, tailored for the integration of high-stiffness steel fibers into the mortar prior to extrusion. This method permits the use of fibers in more extrusion systems, since the fibers cannot jam in the pump. The research utilized digital image correlation to observe the full displacement field, allowing for an in-depth examination of crack propagation and strain localization. Additionally, X-ray computed tomography was employed to analyze fiber dosage and distribution within the FG-FRC layers. Results indicated that the targeted fiber injection method facilitated effective fiber distribution within FG-FRC layers, leading to enhanced mechanical performance through fiber dosage’s optimization.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"97 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142841569","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}
Colloidal nano silica (CNS) demonstrated positive effects in enhancing the water stability of magnesium phosphate cement (MPC), and the underlying mechanism was investigated systematically in this paper. The experimental results showed that the nucleation effect of CNS accelerated the intermediate phase transition process and significantly enhanced the struvite early formation rate of MPC. Moreover, the addition of CNS led to a shift from macropore to gel pores observed from pore size distribution. Notably, the filling effect of CNS and the formation of novel hydration products were identified as critical factors in enhancing water stability and optimizing pore structure. Simulation experiments provided further validation that CNS could directly react with dead-burnt magnesium oxide to generate a novel gel phase-magnesium silicate hydrate (M-S-H) which confirmed a possible hydration reaction of silica in MPC.
{"title":"Water stability improvement and mechanism of magnesium phosphate cement modified by colloidal nano silica","authors":"Xingyu Gan, Chao Li, Haiming Zhang, Yali Li, Laibo Li, Lingchao Lu","doi":"10.1016/j.cemconcomp.2024.105898","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105898","url":null,"abstract":"Colloidal nano silica (CNS) demonstrated positive effects in enhancing the water stability of magnesium phosphate cement (MPC), and the underlying mechanism was investigated systematically in this paper. The experimental results showed that the nucleation effect of CNS accelerated the intermediate phase transition process and significantly enhanced the struvite early formation rate of MPC. Moreover, the addition of CNS led to a shift from macropore to gel pores observed from pore size distribution. Notably, the filling effect of CNS and the formation of novel hydration products were identified as critical factors in enhancing water stability and optimizing pore structure. Simulation experiments provided further validation that CNS could directly react with dead-burnt magnesium oxide to generate a novel gel phase-magnesium silicate hydrate (M-S-H) which confirmed a possible hydration reaction of silica in MPC.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"18 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142832347","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 massive discharge of copper slag (CS) has led to serious environmental problems. Carbon mineralization, as a treatment method of solid waste, not only achieves carbon sequestration, but also enhances the pozzolanic activity. In this work, a novel exfoliation aqueous carbonation method combining aqueous carbon mineralization and wet grinding was proposed to evaluate the carbon mineralization behavior of CS at mild temperature and pressure. The results indicated that exfoliation aqueous carbonation exhibited higher mineralization degree than that of classical CO2 bubbling carbonation. The carbonation products of CS were mainly composed of amorphous carbonate and silica. Elevated carbonation temperature could promote the dissolution of fayalite in CS to enhance the carbon mineralization degree. Carbon mineralization treatment could improve the pozzolanic reactivity of CS and the 28 d strength activity index could reach up to 106.3%. The outcomes could help provide new technology to facilitate the resource utilization of CS.
{"title":"The carbon mineralization behavior of copper slag and its impact on pozzolanic reactivity","authors":"Yingbin Wang, Xinhao Li, Wenjuan Miao, Ying Su, Xingyang He, Bohumir Strnadel","doi":"10.1016/j.cemconcomp.2024.105899","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105899","url":null,"abstract":"The massive discharge of copper slag (CS) has led to serious environmental problems. Carbon mineralization, as a treatment method of solid waste, not only achieves carbon sequestration, but also enhances the pozzolanic activity. In this work, a novel exfoliation aqueous carbonation method combining aqueous carbon mineralization and wet grinding was proposed to evaluate the carbon mineralization behavior of CS at mild temperature and pressure. The results indicated that exfoliation aqueous carbonation exhibited higher mineralization degree than that of classical CO<sub>2</sub> bubbling carbonation. The carbonation products of CS were mainly composed of amorphous carbonate and silica. Elevated carbonation temperature could promote the dissolution of fayalite in CS to enhance the carbon mineralization degree. Carbon mineralization treatment could improve the pozzolanic reactivity of CS and the 28 d strength activity index could reach up to 106.3%. The outcomes could help provide new technology to facilitate the resource utilization of CS.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"63 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142832277","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 : 2024-12-16DOI: 10.1016/j.cemconcomp.2024.105897
Meiyan Bai, Jianzhuang Xiao, Tao Ding, Kequan Yu
Buildings can be rapidly constructed using 3D printed concrete technology without formwork, garnering increasing attention within the construction industry. The effects of different printing parameters on the splitting tensile strength, shear strength, pore structure, and micromorphology of the interface between 3D printed ECC and post-cast concrete were investigated, including single-layer printing height, fiber content, and recycled sand replacement ratio. The results indicated that as the fiber content and single-layer printing height increased, the interfacial bond strength was initially enhanced while subsequently decreased, with optimal bond strength achieved at a 15 mm single-layer printing height. Moderate fiber content and single-layer printing height were beneficial for interfacial bond strength. Meanwhile, the interfacial bond strength was reduced due to the evolution of interfacial pore structure after the incorporation of recycled sand. The splitting tensile strength and shear strength of the interface between 3D printed ECC and post-cast concrete decreased by 36.1% and 35.8%, respectively, when the replacement ratio of recycled sand in ECC was 100%. Additionally, models for the interfacial shear strength between 3D printed ECC and post-cast concrete were proposed.
{"title":"Interfacial bond properties between 3D printed engineered cementitious composite (ECC) and post-cast concrete","authors":"Meiyan Bai, Jianzhuang Xiao, Tao Ding, Kequan Yu","doi":"10.1016/j.cemconcomp.2024.105897","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105897","url":null,"abstract":"Buildings can be rapidly constructed using 3D printed concrete technology without formwork, garnering increasing attention within the construction industry. The effects of different printing parameters on the splitting tensile strength, shear strength, pore structure, and micromorphology of the interface between 3D printed ECC and post-cast concrete were investigated, including single-layer printing height, fiber content, and recycled sand replacement ratio. The results indicated that as the fiber content and single-layer printing height increased, the interfacial bond strength was initially enhanced while subsequently decreased, with optimal bond strength achieved at a 15 mm single-layer printing height. Moderate fiber content and single-layer printing height were beneficial for interfacial bond strength. Meanwhile, the interfacial bond strength was reduced due to the evolution of interfacial pore structure after the incorporation of recycled sand. The splitting tensile strength and shear strength of the interface between 3D printed ECC and post-cast concrete decreased by 36.1% and 35.8%, respectively, when the replacement ratio of recycled sand in ECC was 100%. Additionally, models for the interfacial shear strength between 3D printed ECC and post-cast concrete were proposed.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"45 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142832346","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 : 2024-12-15DOI: 10.1016/j.cemconcomp.2024.105895
Abasal Hussain, Tao Yu, Fangxin Zou
The use of seawater sea-sand concrete in marine infrastructure not only offers significant sustainability benefits by minimizing the energy consumption and carbon emissions associated with transportation activities, but also helps mitigate the environmental impact caused by excessive sand mining in riverbeds. The study presented in this paper aims to contribute to this growing area of research by introducing self-strain sensing capability to ultra-high-performance seawater sea-sand concrete (UHPSSC) through the incorporation of cost-effective nanocarbon black (nCB) as a functional filler. Mix designs with different nCB contents were formulated and tested for compressive strength, microstructure and piezoresistive behaviour under different curing conditions. The study concludes that, although the addition of nCB generally decreases the workability and compressive strength of UHPSSC, nCB-UHPSSC with reasonably good properties (i.e., slump spread > 160 mm, compressive strength > 140 MPa) can be successfully achieved, and its compressive strength can be further increased by one-day dry curing at 105°C ± 1°C after 28-day water immersion. The study also shows that the developed nCB-UHPSSC possesses stable and repeatable piezoresistive response with a high gauge factor up to over 160. With its outstanding mechanical and piezoresistive properties, the newly developed nCB-UHPSSC is an economically viable and environmentally friendly option for the construction and monitoring of marine and coastal structures.
{"title":"Nanocarbon black based ultra-high-performance seawater sea-sand concrete (UHPSSC) with self-strain sensing capability","authors":"Abasal Hussain, Tao Yu, Fangxin Zou","doi":"10.1016/j.cemconcomp.2024.105895","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105895","url":null,"abstract":"The use of seawater sea-sand concrete in marine infrastructure not only offers significant sustainability benefits by minimizing the energy consumption and carbon emissions associated with transportation activities, but also helps mitigate the environmental impact caused by excessive sand mining in riverbeds. The study presented in this paper aims to contribute to this growing area of research by introducing self-strain sensing capability to ultra-high-performance seawater sea-sand concrete (UHPSSC) through the incorporation of cost-effective nanocarbon black (nCB) as a functional filler. Mix designs with different nCB contents were formulated and tested for compressive strength, microstructure and piezoresistive behaviour under different curing conditions. The study concludes that, although the addition of nCB generally decreases the workability and compressive strength of UHPSSC, nCB-UHPSSC with reasonably good properties (i.e., slump spread > 160 mm, compressive strength > 140 MPa) can be successfully achieved, and its compressive strength can be further increased by one-day dry curing at 105°C ± 1°C after 28-day water immersion. The study also shows that the developed nCB-UHPSSC possesses stable and repeatable piezoresistive response with a high gauge factor up to over 160. With its outstanding mechanical and piezoresistive properties, the newly developed nCB-UHPSSC is an economically viable and environmentally friendly option for the construction and monitoring of marine and coastal structures.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"23 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142825247","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 : 2024-12-13DOI: 10.1016/j.cemconcomp.2024.105890
Yuanyuan Zhu, Zhidan Rong, Qing Jiang, Jinyan Shi
Ferrochrome slag (FCS) is one of the main by-products generated from the smelting of ferrochrome alloy. Its utilization as aggregate can reduce the mining of natural aggregate and cost of ultra-high performance concrete (UHPC). The morphology of aggregate, maximum size (Dmax) and particle gradation are key factors that affect the properties of concrete. Herein, the morphology of FCS compared to river sand was quantitatively characterized. Aggregate gradation was optimized according to the MAA model. Influence mechanisms of aggregate morphology, Dmax, and optimized gradation on the properties of UHPC were clarified. The results indicated that large-size FCS above 2.36 mm had higher circularity and roughness, which was beneficial for enhancing the interface bonding and restraining shrinkage. Grading optimization improved the mechanical properties of UHPC (up to 14.1% at 7 days), interface hardness by 8.6% and reduced the autogenous shrinkage by 6.0%. This shrinkage was further reduced by 12.0% at larger sand-binder ratio of 1.4 due to the enhanced restraint capacity of compactly stacked aggregates. Plastic viscosity of fresh mixture increased with the decrease of Dmax, which resulted in a poor workability. Moreover, small-size FCS below 1.18 mm had less roughness and more needle-like particles, which was detrimental to the mechanical properties. The finer particles in FCS also accelerated the hydration process and led to a larger autogenous shrinkage. Thereby, it is not appropriate to adopt more small-sized porous aggregates in UHPC manufacturing. This study provides a theoretical basis for the mixing design and property improvement of UHPC with porous aggregate.
{"title":"Influence mechanisms of porous aggregate morphology, maximum size and optimized gradation on ultra-high performance concrete with ferrochrome slag","authors":"Yuanyuan Zhu, Zhidan Rong, Qing Jiang, Jinyan Shi","doi":"10.1016/j.cemconcomp.2024.105890","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105890","url":null,"abstract":"Ferrochrome slag (FCS) is one of the main by-products generated from the smelting of ferrochrome alloy. Its utilization as aggregate can reduce the mining of natural aggregate and cost of ultra-high performance concrete (UHPC). The morphology of aggregate, maximum size (D<sub>max</sub>) and particle gradation are key factors that affect the properties of concrete. Herein, the morphology of FCS compared to river sand was quantitatively characterized. Aggregate gradation was optimized according to the MAA model. Influence mechanisms of aggregate morphology, D<sub>max</sub>, and optimized gradation on the properties of UHPC were clarified. The results indicated that large-size FCS above 2.36 mm had higher circularity and roughness, which was beneficial for enhancing the interface bonding and restraining shrinkage. Grading optimization improved the mechanical properties of UHPC (up to 14.1% at 7 days), interface hardness by 8.6% and reduced the autogenous shrinkage by 6.0%. This shrinkage was further reduced by 12.0% at larger sand-binder ratio of 1.4 due to the enhanced restraint capacity of compactly stacked aggregates. Plastic viscosity of fresh mixture increased with the decrease of D<sub>max</sub>, which resulted in a poor workability. Moreover, small-size FCS below 1.18 mm had less roughness and more needle-like particles, which was detrimental to the mechanical properties. The finer particles in FCS also accelerated the hydration process and led to a larger autogenous shrinkage. Thereby, it is not appropriate to adopt more small-sized porous aggregates in UHPC manufacturing. This study provides a theoretical basis for the mixing design and property improvement of UHPC with porous aggregate.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"22 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142816373","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 : 2024-12-13DOI: 10.1016/j.cemconcomp.2024.105891
Mingzhe Zhang, Bing Chen, Weisheng Zhu
This study systematically investigates the influence of ultrafine iron ore tailings (UIOT) on the performance and hydration process of supersulfated cement (SSC) with high phosphogypsum (PG) content. UIOT incorporation retards early-age strength but enhances later-age strength, with a 20% replacement ratio of granulated blast furnace slag (GBFS) leading to a 52% increase in 28-day compressive strength. The performance improvement can be primarily attributed to the following aspects: in the first instance, UIOT regulates the formation rate of ettringite (AFt) by promoting the formation of Fe-Al-bearing AFt ((Fe, Al)-AFt), thereby reducing the excessive formation of AFt typically observed in high-gypsum blended systems. Furthermore, UIOT promotes the formation of calcium-alumino-silicate hydrate (C-(A)-S-H) gel and optimizes the Si/Ca ratio of the gel. The unreacted UIOT particles also play a physical filling role, contributing to the performance enhancement.
{"title":"Performance and hydration mechanisms of ultrafine iron ore tailings enhanced supersulfated cement with high phosphogypsum content.","authors":"Mingzhe Zhang, Bing Chen, Weisheng Zhu","doi":"10.1016/j.cemconcomp.2024.105891","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105891","url":null,"abstract":"This study systematically investigates the influence of ultrafine iron ore tailings (UIOT) on the performance and hydration process of supersulfated cement (SSC) with high phosphogypsum (PG) content. UIOT incorporation retards early-age strength but enhances later-age strength, with a 20% replacement ratio of granulated blast furnace slag (GBFS) leading to a 52% increase in 28-day compressive strength. The performance improvement can be primarily attributed to the following aspects: in the first instance, UIOT regulates the formation rate of ettringite (AFt) by promoting the formation of Fe-Al-bearing AFt ((Fe, Al)-AFt), thereby reducing the excessive formation of AFt typically observed in high-gypsum blended systems. Furthermore, UIOT promotes the formation of calcium-alumino-silicate hydrate (C-(A)-S-H) gel and optimizes the Si/Ca ratio of the gel. The unreacted UIOT particles also play a physical filling role, contributing to the performance enhancement.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"76 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142816374","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 : 2024-12-12DOI: 10.1016/j.cemconcomp.2024.105892
Hyun-Soo Youm, Sung-Gul Hong
The bond-enhancing mechanisms of nano-silica (NS) deposition, described solely by a pozzolanic reaction, have often overlooked its underlying physicochemical nature. We propose a novel framework to quantify spatial disorder in NS deposition and to analyze its impact on the interfacial bond properties of carbon textiles in cement composite. The framework leverages domain knowledge (the morphological characteristics and topochemical hydration mechanisms of cement and NS particles) to estimate the degree of cohesive interconnection between the primary and secondary calcium silicate hydrate (C–S–H) phases precipitated in the textile/matrix interfacial transition zone (ITZ). Utilizing image analysis and rigorous statistical approaches, this framework quantifies latent spatial features derived from the size, polydispersity, and spatial heterogeneity of deposited NS particles. Results confirm that the textile/matrix interfacial bond is a macroscopic property governed not merely by the quantity of NS deposition but also by its topographical complexity, with scale dependence linked to the cement particle size distribution. Strong linear relationships in the inter-scale correlations (R2 > 0.90) demonstrate the consistency of our framework, significantly outperforming other quantitative methods.
{"title":"Insights into nano-silica deposition for carbon textile/cement composite interfacial bond: Quantification of spatial features","authors":"Hyun-Soo Youm, Sung-Gul Hong","doi":"10.1016/j.cemconcomp.2024.105892","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105892","url":null,"abstract":"The bond-enhancing mechanisms of nano-silica (NS) deposition, described solely by a pozzolanic reaction, have often overlooked its underlying physicochemical nature. We propose a novel framework to quantify spatial disorder in NS deposition and to analyze its impact on the interfacial bond properties of carbon textiles in cement composite. The framework leverages domain knowledge (the morphological characteristics and topochemical hydration mechanisms of cement and NS particles) to estimate the degree of cohesive interconnection between the primary and secondary calcium silicate hydrate (C–S–H) phases precipitated in the textile/matrix interfacial transition zone (ITZ). Utilizing image analysis and rigorous statistical approaches, this framework quantifies latent spatial features derived from the size, polydispersity, and spatial heterogeneity of deposited NS particles. Results confirm that the textile/matrix interfacial bond is a macroscopic property governed not merely by the quantity of NS deposition but also by its topographical complexity, with scale dependence linked to the cement particle size distribution. Strong linear relationships in the inter-scale correlations (R<sup>2</sup> > 0.90) demonstrate the consistency of our framework, significantly outperforming other quantitative methods.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142816375","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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