Dhimitrius Neves Paraguassú Smith de Oliveira, Tiago Marcolino de Souza, Nilson dos Santos Ferreira, Jefferson Bezerra Bezerra, Guillaume Polidori, Lina Bufalino
The açaí waste from Amazon contains short fibers that show potential for reinforcing cement-bonded fiberboards (CBFBs), although their compatibility with cement matrix is still unknown. This work aimed to characterize raw and pretreated açaí fibers and analyze their compatibility with Portland cement by different techniques, besides developing a CBFB. The fibers were subjected to thermal (180, 200, and 220 °C), cold and hot water, alkaline (NaOH), and bleaching (NaOH-H2O2) pretreatments. The chemical and water pretreatments raised the fiber crystalline indexes (28%-57%). The chemical pretreatments individualized the fiber bundles and removed hemicelluloses. Alkali-pretreated and raw fibers had the highest (96%) and lowest (65%) cement compatibility indexes. Portlandite and ettringite appeared after 24 h for most pastes but were delayed for raw and 220 °C-pretreated fibers. In contrast, only the raw fiber specimens reached the required compression strength of 34 MPa after 28 days; hence, they were chosen to produce a CBFB. The boards showed proper thickness swelling (1.4%), but low bending strength (MOE = 647.8 MPa; MOR = 1.9 MPa). Overall, the fiber modifications improved the compatibility with cement, but not the composite's mechanical strength. Açai-fiber CBFB is a promising building material, but future studies must overcome its poor mechanical performance.
{"title":"Amazon açaí fiber-Portland cement compatibility: a challenge to produce cement-bonded fiberboards?","authors":"Dhimitrius Neves Paraguassú Smith de Oliveira, Tiago Marcolino de Souza, Nilson dos Santos Ferreira, Jefferson Bezerra Bezerra, Guillaume Polidori, Lina Bufalino","doi":"10.1680/jadcr.23.00074","DOIUrl":"https://doi.org/10.1680/jadcr.23.00074","url":null,"abstract":"The açaí waste from Amazon contains short fibers that show potential for reinforcing cement-bonded fiberboards (CBFBs), although their compatibility with cement matrix is still unknown. This work aimed to characterize raw and pretreated açaí fibers and analyze their compatibility with Portland cement by different techniques, besides developing a CBFB. The fibers were subjected to thermal (180, 200, and 220 °C), cold and hot water, alkaline (NaOH), and bleaching (NaOH-H<sub>2</sub>O<sub>2</sub>) pretreatments. The chemical and water pretreatments raised the fiber crystalline indexes (28%-57%). The chemical pretreatments individualized the fiber bundles and removed hemicelluloses. Alkali-pretreated and raw fibers had the highest (96%) and lowest (65%) cement compatibility indexes. Portlandite and ettringite appeared after 24 h for most pastes but were delayed for raw and 220 °C-pretreated fibers. In contrast, only the raw fiber specimens reached the required compression strength of 34 MPa after 28 days; hence, they were chosen to produce a CBFB. The boards showed proper thickness swelling (1.4%), but low bending strength (MOE = 647.8 MPa; MOR = 1.9 MPa). Overall, the fiber modifications improved the compatibility with cement, but not the composite's mechanical strength. Açai-fiber CBFB is a promising building material, but future studies must overcome its poor mechanical performance.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140884224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There are many different grades of kaolinite clays around the world. Low-grade kaolinite clay is more abundant than high-grade kaolinite clay in various regions. To aim toward the utilization of low-grade kaolinite clay having an original kaolinite content of about 40% to produce calcined clay, this paper investigated the durability properties of concrete incorporating calcined clay produced from high-grade kaolinite clay or high kaolinite content (commercially available metakaolin or CC1) and calcined clay produced from a low-grade kaolinite clay (CC2). Concrete mixtures were designed to have a water-to-binder ratio of 0.60. A fly ash-to-binder ratio of 0.20 and calcined kaolinite clay-to-binder ratios of 0.10 and 0.20 were studied. The chloride penetration resistance and the electrical resistivity of concrete were assessed, while the mercury intrusion porosimetry (MIP) was utilized in evaluating the pore structure of concrete. The test results revealed that concrete with CC1 and CC2 exhibited superior chloride penetration resistance and chloride binding capacity than OPC and FA20 concretes. Moreover, using a higher calcined clay-to-binder ratio resulted in a more refined pore structure, which significantly enhanced the chloride resistance of concrete. Although CC2 revealed less performance in improving chloride resistance than CC1, it had superior performance compared to fly ash.
{"title":"Influences of metakaolin and calcined clay blended cement on chloride resistance and electrical resistivity of concrete","authors":"Aunchana Kijjanon, Taweechai Sumranwanich, Somnuk Tangtermsirikul","doi":"10.1680/jadcr.23.00162","DOIUrl":"https://doi.org/10.1680/jadcr.23.00162","url":null,"abstract":"There are many different grades of kaolinite clays around the world. Low-grade kaolinite clay is more abundant than high-grade kaolinite clay in various regions. To aim toward the utilization of low-grade kaolinite clay having an original kaolinite content of about 40% to produce calcined clay, this paper investigated the durability properties of concrete incorporating calcined clay produced from high-grade kaolinite clay or high kaolinite content (commercially available metakaolin or CC1) and calcined clay produced from a low-grade kaolinite clay (CC2). Concrete mixtures were designed to have a water-to-binder ratio of 0.60. A fly ash-to-binder ratio of 0.20 and calcined kaolinite clay-to-binder ratios of 0.10 and 0.20 were studied. The chloride penetration resistance and the electrical resistivity of concrete were assessed, while the mercury intrusion porosimetry (MIP) was utilized in evaluating the pore structure of concrete. The test results revealed that concrete with CC1 and CC2 exhibited superior chloride penetration resistance and chloride binding capacity than OPC and FA20 concretes. Moreover, using a higher calcined clay-to-binder ratio resulted in a more refined pore structure, which significantly enhanced the chloride resistance of concrete. Although CC2 revealed less performance in improving chloride resistance than CC1, it had superior performance compared to fly ash.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140889827","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Liuhua Yang, Yang Gao, Hui Chen, Huazhe Jiao, Mengmeng Dong, Thomas A. Bier, Mintae Kim
The flow and deformation of cement-based materials accompanies the full cycle of 3DPC technology and profoundly affects the quality of printed structures. Therefore, rheology is closely related to this technology. However, since printing materials undergo complex changes (from fluid to solid) during the entire technical process, it is extremely difficult to accurately obtain the rheological parameters of the material, which makes it difficult to characterize the material properties and explore the rheological laws within the technical cycle. In this regard, this article starts from the perspective of rheology, systematically reviews the performance requirements of 3DPC technology for printing materials, critically discusses the existing methods for characterization of material printability, including various conventional and unconventional methods, and clarifies the scope of application of each method. In addition, this article introduces several buildability models based on considering material time dependence, pointing out the direction for the performance optimization of printing materials.
{"title":"3D printing concrete technology from a rheology perspective: a review","authors":"Liuhua Yang, Yang Gao, Hui Chen, Huazhe Jiao, Mengmeng Dong, Thomas A. Bier, Mintae Kim","doi":"10.1680/jadcr.23.00205","DOIUrl":"https://doi.org/10.1680/jadcr.23.00205","url":null,"abstract":"The flow and deformation of cement-based materials accompanies the full cycle of 3DPC technology and profoundly affects the quality of printed structures. Therefore, rheology is closely related to this technology. However, since printing materials undergo complex changes (from fluid to solid) during the entire technical process, it is extremely difficult to accurately obtain the rheological parameters of the material, which makes it difficult to characterize the material properties and explore the rheological laws within the technical cycle. In this regard, this article starts from the perspective of rheology, systematically reviews the performance requirements of 3DPC technology for printing materials, critically discusses the existing methods for characterization of material printability, including various conventional and unconventional methods, and clarifies the scope of application of each method. In addition, this article introduces several buildability models based on considering material time dependence, pointing out the direction for the performance optimization of printing materials.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140625434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kemal Karakuzu, Veysel Kobya, Ali Mardani, Burak Felekoğlu, Kambiz Ramyar
This study investigated the compatibility of polycarboxylate-based water reducing admixtures (PCE) having different carboxylate, phosphate and sulfonate anionic groups with paste and mortar mixtures containing fly ash. According to the results, with the increase of the fly ash content of the mixtures, PCE requirement for the target flow decreased, as well as consistency retention performance improved due to the decrease in the amount of hydrated cement. An improvement in rheological parameters was observed with the increase in fly ash content from 15% to 30%. However, increasing the fly ash replacement level beyond 30% caused stability problems in the mixtures. This problem was eliminated with PCE addition. In the paste and mortar mixtures, regardless of the fly ash substitution ratio, the best performance was obtained with PCEs containing 7% and 5% phosphate and sulfonate, respectively. The most suitable fly ash replacement ratio in terms of rheological parameters and 28-day compressive strength was 30% and 15%, respectively. It was observed that PCE anionic group content did not have any significant effect on all fly ash substitution ratios.
{"title":"Investigation of anionic group characteristics of PCEs on the behavior of fly ash cementitious systems","authors":"Kemal Karakuzu, Veysel Kobya, Ali Mardani, Burak Felekoğlu, Kambiz Ramyar","doi":"10.1680/jadcr.23.00201","DOIUrl":"https://doi.org/10.1680/jadcr.23.00201","url":null,"abstract":"This study investigated the compatibility of polycarboxylate-based water reducing admixtures (PCE) having different carboxylate, phosphate and sulfonate anionic groups with paste and mortar mixtures containing fly ash. According to the results, with the increase of the fly ash content of the mixtures, PCE requirement for the target flow decreased, as well as consistency retention performance improved due to the decrease in the amount of hydrated cement. An improvement in rheological parameters was observed with the increase in fly ash content from 15% to 30%. However, increasing the fly ash replacement level beyond 30% caused stability problems in the mixtures. This problem was eliminated with PCE addition. In the paste and mortar mixtures, regardless of the fly ash substitution ratio, the best performance was obtained with PCEs containing 7% and 5% phosphate and sulfonate, respectively. The most suitable fly ash replacement ratio in terms of rheological parameters and 28-day compressive strength was 30% and 15%, respectively. It was observed that PCE anionic group content did not have any significant effect on all fly ash substitution ratios.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140625433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this study, the use of meta-schist as an alternative to sand-clay in preparing cement raw mixtures was investigated for the first time. Although there are high meta-schist reserves in many countries, especially in Turkey and America, there have not been enough experimental studies for their use in cement production, and their superior technical features still need to be demonstrated. To produce the highest quality Portland cement clinker by examining the mineral and chemical properties of meta-schists, two different raw meal samples were prepared, utilizing conventional cement clay as a baseline sample ((PC) Ref) and the other with meta-schist ((PC) MSC). The effects of both raw mixtures on burnability tests and reactivity were evaluated based on the unreacted lime content in samples after sintered at 1200, 1300, 1350, 1400, and 1450 °C. As a result of firing at 1450 °C, ((PC) MSC) exhibited good sintering properties by showing less than 1% free lime by weight. The porosity amount, distribution, grain structure of silicate phase crystals and equivalent crystal diameters and amounts of meta-schist clinker phases (C3S, C2S, C3A and C4AF) examined by polarizing optical microscope showed that they are suitable for the production of PC. The point counting method, Bogue model calculations, and XRD patterns have confirmed this result. The hydration products of the cement mortars were determined by SEM and EDX analysis at 2, 7, and 28 days. In addition, the compressive strength test results of ((PC) MSC) and ((PC) Ref) mortars after 28 days of curing ranged between 57 and 55,5 MPa, and the produced cement was classified as CEM I 42,5R.
在这项研究中，首次调查了在制备水泥生料混合物时使用元冲灰岩替代砂粘土的情况。虽然许多国家，特别是土耳其和美国的元页岩储量很高，但在水泥生产中使用元页岩的实验研究还不够多，其优越的技术特性仍有待证明。为了通过研究元片麻岩的矿物和化学特性来生产最高质量的波特兰水泥熟料，我们制备了两种不同的生料样品，一种以传统水泥粘土为基准样品（（PC）Ref），另一种以元片麻岩为基准样品（（PC）MSC）。根据在 1200、1300、1350、1400 和 1450 °C 下烧结后样品中未反应的石灰含量，评估了两种生料混合物对燃烧性测试和反应性的影响。在 1450 °C 煅烧后，（（PC）MSC）表现出良好的烧结性能，游离石灰含量小于 1%（按重量计）。通过偏光光学显微镜检测硅酸盐相晶体的孔隙率、分布、晶粒结构以及元硬石膏相（C3S、C2S、C3A 和 C4AF）的等效晶体直径和数量，结果表明它们适合生产 PC。点计数法、博格模型计算和 X 射线衍射图均证实了这一结果。水泥砂浆的水化产物是在 2 天、7 天和 28 天时通过 SEM 和 EDX 分析测定的。此外，((PC) MSC)和((PC) Ref)砂浆在 28 天固化后的抗压强度测试结果介于 57 和 55.5 兆帕之间，生产的水泥被归类为 CEM I 42.5R。
{"title":"Assessment of meta-schist as a novel sustainable resource for Portland cement manufacturing","authors":"Abdul Korkmaz, Hasan Hacifazlioğlu","doi":"10.1680/jadcr.23.00132","DOIUrl":"https://doi.org/10.1680/jadcr.23.00132","url":null,"abstract":"In this study, the use of meta-schist as an alternative to sand-clay in preparing cement raw mixtures was investigated for the first time. Although there are high meta-schist reserves in many countries, especially in Turkey and America, there have not been enough experimental studies for their use in cement production, and their superior technical features still need to be demonstrated. To produce the highest quality Portland cement clinker by examining the mineral and chemical properties of meta-schists, two different raw meal samples were prepared, utilizing conventional cement clay as a baseline sample ((PC) Ref) and the other with meta-schist ((PC) MSC). The effects of both raw mixtures on burnability tests and reactivity were evaluated based on the unreacted lime content in samples after sintered at 1200, 1300, 1350, 1400, and 1450 °C. As a result of firing at 1450 °C, ((PC) MSC) exhibited good sintering properties by showing less than 1% free lime by weight. The porosity amount, distribution, grain structure of silicate phase crystals and equivalent crystal diameters and amounts of meta-schist clinker phases (C<sub>3</sub>S, C<sub>2</sub>S, C<sub>3</sub>A and C<sub>4</sub>AF) examined by polarizing optical microscope showed that they are suitable for the production of PC. The point counting method, Bogue model calculations, and XRD patterns have confirmed this result. The hydration products of the cement mortars were determined by SEM and EDX analysis at 2, 7, and 28 days. In addition, the compressive strength test results of ((PC) MSC) and ((PC) Ref) mortars after 28 days of curing ranged between 57 and 55,5 MPa, and the produced cement was classified as CEM I 42,5R.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140322746","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work aims to provide new composite material for thermal insulating building applications. The composite was made with mortar reinforced with natural fibers that were extracted from petiole of WR palm tree. The used fibers were first chemically characterized by EDS, SEM, X-ray and infrared diffractometry spectroscopies as well as tensile test to know their morphological structure. Afterward, the fibers were incorporated into mortar with different mass percentages varying from 0 to 4% to experimentally determine the thermomechanical properties of the manufactured samples. The chemical findings indicated that the WR fibers are rich in cellulose, hemicellulose, and lignin, and possess high crystallinity index; which enhance the mechanical properties and durability of the composite. Furthermore, the obtained density of the composite W2RC4% is of 1305 kg/m3 and less than 2000 kg/m³; this composite can be then classified as lightweight concretes according to the standard NF EN 206+A2/CN (2022). The thermal conductivity and thermal effusivity dropped by about 60% and 42% respectively. Moreover, the WR reduces the compressive strength (76%) and the flexural strength (36%) to minimum values respectively of 5.9 MPa and 3.8 MPa. These values meet the mechanical requirements of lightweight concretes (>3.5 MPa).
{"title":"Experimental investigation on chemical and thermomechanical properties of concrete incorporating Washingtonia Robusta fibers","authors":"Sakami Siham, Lahcen Boukhattem, Mustapha Boumhaout","doi":"10.1680/jadcr.23.00036","DOIUrl":"https://doi.org/10.1680/jadcr.23.00036","url":null,"abstract":"This work aims to provide new composite material for thermal insulating building applications. The composite was made with mortar reinforced with natural fibers that were extracted from petiole of WR palm tree. The used fibers were first chemically characterized by EDS, SEM, X-ray and infrared diffractometry spectroscopies as well as tensile test to know their morphological structure. Afterward, the fibers were incorporated into mortar with different mass percentages varying from 0 to 4% to experimentally determine the thermomechanical properties of the manufactured samples. The chemical findings indicated that the WR fibers are rich in cellulose, hemicellulose, and lignin, and possess high crystallinity index; which enhance the mechanical properties and durability of the composite. Furthermore, the obtained density of the composite W2RC4% is of 1305 kg/m<sup>3</sup> and less than 2000 kg/m³; this composite can be then classified as lightweight concretes according to the standard NF EN 206+A2/CN (2022). The thermal conductivity and thermal effusivity dropped by about 60% and 42% respectively. Moreover, the WR reduces the compressive strength (76%) and the flexural strength (36%) to minimum values respectively of 5.9 MPa and 3.8 MPa. These values meet the mechanical requirements of lightweight concretes (>3.5 MPa).","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140314963","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Durability of concrete under the combined exposure of acidic environment and flexural loading has been studied. Concrete specimens were made and subjected to 168 days exposure to the flexural loading (stress levels of 0.0, 0.35 and 0.5 of their 28d flexural strength) and acidic exposure environment. Concrete properties including neutralization depth, mass change, compressive strength and flexural strength were measured. Compositions of samples were determined by means of x-ray diffraction and chemical analysis. Microstructure of samples was conducted using scanning electron microscope. Results indicate that with the stress level rising from 0.0 to 0.5, the performance of concrete deteriorated gradually and the deterioration of the tension zone was greater than that of the compression zone; concrete performances improved within 28 days and afterwards deteriorated dramatically; acidic solution reacted with cement paste, leading to the formation of harmful gypsum and the decomposition and dissolution of hydration products of cement; the increase of stress level increased the porosity of concrete, accelerating the rate of acid erosion, which led to the deterioration of concrete performance.
{"title":"Durability of concrete subjected to acidic exposure attack under flexural loading","authors":"Beixing Li, Hongtian Yang, Xiaolu Yuan","doi":"10.1680/jadcr.23.00101","DOIUrl":"https://doi.org/10.1680/jadcr.23.00101","url":null,"abstract":"Durability of concrete under the combined exposure of acidic environment and flexural loading has been studied. Concrete specimens were made and subjected to 168 days exposure to the flexural loading (stress levels of 0.0, 0.35 and 0.5 of their 28d flexural strength) and acidic exposure environment. Concrete properties including neutralization depth, mass change, compressive strength and flexural strength were measured. Compositions of samples were determined by means of x-ray diffraction and chemical analysis. Microstructure of samples was conducted using scanning electron microscope. Results indicate that with the stress level rising from 0.0 to 0.5, the performance of concrete deteriorated gradually and the deterioration of the tension zone was greater than that of the compression zone; concrete performances improved within 28 days and afterwards deteriorated dramatically; acidic solution reacted with cement paste, leading to the formation of harmful gypsum and the decomposition and dissolution of hydration products of cement; the increase of stress level increased the porosity of concrete, accelerating the rate of acid erosion, which led to the deterioration of concrete performance.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-03-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140210890","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The AFm phase found in hydrated Portland cements refers to a family of calcium aluminate phases. Their layer structure is derived from that of portlandite, Ca(OH)2, but with one third of the Ca2+ ions replaced by a trivalent ion, nominally Al2+ or Fe2+. The resulting charge imbalance gives the layers a positive charge which is compensated by intercalated anions the remaining interlayer space is filled with H2O. Hydrated cements will contain mixtures of AFm phases and their solid solutions. Portland cement is often modified by addition of soluble nitrate or nitrite salts to protect embedded steel or to shorten the set time. These nitrate and nitrite ions are capable of entering and occupying AFm anion sites hence impacting overall phase balances between cement hydrates. In this study AFm phases and solid solution formations were investigated between AFm phases containing SO42+, CO32+, OH2+, Cl2+ and NO22+NO32+ ions. Samples were synthesized and subsequently characterized using X-ray Diffraction (XRD) and through the measurement of aqueous solution compositions after 180 days of equilibration in water.
{"title":"Solid solutions amongst cement AFm phases containing nitrate and nitrite ions","authors":"Magdalena Balonis","doi":"10.1680/jadcr.23.00010","DOIUrl":"https://doi.org/10.1680/jadcr.23.00010","url":null,"abstract":"The AFm phase found in hydrated Portland cements refers to a family of calcium aluminate phases. Their layer structure is derived from that of portlandite, Ca(OH)2, but with one third of the Ca2+ ions replaced by a trivalent ion, nominally Al2+ or Fe2+. The resulting charge imbalance gives the layers a positive charge which is compensated by intercalated anions the remaining interlayer space is filled with H2O. Hydrated cements will contain mixtures of AFm phases and their solid solutions. Portland cement is often modified by addition of soluble nitrate or nitrite salts to protect embedded steel or to shorten the set time. These nitrate and nitrite ions are capable of entering and occupying AFm anion sites hence impacting overall phase balances between cement hydrates. In this study AFm phases and solid solution formations were investigated between AFm phases containing SO42+, CO32+, OH2+, Cl2+ and NO22+NO32+ ions. Samples were synthesized and subsequently characterized using X-ray Diffraction (XRD) and through the measurement of aqueous solution compositions after 180 days of equilibration in water.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140236552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study aims to evaluate the sulfate resistant of mortars containing sulfate-resistant cementitious materials (SRCMs) developed by mixing ground granulated blast furnace slag, fly ash, silica fume, and desulfurization gypsum. Compressive strength test, XRD, DTA, and MIP were carried out in this work. The results showed that the sulfate resistance of mortars mixed with SRCMs at replacement percentage of 74 wt.% was superior to that of mortars with 30 wt.% fly ash when they were exposed to drying-wetting cycle in sodium sulfate solution, which was because adding SRCMs decreased Ca(OH)2 content, causing a reduction in gypsum formation. Moreover, reducing W/B from 0.50 to 0.35 increased the loss of compressive strength ratio (Lf) of mortars with SRCMs immersed in ammonium-magnesium sulfate complex solution. Specifically, Lf values of mortars with W/B of 0.50 and 0.35 were 42.7% and 36.0% after 100 days of immersion, respectively. Furthermore, the main components of samples subjected to complex solution were identified as gypsum. Further, both Lf and porosity presented a strong linear positive correlation with W/B. At last, the findings of this study confirmed that optimizing the composition of cementitious materials and lowering W/B could improve the sulfate resistance of concretes used for sulfate-rich sewage environment.
{"title":"Investigating the sulfate resistance of mortars with multiple mineral admixtures in ammonium-magnesium sulfate solution","authors":"Junfeng Wang, Yiming Chen, Qionglin Fu, Liulei Lu","doi":"10.1680/jadcr.23.00193","DOIUrl":"https://doi.org/10.1680/jadcr.23.00193","url":null,"abstract":"This study aims to evaluate the sulfate resistant of mortars containing sulfate-resistant cementitious materials (SRCMs) developed by mixing ground granulated blast furnace slag, fly ash, silica fume, and desulfurization gypsum. Compressive strength test, XRD, DTA, and MIP were carried out in this work. The results showed that the sulfate resistance of mortars mixed with SRCMs at replacement percentage of 74 wt.% was superior to that of mortars with 30 wt.% fly ash when they were exposed to drying-wetting cycle in sodium sulfate solution, which was because adding SRCMs decreased Ca(OH)2 content, causing a reduction in gypsum formation. Moreover, reducing W/B from 0.50 to 0.35 increased the loss of compressive strength ratio (Lf) of mortars with SRCMs immersed in ammonium-magnesium sulfate complex solution. Specifically, Lf values of mortars with W/B of 0.50 and 0.35 were 42.7% and 36.0% after 100 days of immersion, respectively. Furthermore, the main components of samples subjected to complex solution were identified as gypsum. Further, both Lf and porosity presented a strong linear positive correlation with W/B. At last, the findings of this study confirmed that optimizing the composition of cementitious materials and lowering W/B could improve the sulfate resistance of concretes used for sulfate-rich sewage environment.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140251380","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The aggregation of graphene oxide (GO) in alkaline solutions is a critical factor that limits its potential application in cement-based materials. In this study, a novel superplasticizer was employed as a dispersant, and the GO@PCE water-reducing agent was synthesized through a dropwise addition method. This synthesis approach not only preserves the water-reducing capabilities of PCE but also enhances the dispersibility of GO in alkaline cement solutions. Furthermore, the synthesis method is straightforward. The results demonstrate that GO@PCE maintains excellent dispersion in saturated calcium hydroxide solution. Furthermore, it was observed that GO@PCE can enhance the workability of cement, accelerate cement hydration, reduce the crystallite size of calcium hydroxide, and effectively increase the compressive strength of cement mortar.
氧化石墨烯（GO）在碱性溶液中的聚集是限制其在水泥基材料中潜在应用的一个关键因素。本研究采用了一种新型超塑化剂作为分散剂，并通过滴加法合成了 GO@PCE 减水剂。这种合成方法不仅保留了 PCE 的减水功能，还提高了 GO 在碱性水泥溶液中的分散性。此外，该合成方法简单易行。结果表明，GO@PCE 在饱和氢氧化钙溶液中能保持良好的分散性。此外，还观察到 GO@PCE 可增强水泥的可操作性，加速水泥水化，降低氢氧化钙的结晶尺寸，并有效提高水泥砂浆的抗压强度。
{"title":"The dispersion and influence of graphene oxide modified polycarboxylate superplasticizer in alkaline cement solution","authors":"Han Zhou, Dongxu Li","doi":"10.1680/jadcr.23.00217","DOIUrl":"https://doi.org/10.1680/jadcr.23.00217","url":null,"abstract":"The aggregation of graphene oxide (GO) in alkaline solutions is a critical factor that limits its potential application in cement-based materials. In this study, a novel superplasticizer was employed as a dispersant, and the GO@PCE water-reducing agent was synthesized through a dropwise addition method. This synthesis approach not only preserves the water-reducing capabilities of PCE but also enhances the dispersibility of GO in alkaline cement solutions. Furthermore, the synthesis method is straightforward. The results demonstrate that GO@PCE maintains excellent dispersion in saturated calcium hydroxide solution. Furthermore, it was observed that GO@PCE can enhance the workability of cement, accelerate cement hydration, reduce the crystallite size of calcium hydroxide, and effectively increase the compressive strength of cement mortar.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2024-03-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140251250","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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