Yang Wang, Yong Ge, Haibo Fang, Yupo Pan, Xin Chen, Qinfei Li
Scanning transmission X-ray microscope (STXM) and Ca L2,3-edge near-edge X-ray Absorption structure (NEXAFS) spectra investigate simultaneously the morphological and chemical information of various cement-based materials. The interaction between calcium chloride and monosulfoaluminate and the validation of intermediate phases were investigated. As the concentration of CaCl2 solution increases, calcium monosulfoaluminate (Ms) is converted into ettringite, Kuzel's salt (Ks) and Friedel's salt (Fs) in varying degree, while SO42- units in the ettringite and Kuzel's salt are continuously replaced by Cl2- in the solution, eventually forming Fs and gypsum. Based on Ca L2,3-edge NEXAFS absorption spectra, ettringite, Ms, Ks and Ms were greatly distinguished by the number and the shape of the leading peaks in the spectra since the difference in SO42- content among the interlayer structure of Ms, Ks and Fs. The present work is based on the references for the STXM study of the calcium (sulfo)aluminates, for demonstrating a more complete understanding of the phase evolution under chloride environments.
{"title":"The Interaction between Monosulfoaluminate and Calcium Chloride Aqueous Solution","authors":"Yang Wang, Yong Ge, Haibo Fang, Yupo Pan, Xin Chen, Qinfei Li","doi":"10.1680/jadcr.21.00232","DOIUrl":"https://doi.org/10.1680/jadcr.21.00232","url":null,"abstract":"Scanning transmission X-ray microscope (STXM) and Ca L2,3-edge near-edge X-ray Absorption structure (NEXAFS) spectra investigate simultaneously the morphological and chemical information of various cement-based materials. The interaction between calcium chloride and monosulfoaluminate and the validation of intermediate phases were investigated. As the concentration of CaCl2 solution increases, calcium monosulfoaluminate (Ms) is converted into ettringite, Kuzel's salt (Ks) and Friedel's salt (Fs) in varying degree, while SO42- units in the ettringite and Kuzel's salt are continuously replaced by Cl2- in the solution, eventually forming Fs and gypsum. Based on Ca L2,3-edge NEXAFS absorption spectra, ettringite, Ms, Ks and Ms were greatly distinguished by the number and the shape of the leading peaks in the spectra since the difference in SO42- content among the interlayer structure of Ms, Ks and Fs. The present work is based on the references for the STXM study of the calcium (sulfo)aluminates, for demonstrating a more complete understanding of the phase evolution under chloride environments.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2022-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41697941","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}
Mukhtar Hamid Abed, Israa Sabbar Abbas, H. Çanakçi
One-part geopolymer (OPG) grout offers advantages over two-part geopolymer grout concerning the handling and storage of feedstocks. This is mainly due to the large quantities of caustic solutions that should be handled for producing two-part geopolymer. However, OPG often suffers from a low degree of reaction, a high number of crystalline byproducts, and as a result, low strength. In this research, one-part geopolymer has been assisted by a mechanochemical activation (MC-OPG) to produce grout. In this method, the precursor material (slag and fly ash) and sodium silicate were mechanochemically activated utilizing co-grinding to produce a geopolymeric precursor, after which water is the only additive required to initiate the geopolymerization reaction. The effects of slag/fly ash ratios on grout mixtures were also investigated. A series of tests were examined, such as rheological characteristics, setting time, bleeding, unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The experimental results showed that the mechanochemical activation technique increased the rheological characteristics and reduced the fresh properties (setting time and bleeding) of geopolymer grout compared to the one-part geopolymer. Considering mechanical properties, the UCS of MC-OPG grout was higher (41%-73%) than that of OPG grout. Furthermore, slag content significantly affected the rheological, fresh, and mechanical properties of all the geopolymer grouts regardless of the activation method.
{"title":"Influence of mechanochemical activation on the rheological, fresh, and mechanical properties of one-part geopolymer grout","authors":"Mukhtar Hamid Abed, Israa Sabbar Abbas, H. Çanakçi","doi":"10.1680/jadcr.21.00205","DOIUrl":"https://doi.org/10.1680/jadcr.21.00205","url":null,"abstract":"One-part geopolymer (OPG) grout offers advantages over two-part geopolymer grout concerning the handling and storage of feedstocks. This is mainly due to the large quantities of caustic solutions that should be handled for producing two-part geopolymer. However, OPG often suffers from a low degree of reaction, a high number of crystalline byproducts, and as a result, low strength. In this research, one-part geopolymer has been assisted by a mechanochemical activation (MC-OPG) to produce grout. In this method, the precursor material (slag and fly ash) and sodium silicate were mechanochemically activated utilizing co-grinding to produce a geopolymeric precursor, after which water is the only additive required to initiate the geopolymerization reaction. The effects of slag/fly ash ratios on grout mixtures were also investigated. A series of tests were examined, such as rheological characteristics, setting time, bleeding, unconfined compressive strength (UCS), ultrasonic pulse velocity (UPV), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The experimental results showed that the mechanochemical activation technique increased the rheological characteristics and reduced the fresh properties (setting time and bleeding) of geopolymer grout compared to the one-part geopolymer. Considering mechanical properties, the UCS of MC-OPG grout was higher (41%-73%) than that of OPG grout. Furthermore, slag content significantly affected the rheological, fresh, and mechanical properties of all the geopolymer grouts regardless of the activation method.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2022-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44777190","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}
Coal gasification ash (CGA) is the solid waste produced by coal in the process of gasification. This can be used to produce autoclaved building materials because tobermorite, the main hydration product in such materials, can be formed from CGA and CaO. In this study, tobermorite was prepared through the hydrothermal treatment of CGA. Given that residual carbon is usually present to some degree in CGA, its effects on the formation of tobermorite were specifically studied using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and N2 adsorption–desorption tests. The results show that tobermorite can be prepared from a CGA/CaO mixture at 160°C without additional alkaline material. However, residual carbon can retard the transformation of calcium silicate hydrate into tobermorite and thus increase the required formation temperature while prolonging the formation time. With increasing residual carbon content, the morphology of the resulting tobermorite changes from needle-like and plate-like to irregular, which may also have a detrimental effect on the mechanical properties of the material.
{"title":"Effects of residual carbon on synthesis of 11 Å tobermorite from coal gasification ash","authors":"Feng Luo, Cundi Wei, Yin-shan Jiang","doi":"10.1680/jadcr.21.00092","DOIUrl":"https://doi.org/10.1680/jadcr.21.00092","url":null,"abstract":"Coal gasification ash (CGA) is the solid waste produced by coal in the process of gasification. This can be used to produce autoclaved building materials because tobermorite, the main hydration product in such materials, can be formed from CGA and CaO. In this study, tobermorite was prepared through the hydrothermal treatment of CGA. Given that residual carbon is usually present to some degree in CGA, its effects on the formation of tobermorite were specifically studied using X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and N2 adsorption–desorption tests. The results show that tobermorite can be prepared from a CGA/CaO mixture at 160°C without additional alkaline material. However, residual carbon can retard the transformation of calcium silicate hydrate into tobermorite and thus increase the required formation temperature while prolonging the formation time. With increasing residual carbon content, the morphology of the resulting tobermorite changes from needle-like and plate-like to irregular, which may also have a detrimental effect on the mechanical properties of the material.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2022-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49218549","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}
Rongjiang Wen, Y. Tu, Tong Guo, Qian Yu, Pan Shi, Yuanhui Ji, Oisik Das, M. Försth, G. Sas, L. Elfgren
The mutual inhibition effect of transport of sulphate and chloride in concrete specimen was determined in a macroscopic experiment. Higher concentration of sulphate has a better inhibition effect on chloride transport and the opposite is also true. In this paper, molecular dynamics (MD) simulation was performed to explore the effect of concentration (0, 0.5, 1.0 mol/L) on the transport of mixed solutions (NaCl and Na2SO4) in the main hydration products of aluminium-doped cement-based materials (i.e., calcium-aluminium-silicate-hydrate (C-A-S-H) gel). Sulphate was found to promote the aggregation of other ions to form ion clusters, which can reduce the effective width of the channel entrance and create a “necking” effect, thus reducing the overall transport rate of the solution. With the increase of NaCl concentration, sulphate ions in the mixed solution can adsorb more Na+ and Cl+ ions, and then form larger ion clusters to block the nanopores. Moreover, with increasing Na2SO4 concentration, higher amount of sulphate ions existing in the solution makes it possible to form more ion clusters. The results can provide a reasonable nanoscale explanation for macroscopic experiment.
{"title":"Molecular dynamics study on coupled ion transport in aluminium-doped cement-based materials: Effect of concentration","authors":"Rongjiang Wen, Y. Tu, Tong Guo, Qian Yu, Pan Shi, Yuanhui Ji, Oisik Das, M. Försth, G. Sas, L. Elfgren","doi":"10.1680/jadcr.22.00028","DOIUrl":"https://doi.org/10.1680/jadcr.22.00028","url":null,"abstract":"The mutual inhibition effect of transport of sulphate and chloride in concrete specimen was determined in a macroscopic experiment. Higher concentration of sulphate has a better inhibition effect on chloride transport and the opposite is also true. In this paper, molecular dynamics (MD) simulation was performed to explore the effect of concentration (0, 0.5, 1.0 mol/L) on the transport of mixed solutions (NaCl and Na2SO4) in the main hydration products of aluminium-doped cement-based materials (i.e., calcium-aluminium-silicate-hydrate (C-A-S-H) gel). Sulphate was found to promote the aggregation of other ions to form ion clusters, which can reduce the effective width of the channel entrance and create a “necking” effect, thus reducing the overall transport rate of the solution. With the increase of NaCl concentration, sulphate ions in the mixed solution can adsorb more Na+ and Cl+ ions, and then form larger ion clusters to block the nanopores. Moreover, with increasing Na2SO4 concentration, higher amount of sulphate ions existing in the solution makes it possible to form more ion clusters. The results can provide a reasonable nanoscale explanation for macroscopic experiment.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2022-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49144758","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 experimental work aims to develop cement-based composites with low cost and high performance using straw cotton stalk fiber (CSF) and expanded polystyrene(EPS). 5%, 10%, 15% CSF and 1%, 2%, 3% EPS were mixed into cement mortar, taking the specimens without CSF and EPS as the control group (CK), the compressive strength, splitting strength, and flexural strength of the specimens with different mix proportions for 7-day and 28-day were tested, and the mechanical properties of the materials were verified. The thermal conductivity and water absorption of the 28-day specimens were measured, and the physical properties of the materials were obtained. The results show that when the content of CSF or EPS is constant, the compressive strength and axial compressive strength of the samples at 28-day decrease with the increase of EPS or CSF content. The maximum compressive and axial compressive strengths of CSF and EPS specimens are 33% and 42.6% lower than CK. The maximum flexural and anti-splitting strengths are 33% and 42.6% more than that of CK. The water absorption of specimens increases with the content of CSF and EPS increasing. The thermal conductivity of specimens decreases with the increase of CSF and EPS content respectively. The results show that the composite made by adding 5%-10% CSF and 1%-2% EPS to cement mortar can meet the mechanical property standard of self-insulation block and meet its thermal insulation performance.
{"title":"Physical and Mechanical Properties of the Cotton Straw Fibre and Expanded Polystyrene Cementitious Composite","authors":"Gang Wu, Q. An, Hongwei Li, D. Mou","doi":"10.1680/jadcr.21.00097","DOIUrl":"https://doi.org/10.1680/jadcr.21.00097","url":null,"abstract":"This experimental work aims to develop cement-based composites with low cost and high performance using straw cotton stalk fiber (CSF) and expanded polystyrene(EPS). 5%, 10%, 15% CSF and 1%, 2%, 3% EPS were mixed into cement mortar, taking the specimens without CSF and EPS as the control group (CK), the compressive strength, splitting strength, and flexural strength of the specimens with different mix proportions for 7-day and 28-day were tested, and the mechanical properties of the materials were verified. The thermal conductivity and water absorption of the 28-day specimens were measured, and the physical properties of the materials were obtained. The results show that when the content of CSF or EPS is constant, the compressive strength and axial compressive strength of the samples at 28-day decrease with the increase of EPS or CSF content. The maximum compressive and axial compressive strengths of CSF and EPS specimens are 33% and 42.6% lower than CK. The maximum flexural and anti-splitting strengths are 33% and 42.6% more than that of CK. The water absorption of specimens increases with the content of CSF and EPS increasing. The thermal conductivity of specimens decreases with the increase of CSF and EPS content respectively. The results show that the composite made by adding 5%-10% CSF and 1%-2% EPS to cement mortar can meet the mechanical property standard of self-insulation block and meet its thermal insulation performance.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2022-06-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48666270","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 main contribution of this research is the study of the effect of the thermal inertia in the activation energy in calcium aluminate cement pastes. For this, several formulations of calcium aluminate cements paste with 51wt% and 71wt% of Al2O3 were made at 0.4 water to cement ratios, and with additions of 0.0wt% and 20wt% of silica contents. The characterization was done using x-ray fluorescent and X-ray diffraction, while the behavior of the phases with the temperature was studied through of thermal gravimetric analysis, including the corresponding derivative thermogravimetry. The influence of the thermal inertia on the activation energies and its dependence on the heating rate is established. The effect of thermal inertia on peaks of DTG curves and activation energies is analyzed. The activation energies for the dehydroxylation of the gibbsite were calculated based on the Kissenger-Akahira-Sunose method. The activation energies values obtained in kJ/mol, for CACP71 - 0, 20wt%; CACP51 - 0, 20wt% silica content, were 19.9, 6.37, 19.8, 17.2, respectively. The influence of silica on phases formation, activation energies, and the effect of thermal inertia is also analyzed.
{"title":"Thermal Behavior and Inertia Effect in Calcium Aluminate Cement Pastes with Microsilica","authors":"J. Zapata, O. J. Restrepo, M. Gómez, H. Colorado","doi":"10.1680/jadcr.21.00053","DOIUrl":"https://doi.org/10.1680/jadcr.21.00053","url":null,"abstract":"The main contribution of this research is the study of the effect of the thermal inertia in the activation energy in calcium aluminate cement pastes. For this, several formulations of calcium aluminate cements paste with 51wt% and 71wt% of Al2O3 were made at 0.4 water to cement ratios, and with additions of 0.0wt% and 20wt% of silica contents. The characterization was done using x-ray fluorescent and X-ray diffraction, while the behavior of the phases with the temperature was studied through of thermal gravimetric analysis, including the corresponding derivative thermogravimetry. The influence of the thermal inertia on the activation energies and its dependence on the heating rate is established. The effect of thermal inertia on peaks of DTG curves and activation energies is analyzed. The activation energies for the dehydroxylation of the gibbsite were calculated based on the Kissenger-Akahira-Sunose method. The activation energies values obtained in kJ/mol, for CACP71 - 0, 20wt%; CACP51 - 0, 20wt% silica content, were 19.9, 6.37, 19.8, 17.2, respectively. The influence of silica on phases formation, activation energies, and the effect of thermal inertia is also analyzed.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2022-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48952058","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 paper, new foamed cement has been formulated and designed for oil-gas wells liner and casing cementing jobs. Ultra-lightweight cements such as foamed cements are appropriate for formation damage prevention in fractured and depleted reservoirs. Current foamed cements have been prepared at high shear rates by boric acid and HA-(SLES) as a foaming agent. Different tests such as density, rheology, free water, settling, thickening time, compressive strength, fluid loss, porosity, permeability, microscopic photography and CT scanning are conducted for each sample. The results illustrate that the designed foamed cement (FBJ) has one of the lowest densities (1200 kg/m3) between drilling-cements, the compressive strength of 8963 kPa, thickening time near 3 hours. Also, its rheology becomes better in HPHT conditions. The porous media of FBJ's set-cement is not interconnected and this has been proved by porosity, permeability, microscopic photography and CT scan tests. Helium porosimeter demonstrated that FBJ's porosity is more than 73% and CT scan image processing proved that 28% of FBJ is the matrix. Moreover, the cement permeameter indicated that the permeability of FBJ's porous media is just 0.0109 mD. All of these experimental analyses show that FBJ has acceptable properties for oil-gas wells cementing jobs.
{"title":"The Acidic Foamed Cement Formulation with Particular Characteristics for Oil and Gas Wells Cementing Jobs: An Experimental Approach","authors":"Hossein Ameri, S. Shadizadeh, J. Moghadasi","doi":"10.1680/jadcr.21.00154","DOIUrl":"https://doi.org/10.1680/jadcr.21.00154","url":null,"abstract":"In this paper, new foamed cement has been formulated and designed for oil-gas wells liner and casing cementing jobs. Ultra-lightweight cements such as foamed cements are appropriate for formation damage prevention in fractured and depleted reservoirs. Current foamed cements have been prepared at high shear rates by boric acid and HA-(SLES) as a foaming agent. Different tests such as density, rheology, free water, settling, thickening time, compressive strength, fluid loss, porosity, permeability, microscopic photography and CT scanning are conducted for each sample. The results illustrate that the designed foamed cement (FBJ) has one of the lowest densities (1200 kg/m3) between drilling-cements, the compressive strength of 8963 kPa, thickening time near 3 hours. Also, its rheology becomes better in HPHT conditions. The porous media of FBJ's set-cement is not interconnected and this has been proved by porosity, permeability, microscopic photography and CT scan tests. Helium porosimeter demonstrated that FBJ's porosity is more than 73% and CT scan image processing proved that 28% of FBJ is the matrix. Moreover, the cement permeameter indicated that the permeability of FBJ's porous media is just 0.0109 mD. All of these experimental analyses show that FBJ has acceptable properties for oil-gas wells cementing jobs.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2022-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42557998","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 is devoted to the study of the influence of the sand-cement ratio and microstructure of cement mortar on their water permeability. For that purpose, laboratory experiments were carried out to study the influence of sand-cement ratio on the seepage failure of cement mortar. The results show that the contact relationship of aggregate grain can be divided into three types: wrapped-contact, surface-contact and point-contact. The relationships of water permeability with porosity and velocity of cement mortar has also been investigated. It is found that permeability coefficient of cement mortar exponentially increases with the increase of sand-cement ratio. There exists a critical sand-cement ratio of range around 5∼6, at which the porosity and wave velocity change remarkably. After exceeding the critical sand-cement ratio, there exists a threshold value named critical seepage pressure at which the samples will meet with seepage failure. Power function is obtained between the permeability and critical seepage pressure. Highlights: Variation between permeability and sand-cement ratio can be expressed by exponential law; (1) The permeability, porosity and wave velocity will be significantly changed, once the sand-cement ratio is higher than critical range value of around 5∼6; (2) (3) The contact relationship of aggregate grains can be divided into three types including wrapped-contact, surface-contact and point-contact. Seepage failure occurs when critical seepage pressure of the cement mortar is reached. Power function relationship exists between permeability coefficient and critical seepage pressure. (4)
{"title":"Laboratory investigation of permeability properties of cement mortar with different sand-cement ratio","authors":"Liangliang Lu, Shu-yun Zhu, Zhi-bin Liu","doi":"10.1680/jadcr.21.00111","DOIUrl":"https://doi.org/10.1680/jadcr.21.00111","url":null,"abstract":"This paper is devoted to the study of the influence of the sand-cement ratio and microstructure of cement mortar on their water permeability. For that purpose, laboratory experiments were carried out to study the influence of sand-cement ratio on the seepage failure of cement mortar. The results show that the contact relationship of aggregate grain can be divided into three types: wrapped-contact, surface-contact and point-contact. The relationships of water permeability with porosity and velocity of cement mortar has also been investigated. It is found that permeability coefficient of cement mortar exponentially increases with the increase of sand-cement ratio. There exists a critical sand-cement ratio of range around 5∼6, at which the porosity and wave velocity change remarkably. After exceeding the critical sand-cement ratio, there exists a threshold value named critical seepage pressure at which the samples will meet with seepage failure. Power function is obtained between the permeability and critical seepage pressure. Highlights: Variation between permeability and sand-cement ratio can be expressed by exponential law; (1) The permeability, porosity and wave velocity will be significantly changed, once the sand-cement ratio is higher than critical range value of around 5∼6; (2) (3) The contact relationship of aggregate grains can be divided into three types including wrapped-contact, surface-contact and point-contact. Seepage failure occurs when critical seepage pressure of the cement mortar is reached. Power function relationship exists between permeability coefficient and critical seepage pressure. (4) ","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2022-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43656613","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}
A self-expanding filling material for mine-sealing walls (SEFM–MSW) was developed to solve the problems of large solid material amounts, high labour intensities and poor sealing effects. This study examines material composition and structure. The results are as follows. First, the SEFM–MSW could be optimised with an expansion agent at 0.4∼1.0%, an admixture at 1.0∼1.5%, a fibre at 0.1% and a w/c (water/cement) ratio of 0.45∼0.5. Second, the fitting results were highly consistent of the relationship between the 28d-compressive strength and the porosity of the SEFM–MSW with the Ryshkewitch and Balshin models. Third, when the SEFM–MSW expansion ratio was higher, the average pore size was larger, the pore size distribution was wider and the compressive strength was lower. These results have realistic impacts for practical engineering applications.
{"title":"Experimental study of a self-expanding filling material for mine-sealing walls","authors":"Sun Liu, G. Shi, Yihang Xu, Xiaoqing Bao","doi":"10.1680/jadcr.22.00016","DOIUrl":"https://doi.org/10.1680/jadcr.22.00016","url":null,"abstract":"A self-expanding filling material for mine-sealing walls (SEFM–MSW) was developed to solve the problems of large solid material amounts, high labour intensities and poor sealing effects. This study examines material composition and structure. The results are as follows. First, the SEFM–MSW could be optimised with an expansion agent at 0.4∼1.0%, an admixture at 1.0∼1.5%, a fibre at 0.1% and a w/c (water/cement) ratio of 0.45∼0.5. Second, the fitting results were highly consistent of the relationship between the 28d-compressive strength and the porosity of the SEFM–MSW with the Ryshkewitch and Balshin models. Third, when the SEFM–MSW expansion ratio was higher, the average pore size was larger, the pore size distribution was wider and the compressive strength was lower. These results have realistic impacts for practical engineering applications.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2022-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43806662","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, metakaolin and waterglass with a modulus of 1.3 were mixed to prepare metakaolin based geopolymer grouting materials (MKGPGM) with different alkalinity of 11 wt%, 12 wt%, and 13 wt% The linear expansion, mass change, mechanical properties and microstructure of the specimens were investigated after being immersed in pure water and sodium sulfate solutions with a concentration of 1-4 wt% for 90 days. The results indicate that the main gel products were sodium silicoaluminate hydrate (N-A-S-H) gel, gypsum and ettringite were not detected in the specimens. The MKGPGM samples showed slight expansion first and then followed by a micro-shrinkage. When the mass concentration of Na2O is 12 wt%, the maximum expansion rate was less than 0.12%. MKGPGM samples showed a small increase in mass, essentially unchanged compressive strength and good anti- sulfate corrosion performance.
{"title":"Chemical deformation and mass change of metakaolin-based geopolymer grouting material in sulfate environment","authors":"Leping Liu, H. Liu, Yue Xu, Maojia Xie, Yan He","doi":"10.1680/jadcr.21.00090","DOIUrl":"https://doi.org/10.1680/jadcr.21.00090","url":null,"abstract":"In this study, metakaolin and waterglass with a modulus of 1.3 were mixed to prepare metakaolin based geopolymer grouting materials (MKGPGM) with different alkalinity of 11 wt%, 12 wt%, and 13 wt% The linear expansion, mass change, mechanical properties and microstructure of the specimens were investigated after being immersed in pure water and sodium sulfate solutions with a concentration of 1-4 wt% for 90 days. The results indicate that the main gel products were sodium silicoaluminate hydrate (N-A-S-H) gel, gypsum and ettringite were not detected in the specimens. The MKGPGM samples showed slight expansion first and then followed by a micro-shrinkage. When the mass concentration of Na2O is 12 wt%, the maximum expansion rate was less than 0.12%. MKGPGM samples showed a small increase in mass, essentially unchanged compressive strength and good anti- sulfate corrosion performance.","PeriodicalId":7299,"journal":{"name":"Advances in Cement Research","volume":" ","pages":""},"PeriodicalIF":2.0,"publicationDate":"2022-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49591328","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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