Gas conditioning or cooling towers have broad industrial applicability, especially in the cement industry. Most cement factories deal with the same problems as others do. However, the solutions to these problems are barely internationally published and have not received much attention, which results in spending a lot of time and money researching the previous solutions. Iran is among the top ten cement manufacturing countries in the world. Therefore, many of these problems have occurred in Iranian cement factories. The purpose of the present paper is to provide a review of studies in this field over the last decades, with a particular focus on advances in Iran. This paper concludes the most important findings of the literature to suggest the best possible solutions for improving the performance and lifetime of gas conditioning towers and for decreasing the common problems, such as dust build-up and wet bottom. Furthermore, the paper reviews the numerical methods for modelling different aspects of these towers. The results can also be used to reduce water and energy consumption, air pollution, and repair and maintenance costs of cement factories.
{"title":"Computational study of multiphase flow in cement plant gas conditioning towers: a review","authors":"Mohammad Hossein Abbaszadeh, J. Sepahi-Younsi","doi":"10.1680/jadcr.22.00128","DOIUrl":"https://doi.org/10.1680/jadcr.22.00128","url":null,"abstract":"Gas conditioning or cooling towers have broad industrial applicability, especially in the cement industry. Most cement factories deal with the same problems as others do. However, the solutions to these problems are barely internationally published and have not received much attention, which results in spending a lot of time and money researching the previous solutions. Iran is among the top ten cement manufacturing countries in the world. Therefore, many of these problems have occurred in Iranian cement factories. The purpose of the present paper is to provide a review of studies in this field over the last decades, with a particular focus on advances in Iran. This paper concludes the most important findings of the literature to suggest the best possible solutions for improving the performance and lifetime of gas conditioning towers and for decreasing the common problems, such as dust build-up and wet bottom. Furthermore, the paper reviews the numerical methods for modelling different aspects of these towers. The results can also be used to reduce water and energy consumption, air pollution, and repair and maintenance costs of cement factories.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43209892","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}
Muftah Mohamed Baroud, Arif Sari, S. S. Abdullaev, M. Samavatian, V. Samavatian
Compressive strength, a crucial mechanical property of cement mortars, is typically measured destructively. However, there is a need to evaluate the strength of unique cement-based samples over various aging periods without causing damage. This study proposes a predictive framework using a genetic algorithm to estimate the compressive strength of ordinary cement-based mortars based on their dynamic elastic modulus, measured non-destructively using the impulse excitation technique. By combining the Popovics and Lydon-Balendran models, the static elastic modulus of the samples is calculated with constant coefficients, representing an equivalent compressive strength. The genetic algorithm is employed to determine the optimal values for these coefficients. The results show that the combining model is more sensitive to the Lydon-Balendran approach within the middle range of the dynamic Young's modulus, while the Popovics-based strength dominates at higher and lower dynamic Young's modulus levels. The model exhibits a low root mean square error (RMSE) value of 3.1%. The findings suggest that this non-destructive model has potential as a candidate for predicting the mechanical properties of cement mortars in the industry. It enables efficient evaluation of compressive strength without destructive testing, offering advantages for assessing cement-based materials reliably.
{"title":"Compressive strength in cement mortars via impulse excitation technique and genetic algorithm","authors":"Muftah Mohamed Baroud, Arif Sari, S. S. Abdullaev, M. Samavatian, V. Samavatian","doi":"10.1680/jadcr.23.00031","DOIUrl":"https://doi.org/10.1680/jadcr.23.00031","url":null,"abstract":"Compressive strength, a crucial mechanical property of cement mortars, is typically measured destructively. However, there is a need to evaluate the strength of unique cement-based samples over various aging periods without causing damage. This study proposes a predictive framework using a genetic algorithm to estimate the compressive strength of ordinary cement-based mortars based on their dynamic elastic modulus, measured non-destructively using the impulse excitation technique. By combining the Popovics and Lydon-Balendran models, the static elastic modulus of the samples is calculated with constant coefficients, representing an equivalent compressive strength. The genetic algorithm is employed to determine the optimal values for these coefficients. The results show that the combining model is more sensitive to the Lydon-Balendran approach within the middle range of the dynamic Young's modulus, while the Popovics-based strength dominates at higher and lower dynamic Young's modulus levels. The model exhibits a low root mean square error (RMSE) value of 3.1%. The findings suggest that this non-destructive model has potential as a candidate for predicting the mechanical properties of cement mortars in the industry. It enables efficient evaluation of compressive strength without destructive testing, offering advantages for assessing cement-based materials reliably.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-08-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47421838","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}
Given the advantages of calcium aluminate cement (CAC) in specific marine engineering, selecting materials directly from the sea when mixing CAC can cut down the construction costs and reduce the ecological pollution to the sea. However, the investigation of using seawater as the mixing water of CAC is still trekking with difficult on account of the strength reduction. In this regard, this paper evaluated the possibility of using NaCl solution as mixing water and diatomite as SCMs to modify CAC. Silica fume (SF) and the corrosion by immersion in NaCl solution is employed as the reference. The strength, mass, and length changes of CAC mortars at both 20 °C and 40 °C were tested, and the phase assemblages and morphology were characterized by XRD, TG-DSC and SEM. Results reveal that using NaCl solution as the mixing water is beneficial to the later strength development of CAC, which promotes the formation of C2ASH8 in CAC pastes and exhibits no strength retraction even at 40 °C. The strength of the diatomite/SF modified CAC mortars mixing with NaCl solution is all higher than that immersed in NaCl solution. By contrast, the cooperation effect of diatomite and NaCl solution can significantly increase the strength of CAC, especially at 20 °C. And diatomite favors strength development of CAC mortars, while SF contributes to a better mass and length stability.
{"title":"Potential of NaCl solution as mixing water in siliceous minerals modified calcium aluminate cement","authors":"Yue Zhou, Yuting Chen, Zhongping Wang, Zheyu Zhu, Linglin Xu","doi":"10.1680/jadcr.23.00009","DOIUrl":"https://doi.org/10.1680/jadcr.23.00009","url":null,"abstract":"Given the advantages of calcium aluminate cement (CAC) in specific marine engineering, selecting materials directly from the sea when mixing CAC can cut down the construction costs and reduce the ecological pollution to the sea. However, the investigation of using seawater as the mixing water of CAC is still trekking with difficult on account of the strength reduction. In this regard, this paper evaluated the possibility of using NaCl solution as mixing water and diatomite as SCMs to modify CAC. Silica fume (SF) and the corrosion by immersion in NaCl solution is employed as the reference. The strength, mass, and length changes of CAC mortars at both 20 °C and 40 °C were tested, and the phase assemblages and morphology were characterized by XRD, TG-DSC and SEM. Results reveal that using NaCl solution as the mixing water is beneficial to the later strength development of CAC, which promotes the formation of C2ASH8 in CAC pastes and exhibits no strength retraction even at 40 °C. The strength of the diatomite/SF modified CAC mortars mixing with NaCl solution is all higher than that immersed in NaCl solution. By contrast, the cooperation effect of diatomite and NaCl solution can significantly increase the strength of CAC, especially at 20 °C. And diatomite favors strength development of CAC mortars, while SF contributes to a better mass and length stability.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41786405","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}
Grid nanoindentation and quantitative X-ray diffraction are employed to provide quantitative information on phase constituents of nanoscale pozzolan-containing ultra-high-performance concrete (UHPC). Three UHPC samples containing nanoscale pozzolan and cured with and without microwave energy are investigated. The volume fraction of each phase constituent is independently evaluated using both techniques: nanoindentation (NI) and quantitative X-ray diffraction (QXRD). For the NI, the volumes have been evaluated by taking into account the thresholds characterising the phase constituents. The NI could assess phase mixtures or composites rather than single phases. The microwave-cured samples (CMW and CPMW) contain in total more hydration products that the sample that was not cured with microwave energy (C000). In all three samples, a nanocomposite (C–S–H/CHnm) consisting of high-density (HD) calcium silicate hydrate (C–S–H) and nanoscale portlandite (CH) is included, and its amount is more than double for the pressure-compacted and microwave-cured sample (CPMW). The heat curing by microwave energy together with the very low amount of water and restriction of the available space for hydration products, favour the formation of the nanocomposite (C–S–H/CHnm) in the CPMW sample.
{"title":"Phase volumes of ultra high performance concrete containing nanoscale pozzolan","authors":"A. Korpa, N. Dhamo, A. Andoni, C. Pritzel","doi":"10.1680/jadcr.21.00069","DOIUrl":"https://doi.org/10.1680/jadcr.21.00069","url":null,"abstract":"Grid nanoindentation and quantitative X-ray diffraction are employed to provide quantitative information on phase constituents of nanoscale pozzolan-containing ultra-high-performance concrete (UHPC). Three UHPC samples containing nanoscale pozzolan and cured with and without microwave energy are investigated. The volume fraction of each phase constituent is independently evaluated using both techniques: nanoindentation (NI) and quantitative X-ray diffraction (QXRD). For the NI, the volumes have been evaluated by taking into account the thresholds characterising the phase constituents. The NI could assess phase mixtures or composites rather than single phases. The microwave-cured samples (CMW and CPMW) contain in total more hydration products that the sample that was not cured with microwave energy (C000). In all three samples, a nanocomposite (C–S–H/CHnm) consisting of high-density (HD) calcium silicate hydrate (C–S–H) and nanoscale portlandite (CH) is included, and its amount is more than double for the pressure-compacted and microwave-cured sample (CPMW). The heat curing by microwave energy together with the very low amount of water and restriction of the available space for hydration products, favour the formation of the nanocomposite (C–S–H/CHnm) in the CPMW sample.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134951516","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 effects of curing temperature (20°C, 40°C and 60°C) and the addition of limestone powder (LP) (6% and 12%) on the capillary water absorption (CWA) of high-volume fly ash (HVFA) cement mortar were investigated. X-ray diffraction analysis and tests for chemically bound water content (CBWC), compressive strength and porosity were also conducted. It was found that, for a fly ash (FA) content exceeding 30%, the CWA increased significantly. When the FA content was 50%, the curing temperature was raised to 40°C or the LP content was 12%, the CBWC increased greatly. Increasing the curing temperature or adding LP increased the compressive strength and decreased the porosity of the HVFA cement mortar. Prediction of the water penetration depth in the HVFA cement mortar was consistent with the CWA results. The results of this work indicate that an increase in curing temperature or the addition of LP could be an efficient way of improving the CWA performance of HVFA cement mortar.
{"title":"Improving capillary water absorption of high-volume fly ash mortar by curing temperature and limestone addition","authors":"Yunfei Di, Haitao Zhao, Xiaoxiong Li, Yun Chen, Zhenqing Shi, Xiaolei Man","doi":"10.1680/jadcr.23.00025","DOIUrl":"https://doi.org/10.1680/jadcr.23.00025","url":null,"abstract":"The effects of curing temperature (20°C, 40°C and 60°C) and the addition of limestone powder (LP) (6% and 12%) on the capillary water absorption (CWA) of high-volume fly ash (HVFA) cement mortar were investigated. X-ray diffraction analysis and tests for chemically bound water content (CBWC), compressive strength and porosity were also conducted. It was found that, for a fly ash (FA) content exceeding 30%, the CWA increased significantly. When the FA content was 50%, the curing temperature was raised to 40°C or the LP content was 12%, the CBWC increased greatly. Increasing the curing temperature or adding LP increased the compressive strength and decreased the porosity of the HVFA cement mortar. Prediction of the water penetration depth in the HVFA cement mortar was consistent with the CWA results. The results of this work indicate that an increase in curing temperature or the addition of LP could be an efficient way of improving the CWA performance of HVFA cement mortar.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":"44 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135656933","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}
Yi Huang, Xiangdong Qing, Li Lin, Bicai Li, Lin Xu, Ying-lin Peng
Fly ash-based geopolymer paste with expanded vermiculite (EV) powder addition was synthesized and its microstructure, compressive strength, setting time, moisture control, efflorescence extent and thermal conductivity were studied. The results showed that EV addition resulted in the increase of standard consistency water consumption and setting time. As a consequence, its excessive addition caused a larger amount of harmful pores, which was detrimental for compressive strength of geopolymer paste. However, geopolymer pastes with an appropriate amount of EV addition (2-7 wt%) presented a slight increase of compressive strength because of the filler effect. Mg2+ and Fe2+diffused from EV interlayer through ions exchange between EV and geoploymer solution participated in geopolymerization. This was reflected by the formation of N-(M)-A-(F)-S-H evidenced through SEM-EDS and FITR analyis. In addition, Na2+/Mg2+or Na2+/Fe2+ ions exchange reduced the mobility of Na2+and therefore decreased the efflorescence extent. Moreover, EV addition favored the improvement of moisture control and thermal conductivity properties of geopolymer paste.
{"title":"Microstructure and physical properties of fly ash-based geopolymer with expanded vermiculite addition","authors":"Yi Huang, Xiangdong Qing, Li Lin, Bicai Li, Lin Xu, Ying-lin Peng","doi":"10.1680/jadcr.23.00006","DOIUrl":"https://doi.org/10.1680/jadcr.23.00006","url":null,"abstract":"Fly ash-based geopolymer paste with expanded vermiculite (EV) powder addition was synthesized and its microstructure, compressive strength, setting time, moisture control, efflorescence extent and thermal conductivity were studied. The results showed that EV addition resulted in the increase of standard consistency water consumption and setting time. As a consequence, its excessive addition caused a larger amount of harmful pores, which was detrimental for compressive strength of geopolymer paste. However, geopolymer pastes with an appropriate amount of EV addition (2-7 wt%) presented a slight increase of compressive strength because of the filler effect. Mg2+ and Fe2+diffused from EV interlayer through ions exchange between EV and geoploymer solution participated in geopolymerization. This was reflected by the formation of N-(M)-A-(F)-S-H evidenced through SEM-EDS and FITR analyis. In addition, Na2+/Mg2+or Na2+/Fe2+ ions exchange reduced the mobility of Na2+and therefore decreased the efflorescence extent. Moreover, EV addition favored the improvement of moisture control and thermal conductivity properties of geopolymer paste.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48226627","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}
Usha Sharma, Reetam Chaudhury, Lok Pratap Singh, Chi-Sun Poon
Concrete technologists use different types of additives such as fly ash, slag, natural pozzolans and nanomaterials toenhance concrete performance and durability. However, a detailed explanation of the early-age hydration process and microstructural modification of concrete in the presence of nanomaterials remains to be presented and extensive research is required for strategic modification of cementitious systems. This study focused on the precise monitoring of early-age hydration with the incorporation of nanoalumina (nAl) in tricalcium silicate (C3S) and Portland cement paste and mortar. The dosage of nAl was varied from 1 to 5% (by weight) in C3S and from 0.1 to 1.0% in Portland cement, with a water/cement ratio of 0.4. The hydration studies showed that the nAl increased the cross-linkage in calcium silicate hydrate gel through substitution of aluminium by silicon, which was responsible for the enhancement of the modulus of elasticity (by 40%) with 1.0% nAl) after 7 days of hydration. In summary, the incorporation of nAl modified the concrete microstructure in the initial days of hydration, leading to higher concrete performance and longer service lives of concrete structures.
{"title":"Early hydration studies of cementitious materials incorporating nanoalumina","authors":"Usha Sharma, Reetam Chaudhury, Lok Pratap Singh, Chi-Sun Poon","doi":"10.1680/jadcr.22.00190","DOIUrl":"https://doi.org/10.1680/jadcr.22.00190","url":null,"abstract":"Concrete technologists use different types of additives such as fly ash, slag, natural pozzolans and nanomaterials toenhance concrete performance and durability. However, a detailed explanation of the early-age hydration process and microstructural modification of concrete in the presence of nanomaterials remains to be presented and extensive research is required for strategic modification of cementitious systems. This study focused on the precise monitoring of early-age hydration with the incorporation of nanoalumina (nAl) in tricalcium silicate (C<sub>3</sub>S) and Portland cement paste and mortar. The dosage of nAl was varied from 1 to 5% (by weight) in C<sub>3</sub>S and from 0.1 to 1.0% in Portland cement, with a water/cement ratio of 0.4. The hydration studies showed that the nAl increased the cross-linkage in calcium silicate hydrate gel through substitution of aluminium by silicon, which was responsible for the enhancement of the modulus of elasticity (by 40%) with 1.0% nAl) after 7 days of hydration. In summary, the incorporation of nAl modified the concrete microstructure in the initial days of hydration, leading to higher concrete performance and longer service lives of concrete structures.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":"119 1-3","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138509761","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 use of high-temperature X-ray diffraction (HT-XRD) to study the mass transfer of raw meal constituents towards forming clinker phases and the occurrence of free lime (calcium oxide), also known as burnability, was assessed. A measuring strategy with temperature ranging from 1000°C to 1450°C was developed and compared with a conventional burnability method. The free lime determined by the methods showed that HT-XRD produced good results for the evaluation of burnability. In addition, HT-XRD revealed the formation of intermediate phases, providing insight into early reactions in a cement kiln. The particle size of quartz was found to affect crystal expansion of the phase at a high temperature, subsequently affecting the formation of silica polymorphs. The different raw meals used in this study also indicate that the formation of different silica polymorphs affects the formation of C2S. The lack of knowledge regarding the influence of β-quartz on the reduction of free lime is highlighted.
{"title":"Phase evolution and burnability of cement raw meal","authors":"José Aguirre Castillo, M. Broström, M. Eriksson","doi":"10.1680/jadcr.23.00034","DOIUrl":"https://doi.org/10.1680/jadcr.23.00034","url":null,"abstract":"The use of high-temperature X-ray diffraction (HT-XRD) to study the mass transfer of raw meal constituents towards forming clinker phases and the occurrence of free lime (calcium oxide), also known as burnability, was assessed. A measuring strategy with temperature ranging from 1000°C to 1450°C was developed and compared with a conventional burnability method. The free lime determined by the methods showed that HT-XRD produced good results for the evaluation of burnability. In addition, HT-XRD revealed the formation of intermediate phases, providing insight into early reactions in a cement kiln. The particle size of quartz was found to affect crystal expansion of the phase at a high temperature, subsequently affecting the formation of silica polymorphs. The different raw meals used in this study also indicate that the formation of different silica polymorphs affects the formation of C2S. The lack of knowledge regarding the influence of β-quartz on the reduction of free lime is highlighted.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47260428","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}
Bingcong Chen, Junping Zhang, Airong Liu, Liwen Zhang, Zhujian Xie, Xiaowei Ouyang, Z. Ma
Using oyster shell powder (OSP) to prepare magnesium phosphate cement (MPC) not only reduces the pollution caused by the wasted oyster shell disposal, but also benefits the development of more environmentally friendly cement. The effect of OSP on the hydration and strength development of MPC was studied. An axial compression experiment including 45 cuboid specimens was executed to investigate the compressive strength, failure mode, stress–strain relationship, and energy absorption of MPC mixing with different mass contents (0% to 12%) of OSP over the curing times of 7, 14, and 28 days. Scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy were utilized for measuring the variation of MPC microstructure and hydration products caused by OSP. Results indicated that a new reactant CaHPO4·2H2O was formed, which optimized matrix strength. The substitution of OSP could reduce the cost of MPC by 2–9% without decreasing the strength. Compared with MPC without OSP, the compressive strength of the specimen with 3% OSP is increased by 6%. However, with the continuous increase of OSP, the compressive strength gradually decreases. Similarly, the elastic modulus of MPC increases first and then decreases with the increase of OSP.
{"title":"Effect of recycled oyster shell powder on hydration and strength development of magnesium phosphate cement","authors":"Bingcong Chen, Junping Zhang, Airong Liu, Liwen Zhang, Zhujian Xie, Xiaowei Ouyang, Z. Ma","doi":"10.1680/jadcr.22.00103","DOIUrl":"https://doi.org/10.1680/jadcr.22.00103","url":null,"abstract":"Using oyster shell powder (OSP) to prepare magnesium phosphate cement (MPC) not only reduces the pollution caused by the wasted oyster shell disposal, but also benefits the development of more environmentally friendly cement. The effect of OSP on the hydration and strength development of MPC was studied. An axial compression experiment including 45 cuboid specimens was executed to investigate the compressive strength, failure mode, stress–strain relationship, and energy absorption of MPC mixing with different mass contents (0% to 12%) of OSP over the curing times of 7, 14, and 28 days. Scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy were utilized for measuring the variation of MPC microstructure and hydration products caused by OSP. Results indicated that a new reactant CaHPO4·2H2O was formed, which optimized matrix strength. The substitution of OSP could reduce the cost of MPC by 2–9% without decreasing the strength. Compared with MPC without OSP, the compressive strength of the specimen with 3% OSP is increased by 6%. However, with the continuous increase of OSP, the compressive strength gradually decreases. Similarly, the elastic modulus of MPC increases first and then decreases with the increase of OSP.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46802881","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}
Y. Tu, Tongfang Wang, Rongjiang Wen, Jie Cao, M. Fang, Chao Wang, G. Sas, L. Elfgren
The construction of nuclear power plants necessitates careful consideration of the discharge and fixation of nuclear waste. Geopolymers are new cement-based materials (CBMs) with three-dimensional cage-like structures that enable effective nuclear waste fixation. In this work, the adsorption of radioactive caesium and strontium ions by sodium aluminosilicate hydrate (NASH) gel, the main component of geopolymers, was investigated using molecular dynamics simulations to obtain nanoscale insights into the ions’ interactions with the gel. The formation of strong ion–oxygen bonds allowed both ions to be effectively adsorbed on the NASH surface, but the adsorption ratio of strontium ions (17.2%) was slightly lower than that of caesium ions (21.0%). Because strontium ions are divalent, they can form stronger electrostatic interactions with water molecules and chloride ions, which hinders their approach to the interface. For the same reason, the diffusion coefficient of strontium ions in solution is lower than that of caesium ions. These results provide new insights into the nuclear waste fixation capacity of NASH gel and guidance for the design of new CBMs for radioactive waste disposal.
{"title":"Molecular dynamics study on the adsorption of radioactive ions by geopolymers","authors":"Y. Tu, Tongfang Wang, Rongjiang Wen, Jie Cao, M. Fang, Chao Wang, G. Sas, L. Elfgren","doi":"10.1680/jadcr.22.00085","DOIUrl":"https://doi.org/10.1680/jadcr.22.00085","url":null,"abstract":"The construction of nuclear power plants necessitates careful consideration of the discharge and fixation of nuclear waste. Geopolymers are new cement-based materials (CBMs) with three-dimensional cage-like structures that enable effective nuclear waste fixation. In this work, the adsorption of radioactive caesium and strontium ions by sodium aluminosilicate hydrate (NASH) gel, the main component of geopolymers, was investigated using molecular dynamics simulations to obtain nanoscale insights into the ions’ interactions with the gel. The formation of strong ion–oxygen bonds allowed both ions to be effectively adsorbed on the NASH surface, but the adsorption ratio of strontium ions (17.2%) was slightly lower than that of caesium ions (21.0%). Because strontium ions are divalent, they can form stronger electrostatic interactions with water molecules and chloride ions, which hinders their approach to the interface. For the same reason, the diffusion coefficient of strontium ions in solution is lower than that of caesium ions. These results provide new insights into the nuclear waste fixation capacity of NASH gel and guidance for the design of new CBMs for radioactive waste disposal.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2023-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49478510","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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