CEMENT最新文献

{"title":"The efficacy of portland-limestone cements with supplementary cementitious materials to prevent alkali-silica reaction","authors":"Krishna Siva Teja Chopperla ,&nbsp;Jeremy A. Smith ,&nbsp;Jason H. Ideker","doi":"10.1016/j.cement.2022.100031","DOIUrl":"10.1016/j.cement.2022.100031","url":null,"abstract":"<div><p>This paper details a study on the efficacy of portland-limestone cements (PLCs) in combination with supplementary cementitious materials (SCMs) to prevent expansion due to alkali-silica reaction (ASR). The PLCs studied include both interground (10–15% limestone by mass) and interblended (10% limestone by mass) systems. In this study, ASTM Type II/V cements, five different SCMs, two very-highly reactive fine aggregates, and six SCM combinations were investigated. A total of 100 mixtures were assessed using three different accelerated laboratory test methods to investigate if the SCM combinations that are used with OPCs can be utilized as-is, increased, or decreased when used instead with PLCs. The test methods used to evaluate ASR included the Pyrex mortar bar test (PMBT, ASTM C441), the accelerated mortar bar test (AMBT, ASTM C1567), and the miniature concrete prism test (MCPT, AASHTO T 380). The difference in performance between PLCs with SCMs and parent OPCs with SCMs in the MCPT conditions was further evaluated using pore solution alkalinity and electrical resistivity analysis. The efficacy of the SCM combinations to prevent ASR was also evaluated with a pozzolanic reactivity test. The expansion results from the accelerated laboratory test methods revealed that the mixtures with PLCs and SCMs had similar or better overall performance when compared to the mixtures with the parent OPCs and SCMs. It was observed that the particle size of the added limestone in interblended PLC with SCM mixtures could have a significant influence on the ASR expansion that may alter the output of the test (pass/fail). Consequently, the SCM combinations that are used with OPCs can likely be utilized as-is when used with interground PLCs with up to 15% limestone to prevent ASR. The pore solution and bulk electrical resistivity analysis showed that the lower pore solution alkalinity and higher resistance to mass transport are the main contributing factors towards PLCs’ overall improved performance for ASR mitigation in the presence of SCMs.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"8 ","pages":"Article 100031"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000111/pdfft?md5=c38d67f918a1547be2aaa2217548e1af&pid=1-s2.0-S2666549222000111-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87918540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrostatic compression and pressure phase transition of major Portland cement constituents – Insights via molecular dynamics modeling","authors":"Ingrid M. Padilla Espinosa,&nbsp;Nirmalay Barua,&nbsp;Ram V. Mohan","doi":"10.1016/j.cement.2021.100017","DOIUrl":"10.1016/j.cement.2021.100017","url":null,"abstract":"<div><p>The complex composite material cement paste (CP) is under high pressures in underwater applications and when impact loading occurs. The mechanical behavior of cement paste to hydrostatic compression results from mechanical deformations of each phase, including unhydrated and hydrated minerals. Molecular Dynamics was used to study the atomistic deformation of individual unhydrated cement phases with increasing hydrostatic pressures. The pressure-specific volume Birch-Murnaghan equation of state (EoS) and the bulk modulus at zero pressure were determined for each phase. Results show that the bulk modulus and compressibility are pressure dependent. For tricalcium silicate (C₃S), dicalcium silicate (C₂S), and tricalcium aluminate (C₃A), the bulk modulus increases, while the volume compression decreases with increasing pressure. The C₃S and C₃A phases are stable during hydrostatic compression and exhibit isotropic behavior. The C₂S phase is not stable and shows anisotropic behavior. These results explain the effect of unreacted cement clinkers on cement paste mechanical behavior under high pressure based on the response of individual phases.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"7 ","pages":"Article 100017"},"PeriodicalIF":0.0,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549221000141/pdfft?md5=a33f95fab9df10e800344575a682d53e&pid=1-s2.0-S2666549221000141-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75922014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phase changes during the drying of calcium aluminate cement bond castables – the influence of curing and drying conditions","authors":"A. Koehler,&nbsp;J. Neubauer,&nbsp;F. Goetz-Neunhoeffer","doi":"10.1016/j.cement.2021.100020","DOIUrl":"https://doi.org/10.1016/j.cement.2021.100020","url":null,"abstract":"<div><p>This study presents the influence of different curing temperatures and the availability of unbound H₂O on the phase changes during the drying process of a simplified calcium aluminate cement bond castable. A mixture of CAC and alumina was hydrated for 48 h at 5, 23 and 40 °C, which represents different working conditions during casting. After the curing process, these samples were heated up to 180 °C, and in some of them, the remaining unbound H₂O had been removed by vacuum drying beforehand. The quantitative phase composition was determined by QXRD. Thermogravimetric analysis and gravimetric measurements were also used to characterize the differently cured samples. While the mineral phases in the samples cured at 40 °C were barely affected by the heating process in the investigated temperature range, the initial conditions before the drying of the samples cured at 5 and 23 °C strongly affected the final phase composition.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"7 ","pages":"Article 100020"},"PeriodicalIF":0.0,"publicationDate":"2022-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549221000177/pdfft?md5=885f048af5f9094f1c7de99b39557b2c&pid=1-s2.0-S2666549221000177-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91599659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Heat capacity, isothermal compressibility, isosteric heat of adsorption and thermal expansion of water confined in C-S-H","authors":"Tulio Honorio,&nbsp;Fatima Masara,&nbsp;Farid Benboudjema","doi":"10.1016/j.cement.2021.100015","DOIUrl":"10.1016/j.cement.2021.100015","url":null,"abstract":"<div><p>Nanoconfinement is known to affect the property of fluids. The changes in some thermo-mechanical properties of water confined in C-S-H are still to be quantified. Here, we perform molecular simulations to obtain the adsorption isotherms in C-S-H as a function of the pore size (spanning interlayer up to large gel pores). Then, fluctuations formula in the grand canonical ensemble are used to compute the isothermal compressibility (and its reciprocal, the bulk modulus), the heat capacity, the coefficient of thermal expansion and thermal pressure, and the isosteric heat of adsorption of confined water as a function of the (nano)pore size. All these properties exhibit a pore size dependence, retrieving the bulk values for basal spacing above 2 nm. To understand why property changes with confinement, we compute structural descriptors including the radial distribution function, apparent density, hydrogen bonds counting, and excess pair entropy of water as a function of the confinement. These descriptors reveal significant structural changes in confined water. The heat capacity shows a good linear correlation with the apparent density, entropy, and hydrogen bond number. The values of water property as a function of the basal spacing are a valuable input for multiscale modeling of cement-based materials.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"6 ","pages":"Article 100015"},"PeriodicalIF":0.0,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549221000128/pdfft?md5=d7b2b1b5e7c8af1fc25eac2c34175f40&pid=1-s2.0-S2666549221000128-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78827932","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A critical review of the testing and benefits of permeability-reducing admixtures for use in concrete","authors":"Caitlin M. Tibbetts Ph.D. ,&nbsp;Kyle A. Riding Ph.D. ,&nbsp;Christopher C. Ferraro Ph.D.","doi":"10.1016/j.cement.2021.100016","DOIUrl":"10.1016/j.cement.2021.100016","url":null,"abstract":"<div><p>Permeability-reducing admixtures (PRAs) are marketed as an option to improve the concrete durability and reduce water ingress in structures. Two categories of PRAs that have become more prominent recently are hydrophobic pore blockers and crystalline waterproofers. A literature review was performed to determine the composition, mechanism of action, test methods to indicate durability, and performance of PRAs in concrete, with focus on their use in infrastructure. The test methods for evaluating the performance of PRAs and their effects have varying degrees of frequency and standardization and there is a lack of consistency in the experimental methods used to evaluate PRAs based on the studies found in the literature; the dosage, water to cementitious ratio (w/cm), testing age, and mixture designs were variable. There remains a need for studies with both field and lab data to establish relationships between lab results and field performance to determine laboratory test method validity for PRAs.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"6 ","pages":"Article 100016"},"PeriodicalIF":0.0,"publicationDate":"2021-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S266654922100013X/pdfft?md5=816ac328a40b46f0a41f222395fa4a55&pid=1-s2.0-S266654922100013X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78149839","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of phase formation and physical-mechanical properties of Portland cements produced with civil construction waste","authors":"F.N. Costa ,&nbsp;D.V. Ribeiro","doi":"10.1016/j.cement.2021.100012","DOIUrl":"https://doi.org/10.1016/j.cement.2021.100012","url":null,"abstract":"<div><p>Cement is the most widely used building material worldwide. Its production demands a large amount of natural resources, in addition to high energy consumption. Thus, the cement industry has been looking for solutions that effectively reduce the use of these resources as well as greenhouse gas emissions. This research aims to show the technical feasibility of incorporating civil construction waste (CCW) in the production of Portland cement. To this purpose, the physicochemical characterization of the raw materials used was carried out, dosage and manufacture of the raw mix, which were calcined at 1450 °C. Clinkers were characterized mineralogically, by means of XRD, to verify the formation of the crystalline phases. Subsequently, the clinkers were ground, resulting in Portland cements, and their physical-mechanical properties were evaluated. The results showed the potential of using CCW as an alternative raw material, since experimental cements presented performance similar to industrial cements used as a reference.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"5 ","pages":"Article 100012"},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cement.2021.100012","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91695902","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Temperature-dependent late hydration of calcium aluminate cement in a mix with calcite – Potential of G-factor quantification combined with GEMS-predicted phase content","authors":"J. Goergens,&nbsp;F. Goetz-Neunhoeffer","doi":"10.1016/j.cement.2021.100011","DOIUrl":"https://doi.org/10.1016/j.cement.2021.100011","url":null,"abstract":"<div><p>In continuation of earlier work on early hydration, this study evaluates the late hydration of CAC and CaCO₃ using QXRD and thermodynamic modelling at different temperatures. Experiments were performed at 5, 23, 40 and 60 °C for up to one year. As stated in the preceding study, C₂AH_X might act as a precursor for monocarbonate in early hydration, and thus no or only little monocarbonate should form at temperatures below 20 °C. At 5 °C, monocarbonate starts precipitating after 7 d and remains alongside CAH₁₀. At all other investigated temperatures, monocarbonate is the dominant hydrate phase. Primarily formed CAH₁₀ at 23 °C is visible up to 14 d but then becomes unstable with respect to monocarbonate. At 23 °C and 40 °C the thermodynamically stable phase assemblage is reached within one year. However, the precipitation of C₃AH₆ is detected in all samples at 60 °C, which results from an insufficient w/CAC ratio for carbonate-AFm in the paste due to the inevitable evaporation of mixing water for this condition. However, C₃AH₆ can partly be “re-converted” at 60 °C when the sample is subsequently stored under water and monocarbonate is stable again.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"5 ","pages":"Article 100011"},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cement.2021.100011","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90006586","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Evaluation of corn straw ash as supplementary cementitious material: Effect of acid leaching on its pozzolanic activity","authors":"Charles Prado Ferreira de Lima,&nbsp;Guilherme Chagas Cordeiro","doi":"10.1016/j.cement.2021.100007","DOIUrl":"10.1016/j.cement.2021.100007","url":null,"abstract":"<div><p>The use of biomass ash is an environmentally friendly practice in the search for sustainable construction materials. This study aimed to produce pozzolanic ash from corn straw with a high amorphous silica content, low carbon content, and high specific surface area via controlled acid leaching, two-step burning, and grinding. The effect of pretreating corn straw on the properties of the material was assessed by comparative analysis with corn straw and rice husk ashes produced without acid pretreatment. To this end, characterization data, hydration heat, chemically bound water, and portlandite consumption in pastes, and mortar compressive strength were used to evaluate the pozzolanicity of the ashes. The results indicated that all the ashes exhibited pozzolanic behavior and that the leaching process significantly improved the physical and chemical properties of corn straw ash, with reduction in portlandite content. The calorimetric results showed a change in hydration kinetics with an increase in ash in the cement mixes. Moreover, the compressive strength of leached corn straw ash-based mortars was greater than that of the other mortars, primarily for high levels of cement replacement (20 and 30% by mass).</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"4 ","pages":"Article 100007"},"PeriodicalIF":0.0,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cement.2021.100007","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"111284388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The effective volumes of waters of crystallization & the thermodynamics of cementitious materials","authors":"Leslie Glasser","doi":"10.1016/j.cement.2021.100004","DOIUrl":"10.1016/j.cement.2021.100004","url":null,"abstract":"<div><p>Hydrates are significant components of cements and concrete. We examine the effective volumes of waters of crystallization for these materials, where the “effective volumes” are the difference per water molecule between the formula volume of the hydrate and of its parent anhydrate. These effective volumes cover a small range around 15 cm³ mol⁻¹ (≅ 23 ų per water molecule), unlike the wider range for general inorganic materials.</p><p>We also examine the thermodynamic properties of the cementitious phase, which follow the generally observed correlation of relating to their molar volumes. We establish “effective” additive oxide parameters for enthalpy and for molar volume, which are useful in confirming experimental values and in predicting as-yet undetermined values. Their Debye temperatures approximate to 600 K; this Debye temperature is well above ambient temperature and suggests that the vibrational modes of these cementitious phases are only partially excited and that the materials are hard. Ferrate-containing materials generally have a lower Debye temperature (∼273 K) implying that they may be softer than other cementitious materials.</p><p>These observations may be useful in checking for errors in data and anomalies in behavior among related cementitious materials.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"3 ","pages":"Article 100004"},"PeriodicalIF":0.0,"publicationDate":"2021-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cement.2021.100004","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"96790825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Assessing condition of concrete affected by internal swelling reactions (ISR) through the Damage Rating Index (DRI)","authors":"L.F.M. Sanchez ,&nbsp;T. Drimalas ,&nbsp;B. Fournier","doi":"10.1016/j.cement.2020.100001","DOIUrl":"10.1016/j.cement.2020.100001","url":null,"abstract":"<div><p>The Damage Rating Index (DRI) has been increasingly used in North America since it answers interesting questions on the cause and extent of damage in concrete. Currently, the DRI is mostly used to appraise alkali-silica reaction (ASR) affected concrete and there is very few research on the evaluation of other distress mechanisms through this method. This work presents the use of the DRI to assess condition of concrete affected by internal swelling reaction (ISR) mechanisms (i.e. ASR, delayed ettringite formation and freeze-thaw cycles), with the aim of verifying the suitability of the method to become a comprehensive damage evaluation protocol. Results show that the DRI number, represented by plots or bar charts, enables a quantitative damage evaluation of concrete regardless of the distress mechanism type and degree. Moreover, the implementation of an extended DRI version makes the method more suitable to describe progress of different ISR deterioration processes in concrete.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"1 ","pages":"Article 100001"},"PeriodicalIF":0.0,"publicationDate":"2020-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1016/j.cement.2020.100001","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"95647105","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}