Cement and Concrete Research最新文献

{"title":"Thermodynamic modeling of alkali-activated fly ash paste","authors":"Yun Chen ,&nbsp;Bin Ma ,&nbsp;Jiayi Chen ,&nbsp;Zhenming Li ,&nbsp;Xuhui Liang ,&nbsp;Luiz Miranda de Lima ,&nbsp;Chen Liu ,&nbsp;Suhong Yin ,&nbsp;Qijun Yu ,&nbsp;Barbara Lothenbach ,&nbsp;Guang Ye","doi":"10.1016/j.cemconres.2024.107699","DOIUrl":"10.1016/j.cemconres.2024.107699","url":null,"abstract":"<div><div>Previously, the lack of a thermodynamic database for N-(C-)A-S-H gel limited the application of thermodynamic modeling to alkali-activated fly ash (AAFA). This study pioneers thermodynamic modeling of AAFA using a recently developed thermodynamic dataset for N-(C-)A-S-H gel. The reaction products, pore solutions and reaction kinetics of AAFA pastes were experimentally determined. Based on the reaction kinetics, the composition of the solid phases and the pore solution of AAFA were modeled over time. The results showed that the simulated compositions of the solid reaction products and pore solution match closely with the experimental results, especially for the sodium hydroxide-activated system. Moreover, modeling results point out the potential presence of minor reaction products (e.g., C-(N-)A-S-H gel, microcrystalline ferrihydrite, Mg-containing phases) undetectable by experimental techniques. The study also demonstrated that thermodynamic modeling accurately captured the amount of bound water in reaction products, highlighting its robustness in both qualitative and quantitative analysis.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107699"},"PeriodicalIF":10.9,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142452633","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}

{"title":"Whether so-called MgSi gels are produced under dolomite-quartz system under alkaline conditions","authors":"Xiaoming Song ,&nbsp;Min Deng ,&nbsp;Wei Li ,&nbsp;Xianghui Lan ,&nbsp;Mingshu Tang","doi":"10.1016/j.cemconres.2024.107701","DOIUrl":"10.1016/j.cemconres.2024.107701","url":null,"abstract":"<div><div>Micro-crystalline to crypto-crystalline quartz exists always in dolomitic limestones. When the dolomitic limestones are used as aggregates of concrete, pore solutions mainly composed of K⁺, Na⁺, Ca²⁺ and OH⁻ ions may interacts simultaneously with dolomite and micro-crystalline to crypto-crystalline quartz. To understand mechanisms of alkali-silica-dolomite reactions in concrete, chemical reaction products in system of CaMg (CO₃)₂-SiO₂-Ca(OH)₂-KOH-NaOH-H₂O cured at 20 °C, 38 °C and 60 °C were analyzed by X-ray diffraction, infrared spectroscopy, differential scanning calorimeter-thermo gravity and scanning electron microscope. Results show that magnesium derived from dolomite was mainly incorporated in brucite and silicon derived from micro-crystalline to crypto-crystalline quartz was in alkali-silica gel. No evident magnesium silicate gels were detected under high alkaline condition. It is expected that magnesium silicate gels will not be formed accompanying with alkali-silica/dolomite reaction in concrete. Reaction in dolomite-quartz system is a superposition of ASR and ACR.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107701"},"PeriodicalIF":10.9,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142452632","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":"Understanding nanoscale mechanism of compression casting on rubber-cement interface: A molecular dynamics study","authors":"Juntao Kang,&nbsp;Kai Wang,&nbsp;Yugui Cao,&nbsp;Lei Wang,&nbsp;Xingxiang Chen,&nbsp;Tianyue Wu,&nbsp;Zechuan Yu","doi":"10.1016/j.cemconres.2024.107700","DOIUrl":"10.1016/j.cemconres.2024.107700","url":null,"abstract":"<div><div>Using rubber particles as concrete aggregate can effectively address the issue of “black pollution” caused by waste tires. Although the inclusion of rubber particles reduces concrete strength, a compression casting method can enhance its mechanical properties, offering a novel approach to expanding the application range of rubber-concrete. Further development of the compression casting method requires an in-depth understanding of the mechanism behind the novel technique. This study focuses on the nanoscale mechanism of the compression casting, via all-atom molecular dynamics simulations of a C-S-H/rubber interface. Surface roughness is introduced to the employed C-S-H model, providing a more realistic representation of the cement surface compared to existing studies. Models subjected to various levels of compression casting are prepared and tested. Interface integrity is found to be significantly improved with sufficient pre-compression. When the pre-compression force increases from 100 atm to 4000 atm, the peak pullout force of the C-S-H/rubber interface transition zone increases by 90.26%, and the interfacial bond energy increase by 56.65% to 2.27 J/m². Lastly, a novel pre-compression method for rubber-concrete aggregate is proposed to enhance its economic and engineering applicability. This study reports an in-depth investigation on compression casting mechanisms and contributes to advancement of compression casting methods.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107700"},"PeriodicalIF":10.9,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142449863","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":"Full-scale observation of drying-induced microstructure change in hardened cement paste by water and 2-propanol 1H NMR relaxometry","authors":"Ryusei Igami ,&nbsp;Go Igarashi ,&nbsp;Abudushalamu Aili ,&nbsp;Ryo Kurihara ,&nbsp;Takahiro Ohkubo ,&nbsp;Ippei Maruyama","doi":"10.1016/j.cemconres.2024.107698","DOIUrl":"10.1016/j.cemconres.2024.107698","url":null,"abstract":"<div><div>To understand the microstructural changes in the hardened cement paste during the drying, hardened white Portland cement pastes were D-dried or dried under 11, 33, 40, and 75% relative humidity, and then, pastes were impregnated with 2-propanol or water under vacuum. Measurement of ¹H NMR relaxometry was employed for the pastes before and after impregnation, and the full-scale microstructural changes of the hardened cement paste after drying were successfully visualized. It was observed that the volume of the coarse pores outside the agglomeration of calcium-silicate-hydrate (C-S-H) increased, and the volume of the C-S-H interlayer spaces and gel pores decreased as the drying relative humidity decreased. Thus, it was evidenced that interlayer space is decreasing during drying. It was also confirmed that 2-propanol can enter some of the interlayer space of C-S-H after harsh drying.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107698"},"PeriodicalIF":10.9,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142449864","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}

{"title":"Investigation of the AFm-Cl system: Fe-to-Al solid solution, thermal behavior and carbonation","authors":"Aurore Lechevallier ,&nbsp;Mohend Chaouche ,&nbsp;Jérôme Soudier ,&nbsp;Evelyne Prat ,&nbsp;Guillaume Renaudin","doi":"10.1016/j.cemconres.2024.107696","DOIUrl":"10.1016/j.cemconres.2024.107696","url":null,"abstract":"<div><div>Due to increasing interest in reducing CO₂ emissions, new hydraulic binders are emerging, many of which contain significant amounts of iron and aluminum oxides. The reactivity of such binders can be activated using CaCl₂. It thus appears essential to investigate mixed Al/Fe-Cl hydrates to better characterize the hydration products and hydration processes of these new hydraulic binders. AFm-Cl phases with varying proportions of Al³⁺ and Fe³⁺ trivalent cations were synthesized and characterized. Carbonation of AFm-Cl samples is unavoidable at ambient atmosphere and leads to phases with Ca₂Al_1-<em>x</em>Fe_<em>x</em>(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O general composition (samples were synthesized for <em>x</em> = 0, 0.17, 0.33, 0.50, 0.67, 0.83 and 1). A complete solid solution between the two Ca₂Al(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O and Ca₂Fe(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O endmembers was demonstrated. Two hydration states were identified with characteristic interlayer distances of about 7.8 Å and 6.8 Å for, respectively, the Ca₂Al_1-<em>x</em>Fe_<em>x</em>(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O hydrate and the Ca₂Al_1-<em>x</em>Fe_<em>x</em>(OH)₆·Cl_0.7(CO₃)_0.15 dehydrated phase. Thermal studies indicated a similar succession of thermal events for Ca₂Al_1-<em>x</em>Fe_<em>x</em>(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O regardless of the nature of the trivalent cation; the presence of iron however decreasing the degradation temperatures. Finally, the Ca₂Al_1-<em>x</em>Fe_<em>x</em>(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O phase was investigated in the presence of carbonate anions, showing a progressive exchange of chloride for carbonate within the interlayer to form Ca₂Al_1-<em>x</em>Fe_<em>x</em>(OH)₆·(CO₃)_0.5·3H₂O before degrading into calcite.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107696"},"PeriodicalIF":10.9,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142431849","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":"Revealing the connection between carbonation regimes and early pozzolanic reactivity of recycled concrete powder: Impact of composition and microstructure","authors":"Zihan Ma ,&nbsp;Yi Jiang ,&nbsp;Jionghuang He ,&nbsp;Peiliang Shen ,&nbsp;Qinglong Qin ,&nbsp;Zhenjiang Gu ,&nbsp;Jiangshan Li ,&nbsp;Chi Sun Poon","doi":"10.1016/j.cemconres.2024.107697","DOIUrl":"10.1016/j.cemconres.2024.107697","url":null,"abstract":"<div><div>This study aims to establish relationship between carbonation regimes and the early pozzolanic reactivity of carbonated recycled concrete powder (CRCP) by comparing the composition, structure and surface properties of the carbonation products. The surface of dry CRCP was characterized by a silica-rich layer and contains low-polymerized silica phases along with over 18 % of unstable calcium carbonate (Cc). Wet CRCP exhibits a silica-rich surface with the highest degree of silica polymerization and stable calcite in its composition. Semi-dry CRCP has a calcium-rich surface also contains high silica polymerization and over 29 % unstable calcium carbonate, and the highest specific surface area, leading to the fastest silicon dissolution and calcium consumption during pozzolanic reactions. The early pozzolanic reaction kinetics in semi-dry and wet carbonation are limited by the dissolution of carbonation products, whereas dry carbonation does not exhibit this limitation. Understanding this connection is crucial for selecting optimal carbonation techniques to enhance waste concrete utilization.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107697"},"PeriodicalIF":10.9,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142431743","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":"The Cement and Concrete Research Le Chatelier Awards","authors":"Robert J. Flatt","doi":"10.1016/j.cemconres.2024.107689","DOIUrl":"10.1016/j.cemconres.2024.107689","url":null,"abstract":"","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107689"},"PeriodicalIF":10.9,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142415772","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":"Quantifying the immobilization mechanisms of heavy metals by Calcium Silicate Hydrate (C-S-H): The case of Cu2+","authors":"Qi Liu ,&nbsp;Pan Feng ,&nbsp;Lijing Shao ,&nbsp;Chen Chen ,&nbsp;Xin Liu ,&nbsp;Yuefeng Ma ,&nbsp;Lizhi Zhang ,&nbsp;Guoqing Geng","doi":"10.1016/j.cemconres.2024.107695","DOIUrl":"10.1016/j.cemconres.2024.107695","url":null,"abstract":"<div><div>Understanding the interactions between calcium silicate hydrate (C-S-H) and heavy metals is vital for optimizing the use of solid waste in cementitious materials. This paper introduces an innovative approach to elucidate the immobilization mechanism of Cu²⁺, a representative heavy metal. The roles of Ca²⁺ and OH⁻ in Cu²⁺ immobilization were comprehensively investigated through being treated by C-S-H samples with varying interlayer Ca²⁺ contents via meticulous immersion in ammonium chloride (NH₄Cl). Our results indicate that Cu²⁺ immobilization primarily occurs via complete substitution of interlayer Ca²⁺ and partial substitution of intralayer Ca²⁺, with contributions of 40 % and 59 %, respectively, for a Ca/Si ratio of 1.2. Minor mechanisms like OH⁻ complexation and surface adsorption account for the remaining immobilization. The formation of Si-O-Cu complexes was confirmed by X-ray photoelectron (XPS) and Extended X-ray Absorption Fine Structure (EXAFS) analysis. This study provides a quantitative methodology that informs strategies for sustainable cementitious waste utilization.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107695"},"PeriodicalIF":10.9,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142397812","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":"Setting reaction of a olivine-based Mg-phosphate cement","authors":"Davide Bernasconi ,&nbsp;Alberto Viani ,&nbsp;Lucie Zárybnická ,&nbsp;Simone Bordignon ,&nbsp;Jose R.A. Godinho ,&nbsp;Alexey Maximenko ,&nbsp;Cem Celikutku ,&nbsp;Sadaf Fatima Jafri ,&nbsp;Elisa Borfecchia ,&nbsp;Quentin Wehrung ,&nbsp;Roberto Gobetto ,&nbsp;Alessandro Pavese","doi":"10.1016/j.cemconres.2024.107694","DOIUrl":"10.1016/j.cemconres.2024.107694","url":null,"abstract":"<div><div>The cementitious properties of natural Mg-rich olivine when reacted with a phosphoric acid solution are investigated, as a function of acid concentration and liquid/solid mass ratio. The obtained cements are composed of residual olivine crystals and amorphous silica nanoparticles dispersed in a dense and compact newberyite (MgHPO₄∙3H₂O) matrix. The latter was mostly formed by packed micrometric tabular crystals, although evidence of the presence of a fraction of amorphous MgHPO₄ was also found. Water content in the raw mix was observed to play a pivotal role on the reaction pathway, either promoting porosity or hindering the crystallization of the products. Up to 57 % of olivine reactivity, whose dissolution was promoted by the curing temperature (60 °C) and low pH, was achieved. All in all, these results indicate that the industrial mineral olivine may serve a viable source of Mg for the production of phosphate cements.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107694"},"PeriodicalIF":10.9,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142398535","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}

{"title":"Phase, structure, and hygroscopic property evolutions of alkali-silica reaction gels under freeze drying","authors":"Arkabrata Sinha,&nbsp;Jianqiang Wei","doi":"10.1016/j.cemconres.2024.107692","DOIUrl":"10.1016/j.cemconres.2024.107692","url":null,"abstract":"<div><div>Alkali-silica reaction (ASR), a detrimental process causing volume expansion and cracking in concrete by forming hygroscopic and swellable gel-like products, has been a long-standing challenge faced by concrete structures across the world. Understanding the underlying mechanisms of formation, moisture uptake and swelling of ASR gels requires thorough characterizations, where an appropriate drying method to remove free water and stop the reactions in the samples is essential. This study aims to elucidate the effect of freeze-drying, an emerging drying technique increasingly employed in sample preparations, on the phase, molecular structure, and moisture absorption behavior of ASR gels. Towards this end, six ASR gels with three calcium-to-silica (Ca/Si) ratios (0.1, 0.3, and 0.5) and two alkali-to-silica [(Na + K)/Si] ratios of 0.3 (low-alkali gels) and 1.0 (high-alkali gels) were studied. The results indicate that the chemical bonds and mineral components of ASR gels can be maintained during the removal of free and loosely bound water in freeze drying, while slight changes in crystallization and relative contents of alkali-silicate hydrate and calcium silicate hydrate phases were observed, in particular, for the high-alkali ASR gels. Although slight decreases in Q¹, Q^2, and Q³ silica polymerization sites and increases in the mean chain length and degree of polymerization were observed from the nuclear magnetic resonance (NMR) spectroscopy, the intrinsic layered silicate structure of ASR gels remains. The moisture absorption of low-alkali and high-alkali ASR gels was found to be governed by gel pores and mesopores, respectively. After freeze-drying, slight increases in moisture sorption (a 6.8 % increase in absorption and a 2.2 % decrease in desorption) and enhanced hysteresis were observed from the low-alkali gels. The high-alkali gels, however, showed a slight decrease in hygroscopicity along with a 16.6 % reduction of mesopores.</div></div>","PeriodicalId":266,"journal":{"name":"Cement and Concrete Research","volume":"186 ","pages":"Article 107692"},"PeriodicalIF":10.9,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142385993","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}