Pub Date : 2024-11-06DOI: 10.1016/j.cemconres.2024.107712
Qiaomu Zheng , En-hua Yang , Chen Li , Qiang Ren , Hongen Zhang , Facheng Song , Bo Liu , Zhengwu Jiang
This work studies the autogenous self-healing of ultra-high performance concrete (UHPC) incorporating two ultra-fine pozzolanic materials, silica fume (USF) and ultra-fine fly ash (UFFA), under carbonation conditioning. Both ultra-fine pozzolanic materials stimulate the healing of cracks by promoting the secondary hydration of the cement matrix. USF and UFFA form healing products primarily consisting of C-S-H and ettringite, respectively, and the latter product closes the cracks more effectively. Under carbonation conditioning, UFFA accelerates CaCO3 formation with residual uncarbonated ettringites as the structural skeleton, improving the impermeability recovery. USF generates silica gel as a bonding layer between the CaCO3 crystals and the cement matrix after decalcification, which induces more multi-dimensional cracking upon regenerated structures under flexural reloading, thereby enhancing the mechanical property restoration of UHPC. UFFA-modified UHPC is ideal for applications requiring high impermeability, whereas USF-incorporated UHPC is better suited for scenarios with high load-bearing demands.
{"title":"Influence of ultra-fine pozzolanic materials on the self-healing capabilities of ultra-high performance concrete under carbonation conditioning","authors":"Qiaomu Zheng , En-hua Yang , Chen Li , Qiang Ren , Hongen Zhang , Facheng Song , Bo Liu , Zhengwu Jiang","doi":"10.1016/j.cemconres.2024.107712","DOIUrl":"10.1016/j.cemconres.2024.107712","url":null,"abstract":"<div><div>This work studies the autogenous self-healing of ultra-high performance concrete (UHPC) incorporating two ultra-fine pozzolanic materials, silica fume (USF) and ultra-fine fly ash (UFFA), under carbonation conditioning. Both ultra-fine pozzolanic materials stimulate the healing of cracks by promoting the secondary hydration of the cement matrix. USF and UFFA form healing products primarily consisting of C-S-H and ettringite, respectively, and the latter product closes the cracks more effectively. Under carbonation conditioning, UFFA accelerates CaCO<sub>3</sub> formation with residual uncarbonated ettringites as the structural skeleton, improving the impermeability recovery. USF generates silica gel as a bonding layer between the CaCO<sub>3</sub> crystals and the cement matrix after decalcification, which induces more multi-dimensional cracking upon regenerated structures under flexural reloading, thereby enhancing the mechanical property restoration of UHPC. UFFA-modified UHPC is ideal for applications requiring high impermeability, whereas USF-incorporated UHPC is better suited for scenarios with high load-bearing demands.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"187 ","pages":"Article 107712"},"PeriodicalIF":10.9,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142588855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-06DOI: 10.1016/j.cemconres.2024.107705
Sophie J. Schmid , Luis Zelaya-Lainez , Olaf Lahayne , Martin Peyerl , Bernhard Pichler
In this study, hourly three-minute creep testing is used to elucidate the evolution of the viscoelastic behavior of cement pastes produced with ordinary Portland cement (OPC), limestone Portland cement (LPC), and limestone calcined clay cement (LC3), from 1 to 7 days after production. An innovative test evaluation protocol, accounting for shrinkage, is used to identify values of the elastic modulus, the creep modulus, and the creep exponent, without making assumptions. The S-shaped shrinkage evolution of the LC3 paste is explained by Portlandite dissolution and the associated redistribution of chemical shrinkage-induced compressive stresses to the remaining solid skeleton. The evolution of the elastic stiffness of the LC3 paste is explained by space filling by C-A-S-H phases. The small creep compliance of the LC3 paste is explained by C-A-S-H which creeps less than C-S-H, and by AFm phases which precipitate in nanoscopic slit pores between C-S-H structures, gluing viscous interfaces.
{"title":"Hourly three-minute creep testing of an LC3 paste at early ages: Advanced test evaluation and the effects of the pozzolanic reaction on shrinkage, elastic stiffness, and creep","authors":"Sophie J. Schmid , Luis Zelaya-Lainez , Olaf Lahayne , Martin Peyerl , Bernhard Pichler","doi":"10.1016/j.cemconres.2024.107705","DOIUrl":"10.1016/j.cemconres.2024.107705","url":null,"abstract":"<div><div>In this study, hourly three-minute creep testing is used to elucidate the evolution of the viscoelastic behavior of cement pastes produced with ordinary Portland cement (OPC), limestone Portland cement (LPC), and limestone calcined clay cement (LC3), from 1 to 7 days after production. An innovative test evaluation protocol, accounting for shrinkage, is used to identify values of the elastic modulus, the creep modulus, and the creep exponent, <em>without</em> making assumptions. The S-shaped shrinkage evolution of the LC3 paste is explained by Portlandite dissolution and the associated redistribution of chemical shrinkage-induced compressive stresses to the remaining solid skeleton. The evolution of the elastic stiffness of the LC3 paste is explained by space filling by C-A-S-H phases. The small creep compliance of the LC3 paste is explained by C-A-S-H which creeps less than C-S-H, and by AFm phases which precipitate in nanoscopic slit pores between C-S-H structures, gluing viscous interfaces.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"187 ","pages":"Article 107705"},"PeriodicalIF":10.9,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142588456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-04DOI: 10.1016/j.cemconres.2024.107713
Zengliang Yue, Yuvaraj Dhandapani, Susan A. Bernal
The impact of carbonation, induced at different CO2 concentrations (0.04 or 1 %), in the phase assemblages and compressive strength of Na2SO4-activated slag materials was determined. Carbonation led to Ca-bearing phases' decalcification (mainly C-(A)-S-H type gel and ettringite) forming different CaCO3 polymorphs, independent of the slag composition or carbonation conditions adopted. In specimens exposed to 0.04 % CO2, a negligible carbonation front was observed, along with a continued phase assemblage evolution and compressive strength gain after 500 days of exposure. Conversely, exposure to 1 % CO2 led to complete carbonation after 28 days, and a significant compressive strength reduction. Accelerated carbonation does not lead to the development of comparable microstructures to those observed in naturally carbonated pastes. The accelerated carbonation rates were ~ 33 times higher than those determined under natural carbonation exposure. Therefore, accelerated tests are considered unsuitable for predicting the long-term carbonation performance of Na2SO4-activated slag cements.
{"title":"Structural alterations in alkali-sulfate-activated slag cement pastes induced by natural and accelerated carbonation","authors":"Zengliang Yue, Yuvaraj Dhandapani, Susan A. Bernal","doi":"10.1016/j.cemconres.2024.107713","DOIUrl":"10.1016/j.cemconres.2024.107713","url":null,"abstract":"<div><div>The impact of carbonation, induced at different CO<sub>2</sub> concentrations (0.04 or 1 %), in the phase assemblages and compressive strength of Na<sub>2</sub>SO<sub>4</sub>-activated slag materials was determined. Carbonation led to Ca-bearing phases' decalcification (mainly C-(A)-S-H type gel and ettringite) forming different CaCO<sub>3</sub> polymorphs, independent of the slag composition or carbonation conditions adopted. In specimens exposed to 0.04 % CO<sub>2</sub>, a negligible carbonation front was observed, along with a continued phase assemblage evolution and compressive strength gain after 500 days of exposure. Conversely, exposure to 1 % CO<sub>2</sub> led to complete carbonation after 28 days, and a significant compressive strength reduction. Accelerated carbonation does not lead to the development of comparable microstructures to those observed in naturally carbonated pastes. The accelerated carbonation rates were ~ 33 times higher than those determined under natural carbonation exposure. Therefore, accelerated tests are considered unsuitable for predicting the long-term carbonation performance of Na<sub>2</sub>SO<sub>4</sub>-activated slag cements.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"187 ","pages":"Article 107713"},"PeriodicalIF":10.9,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142574541","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ca2SiO4 is the primary carbonation-reactive mineral in steel slag, and demonstrates significant carbon sequestration potential, yet its microscopic reaction processes remain unclear. This study investigated the carbonation behavior of Ca2SiO4 using ReaxFF MD simulations. The results indicated that as CO2 concentration increased, the capture rate of Ca2SiO4 decreased, and the molecular structure of the resulting CaCO3 varied in oxygen origin. At room temperature, the carbonation rate of Ca₂SiO₄ gradually decreased over time until it reached equilibrium. Increasing the temperature could reactivate the carbonation, but the rate would still decline until it reached equilibrium again. Higher temperatures could accelerate the formation of the intermediate C2O52− and internal CO32− diffusion, thereby boosting the carbonation and increasing CO2 adsorption. This study investigated the carbonation of Ca2SiO4 at the atomic level, aiming to link microscopic molecular processes with macroscopic experimental phenomena, thereby providing a theoretical foundation for enhancing the carbonation efficiency of steel slag.
{"title":"Insight into the direct carbonation process of Ca2SiO4 based on ReaxFF MD simulation and experiments","authors":"Ya-Jun Wang, Xiao-Pei Zhang, Dong-Mei Liu, Jun-Guo Li, Jian-Bao Zhang, Yu-Wei Zhang, Ya-Nan Zeng, Yi-Tong Wang, Bao Liu, Xi Zhang, Ya-Jing Zhang","doi":"10.1016/j.cemconres.2024.107711","DOIUrl":"10.1016/j.cemconres.2024.107711","url":null,"abstract":"<div><div>Ca<sub>2</sub>SiO<sub>4</sub> is the primary carbonation-reactive mineral in steel slag, and demonstrates significant carbon sequestration potential, yet its microscopic reaction processes remain unclear. This study investigated the carbonation behavior of Ca<sub>2</sub>SiO<sub>4</sub> using ReaxFF MD simulations. The results indicated that as CO<sub>2</sub> concentration increased, the capture rate of Ca<sub>2</sub>SiO<sub>4</sub> decreased, and the molecular structure of the resulting CaCO<sub>3</sub> varied in oxygen origin. At room temperature, the carbonation rate of Ca₂SiO₄ gradually decreased over time until it reached equilibrium. Increasing the temperature could reactivate the carbonation, but the rate would still decline until it reached equilibrium again. Higher temperatures could accelerate the formation of the intermediate C<sub>2</sub>O<sub>5</sub><sup>2−</sup> and internal CO<sub>3</sub><sup>2−</sup> diffusion, thereby boosting the carbonation and increasing CO<sub>2</sub> adsorption. This study investigated the carbonation of Ca<sub>2</sub>SiO<sub>4</sub> at the atomic level, aiming to link microscopic molecular processes with macroscopic experimental phenomena, thereby providing a theoretical foundation for enhancing the carbonation efficiency of steel slag.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"187 ","pages":"Article 107711"},"PeriodicalIF":10.9,"publicationDate":"2024-11-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142574540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-02DOI: 10.1016/j.cemconres.2024.107708
Ziga Casar , Tecla Bottinelli Montandon , Manuel Cordova , Karen Scrivener , Paul Bowen , Aslam Kunhi Mohamed
A general-purpose formal charge polarizable force field for cementitious systems, CementFF4, is presented. The force field includes the following species: Ca, Si, O, H, Al, Zn, OH− and H2O. The force field is a significant extension of previous force fields and is validated by comparison of structural features, elastic constants, reaction enthalpies, and vibrational density of states to experimental and ab initio values for known crystals. Particular attention is given to the tobermorite 14 Å structure, due to its similarity to the main hydration phase of Portland cements, calcium silicate hydrate. The results are in very good agreement with experimental and ab initio data over the entire range of simulated properties (less than 5 % deviation on structural properties and less than 10 % on mechanical properties for non-hydroxide minerals).
介绍了水泥基系统的通用形式电荷可极化力场 CementFF4。该力场包括以下物种：Ca、Si、O、H、Al、Zn、OH- 和 H2O：Ca、Si、O、H、Al、Zn、OH- 和 H2O。该力场是以往力场的重要扩展，并通过将结构特征、弹性常数、反应焓和振动状态密度与已知晶体的实验值和 ab initio 值进行比较而得到验证。由于托勃莫来石的 14 Å 结构与波特兰水泥的主要水化相硅酸钙水合物相似，因此受到了特别关注。在整个模拟特性范围内，结果与实验数据和 ab initio 数据非常吻合（非氢氧化物矿物的结构特性偏差小于 5%，机械特性偏差小于 10%）。
{"title":"CementFF4: Formal atomic charge polarizable force field for cementitious systems – Bulk and surface","authors":"Ziga Casar , Tecla Bottinelli Montandon , Manuel Cordova , Karen Scrivener , Paul Bowen , Aslam Kunhi Mohamed","doi":"10.1016/j.cemconres.2024.107708","DOIUrl":"10.1016/j.cemconres.2024.107708","url":null,"abstract":"<div><div>A general-purpose formal charge polarizable force field for cementitious systems, CementFF4, is presented. The force field includes the following species: Ca, Si, O, H, Al, Zn, OH<sup>−</sup> and H<sub>2</sub>O. The force field is a significant extension of previous force fields and is validated by comparison of structural features, elastic constants, reaction enthalpies, and vibrational density of states to experimental and ab initio values for known crystals. Particular attention is given to the tobermorite 14 Å structure, due to its similarity to the main hydration phase of Portland cements, calcium silicate hydrate. The results are in very good agreement with experimental and ab initio data over the entire range of simulated properties (less than 5 % deviation on structural properties and less than 10 % on mechanical properties for non-hydroxide minerals).</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"187 ","pages":"Article 107708"},"PeriodicalIF":10.9,"publicationDate":"2024-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142563098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.cemconres.2024.107709
Chang Gao , Haoyu Zeng , Jie Xu , Disheng Xu , Yuefeng Ma , Wei She , Zhangli Hu , Jinhui Tang , Jiaping Liu
Strength and toughness are destined conflicts in traditional inorganic materials. Herein, we prepared a high-performance calcium-silicate-hydrate (C-S-H) based organic-inorganic composites, with a trace of sodium alginate (about 8 wt%). A 1.9-fold increase in flexural strength and a nearly 6.8-fold enhancement for work of fracture are achieved in the composites, and importantly, the elastic modulus is increased by 22.2 %. Here, flawless C-S-H gel devoid of obvious interphase boundary was formulated attributed to the intercalation of sodium alginate into the C-S-H layer, creating a hybrid bonding network of hydrogen bonds together with the ion complexation effect. Concurrently, sodium alginate is to establish an organic plasticizing zone, aiding in the mitigation of stress within cracks. Hence, our study overcomes the challenge of achieving a harmonious balance between strength and toughness, offering innovative pathways for advancing the development of high-performance organic-inorganic composite materials. Besides, the improvement mechanism proposed in this research provides a pristine and feasible methodology for strengthening and toughening of Portland cement-based materials.
{"title":"Collaborative enhancement in “strength-toughness-elastic modulus” of calcium-silicate-hydrate (C-S-H) based organic-inorganic composites: Chemical bonding and cracking path optimization","authors":"Chang Gao , Haoyu Zeng , Jie Xu , Disheng Xu , Yuefeng Ma , Wei She , Zhangli Hu , Jinhui Tang , Jiaping Liu","doi":"10.1016/j.cemconres.2024.107709","DOIUrl":"10.1016/j.cemconres.2024.107709","url":null,"abstract":"<div><div>Strength and toughness are destined conflicts in traditional inorganic materials. Herein, we prepared a high-performance calcium-silicate-hydrate (C-S-H) based organic-inorganic composites, with a trace of sodium alginate (about 8 wt%). A 1.9-fold increase in flexural strength and a nearly 6.8-fold enhancement for work of fracture are achieved in the composites, and importantly, the elastic modulus is increased by 22.2 %. Here, flawless C-S-H gel devoid of obvious interphase boundary was formulated attributed to the intercalation of sodium alginate into the C-S-H layer, creating a hybrid bonding network of hydrogen bonds together with the ion complexation effect. Concurrently, sodium alginate is to establish an organic plasticizing zone, aiding in the mitigation of stress within cracks. Hence, our study overcomes the challenge of achieving a harmonious balance between strength and toughness, offering innovative pathways for advancing the development of high-performance organic-inorganic composite materials. Besides, the improvement mechanism proposed in this research provides a pristine and feasible methodology for strengthening and toughening of Portland cement-based materials.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"187 ","pages":"Article 107709"},"PeriodicalIF":10.9,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142562163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Drying shrinkage of cement pastes (CPs) facilitating superficial cracking deserves primary concern when evaluating durability performance. To clarify shrinkage mechanism, the changes of mass, length and pore-scale water allocation of two mature CPs were monitored non-destructively through low-field NMR relaxometry. Experimental results indicated that, heat treatment under hot water slightly coarsens the pore structure of CPs through modifying packing, and reduces shrinkage remarkably through stiffening clusters. Upon drying at 43% RH, the interlayer pores are still saturated and compacted with reduced volume. At 80% RH, although the interlayer and gel pores are both saturated, they lose water gradually at reducing rates. Drying shrinkages of CPs are caused by compaction of interlayer and gel pores, whose contributions to shrinkage are at the ratio of 1:3 roughly. Most of compaction is compensated by the coarsening of pore structure, and only 2–6 percent shows up as observable shrinkage.
{"title":"The deformation of CSH gels and its link with dynamic length change of cement pastes upon drying and resaturation","authors":"Chunsheng Zhou , Xiaoyu Zhang , Jing Qiao , Jingjing Feng , Qiang Zeng","doi":"10.1016/j.cemconres.2024.107693","DOIUrl":"10.1016/j.cemconres.2024.107693","url":null,"abstract":"<div><div>Drying shrinkage of cement pastes (CPs) facilitating superficial cracking deserves primary concern when evaluating durability performance. To clarify shrinkage mechanism, the changes of mass, length and pore-scale water allocation of two mature CPs were monitored non-destructively through low-field NMR relaxometry. Experimental results indicated that, heat treatment under hot water slightly coarsens the pore structure of CPs through modifying <figure><img></figure> packing, and reduces shrinkage remarkably through stiffening <figure><img></figure> clusters. Upon drying at 43% RH, the interlayer pores are still saturated and compacted with reduced volume. At 80% RH, although the interlayer and gel pores are both saturated, they lose water gradually at reducing rates. Drying shrinkages of CPs are caused by compaction of interlayer and gel pores, whose contributions to shrinkage are at the ratio of 1:3 roughly. Most of <figure><img></figure> compaction is compensated by the coarsening of pore structure, and only 2–6 percent shows up as observable shrinkage.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"187 ","pages":"Article 107693"},"PeriodicalIF":10.9,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142562165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-30DOI: 10.1016/j.cemconres.2024.107703
Arthur Fanara , Luc Courard , Frédéric Collin
The analysis of the impact of Recycled Concrete Aggregates (RCA) on chloride ingress is of prime importance for the development of Recycled Aggregates Concrete. A coupled chemo-hydraulic multiscale model, using the Finite Element squared (FE) method, has been developed, validated and calibrated. The constitutive equations using intrinsic parameters derived from laboratory experiments on concrete samples have been established. The findings indicate that the durability of Recycled Aggregates Concrete (RAC) could be comparable to that of Natural Aggregates Concrete (NAC) depending on the mixture quality and environmental conditions. The main difference in durability comes from the rate of diffusion with regards to the mortar paste adherent content.
{"title":"Numerical FE2 study of chloride ingress in unsaturated recycled aggregates concrete","authors":"Arthur Fanara , Luc Courard , Frédéric Collin","doi":"10.1016/j.cemconres.2024.107703","DOIUrl":"10.1016/j.cemconres.2024.107703","url":null,"abstract":"<div><div>The analysis of the impact of Recycled Concrete Aggregates (RCA) on chloride ingress is of prime importance for the development of Recycled Aggregates Concrete. A coupled chemo-hydraulic multiscale model, using the Finite Element squared (FE<span><math><msup><mrow></mrow><mrow><mn>2</mn></mrow></msup></math></span>) method, has been developed, validated and calibrated. The constitutive equations using intrinsic parameters derived from laboratory experiments on concrete samples have been established. The findings indicate that the durability of Recycled Aggregates Concrete (RAC) could be comparable to that of Natural Aggregates Concrete (NAC) depending on the mixture quality and environmental conditions. The main difference in durability comes from the rate of diffusion with regards to the mortar paste adherent content.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107703"},"PeriodicalIF":10.9,"publicationDate":"2024-10-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142541708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-28DOI: 10.1016/j.cemconres.2024.107706
Zhaoheng Guo , Cheng Liu , Yasong Zhao , Gaofeng Chen , Huixia Wu , Jianming Gao , Hongjian Du
Nanosilica (NS) has the potential to enhance the performance of cement-based materials through improvements in pore structure, hydration product content, and the properties of calcium–(aluminum)–silicate–hydrate (C–(A)–S–H) gel, ultimately increasing resistance to sulfate attack. However, the underlying mechanisms of these enhancements remain incompletely understood, particularly with respect to the presence of unhydrated NS particles in blended cementitious materials under sulfate attack. C3A (tricalcium aluminate) is one of the main components of cement and a major source of aluminum phases during sulfate attack. This study aims to investigate the effects of NS on the hydration of the C3A–gypsum system and the subsequent reaction between the hydration products and sulfates. The investigation involves qualitative and quantitative analyses of the reaction products, and microscopic morphology, as well as tests on ion concentrations, zeta potentials, and sulfate concentrations in the reaction solution. Findings suggest that NS inhibits the formation of ettringite during the C3A–gypsum hydration process, but does not exert a notable influence on the final hydration product content. Furthermore, residual NS particles in the C3A–NS hydration system further impede the reaction between hydrogarnet and sulfate, thereby reducing ettringite formation. NS also impedes the dissolution of hydrogarnet, resulting in lower concentrations of Ca2+ and Al3+ ions and limited consumption of SO42−. Based on the analysis of the research results, this inhibitory effect is attributed to the adsorption of NS particles onto the hydrogarnet surface, which attracts Ca2+, SO42−, or CaS ion pair complexes, leading to surface ion overcharging and reduced hydrogarnet dissolution. In addition, NS particles may adsorb onto the surface of ettringite, preventing the adsorption of Ca2+, SO42−, or CaS ion pair complexes, thereby inhibiting the formation and growth of ettringite.
{"title":"Impact of nanosilica on tricalcium aluminate hydration and its reaction with sulfate solutions","authors":"Zhaoheng Guo , Cheng Liu , Yasong Zhao , Gaofeng Chen , Huixia Wu , Jianming Gao , Hongjian Du","doi":"10.1016/j.cemconres.2024.107706","DOIUrl":"10.1016/j.cemconres.2024.107706","url":null,"abstract":"<div><div>Nanosilica (NS) has the potential to enhance the performance of cement-based materials through improvements in pore structure, hydration product content, and the properties of calcium–(aluminum)–silicate–hydrate (C–(A)–S–H) gel, ultimately increasing resistance to sulfate attack. However, the underlying mechanisms of these enhancements remain incompletely understood, particularly with respect to the presence of unhydrated NS particles in blended cementitious materials under sulfate attack. C<sub>3</sub>A (tricalcium aluminate) is one of the main components of cement and a major source of aluminum phases during sulfate attack. This study aims to investigate the effects of NS on the hydration of the C<sub>3</sub>A–gypsum system and the subsequent reaction between the hydration products and sulfates. The investigation involves qualitative and quantitative analyses of the reaction products, and microscopic morphology, as well as tests on ion concentrations, zeta potentials, and sulfate concentrations in the reaction solution. Findings suggest that NS inhibits the formation of ettringite during the C<sub>3</sub>A–gypsum hydration process, but does not exert a notable influence on the final hydration product content. Furthermore, residual NS particles in the C<sub>3</sub>A–NS hydration system further impede the reaction between hydrogarnet and sulfate, thereby reducing ettringite formation. NS also impedes the dissolution of hydrogarnet, resulting in lower concentrations of Ca<sup>2+</sup> and Al<sup>3+</sup> ions and limited consumption of SO<sub>4</sub><sup>2−</sup>. Based on the analysis of the research results, this inhibitory effect is attributed to the adsorption of NS particles onto the hydrogarnet surface, which attracts Ca<sup>2+</sup>, SO<sub>4</sub><sup>2−</sup>, or Ca<img>S ion pair complexes, leading to surface ion overcharging and reduced hydrogarnet dissolution. In addition, NS particles may adsorb onto the surface of ettringite, preventing the adsorption of Ca<sup>2+</sup>, SO<sub>4</sub><sup>2−</sup>, or Ca<img>S ion pair complexes, thereby inhibiting the formation and growth of ettringite.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107706"},"PeriodicalIF":10.9,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142519672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-28DOI: 10.1016/j.cemconres.2024.107702
Haemin Song , Taehwan Kim , Ailar Hajimohammadi , Jae Eun Oh , Arnaud Castel
Lightweight porous composites have been widely explored to improve their acoustic and thermal performances. Hempcrete can serve as thermal insulating or soundproofing material by utilising its high porosity. However, the rigorous correlation between hempcrete thermal and acoustic performance and its pore structure remains poorly understood due to its different pore types. In this study, three hempcrete pore types [i.e., i) inter-pore between hemp and mortar, ii) hemp intra-pore, and iii) mortar intra-pore] were modified by tamping, delignification, and foaming agent conditions, respectively. Then the volumes of three types of pores were estimated using X-ray micro-computed tomography (μCT) and mercury intrusion porosimetry. The new segmentation methods were developed and their reliability and accuracy were validated. Then, the pore volumes were correlated to the thermal and acoustic properties of hempcrete. Low tamping and high delignification conditions are recommended to increase inter-pore volume and enhance hempcrete performances relating to both thermal insulation and sound absorption for real-world hempcrete applications.
为改善轻质多孔复合材料的隔音和隔热性能，人们对其进行了广泛的研究。大麻混凝土可利用其高孔隙率作为隔热或隔音材料。然而，由于麻混凝土的孔隙类型不同，人们对其热性能和隔音性能与其孔隙结构之间的密切联系仍然知之甚少。在本研究中，分别通过捣实、脱木质素和发泡剂条件改变了三种麻混凝土孔隙类型[即：i) 麻与砂浆之间的孔隙；ii) 麻内部孔隙；iii) 砂浆内部孔隙]。然后使用 X 射线显微计算机断层扫描（μCT）和汞侵入孔隙测定法估算了三种孔隙的体积。开发了新的细分方法，并验证了其可靠性和准确性。然后，将孔隙体积与麻混凝土的热学和声学特性相关联。建议在低振捣和高脱木质素条件下增加孔隙间容积，提高麻混凝土在实际应用中的隔热和吸音性能。
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