Pub Date : 2026-01-02DOI: 10.1016/j.cement.2025.100167
Thinh Nguyen , Quoc Tri Phung , Norbert Maes , Lander Frederickx , Rodrigo de Oliveira Silva , Dimitrios Sakellariou , Geert De Schutter , Özlem Cizer
Carbonation lowers the pH, leading to decalcification, shrinkage, and densification of the pore structure. Recalcification, the process of reintroducing calcium ions into decalcified cementitious materials, is a promising approach for restoring carbonated cement pastes. However, its impact on carbonated cementitious materials remains unelucidated. This study demonstrates, for the first time, how recalcification not only restores the Ca/Si ratio of calcium–(aluminum)-silicate-hydrate (C–(A)-S-H) to levels comparable with intact gel but also fundamentally alters its nanostructure. Using solid-state ²⁹Si NMR, we show that recalcification turned silica gel into cross-linked Q3(1Al) sites, introducing small capillary pores and reducing the surface area. The extent of microstructural changes depended on the initial degree of carbonation. Importantly, 29Si NMR suggested that recalcification is a diffusion-controlled process, similar to calcium leaching and carbonation. These findings highlight the potential of recalcification to restore the binding phase and improve the durability of carbonated cement pastes, with implications for the development of targeted repair techniques in the construction industry.
碳化作用降低了pH值，导致孔隙结构脱钙、收缩和致密化。再钙化是将钙离子重新引入脱钙胶凝材料的过程，是一种很有前途的恢复碳酸水泥浆的方法。然而，其对碳化胶凝材料的影响尚不清楚。这项研究首次证明了钙-（铝）-硅酸盐水合物（C - (A)- s -h）的钙/硅比如何恢复到与完整凝胶相当的水平，而且从根本上改变了其纳米结构。利用固态2⁹Si NMR，我们发现再钙化使硅胶变成交联的Q3（1Al）位点，引入小毛细孔并减少表面积。微观结构变化的程度取决于初始碳酸化程度。重要的是，29Si核磁共振表明，重钙化是一个扩散控制的过程，类似于钙浸出和碳酸化。这些发现强调了重钙化在恢复结合阶段和提高碳化水泥浆料耐久性方面的潜力，这对建筑行业中针对性修复技术的发展具有重要意义。
{"title":"Recalcification of carbonated cement paste","authors":"Thinh Nguyen , Quoc Tri Phung , Norbert Maes , Lander Frederickx , Rodrigo de Oliveira Silva , Dimitrios Sakellariou , Geert De Schutter , Özlem Cizer","doi":"10.1016/j.cement.2025.100167","DOIUrl":"10.1016/j.cement.2025.100167","url":null,"abstract":"<div><div>Carbonation lowers the pH, leading to decalcification, shrinkage, and densification of the pore structure. Recalcification, the process of reintroducing calcium ions into decalcified cementitious materials, is a promising approach for restoring carbonated cement pastes. However, its impact on carbonated cementitious materials remains unelucidated. This study demonstrates, for the first time, how recalcification not only restores the Ca/Si ratio of calcium–(aluminum)-silicate-hydrate (C–(A)-S-H) to levels comparable with intact gel but also fundamentally alters its nanostructure. Using solid-state ²⁹Si NMR, we show that recalcification turned silica gel into cross-linked Q<sup>3(1Al)</sup> sites, introducing small capillary pores and reducing the surface area. The extent of microstructural changes depended on the initial degree of carbonation. Importantly, <sup>29</sup>Si NMR suggested that recalcification is a diffusion-controlled process, similar to calcium leaching and carbonation. These findings highlight the potential of recalcification to restore the binding phase and improve the durability of carbonated cement pastes, with implications for the development of targeted repair techniques in the construction industry.</div></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"23 ","pages":"Article 100167"},"PeriodicalIF":0.0,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926162","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 : 2026-01-02DOI: 10.1016/j.cement.2025.100168
Pei B. Ong, Yixiu Zhuge, Christopher Cheeseman, Hong S. Wong
Amorphous precipitated silica (APS) produced by acid leaching of olivine has been characterised and assessed for use as a supplementary cementitious material (SCM). The APS was thermally treated between 400 and 1000°C to modify its pore structure, surface area, composition and reactivity. Pastes and mortars containing APS were cast with CEM I replacement levels from 0 to 30 wt.% and water-to-binder ratio of 0.5. TGA-MS, Q-XRD, FTIR and R3 tests show that APS has moderate to high pozzolanic reactivity. Mortars with 10 wt.% as-produced APS showed 30% increase in 28-day compressive strength compared to the control (50 MPa). Mortars with 20 wt.% replacement had comparable strengths to the control. Thermal treatment moderately reduced APS specific surface area and water demand, and improved mix workability, with mortars retaining comparable strengths to samples containing as-produced APS. The research demonstrates that silica derived from olivine has potential to be used as an SCM.
{"title":"Production and properties of amorphous silica extracted from olivine for use as a supplementary cementitious material","authors":"Pei B. Ong, Yixiu Zhuge, Christopher Cheeseman, Hong S. Wong","doi":"10.1016/j.cement.2025.100168","DOIUrl":"10.1016/j.cement.2025.100168","url":null,"abstract":"<div><div>Amorphous precipitated silica (APS) produced by acid leaching of olivine has been characterised and assessed for use as a supplementary cementitious material (SCM). The APS was thermally treated between 400 and 1000°C to modify its pore structure, surface area, composition and reactivity. Pastes and mortars containing APS were cast with CEM I replacement levels from 0 to 30 wt.% and water-to-binder ratio of 0.5. TGA-MS, Q-XRD, FTIR and R<sup>3</sup> tests show that APS has moderate to high pozzolanic reactivity. Mortars with 10 wt.% as-produced APS showed 30% increase in 28-day compressive strength compared to the control (50 MPa). Mortars with 20 wt.% replacement had comparable strengths to the control. Thermal treatment moderately reduced APS specific surface area and water demand, and improved mix workability, with mortars retaining comparable strengths to samples containing as-produced APS. The research demonstrates that silica derived from olivine has potential to be used as an SCM.</div></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"23 ","pages":"Article 100168"},"PeriodicalIF":0.0,"publicationDate":"2026-01-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926163","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 : 2026-01-01DOI: 10.1016/j.cement.2025.100166
S. Governo , E. Rossi , S. Azad , A. Kaestner , U. Angst
X-ray computed tomography (XCT) provides unique opportunities to investigate steel corrosion in reinforced concrete, the primary degradation mechanism compromising infrastructure durability and safety. Its non-destructive nature, combined with high-resolution three-dimensional imaging and time-lapse capabilities, allows for detailed insights into corrosion processes without altering the specimen. However, applying XCT to reinforced concrete remains challenging due to recurring methodological issues, such as selecting appropriate tube voltage and current, defining pre-filtering combinations, mitigating imaging artefacts, and balancing image resolution with sufficient X-ray transmission. These challenges are particularly pronounced when imaging systems with components of widely differing X-ray attenuation, such as steel, concrete, air, and water.
This paper proposes a systematic guideline for designing XCT acquisitions tailored to the study of corrosion in reinforced concrete specimens, integrating theoretical considerations with practical examples. The guideline is supported by dedicated charts and design criteria, which guide researchers in selecting acquisition parameters, specimen configurations, and imaging strategies to achieve high-quality and reproducible results. This approach is built upon a critical review of previous studies, highlighting past limitations and identifying future research opportunities for the application of XCT to study corrosion in steel-concrete systems.
By providing a coherent framework for experimental design, this paper allows researchers to fully exploit the potential of XCT for studying in-situ steel corrosion and to advance understanding of reinforced concrete degradation, thereby addressing an important challenge in engineering.
{"title":"X-ray computed tomography to investigate steel corrosion in cementitious media: Experimental guidance, challenges and opportunities","authors":"S. Governo , E. Rossi , S. Azad , A. Kaestner , U. Angst","doi":"10.1016/j.cement.2025.100166","DOIUrl":"10.1016/j.cement.2025.100166","url":null,"abstract":"<div><div>X-ray computed tomography (XCT) provides unique opportunities to investigate steel corrosion in reinforced concrete, the primary degradation mechanism compromising infrastructure durability and safety. Its non-destructive nature, combined with high-resolution three-dimensional imaging and time-lapse capabilities, allows for detailed insights into corrosion processes without altering the specimen. However, applying XCT to reinforced concrete remains challenging due to recurring methodological issues, such as selecting appropriate tube voltage and current, defining pre-filtering combinations, mitigating imaging artefacts, and balancing image resolution with sufficient X-ray transmission. These challenges are particularly pronounced when imaging systems with components of widely differing X-ray attenuation, such as steel, concrete, air, and water.</div><div>This paper proposes a systematic guideline for designing XCT acquisitions tailored to the study of corrosion in reinforced concrete specimens, integrating theoretical considerations with practical examples. The guideline is supported by dedicated charts and design criteria, which guide researchers in selecting acquisition parameters, specimen configurations, and imaging strategies to achieve high-quality and reproducible results. This approach is built upon a critical review of previous studies, highlighting past limitations and identifying future research opportunities for the application of XCT to study corrosion in steel-concrete systems.</div><div>By providing a coherent framework for experimental design, this paper allows researchers to fully exploit the potential of XCT for studying in-situ steel corrosion and to advance understanding of reinforced concrete degradation, thereby addressing an important challenge in engineering.</div></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"23 ","pages":"Article 100166"},"PeriodicalIF":0.0,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145926164","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}
Cement is a critical construction material globally and particularly in Ethiopia, where its production is energy-intensive, costly, and a major source of greenhouse gas emissions. This study explores the partial replacement of Portland cement with volcanic ash and crushed laterite powder in cement mortar as a sustainable and cost-effective alternative. Preliminary mix designs were prepared with varying proportions of volcanic ash and laterite powder to determine optimal combinations which is equal percentage of volcanic ash and laterite powder as selected based the compressive strength result. Subsequent experimental mixes replaced cement with equal proportion of volcanic ash and laterite soil at 0%, 5%, 10%, 15%, 20%, 25%, and 30% by weight, following ASTM C109 standards. The study assessed characterization, mechanical (compressive strength and ultrasonic pulse velocity), durability (sulfate resistance, porosity, and water absorption), and microstructural properties using Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), and differential thermal analysis (DTA) analyses. Characterization results showed that volcanic ash and crushed laterite are finer than cement and are predominantly pozzolanic. Bernauer-Emmett-Teller (BET) analysis confirmed their fine particle sizes, contributing to the dense packing of the mortar. At 10% of replacement of cement by equal amount of volcanic ash and laterite soil, the highest compressive strength was recorded 33.1 MPa at 28 days and 46.2 MPa at 56 days. Water absorption decreased with increasing the replacement percentage up to 15%, indicating improved durability. Microstructural analysis revealed a denser morphology due to secondary C-S-H formation and filler effects. Overall, volcanic ash and laterite powder improved both mechanical and durability properties of mortar up to 15% replacement, with optimal performance at 10%. This shows the potential of those pozzolanic as a viable partial cement substitute, promoting sustainable construction practices in Ethiopia.
{"title":"Sustainable mortar production using volcanic ash and crushed laterite as partial cement replacements","authors":"Bahiru Bewket Mitikie , Demelash Leyekun Kebede , Walied A. Elsaigh","doi":"10.1016/j.cement.2025.100162","DOIUrl":"10.1016/j.cement.2025.100162","url":null,"abstract":"<div><div>Cement is a critical construction material globally and particularly in Ethiopia, where its production is energy-intensive, costly, and a major source of greenhouse gas emissions. This study explores the partial replacement of Portland cement with volcanic ash and crushed laterite powder in cement mortar as a sustainable and cost-effective alternative. Preliminary mix designs were prepared with varying proportions of volcanic ash and laterite powder to determine optimal combinations which is equal percentage of volcanic ash and laterite powder as selected based the compressive strength result. Subsequent experimental mixes replaced cement with equal proportion of volcanic ash and laterite soil at 0%, 5%, 10%, 15%, 20%, 25%, and 30% by weight, following ASTM C109 standards. The study assessed characterization, mechanical (compressive strength and ultrasonic pulse velocity), durability (sulfate resistance, porosity, and water absorption), and microstructural properties using Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), and differential thermal analysis (DTA) analyses. Characterization results showed that volcanic ash and crushed laterite are finer than cement and are predominantly pozzolanic. Bernauer-Emmett-Teller (BET) analysis confirmed their fine particle sizes, contributing to the dense packing of the mortar. At 10% of replacement of cement by equal amount of volcanic ash and laterite soil, the highest compressive strength was recorded 33.1 MPa at 28 days and 46.2 MPa at 56 days. Water absorption decreased with increasing the replacement percentage up to 15%, indicating improved durability. Microstructural analysis revealed a denser morphology due to secondary C-S-H formation and filler effects. Overall, volcanic ash and laterite powder improved both mechanical and durability properties of mortar up to 15% replacement, with optimal performance at 10%. This shows the potential of those pozzolanic as a viable partial cement substitute, promoting sustainable construction practices in Ethiopia.</div></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"23 ","pages":"Article 100162"},"PeriodicalIF":0.0,"publicationDate":"2025-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145798979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-29DOI: 10.1016/j.cement.2025.100161
L.F.M. Sanchez , M. Griffa , A. Leemann
Numerous characterization techniques have been used to assess ASR-induced development (i.e., the formation of ASR products and cracks during expansion). Amongst those, scanning electron microscopy (SEM), coupled with energy dispersive X-ray spectroscopy (EDS), is a well-recognized technique enabling assessing the presence, morphology, and composition of ASR products. However, the correlation between ASR products' amounts and physicochemical features with induced damage (i.e., crack formation and impact on the mechanical performance of the affected concrete) via SEM is purely qualitative. Preliminary results showed that resonant ultrasound spectroscopy (RUS) could be a suitable technique to evaluate ASR-induced damage because it allows assessing the corresponding changes in the linear viscoelastic properties. Nonetheless, a systematic study fully demonstrating its potential to appraise ASR-induced expansion and deterioration, especially from ASR originating both from natural and from recycled aggregates, is still lacking in literature. This work aims to quantitatively appraise ASR-induced products and associated deterioration by the coupling of SEM-EDS and RUS, particularly a version thereof called SIngle MOde RUS (SIMORUS). Concrete mixtures incorporating highly reactive natural and recycled fine and coarse aggregates were cast and stored in conditions accelerating ASR development. At 4, 11, 16, 24 and 36 weeks, the samples were characterized by the abovementioned techniques. Quantifications of ASR-induced damage proxy parameters (i.e., Young’s, E, and shear, G, moduli), and the respective quality (Q-)factor, were performed over time. The results reported here suggest that SIMORUS is a promising technique to describe the impact of the ASR-induced development on the linear viscoelastic properties of an affected concrete. However, as shown, such an impact depends on the reactive aggregate type used in the mixture.
{"title":"Assessment of ASR-induced development in concrete with natural and recycled reactive aggregates via resonant ultrasound spectroscopy coupled with imaging techniques","authors":"L.F.M. Sanchez , M. Griffa , A. Leemann","doi":"10.1016/j.cement.2025.100161","DOIUrl":"10.1016/j.cement.2025.100161","url":null,"abstract":"<div><div>Numerous characterization techniques have been used to assess ASR-induced development (<em>i.e.</em>, the formation of ASR products and cracks during expansion). Amongst those, scanning electron microscopy (SEM), coupled with energy dispersive X-ray spectroscopy (EDS), is a well-recognized technique enabling assessing the presence, morphology, and composition of ASR products. However, the correlation between ASR products' amounts and physicochemical features with induced damage (<em>i.e.</em>, crack formation and impact on the mechanical performance of the affected concrete) via SEM is purely qualitative. Preliminary results showed that resonant ultrasound spectroscopy (RUS) could be a suitable technique to evaluate ASR-induced damage because it allows assessing the corresponding changes in the linear viscoelastic properties. Nonetheless, a systematic study fully demonstrating its potential to appraise ASR-induced expansion and deterioration, especially from ASR originating both from natural and from recycled aggregates, is still lacking in literature. This work aims to quantitatively appraise ASR-induced products and associated deterioration by the coupling of SEM-EDS and RUS, particularly a version thereof called SIngle MOde RUS (SIMORUS). Concrete mixtures incorporating highly reactive natural and recycled fine and coarse aggregates were cast and stored in conditions accelerating ASR development. At 4, 11, 16, 24 and 36 weeks, the samples were characterized by the abovementioned techniques. Quantifications of ASR-induced damage proxy parameters (<em>i.e.</em>, Young’s, <em>E</em>, and shear, <em>G</em>, moduli), and the respective quality (Q-)factor, were performed over time. The results reported here suggest that SIMORUS is a promising technique to describe the impact of the ASR-induced development on the linear viscoelastic properties of an affected concrete. However, as shown, such an impact depends on the reactive aggregate type used in the mixture.</div></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"23 ","pages":"Article 100161"},"PeriodicalIF":0.0,"publicationDate":"2025-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145705872","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}
Concrete expansion due to an alkali-silica reaction (ASR) occurs when alkali ions (OH⁻) in the pore water react with silica minerals in reactive aggregates. To mitigate ASR expansion, the concentration of alkali ions determined primarily by the amount of alkali metals derived from cement has to be controlled. In addition to silica minerals, minerals in the aggregates containing alkali metals may also undergo reactions, resulting in the dissolution of alkali metals. It is considered that this release increases the OH⁻ concentration. This alkali metal dissolution reaction is referred to as alkali release. This phenomenon was investigated through the concrete prism test using a reactive chert aggregate and nepheline syenite (NS) powder, an alkali-rich rock. The results indicated that the addition of NS contributed to increased expansion over the storage period. At an NS addition of 5 % by mass of fine aggregate (NS5 %), the alkali dissolution from NS, estimated from the expansion, was 9.2 kg/m³, which closely matched the measured water-soluble alkali content of the concrete, 8.2 kg/m³. However, when the NS addition was increased to 10 % (NS10 %), the water-soluble alkali content increased to 11.2 kg/m³, yet the expansion rate remained unchanged compared to NS5 %. Thus, alkali dissolution beyond a certain threshold did not contribute further to expansion. Additionally, the alkali dissolution from NS, as evaluated using RILEM AAR-8, was considerably underestimated, with values of 0.13 kg/m³ for NS5 % and 0.25 kg/m³ for NS10 %.
{"title":"Alkali dissolution from aggregates and its effect on ASR expansion simulated by the use of alkali rock powder","authors":"Kannosuke Shiraishi , Kazuo Yamada , Takashi Kawakami , Yasutaka Sagawa , Soshiro Miyama","doi":"10.1016/j.cement.2025.100160","DOIUrl":"10.1016/j.cement.2025.100160","url":null,"abstract":"<div><div>Concrete expansion due to an alkali-silica reaction (ASR) occurs when alkali ions (OH⁻) in the pore water react with silica minerals in reactive aggregates. To mitigate ASR expansion, the concentration of alkali ions determined primarily by the amount of alkali metals derived from cement has to be controlled. In addition to silica minerals, minerals in the aggregates containing alkali metals may also undergo reactions, resulting in the dissolution of alkali metals. It is considered that this release increases the OH⁻ concentration. This alkali metal dissolution reaction is referred to as alkali release. This phenomenon was investigated through the concrete prism test using a reactive chert aggregate and nepheline syenite (NS) powder, an alkali-rich rock. The results indicated that the addition of NS contributed to increased expansion over the storage period. At an NS addition of 5 % by mass of fine aggregate (NS5 %), the alkali dissolution from NS, estimated from the expansion, was 9.2 kg/m³, which closely matched the measured water-soluble alkali content of the concrete, 8.2 kg/m³. However, when the NS addition was increased to 10 % (NS10 %), the water-soluble alkali content increased to 11.2 kg/m³, yet the expansion rate remained unchanged compared to NS5 %. Thus, alkali dissolution beyond a certain threshold did not contribute further to expansion. Additionally, the alkali dissolution from NS, as evaluated using RILEM AAR-8, was considerably underestimated, with values of 0.13 kg/m³ for NS5 % and 0.25 kg/m³ for NS10 %.</div></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"22 ","pages":"Article 100160"},"PeriodicalIF":0.0,"publicationDate":"2025-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145578884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-10-27DOI: 10.1016/j.cement.2025.100159
Mengxin Bu , Biqin Dong , Muhammad Riaz Ahmad , Yanshuai Wang
Clarifying the dissolution behaviour and mechanism of fly ash in acid activators is essential to understand the properties of fly ash-based silico-aluminophosphate geopolymer. This paper investigated the in-situ dissolution behaviour of fly ash (FA) in aluminium dihydrogen phosphate (MAP), phosphoric acid (PA), citric acid (CA), oxalic acid (OA), and tartaric acid (TA) using optical microscopy and electron probe microscopic analysis (EPMA). The phase and elemental changes before and after dissolution were further investigated using quantitative X-ray Diffraction (QXRD) and 2D-Fourier transform infrared (FTIR) spectrometry. In addition, the changes in dissolved elements were elucidated from a liquid phase perspective. The results showed that the capacity of each acid to dissolve FA was CA>MAP>PA>TA>OA. Ca-containing phases in FA were preferentially dissolved in all acids. The main contributor to FA dissolution in acid was the amorphous phase, and the SiOSi bond in quartz was more sensitive than other chemical bonds to acid. When FA was dissolved in OA and TA, new crystalline phases—calcium oxalate and calcium citrate—formed on the FA surface, inhibiting further dissolution.
{"title":"Dissolution behaviour and mechanism of fly ash in acid activators","authors":"Mengxin Bu , Biqin Dong , Muhammad Riaz Ahmad , Yanshuai Wang","doi":"10.1016/j.cement.2025.100159","DOIUrl":"10.1016/j.cement.2025.100159","url":null,"abstract":"<div><div>Clarifying the dissolution behaviour and mechanism of fly ash in acid activators is essential to understand the properties of fly ash-based silico-aluminophosphate geopolymer. This paper investigated the <em>in-situ</em> dissolution behaviour of fly ash (FA) in aluminium dihydrogen phosphate (MAP), phosphoric acid (PA), citric acid (CA), oxalic acid (OA), and tartaric acid (TA) using optical microscopy and electron probe microscopic analysis (EPMA). The phase and elemental changes before and after dissolution were further investigated using quantitative X-ray Diffraction (QXRD) and 2D-Fourier transform infrared (FTIR) spectrometry. In addition, the changes in dissolved elements were elucidated from a liquid phase perspective. The results showed that the capacity of each acid to dissolve FA was CA>MAP>PA>TA>OA. Ca-containing phases in FA were preferentially dissolved in all acids. The main contributor to FA dissolution in acid was the amorphous phase, and the Si<img>O<img>Si bond in quartz was more sensitive than other chemical bonds to acid. When FA was dissolved in OA and TA, new crystalline phases—calcium oxalate and calcium citrate—formed on the FA surface, inhibiting further dissolution.</div></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"22 ","pages":"Article 100159"},"PeriodicalIF":0.0,"publicationDate":"2025-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145417236","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-09-14DOI: 10.1016/j.cement.2025.100156
Lucas B.R. Araújo , Madson L. de Souza , Abcael R.S. Melo , Heloina N. Costa , Lucas F.A.L. Babadopulos , Antonio E.B. Cabral , Rafael G. Pileggi
The construction industry has recently seen a growing demand for sustainable materials. Alkali-activated binders (AAB) have emerged as a viable alternative to Portland cement-based materials. This study investigates the influences of the composition and mixing methods on the rheological and mechanical properties of an alkali-activated concrete (AAC) based on fly ash (FA) and steel slag (SS), compared to a reference Portland cement concrete (PCC) with equivalent volume fractions of aggregate and paste. Two mixing methods were examined: a free fall mixer and a planetary mixer that also functions as a rheometer. In the fresh state, the performance of concretes was assessed, focusing on rheological parameters such as mixing energy, maximum torque, and equivalent apparent viscosity indicator. In the hardened state, compressive strength tests were conducted. Pseudoplastic rheological model effectively described AAC behavior, while the Bingham model better characterized PCC. AAC demonstrated high passing ability and extended flow time, with flow behavior significantly influenced by the mixing process. Rheological analysis revealed that AAC required five times more mixing energy and exhibited greater equivalent apparent viscosity indicator compared to PCC. Additionally, AAC achieved higher compressive strength than PCC, which presented values from 34 to 43 MPa (PCC) depending on curing conditions. Thermal curing increased compressive strength by nearly 60 % at 28 days for AAC, from 48.6 MPa to 76.8 MPa. Furthermore, the mixing procedure influenced the fresh and hardened properties of both AAC and PCC, though PCC exhibited only minor variations. Mixing methods with higher energy input led to improved compressive strength.
{"title":"High-strength self-compacting alkali-activated concrete produced with fly ash and steel slag: rheological behavior and mixing rheology comparisons with a Portland cement concrete","authors":"Lucas B.R. Araújo , Madson L. de Souza , Abcael R.S. Melo , Heloina N. Costa , Lucas F.A.L. Babadopulos , Antonio E.B. Cabral , Rafael G. Pileggi","doi":"10.1016/j.cement.2025.100156","DOIUrl":"10.1016/j.cement.2025.100156","url":null,"abstract":"<div><div>The construction industry has recently seen a growing demand for sustainable materials. Alkali-activated binders (AAB) have emerged as a viable alternative to Portland cement-based materials. This study investigates the influences of the composition and mixing methods on the rheological and mechanical properties of an alkali-activated concrete (AAC) based on fly ash (FA) and steel slag (SS), compared to a reference Portland cement concrete (PCC) with equivalent volume fractions of aggregate and paste. Two mixing methods were examined: a free fall mixer and a planetary mixer that also functions as a rheometer. In the fresh state, the performance of concretes was assessed, focusing on rheological parameters such as mixing energy, maximum torque, and equivalent apparent viscosity indicator. In the hardened state, compressive strength tests were conducted. Pseudoplastic rheological model effectively described AAC behavior, while the Bingham model better characterized PCC. AAC demonstrated high passing ability and extended flow time, with flow behavior significantly influenced by the mixing process. Rheological analysis revealed that AAC required five times more mixing energy and exhibited greater equivalent apparent viscosity indicator compared to PCC. Additionally, AAC achieved higher compressive strength than PCC, which presented values from 34 to 43 MPa (PCC) depending on curing conditions. Thermal curing increased compressive strength by nearly 60 % at 28 days for AAC, from 48.6 MPa to 76.8 MPa. Furthermore, the mixing procedure influenced the fresh and hardened properties of both AAC and PCC, though PCC exhibited only minor variations. Mixing methods with higher energy input led to improved compressive strength.</div></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"22 ","pages":"Article 100156"},"PeriodicalIF":0.0,"publicationDate":"2025-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145107884","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-08-21DOI: 10.1016/j.cement.2025.100155
Mohsen Torabi , Peter C Taylor
Hydration of Portland cement + slag blends with different slag replacements at various hydration times has been studied. Findings from QXRD, TGA, ESEM(EDS) & NMR have provided us with insights into the hydration mechanisms and phase assemblage of cement and slag mixtures. Phase assemblage and quantification of the AFm phases has been made possible using the parallel beam X-ray diffraction and it was observed that AFm formation is favored in these blends in direct proportion with the slag level. In fact, AFm formation after pozzolanic reaction can be considered as one of the consumers of portlandite in portland cement+slag blends. Hydrocalumite has been observed to be present among the hydration phases of these blends at various hydration times and its concentration has been observed to increase with increasing slag replacement. The presence of this phase might have implications on the durability aspects of the resulting concrete. Furthermore, some chemical reactions during slag hydration as well as its interactions with hydration of clinker phases have also been proposed.
{"title":"Hydration of portland cement and slag cement mixtures with insights on AFm phases and reaction mechanism","authors":"Mohsen Torabi , Peter C Taylor","doi":"10.1016/j.cement.2025.100155","DOIUrl":"10.1016/j.cement.2025.100155","url":null,"abstract":"<div><div>Hydration of Portland cement + slag blends with different slag replacements at various hydration times has been studied. Findings from QXRD, TGA, ESEM(EDS) & NMR have provided us with insights into the hydration mechanisms and phase assemblage of cement and slag mixtures. Phase assemblage and quantification of the AFm phases has been made possible using the parallel beam X-ray diffraction and it was observed that AFm formation is favored in these blends in direct proportion with the slag level. In fact, AFm formation after pozzolanic reaction can be considered as one of the consumers of portlandite in portland cement+slag blends. Hydrocalumite has been observed to be present among the hydration phases of these blends at various hydration times and its concentration has been observed to increase with increasing slag replacement. The presence of this phase might have implications on the durability aspects of the resulting concrete. Furthermore, some chemical reactions during slag hydration as well as its interactions with hydration of clinker phases have also been proposed.</div></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"21 ","pages":"Article 100155"},"PeriodicalIF":0.0,"publicationDate":"2025-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144903387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-07-27DOI: 10.1016/j.cement.2025.100153
Cassandra Trottier , Laurent Ramos Cheret , Haoye Lu , Anthony Allard , Maia Fraser , Leandro F.M. Sanchez
The damage rating index (DRI) is a valuable microscopy tool for collecting and counting data on different types of concrete cracks, such as those associated with alkali-silica reaction (ASR) induced deterioration. Yet, the procedure presents drawbacks such as time consumption and variability linked to operator experience, which has sparked debates about the subjectivity of its outcomes. Embracing the forefront of technological advancements, this study explores the practicality of automating the DRI's data collection through artificial intelligence (AI) and machine learning. Like many image processing and analysis applications that use AI, the DRI is an object classification and segmentation task. This study represents a step forward in leveraging automation to enhance the objectivity and efficiency of ASR damage characterization in concrete through point-count microscopy, along with proposing a set of tools to evaluate the outcomes from the application’s perspective for more efficient training data selection. Results show that despite obtaining acceptable performance individually, where the detector-classifier performance was found to have an accuracy of 0.744, and the crack counter accuracy was 0.988, the current version of the proposed machine still displays high variability in detecting, classifying, and counting distinct crack types. Overall, the machine overestimates ASR-induced damage, which was further verified through the Chi-square goodness of fit test, indicating that further training and enhancement of the proposed machine are required.
{"title":"Enhancing efficiency in evaluating alkali-silica reaction (ASR) damage: an automated approach to point-count microscopy","authors":"Cassandra Trottier , Laurent Ramos Cheret , Haoye Lu , Anthony Allard , Maia Fraser , Leandro F.M. Sanchez","doi":"10.1016/j.cement.2025.100153","DOIUrl":"10.1016/j.cement.2025.100153","url":null,"abstract":"<div><div>The damage rating index (DRI) is a valuable microscopy tool for collecting and counting data on different types of concrete cracks, such as those associated with alkali-silica reaction (ASR) induced deterioration. Yet, the procedure presents drawbacks such as time consumption and variability linked to operator experience, which has sparked debates about the subjectivity of its outcomes. Embracing the forefront of technological advancements, this study explores the practicality of automating the DRI's data collection through artificial intelligence (AI) and machine learning. Like many image processing and analysis applications that use AI, the DRI is an object classification and segmentation task. This study represents a step forward in leveraging automation to enhance the objectivity and efficiency of ASR damage characterization in concrete through point-count microscopy, along with proposing a set of tools to evaluate the outcomes from the application’s perspective for more efficient training data selection. Results show that despite obtaining acceptable performance individually, where the detector-classifier performance was found to have an accuracy of 0.744, and the crack counter accuracy was 0.988, the current version of the proposed machine still displays high variability in detecting, classifying, and counting distinct crack types. Overall, the machine overestimates ASR-induced damage, which was further verified through the Chi-square goodness of fit test, indicating that further training and enhancement of the proposed machine are required.</div></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"21 ","pages":"Article 100153"},"PeriodicalIF":0.0,"publicationDate":"2025-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144738408","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号