CEMENT最新文献

{"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}

{"title":"Enhancing carbonation of magnesium oxide (MgO) cement (RMC)-based composites with calcined limestone","authors":"Rotana Hay,&nbsp;Kemal Celik","doi":"10.1016/j.cement.2022.100037","DOIUrl":"10.1016/j.cement.2022.100037","url":null,"abstract":"<div><p>Increasing pore solution pH in a concrete matrix will enhance CO₂ dissolution. In this study, calcined limestone was used as a replacement of reactive magnesium oxide (MgO) cement (RMC) at 5 and 10 wt.% to increase its carbonation rate and content. Its influence on strength development, chemical evolution, and microstructure was also investigated. The calcined limestone was found to increase the pore solution pH and consequentially reduce the hydration of RMC. Aggravated by a smaller particle size of the formed brucite, the composite strength under air curing was significantly reduced. Yet, the high pH environment, smaller hydration products and microporosity enhanced carbonation and retained strength development. The carbonation products were characterized by a mixture of hydrated magnesium carbonates (HMCs), calcite, and amorphous phases. The outcome of the study opens up a possibility for using less pure sources of magnesite and calcium oxide as a brine precipitation agent to produce RMC for construction applications.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"9 ","pages":"Article 100037"},"PeriodicalIF":0.0,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000172/pdfft?md5=894315ab97fada36141efe753bdce7fd&pid=1-s2.0-S2666549222000172-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72371338","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":"Dynamic effect of water penetration on steel corrosion in carbonated mortar: A neutron imaging, electrochemical, and modeling study","authors":"Zhidong Zhang ,&nbsp;Pavel Trtik ,&nbsp;Fangzhou Ren ,&nbsp;Thilo Schmid ,&nbsp;Christopher H. Dreimol ,&nbsp;Ueli Angst","doi":"10.1016/j.cement.2022.100043","DOIUrl":"10.1016/j.cement.2022.100043","url":null,"abstract":"<div><p>Carbonation may potentially lead to corrosion of steel bars in reinforced concrete. This concern presents a major barrier against the implementation of sustainable low-clinker cementitious materials in the design of reinforced concrete structures. Various studies have documented the relationship between different equilibrium moisture states in carbonated concrete and the corrosion rate of the embedded steel. However, limited attempts were focused on visually observing the dynamic (time-dependent) behavior of moisture penetration into concrete and the related corrosion state and rate. Moreover, there is a lack of data on the local moisture state in the cementitious matrix in the steel-concrete interfacial zone. In this study, liquid water uptake in carbonated mortar was <em>in-situ</em> and over time monitored by neutron imaging. The corrosion state of embedded steel was monitored by means of electrochemical measurements. This combined experiment revealed that the arrival of the waterfront at the steel surface led to a sharp decrease of the steel potential. The corrosion rate increased from negligibly low values (&lt;1 µm/year) to about 31 µm/year within a couple of minutes. Based on the neutron images, it is concluded that the moisture ingress through the concrete cover is locally affected by the heterogeneity of projected (depth-averaged) porosity distribution, and that large obstacles such as entrapped air have an effect. These observations were further confirmed by numerical simulation results of water transport, which also showed that liquid water permeability of the studied carbonated mortar determined by the inverse analysis is much higher than reported values in the literature. Overall, this study highlights the importance of considering the dynamic and coupled corrosion and moisture transport behavior during the periods which active corrosion can occur in carbonated concrete exposed to cyclic wetting/drying conditions.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"9 ","pages":"Article 100043"},"PeriodicalIF":0.0,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000226/pdfft?md5=334df034719f5015e611a1a9bb297506&pid=1-s2.0-S2666549222000226-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80037338","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":"Effect of superabsorbent polymers on microstructure and strength of blended cements mortars reinforced by polymeric fibre","authors":"Rostami Rohollah ,&nbsp;Klemm Agnieszka J． ,&nbsp;Fernando C.R. Almeida","doi":"10.1016/j.cement.2022.100041","DOIUrl":"10.1016/j.cement.2022.100041","url":null,"abstract":"<div><p>Superabsorbent polymers (SAPs) efficiently reduce total shrinkage and cracking susceptibility of fibre reinforced mortars (FRM). This paper discusses the effects of SAPs on the microstructure and mechanical properties of FRM containing fly ash (FA) and ground granulated blast-furnace slag (GGBS) during a period of 180 days. Three types of cement including CEM I, CEM II/B-V and CEM III/A and three types of SAP with different chemical compositions and particle gradings were studied. The paper argues SAP's contribution to hydration of FA and GGBS and a subsequent deposition of these products on the fibres surface and in pores below 20 nm diameter. The analysis confirmed that SAPs provide additional water for hydration (internal curing) but also a required space for later hydration products (additional refilling of collapsed SAPs), resulting in more homogenous internal microstructure. This improvement is more prominent in mortars containing finer SAP (around 80 μm), which can facilitate strength recovery of up to 50%. The strength recovering process in FRM-SCM samples is boosted after the 2nd week, and is more dominant for samples containing CEM III/A.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"9 ","pages":"Article 100041"},"PeriodicalIF":0.0,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000202/pdfft?md5=777cbf5779f459db988ba6b5e35b9fe9&pid=1-s2.0-S2666549222000202-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86252727","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":"Effects of pure carbonation on pore structure and water permeability of white cement mortars","authors":"Fangzhou Ren ,&nbsp;Xingyao Chen ,&nbsp;Qiang Zeng ,&nbsp;Chunsheng Zhou","doi":"10.1016/j.cement.2022.100040","DOIUrl":"10.1016/j.cement.2022.100040","url":null,"abstract":"<div><p>The effects of carbonation on cement-based materials have drawn much attention because of its profound influences on durability performance of concrete structures. Most accelerated carbonation in lab is conducted at RH 50%–70%, which also dries out cement-based materials. The introduced drying action changes pore structure significantly, making the effects of carbonation obscure. To clarify the effects of pure carbonation, water permeability and related micro-structural characteristics are measured on mature mortars, which have been carbonated at water-saturated state. It is found that after carbonation, the porosity of mortars decreases slightly, with finer overall pore structure and lower characteristic pore size. The water permeability also decreases by roughly 40% on average. Based on the pore size distribution curves obtained through the low-field proton nuclear magnetic resonance technique, water permeability is predicted by the Katz-Thompson and Kozeny-Carman theories with satisfactory accuracy. The decrease of water permeability after carbonation agrees well with the reduced characteristic pore length, which quantitatively verifies the observed refinement of nanoscale pore structure due to pure carbonation.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"9 ","pages":"Article 100040"},"PeriodicalIF":0.0,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000196/pdfft?md5=bfc1dfdbf8d38329ff8ca0ee7146ce71&pid=1-s2.0-S2666549222000196-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90515758","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 thermodynamic perspective on wind turbine glass fiber waste as a supplementary cementitious material","authors":"Deborah Glosser ,&nbsp;Eli Santykul ,&nbsp;Eric Fagan ,&nbsp;Prannoy Suraneni","doi":"10.1016/j.cement.2022.100039","DOIUrl":"10.1016/j.cement.2022.100039","url":null,"abstract":"<div><p>By the year 2050, glass fiber reinforced polymer (GFRP) material from decommissioned wind turbine blades is expected to generate 40 million tons of waste worldwide. Managing GFRP waste is a vexing problem since the materials cannot be easily recycled. One potential waste management solution is to use the glass fiber (GF) component of GFRP as a supplementary cementitious material (SCM) to replace cement in concrete, which has the additional benefit of reducing CO₂ emissions from cement clinkering. The chemical composition of wind turbine GFs is variable, but is predominantly calcium, silicon, aluminum, and iron, with trace amounts of light and heavy metals, making it an attractive candidate for use as SCM. In this study, thermodynamic modeling was used to evaluate the reaction products, pore solution chemistry, and trace metal immobilization potential of three GF compositions (high silica; high calcium; median calcium/median silica) at varying cement replacement levels. These factors influence pore size and structure, which control mechanical properties, freeze-thaw behavior, transport properties, and corrosion potential. For all GF compositions, replacement levels up to 60% produce cementitious materials with higher volumes of C-S-H (and higher alkali and trace metal binding potential) than control mixtures; pore solution pH values appropriate for mixture designs optimized for either ASR or corrosion prevention; and, at replacement levels below 10% and above 40%, reaction of some trace metals to form insoluble precipitates. While further experimental investigation is essential, these models present evidence that the use of wind turbine GF as an SCM is a viable solution for managing this expanding waste stream.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"9 ","pages":"Article 100039"},"PeriodicalIF":0.0,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000184/pdfft?md5=13d32f94564167104952b005d8a29514&pid=1-s2.0-S2666549222000184-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86679518","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":"DRYING BEHAVIOR OF 3D PRINTED CEMENTITIOUS PASTES CONTAINING CELLULOSE NANOCRYSTALS","authors":"Rita M. Ghantous ,&nbsp;Yvette Valadez-Carranza ,&nbsp;Steven R. Reese ,&nbsp;W. Jason Weiss","doi":"10.1016/j.cement.2022.100035","DOIUrl":"10.1016/j.cement.2022.100035","url":null,"abstract":"<div><p>This study uses neutron radiography to evaluate the drying of printed cement paste samples containing cellulose nanocrystals (CNCs). CNCs have previously been used in printed cement paste to decrease the extrusion pressure and increase the degree of hydration (DOH) of the samples. Three different mixtures were prepared consisting of a plain mixture and mixtures containing two different types of CNCs. The influence of the sample surface to volume ratio (S/V) on the drying of cement paste samples and their DOH was examined. Exposing 3D printed samples to drying immediately after preparation can lead to high levels of water evaporation, which can limit the hydration evolution in the system and increase the porosity. The DOH and the drying behavior of cement paste are found to be dependent on the S/V of the element. The DOH decreased with an increase in the S/V of the sample. The addition of the CNCs to the mixture design did not substantially alter the DOH of poorly cured 3D printed samples. Previous work has shown that CNCs addition to the mixture design can lead to an increase in DOH only if water remains in the sample.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"9 ","pages":"Article 100035"},"PeriodicalIF":0.0,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000159/pdfft?md5=c5a2c928309ae69dfc1ac5ada773917e&pid=1-s2.0-S2666549222000159-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76327270","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}