CEMENT最新文献

{"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}

{"title":"Effects of lignosulfonate on synthesis products of the pozzolanic reaction","authors":"Kanako Toda ,&nbsp;Daisuke Minato ,&nbsp;Takumi Saito ,&nbsp;Ryosuke Kikuchi ,&nbsp;Tsubasa Otake ,&nbsp;Tsutomu Sato","doi":"10.1016/j.cement.2022.100042","DOIUrl":"https://doi.org/10.1016/j.cement.2022.100042","url":null,"abstract":"<div><p>Soil organic matters may inhibit the pozzolanic reaction, and thus influence the strength development of soil-employed construction materials. To understand their interaction, the effect of lignosulfonate, here used as model soil organic matter, on the pozzolanic reaction was investigated through batch experiments. Lignosulfonate inhibited the pozzolanic reaction, suppressing calcium silicate hydrate (C-S-H) formation. The suppression did not take place in a continuous way with the addition of lignosulfonate but was triggered at a certain dosage of lignosulfonate. We propose that the inhibition was primarily due to formation of Si-(Ca)-lignosulfonate complex. Such interaction may illustrate the inhibition of the pozzolanic reaction by organic matters in soils at alkaline activation. Below the threshold, lignosulfonate allowed C-S-H formation though modified its structure, which also suggested the possibility of soil organic matters to influence the strength development of construction materials in coexistence of C-S-H formation.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"9 ","pages":"Article 100042"},"PeriodicalIF":0.0,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000214/pdfft?md5=b8795d6354da5ab2011f26cdf287ff38&pid=1-s2.0-S2666549222000214-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"92022091","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 TiO2 waste on the formation of clinker phases and mechanical performance and hydration of Portand cement","authors":"José S. Andrade Neto ,&nbsp;Bruna B. Mariani ,&nbsp;Nilson S. Amorim Júnior Junior ,&nbsp;Daniel V. Ribeiro","doi":"10.1016/j.cement.2022.100036","DOIUrl":"10.1016/j.cement.2022.100036","url":null,"abstract":"<div><p>The incorporation of different levels of UOW into Portland clinker raw meals and its effects on the clinker and cement properties were evaluated. Clinkers were produced and characterized by X-ray diffractometry (XRD) and optical microscopy; the cements were produced and physically characterized. Finally, pastes were produced and analyzed using isothermal calorimetry, thermogravimetry, XRD, and compressive strength tests. UOW, when added up to 1.29% in Portland clinker raw meal, acts as a mineralizer, increasing the content of alite by 6.44%. The incorporation of UOW reduces the hydration rate in the first days owing to the increase in the size of the alite crystals and delays the point of sulfate depletion due to the increase in the SO₃ content of the clinkers. Owing to the higher content of alite formed, the cement produced from the raw meal with 1.29% of UOW presents the highest early mechanical strength (up to 7 days).</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"9 ","pages":"Article 100036"},"PeriodicalIF":0.0,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000160/pdfft?md5=72ac96e689424284be2f72714f0e0a8b&pid=1-s2.0-S2666549222000160-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74985842","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":"Factors influencing the time dependence of porosity relaxation in cement during sorption: Experimental results from spatially resolved NMR","authors":"Magdalena Janota,&nbsp;Ors Istok,&nbsp;David A. Faux,&nbsp;Peter J. McDonald","doi":"10.1016/j.cement.2022.100028","DOIUrl":"10.1016/j.cement.2022.100028","url":null,"abstract":"<div><p>We use <span><math><msup><mrow></mrow><mn>1</mn></msup></math></span>H nuclear magnetic resonance (NMR) methods to show that the relaxation time governing the redistribution of the gel-pore porosity in cement pastes during sorption depends, not surprisingly, on the dry state saturation and also, more surprisingly, on the sample size. The relaxation time is typically in the range 20 to 40 h for cylindrical samples 60 mm long dried to saturations between about 40 and 55%. It increases up to 200 h for samples dried to between 20 and 30% saturation. The times are all very much longer than for 1 mm samples. There is additional evidence to support the idea that the relaxation of hydrate inter-layer sized spaces occurs on at least two timescales, one of which is very much longer (months) than any of those listed above.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"8 ","pages":"Article 100028"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000081/pdfft?md5=e54d2299bf97d66f1651ac9fa70fd559&pid=1-s2.0-S2666549222000081-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75647325","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":"Reaction kinetics of supplementary cementitious materials in reactivity tests","authors":"Sivakumar Ramanathan ,&nbsp;Luis Ruiz Pestana ,&nbsp;Prannoy Suraneni","doi":"10.1016/j.cement.2022.100022","DOIUrl":"10.1016/j.cement.2022.100022","url":null,"abstract":"<div><p>This work characterizes the reaction kinetics of supplementary cementitious materials (SCMs) with calcium hydroxide in the modified R³ test. The heat flow curves of 58 SCMs of varying reactivities were studied. Based on the heat flow curves, the SCMs were classified as more reactive, less reactive, and inert. Most of the heat flow curves in the modified R³ test exhibit, after the peak of heat flow, an initial slow decaying power-law regime that transitions into a longer and faster decaying power-law regime. The pre-exponent of the first regime depends on the initial SCM reactivity and correlates well with the 24-hour heat release in the modified R³ test, thus making it a useful metric for rapid classification of SCMs.</p></div>","PeriodicalId":100225,"journal":{"name":"CEMENT","volume":"8 ","pages":"Article 100022"},"PeriodicalIF":0.0,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S2666549222000020/pdfft?md5=969451e25c4003ccfd0834763a3e92eb&pid=1-s2.0-S2666549222000020-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81612013","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}