CEMENT最新文献

{"title":"Effects of thermal treatment on the mechanical properties, microstructure and phase composition of an Ettringite rich cement","authors":"Sandra Afflerbach ,&nbsp;Christian Pritzel ,&nbsp;Patrick Hartwich ,&nbsp;Manuela Sonja Killian ,&nbsp;Wolfgang Krumm","doi":"10.1016/j.cement.2023.100058","DOIUrl":"https://doi.org/10.1016/j.cement.2023.100058","url":null,"abstract":"<div><p>Recently calcium sulfoaluminate cements gain increasing attention due to their significant potential to reduce the carbon footprint of cement production compared to Portland cement. However, the conditions applied during its processing play a crucial role for the stability and longevity of the material. Thereby, the temperature has a decisive influence, as it is already known from numerous studies that ettringite structurally changes significantly upon thermal induced dehydration. Within this background, the present study subjects a holistic view of the mechanical, morphological, phase and structural changes of a commercial calcium sulfoaluminate cement related to the dehydration of the contained ettringite upon treatment at drying temperatures from 23 °C to 100 °C for 7 and 28 days. By complementary methods it is shown that with increasing curing temperature, the mechanical stability decreases, the total pore area and porosity increase, while the permeability of the microstructure is lower for samples stored at 100 °C. Removal of water increases the intercolumnar distance within the ettringite lattice, thereby inducing strain which is released upon rehydration. Although during storing at a temperature of 100 °C ettringite is transformed into an X-ray amorphous product, the initial morphology of the crystals embedded in the cementitious matrix is retained.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"11 ","pages":"Article 100058"},"PeriodicalIF":0.0,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50183411","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}

{"title":"A comprehensive study for physical and chemical properties of road dust to utilize in concrete mix design, collected from diversified locations of Delhi NCR","authors":"Tarang Kumar Gondwal ,&nbsp;Amit Bishnoi ,&nbsp;Papiya Mandal","doi":"10.1016/j.cement.2023.100056","DOIUrl":"https://doi.org/10.1016/j.cement.2023.100056","url":null,"abstract":"<div><p>Rising volume of road dust is a serious concern in global as well as Indian scenario. To find out the possible application, chemical and physical characterizations of road dust of six diversified sites of Delhi, National Capital Region, India were carried out prior to utilize in concrete mix design. The chemical characterizations suggest major and minor components are oxides of silicon, aluminium, iron, sodium, calcium, potassium, sulphur, phosphorous, manganese etc. X-ray diffraction studies depicted major phases of silica, muscovite/ illite, K-Feldspar and albite minerals. Scanning Electron Microscopy studies depicted flacks, fibrous, spherical, irregular, voids and hexagonal morphologies. Further detailed studies of road dust of two sites were carried out in concrete mix design following IS and ASTM test methods to know the effects on compressive strength, flexural strength, water and rapid chloride permeability test after replacing upto 50% of stone sand by road dust. The 7th and 28th days compressive strength test results of two sites concrete showed 16.51%, 8.25% and 4.67%, 2.34 % lesser strength in comparison to control concrete respectively. Similarly, 7th and 28th days flexural strength studies of same sites concrete showed 19.67%, 14.75% and 6.85%, 1.37% lesser strength in comparison to control concrete, respectively. The depth of water penetration test results of two selected sites of concrete showed 13.14% and 10.22% lesser extent of water penetration under 5 bars hydrostatic pressure, when compared to control concrete. The RCPT results of same sites concrete showed 33.47% and 9.48% greater extent of chloride ion permeability, in comparison to control concrete. The results obtained after 7th and 28th days of conventional stone sand concrete and road dust concrete, showed quite comparable results. However, in case of water permeability test the road dust concrete showed lesser extent of water percolation in comparison to conventional concrete, this may be due to presence of more fines in road dust, which may have caused better packing and lesser voids for water to ingress.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"11 ","pages":"Article 100056"},"PeriodicalIF":0.0,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50183414","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}

{"title":"Pore solution alkalinity of cement paste as determined by Cold Water Extraction","authors":"Maxime Ranger ,&nbsp;Marianne Tange Hasholt ,&nbsp;Ricardo Antonio Barbosa","doi":"10.1016/j.cement.2023.100055","DOIUrl":"https://doi.org/10.1016/j.cement.2023.100055","url":null,"abstract":"<div><p>Cold Water Extraction (CWE) is a technique used to extract the pore solution of cementitious materials and to study its alkalinity. CWE can be used on paste, mortar or concrete, and requires only standard laboratory equipment. The method is not yet standardised, so several parameters must be arbitrarily selected when conducting the test.</p><p>This work investigated the influence of four parameters on the calculated alkali metal concentrations in the pore solution: the method for determining the amount of pore solution (oven-drying at 40 and 105 °C, desiccator with silica gel and solvent exchange), the size fraction of the powdered material, the leaching duration and the liquid-to-solid ratio. A comparison with values obtained by Pore Water Extraction (PWE) on two cement types emphasises and quantifies the crucial impact of the amount of pore solution on CWE results. The results suggest that some bound alkali metals may be released during CWE. A mechanism is proposed, and recommendations are made to limit any effect of this on CWE results.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"11 ","pages":"Article 100055"},"PeriodicalIF":0.0,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50183412","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}

{"title":"Predicting moisture in field concrete - decisive parameters","authors":"Lars-Olof Nilsson","doi":"10.1016/j.cement.2022.100052","DOIUrl":"https://doi.org/10.1016/j.cement.2022.100052","url":null,"abstract":"<div><p>A review is made of the decisive parameters when predicting moisture conditions in a concrete structure exposed to natural climate. The required material properties such as the desorption isotherm, the scanning curves and the moisture transport coefficient are presented and discussed. The translation of parameters describing a natural climate into boundary conditions at a concrete surface is commented upon and examples are given on the effect of including or neglecting different parameters.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"11 ","pages":"Article 100052"},"PeriodicalIF":0.0,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"50183432","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}

{"title":"Characterization of the white deposit on the surface of cement mortars by correlative light-electron microscopy (CLEM)","authors":"Xianping Liu ,&nbsp;Peiming Wang ,&nbsp;Hanqing Gao ,&nbsp;Herve Fryda ,&nbsp;Linling Cai","doi":"10.1016/j.cement.2022.100046","DOIUrl":"10.1016/j.cement.2022.100046","url":null,"abstract":"<div><p>This study focuses on the characterization of white deposit occurring after wet/dry cycles on the surface of cement mortars presenting large amount of AFt phase. Correlative light-electron microscopy (CLEM) was confirmed to be a powerful method in characterizing and identifying microscopic visible white deposit that causes macroscopic visible surface whitening in those cement mortars. It was discovered that the white deposit formed after wet/dry cycles was caused by solids precipitated on the surface of cement mortars during hydration and/or on drying, and those solids were composed of CaCO₃, AFt, AFm or their solid solutions. Due to the resolution limit of the human eye, there is a threshold size 100 μm for the microscopic visible white deposit or its cluster to become macroscopic visible surface whitening. Partial covering of red pigments by the newly formed solids on the surface of the cement mortars further confirmed the relationship between the size and quantity of microscopic visible white deposit and macroscopic visible surface whitening.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"10 ","pages":"Article 100046"},"PeriodicalIF":0.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000251/pdfft?md5=4598215616433c64b9602d0928bacf54&pid=1-s2.0-S2666549222000251-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84539359","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":"Permeability recovery by self-healing of class F fly ash-based geopolymers","authors":"John H. Ross ,&nbsp;Moneeb Genedy ,&nbsp;Maria C.G. Juenger ,&nbsp;Eric van Oort","doi":"10.1016/j.cement.2022.100048","DOIUrl":"https://doi.org/10.1016/j.cement.2022.100048","url":null,"abstract":"<div><p>Alkali activated materials (AAMs), also known as geopolymers, have been proposed as lower carbon footprint alternative cementitious materials to ordinary portland cement (OPC). Geopolymers are formed from an aluminosilicate precursor, such as fly ash, mixed with an alkaline activating solution. These materials may have self-healing behavior, which makes them promising materials for applications where controlling crack widths is critical, such as in well bores or steel-reinforced concrete structures. In this study, the self-healing ability of a Class F fly ash-based geopolymer was investigated using a pressure transmission test (PTT) to measure the initial permeability of the material, the permeability after damage using freeze-thaw cycling to initiate cracks, and the permeability following post-damage curing to encourage self-healing. The geopolymer was found to have low permeability, 0.26 ± 0.09 µD at 28 days, which is comparable to reported values for OPC. The permeability increased after damage, but then decreased again after the self-healing curing period. The results show an inverse correlation between the level of initial damage and the level of permeability restoration upon self-healing. This work indicates that geopolymers can indeed self-heal cracks to reduce damage, suggesting that they are promising barrier materials for well construction and other applications.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"10 ","pages":"Article 100048"},"PeriodicalIF":0.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000275/pdfft?md5=11a5e118fbeeb352015e875b4c7a93ff&pid=1-s2.0-S2666549222000275-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92022090","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":"Managing Thermal Effects in Waterproofed Concrete with Multi-Crystallization Enhancer","authors":"Radi Al-Rashed ,&nbsp;Maher Al-Jabari","doi":"10.1016/j.cement.2022.100050","DOIUrl":"10.1016/j.cement.2022.100050","url":null,"abstract":"<div><p>Thermal effects in concrete are associated with a heat release from the exothermic cement hydration reactions during concrete curing under normal conditions or under severe cold conditions, or when it is subjected to cycles of freezing and thawing. These thermal effects may cause cracking, impact concrete porosity and affects its thermal, mass and hydraulic conductivities, and hence create major durability problems. This paper presets an experimental study of the thermal management ability of an aqueous waterproofing solution (the Multi-Crystallization Enhancer (MCE)) that is intermixed with water at the time of batching. The experiments were performed according to the applicable ASTM procedures for measuring the rate of heat release, temperature profiles, compressive and flexural strengths, temperature-time factor and thermal and electrical conductivities. Additionally, the impact of cycles of freezing and thawing on the percentages of mass change, length change and relative dynamic modulus were investigated. The findings indicate that the addition of the MCE at a dosage of 2% of cement weight has the potential to mitigate the thermal effects during cement hydration and during curing concrete under freezing conditions providing a solution for thermal problems of mass concrete. The findings demonstrate that the MCE can delay the exothermic heat release and can reduce its rate at the initial stage. It can also increase the resistance of concrete against cycles of freezing and thawing by achieving 92% reduction in the percentage mass change, 15% reduction in the percentage length change and 17% enhancement in the relative dynamic modulus, after 300 cycles. These thermal impacts of the MCE are also associated with 16% reduction in the thermal conductivity and 90.7% reduction in the total charge passage through concrete.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"10 ","pages":"Article 100050"},"PeriodicalIF":0.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000299/pdfft?md5=eec75ce28e329340048ca9e5b2481ace&pid=1-s2.0-S2666549222000299-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85216545","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":"Localized corrosion of steel in alkaline solution with low-level chloride and elevated sulfate concentrations","authors":"Samanbar Permeh,&nbsp;Kingsley Lau","doi":"10.1016/j.cement.2022.100051","DOIUrl":"10.1016/j.cement.2022.100051","url":null,"abstract":"<div><p>Localized corrosion developed on post-tensioned steel strand in deficient grout, relating to elevated concentrations of sulfate ions. The deficient grout can also have low-level chloride ion concentrations below threshold values originating from the base materials. Open-circuit potential, linear polarization resistance (LPR), and electrochemical noise (EN) measurements were made on steel specimens exposed in saturated calcium hydroxide solution with 0.012 M Cl⁻, 0.04 M SO₄²⁻, or combined. Results showed that the combined presence of sulfates in low-level chloride alkaline solutions elevated the corrosion rate and the extent of corrosion pitting. The EN technique was shown to provide corrosion rate estimates consistent with LPR and was able to identify pitting characteristics. The outcomes of the research provides supporting evidence that analysis of deficient grout for chlorides alone may not capture the risk for corrosion and that corrosion associated with elevated sulfate concentrations can be exacerbated in presence of low-level chlorides.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"10 ","pages":"Article 100051"},"PeriodicalIF":0.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000305/pdfft?md5=135436ddccedc624152937ee90734355&pid=1-s2.0-S2666549222000305-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85014113","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":"Comparison of shrinkage and mass change of hardened cement paste under gradual drying and rapid drying","authors":"Miki Segawa ,&nbsp;Abudushalamu Aili ,&nbsp;Ippei Maruyama","doi":"10.1016/j.cement.2022.100047","DOIUrl":"10.1016/j.cement.2022.100047","url":null,"abstract":"<div><p>To identify the impact of drying rate on mechanisms of drying shrinkage, two hardened cement paste (hcp) samples were prepared. Mature samples were dried directly at the target relative humidity (RH), “rapid drying”, or at RH decreasing from 95% step by step till 11%, “gradual drying”. When comparing the relation of mass change versus drying shrinkage, at high RH range over 80%, gradually dried samples showed less mass change for same amount of shrinkage comparing to rapid drying samples. For the range of RH of 80%-40%, the incremental values of both mass change and drying shrinkage were same for two drying methods. The specimens were characterized by XRD, TG-DTA and water vapor sorption isotherms. By combining the results with findings in the literature, we postulated that an additional part of drying shrinkage is activated when dried at high relative humidity for a longer time and we attributed this additional part to gel pores of calcium silicate hydrates.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"10 ","pages":"Article 100047"},"PeriodicalIF":0.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000263/pdfft?md5=a4ed9443cc4f53d5658f4458dfaab1d4&pid=1-s2.0-S2666549222000263-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79832847","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":"Thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) hydrogel particles improve workability loss and autogenous shrinkage in cement paste","authors":"Anastasia N. Aday ,&nbsp;Mohammad G. Matar ,&nbsp;Jorge Osio-Norgaard ,&nbsp;Wil V. Srubar III","doi":"10.1016/j.cement.2022.100049","DOIUrl":"10.1016/j.cement.2022.100049","url":null,"abstract":"<div><p>In this work, we show that non-superabsorbent, thermo-responsive poly(N-isopropyl acrylamide) (PNIPAM) hydrogel particles (&lt; 250 μm) can reduce autogenous shrinkage in cement paste and improve early-age stiffening that can be caused by traditional superabsorbent polymers (SAPs). Swelling measurements in DI water and cement filtrate solution suggest that SAP-induced early-age stiffening is caused by its super-absorbency in low-ionic solutions – a behavior not exhibited by non-superabsorbent PNIPAM. Addition of PNIPAM resulted in a 29% and 60% reduction in autogenous shrinkage strain at 14 days when used alone (0.3 wt% PNIPAM) and in combination with SAP (0.15% PNIPAM, 0.15% SAP), respectively, compared to a Control with no polymer addition. Furthermore, an addition of 0.3 wt.% PNIPAM exhibited a ∼29% and ∼37% decrease in static yield stress compared to a Control and 0.3 wt% SAP-modified cement pastes, respectively. Taken together, the results provide initial evidence to suggest that the use of hydrogels as internal curing agents may not necessarily require super-absorbency to reduce autogenous shrinkage. Non-superabsorbent hydrogels, like PNIPAM, may help reduce autogenous shrinkage while alleviating the effects of SAP-induced early-age stiffening.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"10 ","pages":"Article 100049"},"PeriodicalIF":0.0,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000287/pdfft?md5=054b08183f29a06d4e7564bff9479e61&pid=1-s2.0-S2666549222000287-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75543676","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}