Developing hydrophobic agents that minimize the strength loss of bulk hydrophobic cementitious materials (BHCM) remains a formidable challenge. Substances such as siloxanes can hinder cement mineral hydration and prevent the formation of an initial network structure during the early hydration stages. In this study, a novel hydrophobic emulsion in which polydimethylsiloxane (PDMS) wrapped with modified nano silica (MNS) is designed to enhance the hydrophobic property of cementitious materials while minimizing strength loss. The results show that BHCM exhibits good hydrophobicity (water contact angle 121.8°) while significantly reducing strength loss (decreased by 10.3%). The presence of MNS effectively shields PDMS from direct contact with cement minerals during the initial stages. Moreover, MNS can react with portlandite (CH) to generate C-S-H phase and optimize the pore structure of hardened cement pastes. This study contributes to promoting the structure-function integration of cement composites and achieving an extended service life for concrete.
{"title":"Synthesis of MNS@PDMS Emulsion for Enhancing Hydrophobicity in Cementitious Materials with Limited Strength Loss","authors":"Chen Liang, Mingxu Chen, Dongbing Jiang, Pengkun Hou, Deqiang Zhao, Shoude Wang, Ziyuan Yu, Piqi Zhao, Lingchao Lu","doi":"10.1016/j.cemconcomp.2024.105875","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105875","url":null,"abstract":"Developing hydrophobic agents that minimize the strength loss of bulk hydrophobic cementitious materials (BHCM) remains a formidable challenge. Substances such as siloxanes can hinder cement mineral hydration and prevent the formation of an initial network structure during the early hydration stages. In this study, a novel hydrophobic emulsion in which polydimethylsiloxane (PDMS) wrapped with modified nano silica (MNS) is designed to enhance the hydrophobic property of cementitious materials while minimizing strength loss. The results show that BHCM exhibits good hydrophobicity (water contact angle 121.8°) while significantly reducing strength loss (decreased by 10.3%). The presence of MNS effectively shields PDMS from direct contact with cement minerals during the initial stages. Moreover, MNS can react with portlandite (CH) to generate C-S-H phase and optimize the pore structure of hardened cement pastes. This study contributes to promoting the structure-function integration of cement composites and achieving an extended service life for concrete.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"3 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-12-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142758222","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 : 2024-11-28DOI: 10.1016/j.cemconcomp.2024.105872
Lei Wu, Abdul Majid, Qianghua Tang, Zhe Sun, Yan Cao
Recycling construction solid waste is an immediate need due to the substantial amount of construction waste that occupies valuable land and poses environmental hazards. In response to challenges related to the performance and interfacial transition zone (ITZ) when using recycled aggregate (RA) in concrete, a modified formulation with low calcium phosphate (CaP) content was developed to enhance RA's performance. It was found that when the mass ratio of CaP to RA reached 0.001 g/g, the physical properties of RA were significantly improved through a precoating treatment, resulting in a 31.52% increase in the compressive strength of recycled aggregate concrete (RAC) compared to the control group. An in-depth analysis of the mechanism of action of CaP revealed that the active layer formed by CaP on the RA surface promoted the slow hydrolysis-hydration coupling reaction through the sustained release of Ca2+ and PO₄3- ions. This process and the solid-phase reactions of C-S-H gel, carbonation products, and sulfate ions effectively improved the pore structure, increased the specific surface area by 47.36%, and reduced crack width by 78.95%. Furthermore, the bond strength test between modified RA and freshly hardened mortar showed a 30.29% increase in bond strength, directly demonstrating the effectiveness of CaP in enhancing the ITZ in RAC.
由于大量建筑垃圾占用了宝贵的土地并对环境造成危害，因此回收利用建筑固体废弃物已成为当务之急。为了应对在混凝土中使用再生骨料（RA）时在性能和界面过渡区（ITZ）方面的挑战，我们开发了一种磷酸钙（CaP）含量较低的改良配方，以提高 RA 的性能。研究发现，当 CaP 与 RA 的质量比达到 0.001 g/g 时，通过预涂层处理，RA 的物理性能得到显著改善，与对照组相比，再生骨料混凝土（RAC）的抗压强度提高了 31.52%。对 CaP 作用机理的深入分析显示，CaP 在 RA 表面形成的活性层通过 Ca2+ 和 PO₄3- 离子的持续释放，促进了缓慢的水解-水化耦合反应。这一过程以及 C-S-H 凝胶、碳化产物和硫酸根离子的固相反应有效地改善了孔隙结构，使比表面积增加了 47.36%，裂纹宽度减少了 78.95%。此外，改性 RA 与新硬化砂浆之间的粘结强度测试表明，粘结强度提高了 30.29%，直接证明了 CaP 在增强 RAC 中 ITZ 方面的有效性。
{"title":"Effect of calcium phosphate modification on the interfacial transition zone of recycled aggregate and concrete","authors":"Lei Wu, Abdul Majid, Qianghua Tang, Zhe Sun, Yan Cao","doi":"10.1016/j.cemconcomp.2024.105872","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105872","url":null,"abstract":"Recycling construction solid waste is an immediate need due to the substantial amount of construction waste that occupies valuable land and poses environmental hazards. In response to challenges related to the performance and interfacial transition zone (ITZ) when using recycled aggregate (RA) in concrete, a modified formulation with low calcium phosphate (CaP) content was developed to enhance RA's performance. It was found that when the mass ratio of CaP to RA reached 0.001 g/g, the physical properties of RA were significantly improved through a precoating treatment, resulting in a 31.52% increase in the compressive strength of recycled aggregate concrete (RAC) compared to the control group. An in-depth analysis of the mechanism of action of CaP revealed that the active layer formed by CaP on the RA surface promoted the slow hydrolysis-hydration coupling reaction through the sustained release of Ca<sup>2+</sup> and PO₄<sup>3-</sup> ions. This process and the solid-phase reactions of C-S-H gel, carbonation products, and sulfate ions effectively improved the pore structure, increased the specific surface area by 47.36%, and reduced crack width by 78.95%. Furthermore, the bond strength test between modified RA and freshly hardened mortar showed a 30.29% increase in bond strength, directly demonstrating the effectiveness of CaP in enhancing the ITZ in RAC.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142735674","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 : 2024-11-26DOI: 10.1016/j.cemconcomp.2024.105853
Willy Jin, Jean-François Caron, Claudiane M. Ouellet-Plamondon
Concrete 3D printing proposes an off-site industrial process allowing to deposit material only where required. However, most mixture design methods struggle to perform, which is why a majority of 3D printing materials display high clinker contents. This study proposes a reproducible methodology for tailor-made 3D printing materials. Applied to a low-clinker quaternary blend, an iterative optimization process leads to a significant reduction of labor in material tuning. It involves life cycle assessment and artificial neural networks as objective functions in the Pareto selection of best-performing solutions. Following the constitution of an 18-mixture database with 6 independent variables and 5 objective functions, printable mortars of different strength classes are designed within 2 to 4 active learning runs. Consequently, this optimum-driven technique allows to rapidly converge toward low-carbon solutions for 3D printing, using local materials and custom characterization procedures.
混凝土三维打印是一种场外工业流程，只在需要的地方沉积材料。然而，大多数混合物设计方法都很难奏效，这就是为什么大多数 3D 打印材料都显示出较高的熟料含量。本研究提出了一种用于定制 3D 打印材料的可重复方法。在应用于低熟料四元混合物时，迭代优化过程大大减少了材料调整的工作量。它将生命周期评估和人工神经网络作为帕累托选择最佳性能解决方案的目标函数。在建立一个包含 6 个自变量和 5 个目标函数的 18 种混合物数据库后，可打印的不同强度等级的砂浆可在 2 至 4 次主动学习运行中完成设计。因此，这种最优化驱动技术可以使用本地材料和定制表征程序，快速趋近于三维打印的低碳解决方案。
{"title":"Minimizing the carbon footprint of 3D printing concrete: Leveraging parametric LCA and neural networks through multiobjective optimization","authors":"Willy Jin, Jean-François Caron, Claudiane M. Ouellet-Plamondon","doi":"10.1016/j.cemconcomp.2024.105853","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105853","url":null,"abstract":"Concrete 3D printing proposes an off-site industrial process allowing to deposit material only where required. However, most mixture design methods struggle to perform, which is why a majority of 3D printing materials display high clinker contents. This study proposes a reproducible methodology for tailor-made 3D printing materials. Applied to a low-clinker quaternary blend, an iterative optimization process leads to a significant reduction of labor in material tuning. It involves life cycle assessment and artificial neural networks as objective functions in the Pareto selection of best-performing solutions. Following the constitution of an 18-mixture database with 6 independent variables and 5 objective functions, printable mortars of different strength classes are designed within 2 to 4 active learning runs. Consequently, this optimum-driven technique allows to rapidly converge toward low-carbon solutions for 3D printing, using local materials and custom characterization procedures.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"257 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142713212","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 performance of cementitious materials is highly determined by calcium silicate hydrate (C-S-H). In this work, time of flight secondary ion mass spectrometry (TOF-SIMS) characterized by its high resolution was proposed to quantitatively determine the silicate tetrahedron content of C-S-H in a specific micron area. A C-S-H database in which the silicate content in local hydrates is quantified by ion intensity, was established for TOF-SIMS analysis. Results indicate that 8 negative ions and 19 positive ion fragments can be detected among the decomposition of C-S-H. By selecting the characteristic ions representing different silicate structures from ion fragments, the functional relationship between the intensity of characteristic ions and the silicate contents in C-S-H can be established. The quantification equation was proposed to calculate Qn structure contents for various alite hydrates. The silicate structures with defects allocated in the control and pre-pressed sample was constructed successfully based on the TOF-SIMS quantitative results.
{"title":"A novel method to understand and quantify silicate tetrahedron in C-S-H by Time of flight secondary ion mass spectrometry analysis","authors":"Yue Zhou, Linglin Xu, Zheyu Zhu, Yuting Chen, Zhongping Wang, Yun Gao, Kai Wu","doi":"10.1016/j.cemconcomp.2024.105871","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105871","url":null,"abstract":"The performance of cementitious materials is highly determined by calcium silicate hydrate (C-S-H). In this work, time of flight secondary ion mass spectrometry (TOF-SIMS) characterized by its high resolution was proposed to quantitatively determine the silicate tetrahedron content of C-S-H in a specific micron area. A C-S-H database in which the silicate content in local hydrates is quantified by ion intensity, was established for TOF-SIMS analysis. Results indicate that 8 negative ions and 19 positive ion fragments can be detected among the decomposition of C-S-H. By selecting the characteristic ions representing different silicate structures from ion fragments, the functional relationship between the intensity of characteristic ions and the silicate contents in C-S-H can be established. The quantification equation was proposed to calculate Q<sup>n</sup> structure contents for various alite hydrates. The silicate structures with defects allocated in the control and pre-pressed sample was constructed successfully based on the TOF-SIMS quantitative results.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"79 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142718566","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 internal structure of coating mortars often displays considerable variability, posing challenges in analysing and comparing their diverse performance characteristics. Yet, employing advanced characterization and diagnostic techniques offers a pathway to a deeper comprehension of mortar composition and microstructural traits, thereby establishing crucial performance benchmarks.This study investigates the thermal properties of mortars formulated with lightweight aggregates such as expanded cork, expanded clay, and silica aerogel, employing a suite of techniques including X-ray Microtomography (μ-CT), Electronic Scanning Microscopy (SEM), X-ray Diffraction (XRD), Infrared Spectroscopy Fourier Transform (FTIR), and Stereomicroscopy (SM). Through these methods, we conduct a multi-scale analysis of mortar solid structure, delineating aggregates, binders, aggregate/binder interfaces (ITZ) characteristics, and porous structures in quantity, shape, size, and pore connectivity. Additionally, we explore components used in mortar and curing reaction products.Our proposed methodology involves assessing the applicability of each microstructural characterization technique and its capacity to interpret data from mechanical and physical laboratory tests commonly conducted on hardened mortars. This approach identifies pertinent parameters for microstructural characterization and proposes a limited number of microstructure groups based on aggregate connection type and porous framework. The correlation of these findings with the macroscopic behaviour of the tested mortars demonstrated that different microstructural arrangements led to significant variations in mechanical and physical properties, such as compressive strength, thermal conductivity, and gas permeability. Such systemization proves invaluable in comparing mortar performance and crafting new formulations, culminating in developing a graphical atlas.
{"title":"Visual Atlas of Microstructures: deciphering performance parameters in thermal mortars","authors":"Manuel F.C. Pereira, Mónica Gominho, Léo Pinchard, António Maurício, Inês Flores-Colen","doi":"10.1016/j.cemconcomp.2024.105852","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105852","url":null,"abstract":"The internal structure of coating mortars often displays considerable variability, posing challenges in analysing and comparing their diverse performance characteristics. Yet, employing advanced characterization and diagnostic techniques offers a pathway to a deeper comprehension of mortar composition and microstructural traits, thereby establishing crucial performance benchmarks.This study investigates the thermal properties of mortars formulated with lightweight aggregates such as expanded cork, expanded clay, and silica aerogel, employing a suite of techniques including X-ray Microtomography (μ-CT), Electronic Scanning Microscopy (SEM), X-ray Diffraction (XRD), Infrared Spectroscopy Fourier Transform (FTIR), and Stereomicroscopy (SM). Through these methods, we conduct a multi-scale analysis of mortar solid structure, delineating aggregates, binders, aggregate/binder interfaces (ITZ) characteristics, and porous structures in quantity, shape, size, and pore connectivity. Additionally, we explore components used in mortar and curing reaction products.Our proposed methodology involves assessing the applicability of each microstructural characterization technique and its capacity to interpret data from mechanical and physical laboratory tests commonly conducted on hardened mortars. This approach identifies pertinent parameters for microstructural characterization and proposes a limited number of microstructure groups based on aggregate connection type and porous framework. The correlation of these findings with the macroscopic behaviour of the tested mortars demonstrated that different microstructural arrangements led to significant variations in mechanical and physical properties, such as compressive strength, thermal conductivity, and gas permeability. Such systemization proves invaluable in comparing mortar performance and crafting new formulations, culminating in developing a graphical atlas.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"34 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-11-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142690787","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 the realm of sustainable construction materials, this study delves into the feasibility of utilizing wood-derived biochar as a partial substitute for sand in mortar. Carbon mineralisation potential of mortar increases due to the presence of biochar. Inclusion of biochar leads to improved thermal performance, manifested through reduced thermal conductivity, and increased specific heat capacity. Water vapour resistance factor also benefits from biochar, peaking at a 15% mixture. However, it is essential to acknowledge that these hygrothermal and carbon sequestration advantages comes at a cost: higher biochar contents lead to reduced strength, increased drying shrinkage and reduced sulphate resistance. The primary focus of this research lies in striking a balance between hygrothermal performance and environmental performance, particularly for indoor building applications. Furthermore, this research underscores the necessity of tailoring biochar-cementitious composite materials to their intended application context, capitalizing on their inherent strengths while mitigating potential weaknesses.
{"title":"Carbon sequestering biochar incorporated cementitious composites: Evaluation of hygrothermal, mechanical and durability characteristics","authors":"Madhuwanthi Rupasinghe, Zipeng Zhang, Priyan Mendis, Massoud Sofi","doi":"10.1016/j.cemconcomp.2024.105864","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105864","url":null,"abstract":"In the realm of sustainable construction materials, this study delves into the feasibility of utilizing wood-derived biochar as a partial substitute for sand in mortar. Carbon mineralisation potential of mortar increases due to the presence of biochar. Inclusion of biochar leads to improved thermal performance, manifested through reduced thermal conductivity, and increased specific heat capacity. Water vapour resistance factor also benefits from biochar, peaking at a 15% mixture. However, it is essential to acknowledge that these hygrothermal and carbon sequestration advantages comes at a cost: higher biochar contents lead to reduced strength, increased drying shrinkage and reduced sulphate resistance. The primary focus of this research lies in striking a balance between hygrothermal performance and environmental performance, particularly for indoor building applications. Furthermore, this research underscores the necessity of tailoring biochar-cementitious composite materials to their intended application context, capitalizing on their inherent strengths while mitigating potential weaknesses.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"59 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-11-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142684951","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}
Because of ion exchange properties, the presence of layered double hydroxides (LDHs) influences passivation process of reinforcement embedded in geopolymer concrete. In this study, the ion exchange behavior of MgAl–NO-LDHs and its effect on the characteristics of passivation film and electrochemical behavior of passive reinforcement in simulated slag-fly ash-waste ceramic powders geopolymer solution (SGP) are extensively investigated. The results indicate that LDHs with layered structure improve the protection efficiency of adsorption layer in SGP. Further, the intercalated NO is efficiently exchanged with OH in SGP, thus increasing the thickness and corrosion resistance of the formed passivation film. However, because the adsorption layer halts NO release process, the beneficial effect is mainly observed during later immersion stage.
由于具有离子交换特性，层状双氢氧化物（LDHs）的存在会影响嵌入土工聚合物混凝土中钢筋的钝化过程。本研究广泛研究了 MgAl-NO-LDHs 的离子交换行为及其对模拟矿渣-粉煤灰-废陶瓷粉土工聚合物溶液（SGP）中钝化膜特性和被动钢筋电化学行为的影响。结果表明，具有分层结构的 LDHs 提高了 SGP 中吸附层的保护效率。此外，夹杂的 NO 在 SGP 中与 OH 有效交换，从而增加了所形成的钝化膜的厚度和耐腐蚀性。不过，由于吸附层阻止了 NO 的释放过程，因此这种有益效果主要体现在浸泡后期。
{"title":"Influence of MgAl–NO2-LDHs on passivation of reinforcing steel in simulated geopolymer solution","authors":"Yuchen Wu, Zhipeng Xu, Jiangwei Zhu, Fengjiang Li, Jie Hu, Yuwei Ma, Zuhua Zhang, Haoliang Huang, Jiangxiong Wei, Qijun Yu, Caijun Shi","doi":"10.1016/j.cemconcomp.2024.105676","DOIUrl":"https://doi.org/10.1016/j.cemconcomp.2024.105676","url":null,"abstract":"Because of ion exchange properties, the presence of layered double hydroxides (LDHs) influences passivation process of reinforcement embedded in geopolymer concrete. In this study, the ion exchange behavior of MgAl–NO-LDHs and its effect on the characteristics of passivation film and electrochemical behavior of passive reinforcement in simulated slag-fly ash-waste ceramic powders geopolymer solution (SGP) are extensively investigated. The results indicate that LDHs with layered structure improve the protection efficiency of adsorption layer in SGP. Further, the intercalated NO is efficiently exchanged with OH in SGP, thus increasing the thickness and corrosion resistance of the formed passivation film. However, because the adsorption layer halts NO release process, the beneficial effect is mainly observed during later immersion stage.","PeriodicalId":519419,"journal":{"name":"Cement and Concrete Composites","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141836819","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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