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":"26 1","pages":""},"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":"55 1","pages":""},"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":"196 1","pages":""},"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":"38 1","pages":""},"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":"49 1","pages":""},"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":"31 1","pages":""},"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}
The stainless steel slag's low activity, primarily attributed to its high γ-C2S and low C3S content, impedes its effective utilization. This study employs a thermochemical high-temperature reconstruction method utilizing lime and bauxite as tempering agents to regulate the mineral phase. Through an array of tests and analytical techniques, including compressive strength test, activity index, XRD, SEM, and hydration heat analysis, the impact of Ca/Si ratio and sintering temperature on the mechanical properties and activity of reconstituted stainless steel slag mortar is examined. The findings indicate that at a Ca/Si ratio of 4.2 and a sintering temperature of 1290°C, the reconstructed slag demonstrates optimal mechanical properties and activity, yielding compressive strengths of 43.69 MPa and 62.58 MPa at 7 days and 28 days, respectively, with remarkable 28 day activity index of 143.49%. The proposed thermochemical high-temperature reconstruction method ingeniously employs high temperature to increase the content of C3S while rapid cooling prevents the alteration of the C2S crystalline structure. This innovation significantly enhances the mechanical properties and activity of the stainless steel slag, offering promising avenues to increase its utilization rate.
{"title":"Influence of thermochemical high-temperature reconstruction on mechanical properties and activity of stainless steel slag","authors":"Pengjie Xu, Jintao Fan, Rongjin Liu, Ping Chen, Jiazhan Wei, Yi Yang, Xiaochun Tang","doi":"10.1680/jadcr.23.00083","DOIUrl":"https://doi.org/10.1680/jadcr.23.00083","url":null,"abstract":"The stainless steel slag's low activity, primarily attributed to its high <i>γ</i>-C<sub>2</sub>S and low C<sub>3</sub>S content, impedes its effective utilization. This study employs a thermochemical high-temperature reconstruction method utilizing lime and bauxite as tempering agents to regulate the mineral phase. Through an array of tests and analytical techniques, including compressive strength test, activity index, XRD, SEM, and hydration heat analysis, the impact of Ca/Si ratio and sintering temperature on the mechanical properties and activity of reconstituted stainless steel slag mortar is examined. The findings indicate that at a Ca/Si ratio of 4.2 and a sintering temperature of 1290°C, the reconstructed slag demonstrates optimal mechanical properties and activity, yielding compressive strengths of 43.69 MPa and 62.58 MPa at 7 days and 28 days, respectively, with remarkable 28 day activity index of 143.49%. The proposed thermochemical high-temperature reconstruction method ingeniously employs high temperature to increase the content of C<sub>3</sub>S while rapid cooling prevents the alteration of the C<sub>2</sub>S crystalline structure. This innovation significantly enhances the mechanical properties and activity of the stainless steel slag, offering promising avenues to increase its utilization rate.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":"34 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-02-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140167982","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}
Pore in steam-cured concrete affect its strength and durability, and the optimization of steaming system can improve the pore structure to some extent. However, the influence mechanism of evaporation on recycled aggregate concrete (RCA) remains unclear. In this paper, the effects of curing temperature (20°C, 40°C, 60°C and 80°C), steam curing time (6h, 9h and 12h) and pozzolans (slag powder and fly ash) on the compressive strength and pore structure of RAC were studied. The microstructure characteristics such as pore size and pore size distribution were analyzed by the mercury injection porosimetry. The results shown that steam curing can significantly improve the compressive strength and reduce the most probable aperture and average pore sizes of RAC. Moreover, the effect of slag powder on RAC pore structure is better than that of fly ash. And there is a linear correlation between the compressive strength and the average pore size of steam-cured RAC. This can be an important parameter for constructing future steam cured RAC strength prediction models.
{"title":"Effects of stream curing on the pore structure of recycled aggregate concrete","authors":"Yuzhi Chen, Yingjie Ning, Xudong Chen, Weihong Xuan, Yuzhu Guo","doi":"10.1680/jadcr.22.00092","DOIUrl":"https://doi.org/10.1680/jadcr.22.00092","url":null,"abstract":"Pore in steam-cured concrete affect its strength and durability, and the optimization of steaming system can improve the pore structure to some extent. However, the influence mechanism of evaporation on recycled aggregate concrete (RCA) remains unclear. In this paper, the effects of curing temperature (20°C, 40°C, 60°C and 80°C), steam curing time (6h, 9h and 12h) and pozzolans (slag powder and fly ash) on the compressive strength and pore structure of RAC were studied. The microstructure characteristics such as pore size and pore size distribution were analyzed by the mercury injection porosimetry. The results shown that steam curing can significantly improve the compressive strength and reduce the most probable aperture and average pore sizes of RAC. Moreover, the effect of slag powder on RAC pore structure is better than that of fly ash. And there is a linear correlation between the compressive strength and the average pore size of steam-cured RAC. This can be an important parameter for constructing future steam cured RAC strength prediction models.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":"96 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2024-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140168505","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 setting time and early strength of shotcrete is greatly affected by the gypsum content of cement. In this paper, setting time and compressive strength, and microscopic methods such as XRD quantitative analysis, thermogravimetric analysis and scanning electron microscope observation were used to determine the effects of changes in gypsum content on the hydration and mechanical properties of cement mixed with accelerator at different temperatures. The results showed that an increase in the gypsum content of cement promoted the formation of ettringite (AFt) and decreased the setting times of cement pastes at 0°C, 20°C and 40°C. Mortar compressive strength test revealed that after curing at 0°C, 20 °C and 40°C, the highest compressive strength was exhibited with final molar C3A/SO3 ratio of 0.84, 0.84 and 1.18, respectively. The mechanical properties of hardened cement pastes were adversely affected by C3A/SO3 ratios that were too high or too low. When the C3A/SO3 ratio was too high, which facilitated conversion of AFt to monosulphate(AFm) and slowed C3S hydration. Conversely, when the C3A/SO3 ratio was too low, which enabled large numbers of AFt to occupy the space where C-S-H gels was formed, resulting in decalcification of C-S-H gels.
{"title":"Study on the effect of gypsum content in cement on the adaptability between cement and alkali-free accelerator at different temperatures","authors":"Qin Wang, Zhixiang Guo, Fanchao Zeng, Hongwei Wang, Huaixia Qin","doi":"10.1680/jadcr.23.00165","DOIUrl":"https://doi.org/10.1680/jadcr.23.00165","url":null,"abstract":"The setting time and early strength of shotcrete is greatly affected by the gypsum content of cement. In this paper, setting time and compressive strength, and microscopic methods such as XRD quantitative analysis, thermogravimetric analysis and scanning electron microscope observation were used to determine the effects of changes in gypsum content on the hydration and mechanical properties of cement mixed with accelerator at different temperatures. The results showed that an increase in the gypsum content of cement promoted the formation of ettringite (AFt) and decreased the setting times of cement pastes at 0°C, 20°C and 40°C. Mortar compressive strength test revealed that after curing at 0°C, 20 °C and 40°C, the highest compressive strength was exhibited with final molar C<sub>3</sub>A/SO<sub>3</sub> ratio of 0.84, 0.84 and 1.18, respectively. The mechanical properties of hardened cement pastes were adversely affected by C<sub>3</sub>A/SO<sub>3</sub> ratios that were too high or too low. When the C<sub>3</sub>A/SO<sub>3</sub> ratio was too high, which facilitated conversion of AFt to monosulphate(AFm) and slowed C<sub>3</sub>S hydration. Conversely, when the C<sub>3</sub>A/SO<sub>3</sub> ratio was too low, which enabled large numbers of AFt to occupy the space where C-S-H gels was formed, resulting in decalcification of C-S-H gels.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":"10 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139055614","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}
Linnu Lu, Peng Wang, Yongjia He, Ma Jie, Fazhou Wang, Shuguang Hu
An approach for efficient re-utilization of waste cement paste powders is proposed, that is, the powders are heated to a certain temperature to prepare Regenerated Binding Materials (RBMs), and then rapid carbonated by high concentration CO2 to prepare high-strength products. The structural evolution during the heating process of waste cement paste powder and the carbonation process of RBMs were investigated by XRD, SEM, and 29Si NMR etc., and the compressive strength of the carbonated RBM samples was measured. The results show that the differences in carbonation reactivity, carbonation products of RBMs, and properties of carbonated RBMs are mainly attributed to the differences in structural order degree of newly formed β-C2S, the content of β-C2S, f-CaO and incomplete decomposed C-S-H in RBMs. The strength of the carbonated sample of RBM prepared at 1050 °C was the highest, followed by that prepared at 950 °C, which was significantly higher than those prepared at 650 °C, 750 °C and 850 °C. The content of highly ordered β-C2S in RBMs with high carbonation reactivity, and the dense stacking of the carbonation products are beneficial for the mechanical properties.
{"title":"Accelerated carbonation of regenerated binding material prepared with waste cement paste powder","authors":"Linnu Lu, Peng Wang, Yongjia He, Ma Jie, Fazhou Wang, Shuguang Hu","doi":"10.1680/jadcr.23.00098","DOIUrl":"https://doi.org/10.1680/jadcr.23.00098","url":null,"abstract":"An approach for efficient re-utilization of waste cement paste powders is proposed, that is, the powders are heated to a certain temperature to prepare Regenerated Binding Materials (RBMs), and then rapid carbonated by high concentration CO<sub>2</sub> to prepare high-strength products. The structural evolution during the heating process of waste cement paste powder and the carbonation process of RBMs were investigated by XRD, SEM, and <sup>29</sup>Si NMR etc., and the compressive strength of the carbonated RBM samples was measured. The results show that the differences in carbonation reactivity, carbonation products of RBMs, and properties of carbonated RBMs are mainly attributed to the differences in structural order degree of newly formed <i>β</i>-C<sub>2</sub>S, the content of <i>β</i>-C<sub>2</sub>S, <i>f</i>-CaO and incomplete decomposed C-S-H in RBMs. The strength of the carbonated sample of RBM prepared at 1050 °C was the highest, followed by that prepared at 950 °C, which was significantly higher than those prepared at 650 °C, 750 °C and 850 °C. The content of highly ordered <i>β</i>-C<sub>2</sub>S in RBMs with high carbonation reactivity, and the dense stacking of the carbonation products are beneficial for the mechanical properties.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":"3 1","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-12-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139055687","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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