Yong Zheng , Hui Zhong , Keke Sun , Bo Shen , Kai Cui , Yingliang Zhao , Guangqi Xiong , Qinglong Qin
{"title":"Effect of composite activator on hydration kinetics and micromechanical properties of alkali-activated slag","authors":"Yong Zheng , Hui Zhong , Keke Sun , Bo Shen , Kai Cui , Yingliang Zhao , Guangqi Xiong , Qinglong Qin","doi":"10.1016/j.cemconcomp.2025.106047","DOIUrl":"10.1016/j.cemconcomp.2025.106047","url":null,"abstract":"<div><div>Alkali-activated slag (AAS) materials prepared from traditional activators such as NaOH exhibit low sustainability and workability while replacing NaOH with some weakly alkaline solutions (e.g., Na<sub>2</sub>SO<sub>4</sub>) is promising to mitigate the above issues. This paper performs a comprehensive study on the effect of different composite activator combinations i.e., NaOH + Phosphogypsum (PG), NaOH + Na<sub>2</sub>SO<sub>4</sub> and Na<sub>2</sub>SO<sub>4</sub> + Ca(OH)<sub>2,</sub> on the reaction kinetics, phase assemblage, micromechanical properties and microstructure of AAS. The reaction products and microstructure of AAS were characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), thermogravimetric (TG), backscattered electron microscopy (BSEM) and mercury intrusion porosimetry (MIP) techniques. Inductively coupled plasma optical emission spectrometry (ICP-OES) test was used to investigate the pore solution chemistry of AAS. The nanoindentation test was carried out to evaluate the micromechanical properties of AAS. Results indicate that the use of composite activators can significantly reduce the hydration heat of AAS compared to systems activated by a single activator type. Combining PG and NaOH as the composite activator results in more AFt phases, refining the pore structure of AAS and reducing the average critical pore size. Besides, the elastic modulus of the individual solid phases in AAS prepared by this combination significantly outperformed other AAS mixes.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"160 ","pages":"Article 106047"},"PeriodicalIF":10.8,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143618764","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}
Yingliang Zhao , Yong Zheng , Kai Cui , Peiliang Shen , Chi Sun Poon , Juhyuk Moon , Guangmin Peng , Ruilai Guo , Daohui Xia
{"title":"An innovative ternary carbon-fixing cementitious system of cement-fly ash-carbonated steel slag","authors":"Yingliang Zhao , Yong Zheng , Kai Cui , Peiliang Shen , Chi Sun Poon , Juhyuk Moon , Guangmin Peng , Ruilai Guo , Daohui Xia","doi":"10.1016/j.cemconcomp.2025.106042","DOIUrl":"10.1016/j.cemconcomp.2025.106042","url":null,"abstract":"<div><div>The present work introduced an innovative cementitious system named CFCS, combining cement, fly ash (FA), and carbonated steel slag (CS), which exhibited both high early and later-age compressive strength along with significantly lower carbon emissions. This was achieved by producing highly reactive silica gels and carbon-fixing calcium carbonates (<em>Cc</em>) from steel slag (SS) via CO<sub>2</sub>-assisted wet grinding. The results indicate that CFCS shows remarkable improvements in compressive strength, about 26 % and 34 % higher compared to the system of cement-FA-limestone (CFL) at 1 d and 28 d, respectively. The superior early performance of CFCS is attributed to the high pozzolanic reactivity of silica gels in CS, which facilitates the formation of additional calcium-silicate-hydrate (C-S-H) gels. Additionally, reactive <em>Cc</em> readily reacted with aluminates to form monocarbonate (Mc). These gels act as nucleation sites, promoting a higher cement hydration degree and contributing to early strength development. The accelerated cement hydration induced by CS creates a favorable environment for the higher reaction degree of fly ash (FA), resulting in sustained enhancement of compressive strength at later stages. Moreover, the carbon reduction of CFCS can reach about 64 % compared to ordinary Portland cement, representing an ultra-low carbon cementitous system.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"160 ","pages":"Article 106042"},"PeriodicalIF":10.8,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143608300","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}
{"title":"Regulating the workability of NaOH-activated blast furnace slag pastes by considering the mutual inhibition between calcium-sodium aluminosilicate hydrate and hydrotalcite during precipitation","authors":"Ruiquan Jia , Yanxin Chen , Shaowu Jiu , Shiyu Zhuang","doi":"10.1016/j.cemconcomp.2025.106022","DOIUrl":"10.1016/j.cemconcomp.2025.106022","url":null,"abstract":"<div><div>Regulating the workability of NaOH-activated blast furnace slag (NAS) pastes is essential for their effective application. Based on the mutual inhibition between calcium-sodium aluminosilicate hydrate (C-N-A-S-H) and hydrotalcite (LDH) during precipitation (MICL), a novel strategy for regulating paste workability was developed. The workability losses, including the slump loss and the setting time, occurred through hydrate formation and was controlled by the MICL mechanism. The inhibition of the LDH formation by C-N-A-S-H caused the formation of Ca-containing LDH by replacing Mg<sup>2+</sup> with Ca<sup>2+</sup>. With moderate NaAlO<sub>2</sub> addition, C-N-A-S-H and Ca-containing LDH slowly formed because the difference in the degree of mutual inhibition between C-N-A-S-H and LDH during precipitation (DMICL) was minimized. Therefore, workability losses occurred slowly. However, at relatively high (low) NaAlO<sub>2</sub> addition amounts, the DMICL was large, and Ca-containing LDH (C-N-A-S-H) quickly formed; thus, workability losses occurred rapidly. A moderate addition of NaAlO<sub>2</sub> with 1 % Al<sub>2</sub>O<sub>3</sub> decelerated the workability losses and increased the compressive strength.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"160 ","pages":"Article 106022"},"PeriodicalIF":10.8,"publicationDate":"2025-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143618622","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}
{"title":"Enhanced carbonation performance of rice husk ash blended cement-based composites through in-situ CO2 mixing","authors":"Donggue Lee , Won Kyung Kim , Juhyuk Moon","doi":"10.1016/j.cemconcomp.2025.106040","DOIUrl":"10.1016/j.cemconcomp.2025.106040","url":null,"abstract":"<div><div>The carbon capture, utilization, and storage (CCUS) technology has garnered significant attention in achieving carbon neutrality including construction sector. This study investigates the hydration and carbonation mechanisms of cement-based samples subjected to early mineral carbonation in a CO<sub>2</sub>-rich environment, especially by incorporating rice husk ash (RHA). The in-situ CO<sub>2</sub> mixing of cement samples was conducted under sealed conditions for 60 min at a CO<sub>2</sub> concentration of 10 vol%. The effects of various RHA addition ratios on the early-stage carbonation reaction were examined. The results demonstrated that increasing the RHA content enhanced CO<sub>2</sub> sequestration within the porous structure of RHA, facilitating the formation of various carbonates. This carbonate formation contributed to the improvements in initial strength development and CO<sub>2</sub> sequestration. Meanwhile, during the sealed curing period, a significant transformation of CaCO<sub>3</sub> into monocarboaluminate was observed. These findings suggest the potential for adopting RHA and in-situ CO<sub>2</sub> mixing as an environmentally sustainable and efficient strategy for CO<sub>2</sub> sequestration using cement-based materials.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"160 ","pages":"Article 106040"},"PeriodicalIF":10.8,"publicationDate":"2025-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143599008","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}
{"title":"Low-carbon UHPC with carbonated blast furnace slag: Impact of mineral composition, carbonation degree, and CaCO3 polymorphs","authors":"Hammad Ahmed Shah , Jiang Du , Weina Meng","doi":"10.1016/j.cemconcomp.2025.106039","DOIUrl":"10.1016/j.cemconcomp.2025.106039","url":null,"abstract":"<div><div>As a common supplementary cementitious material (SCM), blast furnace slag (slag) is widely used in ultra-high-performance concrete (UHPC) to enhance properties and reduce its carbon footprint. Slag can be carbonated before use to further improve resilience and sustainability of UHPC. However, using raw/carbonated slag and other SCMs in UHPC presents challenges: (1) Variations in supply and production cause fluctuations in chemical, mineral, and physical properties, resulting in significant variability in carbonated slag and UHPC properties; (2) The utilization rate of slag is limited due to its low reactivity; and (3) How variations in slag's mineral composition impact carbonation kinetics and UHPC properties remains unclear. This study addresses these fundamental limitations through comprehensive research.</div><div>Four slags with unique mineral compositions were studied, replacing 40 % and 60 % of cement in UHPC. Both raw and carbonated slags were used to assess the effects of mineral composition, carbonation degree, and CaCO<sub>3</sub> polymorphs on UHPC properties. The findings revealed three insights: (1) slags with similar particle size and chemical composition showed varying impacts on UHPC properties, emphasizing mineral composition's role; (2) mineral composition significantly affects carbonation degree and CaCO<sub>3</sub> polymorph formation; and (3) slag carbonation notably enhances UHPC properties, potentially boosting slag utilization. Slags rich in alite, belite, and anhydrite show higher carbonation, while those with åkermanite and merwinite promote aragonite due to Mg<sup>2+</sup> ions. Higher alite, belite, diopside, and gehlenite in raw slag increase UHPC compressive strength. Carbonated slag in UHPC increased compressive strength by 20 %, flexural strength by 30 %, and toughness by 45 %.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"160 ","pages":"Article 106039"},"PeriodicalIF":10.8,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143590059","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}
{"title":"Reaction kinetics of Na2CO3-activated blast furnace slag with organic ligands: Insights from electrical conductivity measurements","authors":"Julson Aymard Tchio , Elijah Adesanya , Rafal Sliz , Brant Walkley , Juho Yliniemi","doi":"10.1016/j.cemconcomp.2025.106021","DOIUrl":"10.1016/j.cemconcomp.2025.106021","url":null,"abstract":"<div><div>Electrical conductivity measurement using impedance spectroscopy could be a valuable technique for monitoring the various reaction processes of cementitious materials and predicting their long-term durability. In this study, alternating current impedance spectroscopy was employed to investigate the influence of two ligands, 2,3-dihydroxynaphthalene and 3,4-dihydroxybenzoic acid with a 0.1 wt% dosage, on the hardening process of four types of blast furnace slag (BFS) activated with sodium carbonate solution. The objectives of the study were to investigate whether impedance spectroscopy could be used for estimating the reactivity of BFS and monitoring the reaction kinetics of this type of binder as well as evaluating the correlation between electrical conductivity and reaction heat, pore solution chemistry, setting time, flowability and compressive strength. The results demonstrated that both ligands accelerated the hardening process and increased compressive strength, which was confirmed by the various techniques used. The measured electrical conductivities varied among BFS pastes due to differences in their pore solution composition and microstructure and correlated with compressive strength evolution. The results demonstrated that impedance spectroscopy is sensitive enough to detect differences in conductivity due to differences in the reactivity of BFS and the effect of low a dosage of ligands in the binder. However, because of the overall complexity of reactions in this type of binder, responses in electrical conductivity do not show systematic trends.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"160 ","pages":"Article 106021"},"PeriodicalIF":10.8,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143590060","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}
Dezhi Zhao , Hexiang Wang , Caihong Xue , Qingxin Zhao , Wenyue Qi , Yuyang Tian
{"title":"Investigation on the Cl− and heavy metals stabilization of MSWI fly ash by incorporating Portland cement and carbonation","authors":"Dezhi Zhao , Hexiang Wang , Caihong Xue , Qingxin Zhao , Wenyue Qi , Yuyang Tian","doi":"10.1016/j.cemconcomp.2025.106043","DOIUrl":"10.1016/j.cemconcomp.2025.106043","url":null,"abstract":"<div><div>To achieve CO<sub>2</sub> and municipal solid waste incineration fly ash (MSWI-FA) utilization in construction and building materials production, in this study a novel carbon mixing method was proposed to prepare cement-MSWI-FA pastes with improved properties. The effect of carbon mixing and curing on the compressive strength, Cl<sup>−</sup> as well as heavy metal solidification and pore structure was investigated. The reaction products were analyzed with XRD, SEM-EDS and TG to reveal the role of CO<sub>2</sub> mixing on the phase assemblage development. The results showed that a ‘1.5 min normal mixing followed by 1.5 min carbon mixing’ procedure allowed the cement paste with 60 % MSWI-FA to obtain a compressive strength reaching 20 MPa at 28d. Compared with carbon curing, carbon mixing allowed easier and homogenous CO<sub>2</sub> diffusion, and thus increased the CO<sub>3</sub><sup>2−</sup>/HCO<sub>3</sub><sup>−</sup> in the pore solution for the formation of CaCO<sub>3</sub> and Mc. The CaCO<sub>3</sub> functioned as filler to refine the pore structure and thus contributed to the compressive strength improvement, while the Mc was converted to the Fs and AFt with the presence of Cl<sup>−</sup> and SO<sub>4</sub><sup>2−</sup> at 28d, enhancing the Cl<sup>−</sup> and heavy metals solidification. The proposed method and the test results of this study can provide technique support for the utilization of CO<sub>2</sub> and MSWI-FA.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"160 ","pages":"Article 106043"},"PeriodicalIF":10.8,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143599059","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}
{"title":"On the subtilities of rebar corrosion behaviour in cracked concrete","authors":"Gang Li , Moh Boulfiza , Richard Evitts","doi":"10.1016/j.cemconcomp.2025.106038","DOIUrl":"10.1016/j.cemconcomp.2025.106038","url":null,"abstract":"<div><div>This study presents a comprehensive mechanistic corrosion model to simulate rebar corrosion in non-uniform corrosive microenvironments caused by cracking and exposure conditions. The proposed model comprehensively investigates all possible corrosion mechanisms in cracked concrete, addressing an experimental phenomenon that has perplexed experts for decades. In particular, it aims to elucidate the marked difference in corrosion behaviour observed in the presence of thin versus wide cracks. This study demonstrates that self-healing is the sole mechanism differentiating the corrosion behavior of thin and wide cracks, a finding enabled by advanced numerical modeling and experimental validation. Achieving this required a sophisticated physics-based model capable of capturing the major features of reinforcement corrosion in cracked concrete. The ability to selectively activate or deactivate specific mechanisms in the model provides a unique lens to isolate their contributions, which is often impractical in experimental setups. The findings of this study provide valuable insights into the concept of a “critical crack width”, below which reinforcement corrosion is unlikely to pose a significant concern.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"160 ","pages":"Article 106038"},"PeriodicalIF":10.8,"publicationDate":"2025-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143590057","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}
Pengfei Wu , Chao Wei , Xiaoming Liu , Zengqi Zhang , Yang Xue , Xinyue Liu
{"title":"Impact of hematite in red mud on hydration characteristics and environmental performance of cementitious materials","authors":"Pengfei Wu , Chao Wei , Xiaoming Liu , Zengqi Zhang , Yang Xue , Xinyue Liu","doi":"10.1016/j.cemconcomp.2025.106035","DOIUrl":"10.1016/j.cemconcomp.2025.106035","url":null,"abstract":"<div><div>Red mud (RM), a waste by-product of alumina production, is increasingly used in cementitious materials. However, the high iron content and alkaline substances in RM, in addition to heavy metal elements, hinder its utilisation in cementitious materials. To overcome these issues, a ternary system of RM, blast furnace slag (BFS), and cement was prepared to assess the effects of iron in RM on hydration and environmental performance. The results indicated that 97 % of the iron in RM exists in the form of Hematite. As the Hematite content in the system increases, the cumulative hydration heat, heavy metal immobilisation rate, hydration-product content, degree of polymerisation, initial and final setting times, as well as early compressive strength gradually decrease. However, the later strength of the matrix initially increases and then decreases. In addition, the soluble alkali in RM was utilised. When the Hematite content in the system is between 2.47 % and 7.82 % (corresponding to 9.68 %–31.28 % Hematite in RM), the mechanical properties of the matrix meet PO.42.5 standards, and the concentrations of hazardous elements such as Na in the leachate comply with China's drinking water standards (GB/T 5749-2022).</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"160 ","pages":"Article 106035"},"PeriodicalIF":10.8,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143576158","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}
{"title":"Experimental characterization and constitutive modelling of the anisotropic dynamic compressive behavior of 3D printed engineered cementitious composites","authors":"Meng Chen , Jianhua Cheng , Tong Zhang , Yuting Wang","doi":"10.1016/j.cemconcomp.2025.105995","DOIUrl":"10.1016/j.cemconcomp.2025.105995","url":null,"abstract":"<div><div>Engineered cementitious composites (ECC) offer a potential solution to the weak tensile strength and cracking issues of 3D printed concrete (3DPC), while their great performance under dynamic loading helps to broaden the application scope of 3D printing technology. This study systematically investigates the relationship between the dynamic compressive properties and the anisotropic behavior of 3DP-ECC under various strain rates through ultrasonic pulse velocity, quasi-static and dynamic compression, as well as novel sieving tests. The results indicate that the dynamic compressive behavior of 3DP-ECC shows a pronounced strain rate dependency especially in the Z-direction, while the mechanical anisotropy coefficient of the 3DP specimens decreased by 14.2% as the strain rate rose from 60 s<sup>−1</sup> to 120 s<sup>−1</sup>. In what follows, the fractal theory is applied to characterize the internal damage of 3DP-ECC in different orientations, indicating that the dynamic compressive strength and dissipation energy exhibit a linear relationship with the fractal dimension. Based on the modified viscoelastic theory and spatial transformation tensor method, the anisotropic damage dynamic compression constitutive model is developed to predict the stress-strain behavior of 3DP-ECC at different strain rates. The exploration of dynamic compression behavior and anisotropic constitutive relationships of 3DP-ECC provides a basis for further integrated practical applications under extreme strain rate conditions.</div></div>","PeriodicalId":9865,"journal":{"name":"Cement & concrete composites","volume":"160 ","pages":"Article 105995"},"PeriodicalIF":10.8,"publicationDate":"2025-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143576160","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}