A. Kazlagić, Stephan Dietmar, M. Ostermann, A. Possolo, J. Vogl
This study uses conventional 87Sr/87Sr and 87Nd/87Nd isotope and interelement ratios of Ca, Sr, K, Mn, Mg, and Ti as fingerprints for ordinary Portland cements (OPC) provenancing. Herein, the first database of Sr and Nd isotope ratios investigated in OPCs stemming from twenty-nine cement plants located worldwide was created. The results show that the Sr isotope ratios of OPCs are higher than those of seawater from the observed geological period. The spread of 87Nd/87Nd in OPCs is not as large as the spread for 87Sr/87Sr isotope ratios. However, the combination of both Sr and Nd isotope ratios provides the potential for distinguishing between cements of different production sites. Most of the investigated OPCs have measurable differences in their 87Sr/87Sr and 87Nd/87Nd isotope ratios, which can be employed as a valuable analytical fingerprinting tool. In the case of equivocal results, Divisive Hierarchical Clustering was employed to help overcome this issue. The construction of geochemical profiles allowed computing suitably defined distances between cements and clustering them according to their chemical similarity. By applying this methodology, successful fingerprinting was achieved in 27 out of 29 analysed ordinary Portland cements.
{"title":"Fingerprinting Portland cements by means of 87Sr/86Sr and 143Nd/144Nd isotope ratios and geochemical profiles","authors":"A. Kazlagić, Stephan Dietmar, M. Ostermann, A. Possolo, J. Vogl","doi":"10.1680/jadcr.23.00018","DOIUrl":"https://doi.org/10.1680/jadcr.23.00018","url":null,"abstract":"This study uses conventional 87Sr/87Sr and 87Nd/87Nd isotope and interelement ratios of Ca, Sr, K, Mn, Mg, and Ti as fingerprints for ordinary Portland cements (OPC) provenancing. Herein, the first database of Sr and Nd isotope ratios investigated in OPCs stemming from twenty-nine cement plants located worldwide was created. The results show that the Sr isotope ratios of OPCs are higher than those of seawater from the observed geological period. The spread of 87Nd/87Nd in OPCs is not as large as the spread for 87Sr/87Sr isotope ratios. However, the combination of both Sr and Nd isotope ratios provides the potential for distinguishing between cements of different production sites. Most of the investigated OPCs have measurable differences in their 87Sr/87Sr and 87Nd/87Nd isotope ratios, which can be employed as a valuable analytical fingerprinting tool. In the case of equivocal results, Divisive Hierarchical Clustering was employed to help overcome this issue. The construction of geochemical profiles allowed computing suitably defined distances between cements and clustering them according to their chemical similarity. By applying this methodology, successful fingerprinting was achieved in 27 out of 29 analysed ordinary Portland cements.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43492288","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 view of the difficulty of identifying internal micro corrosion-induced cracks in concrete and the poor accuracy of quantitative analysis that results in inaccurate results of the formation law of internal cracks, RMOCC was subjected to a galvanostatic acceleration test, and X-CT technology was combined with the Support Vector Machines (SVM) identification algorithm and Grey-Level Co-Occurrence Matrix (GLCM) theory. Using the SVM algorithm and GLCM theory, the internal average crack width of concrete and the contrast, correlation, angular second moment (ASM), and inverse difference moment (IDM), which characterize the change in slice texture information, were used as degradation parameters, respectively. Using the average internal crack width and IDM as the degradation index, a reliability degradation competition failure analysis was conducted to study RMOCC's internal crack formation law. The results showed that the SVM algorithm had a greater than 95% accuracy in recognizing cracks. In the entire corrosion-induced crack formation process, IDM and the average internal crack width values were consistent with the normal distribution. Through reliability degradation competition failure analysis between IDM and the average crack width value, the average crack width calculated with SVM is more suitable for the degradation analysis of internal corrosion-induced cracks in RMOCC.
{"title":"Analysis of the evolution of internal corrosion cracks in RMOCC compared with GLCM and SVM","authors":"Penghui Wang, Hongxia Qiao, Qiong Feng, C. Xue","doi":"10.1680/jadcr.22.00070","DOIUrl":"https://doi.org/10.1680/jadcr.22.00070","url":null,"abstract":"In view of the difficulty of identifying internal micro corrosion-induced cracks in concrete and the poor accuracy of quantitative analysis that results in inaccurate results of the formation law of internal cracks, RMOCC was subjected to a galvanostatic acceleration test, and X-CT technology was combined with the Support Vector Machines (SVM) identification algorithm and Grey-Level Co-Occurrence Matrix (GLCM) theory. Using the SVM algorithm and GLCM theory, the internal average crack width of concrete and the contrast, correlation, angular second moment (ASM), and inverse difference moment (IDM), which characterize the change in slice texture information, were used as degradation parameters, respectively. Using the average internal crack width and IDM as the degradation index, a reliability degradation competition failure analysis was conducted to study RMOCC's internal crack formation law. The results showed that the SVM algorithm had a greater than 95% accuracy in recognizing cracks. In the entire corrosion-induced crack formation process, IDM and the average internal crack width values were consistent with the normal distribution. Through reliability degradation competition failure analysis between IDM and the average crack width value, the average crack width calculated with SVM is more suitable for the degradation analysis of internal corrosion-induced cracks in RMOCC.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44421962","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}
Viengsai Phavongkham, S. Wattanasiriwech, D. Wattanasiriwech
Geopolymer prepared with class C-fly ash (FA) often suffers from the flash geopolymerisation rate, making it difficult for working. Class F-FA, however, may have a low reactivity so admixture must be added to solve this problem. This research highlighted the use of mixed class C - and class F-FA as a precursor for geopolymer preparation to alleviate the above problems. Optimization of the precursor recipe and the solid to liquid ratio (S/L) was assessed. The highest compressive strength (30.54 MPa) and the suitable initial (136 min) and final (240 min) setting times were obtained with S/L = 2.00, and 50:50 of class C to class F-FA. The fire resistance test on a 10 mm-thick geopolymer panel at 1000°C for 180 min showed a maximum temperature of ∼570-580 °C on the reversed side without catastrophic failure, suggesting the ability to use in a fire retardation application.
{"title":"Enhancement of geopolymerization reactivity and thermal resistance using mixed types of fly ash","authors":"Viengsai Phavongkham, S. Wattanasiriwech, D. Wattanasiriwech","doi":"10.1680/jadcr.22.00079","DOIUrl":"https://doi.org/10.1680/jadcr.22.00079","url":null,"abstract":"Geopolymer prepared with class C-fly ash (FA) often suffers from the flash geopolymerisation rate, making it difficult for working. Class F-FA, however, may have a low reactivity so admixture must be added to solve this problem. This research highlighted the use of mixed class C - and class F-FA as a precursor for geopolymer preparation to alleviate the above problems. Optimization of the precursor recipe and the solid to liquid ratio (S/L) was assessed. The highest compressive strength (30.54 MPa) and the suitable initial (136 min) and final (240 min) setting times were obtained with S/L = 2.00, and 50:50 of class C to class F-FA. The fire resistance test on a 10 mm-thick geopolymer panel at 1000°C for 180 min showed a maximum temperature of ∼570-580 °C on the reversed side without catastrophic failure, suggesting the ability to use in a fire retardation application.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49400589","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}
Various cooling methods of concrete mixtures are used in mass concrete structures to reduce concrete's thermal cracking and enhance the structures’ integrity. In concrete production, mixing cement with water is associated with hydration heat generation, which may cause concrete mixes to dry out and crack. The experimental work aims to evaluate the effects of using liquid nitrogen (LN) in cooling mortar mixes and concrete. LN was used in doses of 0, 25, 50, 75, and 100% by water volume to either cool the mixing water at T = 4 °C or to inject it into concrete mixtures directly. The proportions of concrete mixtures were based on ACI PRC-207.1-21 for mass concrete. Measurements of the mortars’ initial and final setting times and temperatures indicated that more LN% delayed the hardening process, so the peak hardening rates occurred later, exhibiting a slowdown of the cement hydration. LN cooling enhances the mortar and concrete cubes’ compressive strength when VLN/Vwater≤1. However, concrete compressive strength decreased due to the appearance of ice lenses that turn into voids when VLN/Vwater>1. Cooling concrete with chilled water (at T = 4°C) showed a 30% increase in the mortar cubes’ compressive strength and a maximum of 16.45% when injecting LN into the mixes. The concrete compressive strength increased by 34.51% and 12.97% when mixed with cooled water and injected LN into the mixtures, respectively. The slower cooling process promoted better cement hydration in the chilled water method compared to the injection of LN into the concrete mixture.
{"title":"Cryogenic cooling using liquid nitrogen in production of massive concrete: temperature profile, setting time and compressive strength","authors":"M. I. Alamayreh, Rana A. M. Alhorani, S. Bazlamit","doi":"10.1680/jadcr.23.00003","DOIUrl":"https://doi.org/10.1680/jadcr.23.00003","url":null,"abstract":"Various cooling methods of concrete mixtures are used in mass concrete structures to reduce concrete's thermal cracking and enhance the structures’ integrity. In concrete production, mixing cement with water is associated with hydration heat generation, which may cause concrete mixes to dry out and crack. The experimental work aims to evaluate the effects of using liquid nitrogen (LN) in cooling mortar mixes and concrete. LN was used in doses of 0, 25, 50, 75, and 100% by water volume to either cool the mixing water at T = 4 °C or to inject it into concrete mixtures directly. The proportions of concrete mixtures were based on ACI PRC-207.1-21 for mass concrete. Measurements of the mortars’ initial and final setting times and temperatures indicated that more LN% delayed the hardening process, so the peak hardening rates occurred later, exhibiting a slowdown of the cement hydration. LN cooling enhances the mortar and concrete cubes’ compressive strength when VLN/Vwater≤1. However, concrete compressive strength decreased due to the appearance of ice lenses that turn into voids when VLN/Vwater>1. Cooling concrete with chilled water (at T = 4°C) showed a 30% increase in the mortar cubes’ compressive strength and a maximum of 16.45% when injecting LN into the mixes. The concrete compressive strength increased by 34.51% and 12.97% when mixed with cooled water and injected LN into the mixtures, respectively. The slower cooling process promoted better cement hydration in the chilled water method compared to the injection of LN into the concrete mixture.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45488211","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}
Li Hu, Fan Yang, Yijia Huang, Kaixuan Yang, Binbin Li
Phosphate ester polymers were prepared from phosphate ester monomers for the first time, and their effects on cement grinding and water-reducing as grinding aids were studied. FT-IR, standard viscosity, setting time, mortar fluidity, mortar compressive strength, etc., tested phosphorus series products’ properties. The results show that: (1) Dibutyl hydroxyethyl phosphate can reduce the residue of 45 μm and 80 μm grinding sieves by 68.67% and 98.67%, respectively. (2) By comparing with triethanolamine (TEA). It is found that the grinding effect of hydroxyethyl dibutyl phosphate is not only better, but also the optimal mixing amount is smaller, only 0.167%. Under the same grinding amount, the grinding time can be shortened by 30%, and under the same grinding time, the grinding output can be increased by at least 20%. (3) Polymer grinding aids can significantly improve the fluidity of cement paste by 40.06%, which can make the water-reduction rate of cement mortar reach more than 20%. The experimental results show that as a new generation of grinding aids system, phosphate ester grinding aids not only have a significant grinding effect but also have high molecular designability, which will significantly enrich the grinding aids market and effectively promote energy conservation and emission reduction in the grinding field.
{"title":"Improvement of phosphate ester grinding aids on cement grinding and water-reducing performance","authors":"Li Hu, Fan Yang, Yijia Huang, Kaixuan Yang, Binbin Li","doi":"10.1680/jadcr.23.00017","DOIUrl":"https://doi.org/10.1680/jadcr.23.00017","url":null,"abstract":"Phosphate ester polymers were prepared from phosphate ester monomers for the first time, and their effects on cement grinding and water-reducing as grinding aids were studied. FT-IR, standard viscosity, setting time, mortar fluidity, mortar compressive strength, etc., tested phosphorus series products’ properties. The results show that: (1) Dibutyl hydroxyethyl phosphate can reduce the residue of 45 μm and 80 μm grinding sieves by 68.67% and 98.67%, respectively. (2) By comparing with triethanolamine (TEA). It is found that the grinding effect of hydroxyethyl dibutyl phosphate is not only better, but also the optimal mixing amount is smaller, only 0.167%. Under the same grinding amount, the grinding time can be shortened by 30%, and under the same grinding time, the grinding output can be increased by at least 20%. (3) Polymer grinding aids can significantly improve the fluidity of cement paste by 40.06%, which can make the water-reduction rate of cement mortar reach more than 20%. The experimental results show that as a new generation of grinding aids system, phosphate ester grinding aids not only have a significant grinding effect but also have high molecular designability, which will significantly enrich the grinding aids market and effectively promote energy conservation and emission reduction in the grinding field.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-05-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46085484","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}
Xun Xu, Bei Zhu, Tiancheng Lin, Yingjiang Li, Yongtao Sun, B. Yu, Hai-long Hu, Zong-Hai Hu, Qian Dong
As magnesium oxysulphate cement featured feeble strength and water-resistance, the additive was essential for preparing basic magnesium sulfate cement (BMSC). In this paper, the effects and the mechanism of three organic weak acids on the water-resistance for the flexural strength of BMSC were investigated. The results showed that malic acid failed to ameliorate the water-resistance for the flexural strength, but citric acid and tartaric acid succeeded. The ionization constant and molecular formulas of different weak organic acids would affect the performance, such as the fluidity, strength as well as water-resistance. Therefore, the effect of citric acid was better than tartaric acid, and the optimal dosage of citric acid was 1.0%.
{"title":"Investigation on water-resistance of basic magnesium sulfate cement containing weak organic acids","authors":"Xun Xu, Bei Zhu, Tiancheng Lin, Yingjiang Li, Yongtao Sun, B. Yu, Hai-long Hu, Zong-Hai Hu, Qian Dong","doi":"10.1680/jadcr.22.00192","DOIUrl":"https://doi.org/10.1680/jadcr.22.00192","url":null,"abstract":"As magnesium oxysulphate cement featured feeble strength and water-resistance, the additive was essential for preparing basic magnesium sulfate cement (BMSC). In this paper, the effects and the mechanism of three organic weak acids on the water-resistance for the flexural strength of BMSC were investigated. The results showed that malic acid failed to ameliorate the water-resistance for the flexural strength, but citric acid and tartaric acid succeeded. The ionization constant and molecular formulas of different weak organic acids would affect the performance, such as the fluidity, strength as well as water-resistance. Therefore, the effect of citric acid was better than tartaric acid, and the optimal dosage of citric acid was 1.0%.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42679745","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}
Rentai Liu, Xiuhao Li, Shucai Li, Chunyu Zhang, Mengjun Chen, Canxun Du, Sanlin Du
Cement-sodium silicate (C-S) grout is widely used to control water inrush disasters, and its apparent viscosity considerably impacts its water-plugging effect. However, the traditional grouting materials and methods are inappropriate for high-temperature environments, as high temperatures can affect the grout viscosity. Viscosity-modifying admixtures (VMAs) are used to thicken the grout and increase its apparent viscosity. In this study, two types of bentonite (calcium bentonite, Ca-B, and sodium bentonite, Na-B) and hydroxyethyl methyl cellulose (HEMC) were used to modify the C-S grout, and laboratory tests to evaluate fluidity, gelation time, and rheology were performed. The results showed that both bentonite and HEMC decreased fluidity and prolonged gelation time. HEMC, Ca-B, and Na-B decreased fluidity by 46.8–60.4%, 12.5–31.5%, and 17.7–39.1%, respectively, at different temperatures. HEMC, Ca-B, and Na-B increased gelation time by 23.8–50.1%, 23.3–71.4%, and 20%–57.1%, respectively. Additionally, bentonite can partially resist high temperatures and improve the apparent viscosity of grout owing to its water-absorption capacity. Conversely, HEMC has a negative effect on apparent viscosity, which is attributed to the formation of a complex microstructure resulting from intermolecular crosslinking between the cement particles and HEMC, preventing the connection of sodium silicate.
{"title":"Rheology of cement-sodium silicate grout containing bentonite and cellulose ether at high temperatures","authors":"Rentai Liu, Xiuhao Li, Shucai Li, Chunyu Zhang, Mengjun Chen, Canxun Du, Sanlin Du","doi":"10.1680/jadcr.22.00200","DOIUrl":"https://doi.org/10.1680/jadcr.22.00200","url":null,"abstract":"Cement-sodium silicate (C-S) grout is widely used to control water inrush disasters, and its apparent viscosity considerably impacts its water-plugging effect. However, the traditional grouting materials and methods are inappropriate for high-temperature environments, as high temperatures can affect the grout viscosity. Viscosity-modifying admixtures (VMAs) are used to thicken the grout and increase its apparent viscosity. In this study, two types of bentonite (calcium bentonite, Ca-B, and sodium bentonite, Na-B) and hydroxyethyl methyl cellulose (HEMC) were used to modify the C-S grout, and laboratory tests to evaluate fluidity, gelation time, and rheology were performed. The results showed that both bentonite and HEMC decreased fluidity and prolonged gelation time. HEMC, Ca-B, and Na-B decreased fluidity by 46.8–60.4%, 12.5–31.5%, and 17.7–39.1%, respectively, at different temperatures. HEMC, Ca-B, and Na-B increased gelation time by 23.8–50.1%, 23.3–71.4%, and 20%–57.1%, respectively. Additionally, bentonite can partially resist high temperatures and improve the apparent viscosity of grout owing to its water-absorption capacity. Conversely, HEMC has a negative effect on apparent viscosity, which is attributed to the formation of a complex microstructure resulting from intermolecular crosslinking between the cement particles and HEMC, preventing the connection of sodium silicate.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43507075","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 paper studies the pozzolanic performance of Crushed Brick Powder (CBP) obtained by grounding under- burnt waste bricks from a continuous brick kiln. Two different size fractions of CBP considered for cement replacement are CBP1 passing through 150 μm but retained on 75 μm and CBP 2 passing through 75μm. The compressive strength tests on mortar with CBP reveal that strength does not exceed the control; however, 10 - 15% cement replacement by CBP is optimum. A study of the presence of hydrate phases by XRD and quantification of portlandite in the paste samples by TGA up to 90 days confirms the action of pozzolanicity. Further, To determine the feasibility of CBP1 and CBP2 fractions in concrete, M25 grade concrete's strength and carbonation were studied by replacing 45% cement with a combined proportion of CBP1 (20%) and CBP2 (25%). This replacement reduced the concrete grade from M25 to M20 and increased the accelerated carbonation depth. Despite this, the projected natural carbonation coefficient with accelerated carbonation data is determined as low. The utilised CBP is cost-effective as it requires less mechanical processing and is without any chemical activation, and thus it can satisfactorily be used for low-cost housing construction and lower-grade structural and non-structural uses.
{"title":"Utilizing under burnt waste bricks from kilns as supplementary cementitious material","authors":"M. Mohan, Birendra Singh","doi":"10.1680/jadcr.22.00170","DOIUrl":"https://doi.org/10.1680/jadcr.22.00170","url":null,"abstract":"This paper studies the pozzolanic performance of Crushed Brick Powder (CBP) obtained by grounding under- burnt waste bricks from a continuous brick kiln. Two different size fractions of CBP considered for cement replacement are CBP1 passing through 150 μm but retained on 75 μm and CBP 2 passing through 75μm. The compressive strength tests on mortar with CBP reveal that strength does not exceed the control; however, 10 - 15% cement replacement by CBP is optimum. A study of the presence of hydrate phases by XRD and quantification of portlandite in the paste samples by TGA up to 90 days confirms the action of pozzolanicity. Further, To determine the feasibility of CBP1 and CBP2 fractions in concrete, M25 grade concrete's strength and carbonation were studied by replacing 45% cement with a combined proportion of CBP1 (20%) and CBP2 (25%). This replacement reduced the concrete grade from M25 to M20 and increased the accelerated carbonation depth. Despite this, the projected natural carbonation coefficient with accelerated carbonation data is determined as low. The utilised CBP is cost-effective as it requires less mechanical processing and is without any chemical activation, and thus it can satisfactorily be used for low-cost housing construction and lower-grade structural and non-structural uses.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49335780","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}
F. Rubio-Hernández, L. F. Naranjo-Herrera, N. Páez-Flor, J. F. Velázquez-Navarro
According with what is extensively and logically assumed, anti-thixotropic behavior better than thixotropy was expected for shear-thickening cement pastes. However, shear-thickening Portland and Volcanic cement pastes here studied showed apparent thixotropic behavior when step-up tests were performed. This unexpected result was tentatively justified assuming that just at the beginning of the step-stress virtually instantaneous particle aggregation (for step-up tests) and disaggregation (for step-down tests) take place. In other words, the existence of fast jamming or unblocking mechanisms developed by shear-thickening cement pastes was hypothesized. Then, it was supposed that the initial reorganization of cement particles was followed by a progressive erosion of the jammed state (step-up) or progressive aggregation of the unblocking state (step-down) due to the constant action of shear stress. These ideas were used to model an empirical equation for viscosity dependence on shear stress, which can be used for cement applications.
{"title":"Time-dependent viscous behavior of shear-thinning/shear-thickening cement pastes","authors":"F. Rubio-Hernández, L. F. Naranjo-Herrera, N. Páez-Flor, J. F. Velázquez-Navarro","doi":"10.1680/jadcr.22.00167","DOIUrl":"https://doi.org/10.1680/jadcr.22.00167","url":null,"abstract":"According with what is extensively and logically assumed, anti-thixotropic behavior better than thixotropy was expected for shear-thickening cement pastes. However, shear-thickening Portland and Volcanic cement pastes here studied showed apparent thixotropic behavior when step-up tests were performed. This unexpected result was tentatively justified assuming that just at the beginning of the step-stress virtually instantaneous particle aggregation (for step-up tests) and disaggregation (for step-down tests) take place. In other words, the existence of fast jamming or unblocking mechanisms developed by shear-thickening cement pastes was hypothesized. Then, it was supposed that the initial reorganization of cement particles was followed by a progressive erosion of the jammed state (step-up) or progressive aggregation of the unblocking state (step-down) due to the constant action of shear stress. These ideas were used to model an empirical equation for viscosity dependence on shear stress, which can be used for cement applications.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46399677","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 objective of this paper is to study the fresh concrete flow in the L-box test, predict the final shape deposit after the flow stoppage, and estimate the yield stress. This is very useful in controlling the concrete casting in real structures, detecting problems and preparing solutions on time. Concrete rheometers, used for concrete rheological parameters measurement, are expensive, not always available and resulting in measurements disparity. To overcome this difficulty, the effective method was to analyze the concrete flow phenomena physically and solve the problem analytically based on L-box measurements. In the first part, fresh concrete is considered as a homogeneous yield stress fluid moving under the effect of its self-weight. By developing the momentum equations for an incompressible fluid, a theoretical approach is proposed to study three probable final shapes depending on concrete rheology. Expressions are established for the final shape and yield stress prediction. In the second part, the obtained results were compared to previous models, and a good agreement was observed giving a good validity. This study can be a consolidation of the rheometers' results, allowing an evaluation and perhaps a calibration to reinforce their validity.
{"title":"Analysis of the relationship between the L-Box test and the yield stress of fresh concrete: an analytical approach","authors":"Raoudha Sassi, A. Jelidi, S. Montassar","doi":"10.1680/jadcr.23.00019","DOIUrl":"https://doi.org/10.1680/jadcr.23.00019","url":null,"abstract":"The objective of this paper is to study the fresh concrete flow in the L-box test, predict the final shape deposit after the flow stoppage, and estimate the yield stress. This is very useful in controlling the concrete casting in real structures, detecting problems and preparing solutions on time. Concrete rheometers, used for concrete rheological parameters measurement, are expensive, not always available and resulting in measurements disparity. To overcome this difficulty, the effective method was to analyze the concrete flow phenomena physically and solve the problem analytically based on L-box measurements. In the first part, fresh concrete is considered as a homogeneous yield stress fluid moving under the effect of its self-weight. By developing the momentum equations for an incompressible fluid, a theoretical approach is proposed to study three probable final shapes depending on concrete rheology. Expressions are established for the final shape and yield stress prediction. In the second part, the obtained results were compared to previous models, and a good agreement was observed giving a good validity. This study can be a consolidation of the rheometers' results, allowing an evaluation and perhaps a calibration to reinforce their validity.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49478065","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：