Magnesia-calcium materials have stable hot performance,good resistance to the erosion and corrosion of liquid steel and steel slag,and a special role in purifying liquid steel,so they are widely used in iron and steel...Magnesia-calcium materials have stable hot performance,good resistance to the erosion and corrosion of liquid steel and steel slag,and a special role in purifying liquid steel,so they are widely used in iron and steel industry.However,hydration of magnesia-calcium materials seriously restricts their use,so researches have been done to improve their hydration resistance,obtaining a series of achievements.In this paper,the improvements on the hydration resistance of magnesia-calcium materials by additives in recent 20 years were presented,and their mechanisms were summarized.展开更多
By means of low-field nuclear magnetic resonance(LF-NMR),the transverse relaxation time(T_(2))signals of physically bound water in cement paste were monitored to indicate water content change and characterize the earl...By means of low-field nuclear magnetic resonance(LF-NMR),the transverse relaxation time(T_(2))signals of physically bound water in cement paste were monitored to indicate water content change and characterize the early-age hydration process.With the curves of the T_(2)signals and hydration time obtained,the hydration process could be divided into four typical periods using the null points of the second derivative curve,and the influences of water-cement ratio(w/c)and hydration heat regulating materials(HHRM)on hydration process were analyzed.The experimental results showed that the hydration rate of pure cement paste in accelerated period presented a positive correlation with w/c.Compared to pure cement paste,the addition of HHRM extended all four periods,and led to a much faster hydration rate in initial period as well as a slower rate in accelerated period.Finally,according to the LFNMR test results,the early-age hydration model of cementitious materials was proposed considering w/c and HHRM content.展开更多
The rheological and mechanical properties of high-strength anchorage grouting materials for highway slope were investigated to optimize the mix proportion. The experimental results showed that the optimized mix propor...The rheological and mechanical properties of high-strength anchorage grouting materials for highway slope were investigated to optimize the mix proportion. The experimental results showed that the optimized mix proportion of high-strength anchorage grouting material (HAGM) was C3 (FA:SP-SF= 1:2:2; AGI:AG2=3:7 and 0.03% FC), which is agreement with the limitation of JCT 986-2005. Moreover, the XRD and FTIR results showed the addition of expansive components was in favor of the formation of ettringite. The intensity of AFt oeak of the samnles increased with the increasing of hydration time.展开更多
To elucidate the intrinsic reaction mechanism of cementitious materials composed of red mud and coal gangue(RGC), the hydration kinetics of these cementitious materials at 20°C was investigated on the basis of ...To elucidate the intrinsic reaction mechanism of cementitious materials composed of red mud and coal gangue(RGC), the hydration kinetics of these cementitious materials at 20°C was investigated on the basis of the Krstulovi?-Dabi? model. An isothermal calorimeter was used to characterize the hydration heat evolution. The results show that the hydration of RGC is controlled by the processes of nucleation and crystal growth(NG), interaction at phase boundaries(I), and diffusion(D) in order, and the pozzolanic reactions of slag and compound-activated red mud-coal gangue are mainly controlled by the I process. Slag accelerates the clinker hydration during NG process, whereas the compound-activated red mud-coal gangue retards the hydration of RGC and the time required for I process increases with increasing dosage of red mud-coal gangue in RGC.展开更多
The morphologies and hydration properties of MgO expansive material at different curing temperatures were investigated.When the curing temperature varies from 25℃to 50℃,the conductivity of MgO rises from 40 to 80μs...The morphologies and hydration properties of MgO expansive material at different curing temperatures were investigated.When the curing temperature varies from 25℃to 50℃,the conductivity of MgO rises from 40 to 80μs/cm,the hydration product of MgO expansive material curing in water for 28 days is from 1.5—2 mm to 2—2.5μm in length through SEM observation,and the expansion of pastes with 5%of the magnesium oxide is from 0.36%up to 1.01%,it is increased by 2.78 times.When the content of cement paste increases to 95%and cured in water for 90 days,the brucite forms as hexaflaggy?shaped crystal,which is less than 0.1μm and tends to aggregates.The effect of curing temperature on the hydration of MgO expansive material is obvious.展开更多
To obtain the compositions and microstructure of hydration products of cementitious material in different hydration ages and its growth law of filling strength, the optimal proportion of composite cementitious materia...To obtain the compositions and microstructure of hydration products of cementitious material in different hydration ages and its growth law of filling strength, the optimal proportion of composite cementitious material was determined according to the chemical composition of cement clinker which was composed of the Portland cement 32.5R, CSA 42.5 sulphoaluminate cement and two gypsum(CS). The characterization of composite cementitious materials in different hydration ages was conducted by NMR, XRD and SEM techniques. The mechanism of hydration was explored. It is shown that the compressive strength of the test block increases gradually with the increase of hydration age. The microstructure of composite cementitious material can be changed from Al-O octahedron into Al-O tetrahedron in the hydration process. The hydrated alkali alumi niumsilicate formed with Si-O tetrahedron and Al-O tetrahedron. The degree of polymerization of Si-O tetrahedron gradually increased, and the structural strength of cementitious materials continued to increase. The diffraction peak of clinker minerals gradually decreased with the extension of hydration age. The CaSO4 completely hydrated to produce Aft during hydration which resulted in high early strength of cementitious material. The early hydration product of composite cementitious materials was Aft with a needle bar structure. The main middle and last hydration products were CSH gel and CH gel with dense prismatic shape. The microscopic pore of composite cementitious material gradually decreased and improved the later strength of filling block. The strong support was provided for mined-out area.展开更多
The hydration mechanism of low quality fly ash in cement-based materials was investigated. The hydration heat of the composite cementitious materials was determined by isothermal calorimetry, and the hydration product...The hydration mechanism of low quality fly ash in cement-based materials was investigated. The hydration heat of the composite cementitious materials was determined by isothermal calorimetry, and the hydration products, quantity, pore structure and morphology were measured by X-ray diffraction(XRD), thermalgravity-differential thermal analysis(TG-DTA), mercury intrusion porosimetry(MIP) and scanning electron microscopy(SEM), respectively. The results indicate that grinding could not only improve the physical properties of the low quality fly ash on particle effect, but also improve hydration properties of the cementitious system from various aspects compared with raw low quality fly ash(RLFA). At the early stage of hydration, the low quanlity fly ash acts as almost inert material; but then at the later stage, high chemical activity, especially for ground low quality fly ash(GLFA), could be observed. It can accelerate the formation of hydration products containing more chemical bonded water, resulting in higher degree of cement hydration, thus denser microstructure and more reasonable pore size distribution, but the hydration heat in total is reduced. It can also delay the induction period, but the accelerating period is shortened and there is little influence on the second exothermic peak.展开更多
NMR is becoming increasingly popular for the investigation of building materials as it is a non-invasive technology that does not require any sample preparation nor causes damage to the material.Depending on the speci...NMR is becoming increasingly popular for the investigation of building materials as it is a non-invasive technology that does not require any sample preparation nor causes damage to the material.Depending on the specific application it can offer insights into properties like porosity and spatial saturation degree as well as pore structure.Moreover it enables the determination of moisture transport properties and the(re-)distribution of internal moisture into different reservoirs or chemical phases upon damage and curing.However,as yet most investigations were carried out using devices originally either designed for geophysical applications or the analysis of rather homogeneous small scale(<10 mL)samples.This paper describes the capabilities of an NMR tomograph,which has been specifically optimized for the investigation of larger,heterogeneous building material samples(diameters of up to 72 mm,length of up to 700 mm)with a high flexibility due to interchangeable coils allowing for a high SNR and short echo times(50-80 ms).展开更多
The dielectric permittivity of cementitious materials during 24 hours hydration period at a frequency of 2.45 GHz using a network analyzer with open-ended probe technique was measured. Influences of water-to-cementiti...The dielectric permittivity of cementitious materials during 24 hours hydration period at a frequency of 2.45 GHz using a network analyzer with open-ended probe technique was measured. Influences of water-to-cementitious ratios, cement types, pozzolans and aggregate types are taken into consideration. The results show that dielectric permittivity is strongly affected by initial water-to-cementitious ratio and the rate of hydration reaction which can be changed by fineness of cement (Types 1 and 3), pozzolan materials and aggregates (river sand with/without crushed limestone rock). Dielectric permittivity is relatively high and remains constant during the dormant period, after that it decreases rapidly when the hydration reaction resumes and continues to decrease during the acceleratory period.展开更多
Incorporating small amounts of biochar into cementitious materials has partial effects on the environment.In this present study,rice husk was collected as agricultural biomass from a local area of Roorkee Uttarakhand,...Incorporating small amounts of biochar into cementitious materials has partial effects on the environment.In this present study,rice husk was collected as agricultural biomass from a local area of Roorkee Uttarakhand,which contains siliceous material to a significant extent.Biochar was prepared from agricultural waste in a muffle furnace at a temperature of 500℃for 90 min and ground to a fineness of less than 10μm.Prior to incorporation into building envelopes such as mortar and concrete,a basic study on cement pastes is essentially required.For this purpose,different dosages of biochar such as 0,3%,5%and 10%wt.were replaced with cement in cementitious materials.Physical properties such as water absorption,density and porosity were investigated.Furthermore,mechanical and thermal properties such as compressive strength and thermal conductivity were studied.Advanced tools like field emission scanning electron microscopy(FESEM),X-ray diffraction(XRD)and thermogravimetric analyzer(TGA)were used to identify the hydration products.As the dosages increased in the cement matrix,the physical properties of sample were increased and porosity decreased.The compressive strength of biochar incorporated cement paste improved according to 0,3%,5%and 10%wt.It further reveals that as the dosage increased,the thermal conductivity of the samples decreased significantly.Moreover,the sustainable assessment showed that biochar could reduce embodied carbon,embodied energy and strength efficiency substantially over the control sample.A satisfactory result was obtained at 5%wt.and 10%wt.of biochar.The overall result revealed that biochar up to 10%wt.can be incorporated into mortar and concrete due to better results than the control mix.展开更多
AC impedance is a new method to study the changes of pore structure and the hydration degree during the hydration and hardening process of cement paste by the change of the electrochemical parameters. Employing AC imp...AC impedance is a new method to study the changes of pore structure and the hydration degree during the hydration and hardening process of cement paste by the change of the electrochemical parameters. Employing AC impedance method, we studied the hydration and hardening process of cement paste with fly ash and slag, and analyzed the influence of different hydration age, water-binder ratio and mineral admixture on the impedance parameters. Moreover, we compared the results with those by the conventional porosity testing method and X-ray diffraction method. The results showed that AC impedance could be taken as a new technology in cement and concrete research.展开更多
In this study, we have focused our investigations on effect of adding hydrated lime on a locally made composite material, based on clayey earth (soil) and Hibiscus sabdariffa fibres, for envelope (walls) in the buildi...In this study, we have focused our investigations on effect of adding hydrated lime on a locally made composite material, based on clayey earth (soil) and Hibiscus sabdariffa fibres, for envelope (walls) in the building. Prior to sample’s formulation, we selected an appropriate mineral (soil) material based on criteria as: plasticizer power for good workability, dense coarse particles to withstand loads and finally porous structure to take advantage of air insulating character. We then formulated, following a mixing process by shearing and compaction by vibration that we recommend, two composite materials (A), (B) which contain respectively 1% Fibres plus 1% lime, 1% Fibres plus 3% lime. We determined thermal properties by the mean of KD2 Pro thermal analyzer, compression strength accordingly to the standard NF P 18-406, porosity following volumetric and gravimetric methods and pH of soil-hydrated lime solution. As results, up to 5% of hydrated lime, the measured pH is inferior to 12: mineralization of vegetal fibres is highly unlikely. Moreover, we observe that the addition of hydrated lime resulted in a reduction in the number of cracks and their depths;Samples (A) and (B) have a rather compact appearance than the case 1% Fibres without lime (material (C)). Furthermore, with lime stabilization, the insulating potential is improved while the thermal inertia has been deteriorated compared to material (C). However, compressive strength decreases with lime, which could be due to the presence of fibres that would inhibit the hardening of the lime. At last, with 3.39% ± 3.07% MPa, 2.27% ± 11.30% MPa for samples (A), (B) respectively, the minimum required by CRATerre-EAG (guide of CDI, 1996) for construction of envelope (walls) of single storey (ground floor) buildings is met.展开更多
The interaction of Si anions with AI sites during the hydration process was observed by NMR, IR and SEM to understand the reaction mechanism of the hydrates formation mixed with oil shale calcined at different tempera...The interaction of Si anions with AI sites during the hydration process was observed by NMR, IR and SEM to understand the reaction mechanism of the hydrates formation mixed with oil shale calcined at different temperatures. As the reaction progressed,the coordination of AI (IV, V, and VI) changed almost completely to IV, when mixed with oilshale calcined at 700^(。)C. However, when mixed with oil shale calcined at 400^(。)C, some6-coordination of AI still remained in the hydrates. Under the function of alkaline solutions,which were produced with the hydration of clinker, a certain amount of Si and AI atomsdissolved or hydrolyzed from aluminosilicate, formed geomonomers in solutions, and thenpolycondensed to form networks.展开更多
Main performance of the cement grouting materials made up by Portland cement(PC) and sulphoaluminate cement(SAC) was investigated in this program, a kind of expanding agent(EA) which was mainly constituted by me...Main performance of the cement grouting materials made up by Portland cement(PC) and sulphoaluminate cement(SAC) was investigated in this program, a kind of expanding agent(EA) which was mainly constituted by metakaolin and alunite was utilized for the compensation of the shrinkage, the hydration products and micro structure of the grouting materials were researched by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The results showed that a high expansion rate of the grouting materials could be reached as the expanding agent mixed in 6% of PC mass; the addition of SAC in the S2(PC:SAC:EA=34:6:2.25) brought a further improvement of the expansion rate of the grouting materials, the analysis of XRD and SEM showed that due to the reaction of expanding agent and SAC in the grouting materials, more ettringite crystal was generated, which resulted in a higher early strength, the addition of SAC played an expansion and strength reinforcement role in the grouting materials.展开更多
In recent years,the incorporation of nanoparticles in the cementitious matrix has been regarded as a prominent strategy in the research effort.This paper reviews the influences of the nanomaterial GO(graphene oxide)in...In recent years,the incorporation of nanoparticles in the cementitious matrix has been regarded as a prominent strategy in the research effort.This paper reviews the influences of the nanomaterial GO(graphene oxide)in cement bound materials,as GO has become one of the most well-known inclusion nanoparticles in the cementitious matrix in the last few years.This study describes(i)the influences of the GO on enhancing hydration mechanism in the cementitious materials;and(ii)the improved performance of the cementitious materials,which are highly dependent on the functionalizing behavior of the GO.All this improves the properties of the matrix.The paper reports the influences of GO on the workability of the mixtures and the durability enhancement of the cementitious composites.Therefore,it demonstrates promising results of employing GO in the fabrication of novel building materials.However,tremendous progress in utilizing GO in scientific domains like materials technology has achieved a significant level.Remarkable progress has been achieved by applying the GO in different fields such as solar cells and super capacitors.Hence,more intensive research is required to achieve comparable improvement in building materials which constitutes a significant future challenge.展开更多
文摘Magnesia-calcium materials have stable hot performance,good resistance to the erosion and corrosion of liquid steel and steel slag,and a special role in purifying liquid steel,so they are widely used in iron and steel industry.However,hydration of magnesia-calcium materials seriously restricts their use,so researches have been done to improve their hydration resistance,obtaining a series of achievements.In this paper,the improvements on the hydration resistance of magnesia-calcium materials by additives in recent 20 years were presented,and their mechanisms were summarized.
基金Funded by National Natural Science Foundation of China(Nos.U1965105,51878245)National Key R&D Program of China(No.2021YFF0500802)。
文摘By means of low-field nuclear magnetic resonance(LF-NMR),the transverse relaxation time(T_(2))signals of physically bound water in cement paste were monitored to indicate water content change and characterize the early-age hydration process.With the curves of the T_(2)signals and hydration time obtained,the hydration process could be divided into four typical periods using the null points of the second derivative curve,and the influences of water-cement ratio(w/c)and hydration heat regulating materials(HHRM)on hydration process were analyzed.The experimental results showed that the hydration rate of pure cement paste in accelerated period presented a positive correlation with w/c.Compared to pure cement paste,the addition of HHRM extended all four periods,and led to a much faster hydration rate in initial period as well as a slower rate in accelerated period.Finally,according to the LFNMR test results,the early-age hydration model of cementitious materials was proposed considering w/c and HHRM content.
基金Funded by the National Natural Science Foundation of China(No.41202226)the Program for Department of Communications of Yunnan Province(No.2009(A)1-09)
文摘The rheological and mechanical properties of high-strength anchorage grouting materials for highway slope were investigated to optimize the mix proportion. The experimental results showed that the optimized mix proportion of high-strength anchorage grouting material (HAGM) was C3 (FA:SP-SF= 1:2:2; AGI:AG2=3:7 and 0.03% FC), which is agreement with the limitation of JCT 986-2005. Moreover, the XRD and FTIR results showed the addition of expansive components was in favor of the formation of ettringite. The intensity of AFt oeak of the samnles increased with the increasing of hydration time.
基金financially supported by the National Natural Science Foundation of China(Nos.51302012 and 51234008)the China Postdoctoral Science Foundation(No.2016M590046)
文摘To elucidate the intrinsic reaction mechanism of cementitious materials composed of red mud and coal gangue(RGC), the hydration kinetics of these cementitious materials at 20°C was investigated on the basis of the Krstulovi?-Dabi? model. An isothermal calorimeter was used to characterize the hydration heat evolution. The results show that the hydration of RGC is controlled by the processes of nucleation and crystal growth(NG), interaction at phase boundaries(I), and diffusion(D) in order, and the pozzolanic reactions of slag and compound-activated red mud-coal gangue are mainly controlled by the I process. Slag accelerates the clinker hydration during NG process, whereas the compound-activated red mud-coal gangue retards the hydration of RGC and the time required for I process increases with increasing dosage of red mud-coal gangue in RGC.
基金the Research Center on Levee Safety Disaster Prevention, MWR (No. 2019004)High-level Talent Project Funding Scheme of Jiangsu (No. XCL-CXTD-007)+3 种基金China Postdoctoral Science Foundation (No. 2018M630559)the National Natural Science Foundation of China (No. 51908285)the Fundamental Research Nantong Metro Group Co., Ltdthe traffic construction science and technology project of Shanxi (No. 16-2-08) for its financial support in this project
文摘The morphologies and hydration properties of MgO expansive material at different curing temperatures were investigated.When the curing temperature varies from 25℃to 50℃,the conductivity of MgO rises from 40 to 80μs/cm,the hydration product of MgO expansive material curing in water for 28 days is from 1.5—2 mm to 2—2.5μm in length through SEM observation,and the expansion of pastes with 5%of the magnesium oxide is from 0.36%up to 1.01%,it is increased by 2.78 times.When the content of cement paste increases to 95%and cured in water for 90 days,the brucite forms as hexaflaggy?shaped crystal,which is less than 0.1μm and tends to aggregates.The effect of curing temperature on the hydration of MgO expansive material is obvious.
基金Funded by the National Natural Science Foundation of China(No.51574055)the Natural Science Foundation of Liaoning Province(No.20170540143)
文摘To obtain the compositions and microstructure of hydration products of cementitious material in different hydration ages and its growth law of filling strength, the optimal proportion of composite cementitious material was determined according to the chemical composition of cement clinker which was composed of the Portland cement 32.5R, CSA 42.5 sulphoaluminate cement and two gypsum(CS). The characterization of composite cementitious materials in different hydration ages was conducted by NMR, XRD and SEM techniques. The mechanism of hydration was explored. It is shown that the compressive strength of the test block increases gradually with the increase of hydration age. The microstructure of composite cementitious material can be changed from Al-O octahedron into Al-O tetrahedron in the hydration process. The hydrated alkali alumi niumsilicate formed with Si-O tetrahedron and Al-O tetrahedron. The degree of polymerization of Si-O tetrahedron gradually increased, and the structural strength of cementitious materials continued to increase. The diffraction peak of clinker minerals gradually decreased with the extension of hydration age. The CaSO4 completely hydrated to produce Aft during hydration which resulted in high early strength of cementitious material. The early hydration product of composite cementitious materials was Aft with a needle bar structure. The main middle and last hydration products were CSH gel and CH gel with dense prismatic shape. The microscopic pore of composite cementitious material gradually decreased and improved the later strength of filling block. The strong support was provided for mined-out area.
基金Project(51208391) supported by the National Natural Science Foundation of China
文摘The hydration mechanism of low quality fly ash in cement-based materials was investigated. The hydration heat of the composite cementitious materials was determined by isothermal calorimetry, and the hydration products, quantity, pore structure and morphology were measured by X-ray diffraction(XRD), thermalgravity-differential thermal analysis(TG-DTA), mercury intrusion porosimetry(MIP) and scanning electron microscopy(SEM), respectively. The results indicate that grinding could not only improve the physical properties of the low quality fly ash on particle effect, but also improve hydration properties of the cementitious system from various aspects compared with raw low quality fly ash(RLFA). At the early stage of hydration, the low quanlity fly ash acts as almost inert material; but then at the later stage, high chemical activity, especially for ground low quality fly ash(GLFA), could be observed. It can accelerate the formation of hydration products containing more chemical bonded water, resulting in higher degree of cement hydration, thus denser microstructure and more reasonable pore size distribution, but the hydration heat in total is reduced. It can also delay the induction period, but the accelerating period is shortened and there is little influence on the second exothermic peak.
文摘NMR is becoming increasingly popular for the investigation of building materials as it is a non-invasive technology that does not require any sample preparation nor causes damage to the material.Depending on the specific application it can offer insights into properties like porosity and spatial saturation degree as well as pore structure.Moreover it enables the determination of moisture transport properties and the(re-)distribution of internal moisture into different reservoirs or chemical phases upon damage and curing.However,as yet most investigations were carried out using devices originally either designed for geophysical applications or the analysis of rather homogeneous small scale(<10 mL)samples.This paper describes the capabilities of an NMR tomograph,which has been specifically optimized for the investigation of larger,heterogeneous building material samples(diameters of up to 72 mm,length of up to 700 mm)with a high flexibility due to interchangeable coils allowing for a high SNR and short echo times(50-80 ms).
文摘The dielectric permittivity of cementitious materials during 24 hours hydration period at a frequency of 2.45 GHz using a network analyzer with open-ended probe technique was measured. Influences of water-to-cementitious ratios, cement types, pozzolans and aggregate types are taken into consideration. The results show that dielectric permittivity is strongly affected by initial water-to-cementitious ratio and the rate of hydration reaction which can be changed by fineness of cement (Types 1 and 3), pozzolan materials and aggregates (river sand with/without crushed limestone rock). Dielectric permittivity is relatively high and remains constant during the dormant period, after that it decreases rapidly when the hydration reaction resumes and continues to decrease during the acceleratory period.
文摘Incorporating small amounts of biochar into cementitious materials has partial effects on the environment.In this present study,rice husk was collected as agricultural biomass from a local area of Roorkee Uttarakhand,which contains siliceous material to a significant extent.Biochar was prepared from agricultural waste in a muffle furnace at a temperature of 500℃for 90 min and ground to a fineness of less than 10μm.Prior to incorporation into building envelopes such as mortar and concrete,a basic study on cement pastes is essentially required.For this purpose,different dosages of biochar such as 0,3%,5%and 10%wt.were replaced with cement in cementitious materials.Physical properties such as water absorption,density and porosity were investigated.Furthermore,mechanical and thermal properties such as compressive strength and thermal conductivity were studied.Advanced tools like field emission scanning electron microscopy(FESEM),X-ray diffraction(XRD)and thermogravimetric analyzer(TGA)were used to identify the hydration products.As the dosages increased in the cement matrix,the physical properties of sample were increased and porosity decreased.The compressive strength of biochar incorporated cement paste improved according to 0,3%,5%and 10%wt.It further reveals that as the dosage increased,the thermal conductivity of the samples decreased significantly.Moreover,the sustainable assessment showed that biochar could reduce embodied carbon,embodied energy and strength efficiency substantially over the control sample.A satisfactory result was obtained at 5%wt.and 10%wt.of biochar.The overall result revealed that biochar up to 10%wt.can be incorporated into mortar and concrete due to better results than the control mix.
基金Funded the Major Sate Basic Research Development Program of China(973 Program)(No.2009CB23201)Beijing Natural Science Foundation(No.8100001)National Natural Science Foundation of China(No.51278014)
文摘AC impedance is a new method to study the changes of pore structure and the hydration degree during the hydration and hardening process of cement paste by the change of the electrochemical parameters. Employing AC impedance method, we studied the hydration and hardening process of cement paste with fly ash and slag, and analyzed the influence of different hydration age, water-binder ratio and mineral admixture on the impedance parameters. Moreover, we compared the results with those by the conventional porosity testing method and X-ray diffraction method. The results showed that AC impedance could be taken as a new technology in cement and concrete research.
文摘In this study, we have focused our investigations on effect of adding hydrated lime on a locally made composite material, based on clayey earth (soil) and Hibiscus sabdariffa fibres, for envelope (walls) in the building. Prior to sample’s formulation, we selected an appropriate mineral (soil) material based on criteria as: plasticizer power for good workability, dense coarse particles to withstand loads and finally porous structure to take advantage of air insulating character. We then formulated, following a mixing process by shearing and compaction by vibration that we recommend, two composite materials (A), (B) which contain respectively 1% Fibres plus 1% lime, 1% Fibres plus 3% lime. We determined thermal properties by the mean of KD2 Pro thermal analyzer, compression strength accordingly to the standard NF P 18-406, porosity following volumetric and gravimetric methods and pH of soil-hydrated lime solution. As results, up to 5% of hydrated lime, the measured pH is inferior to 12: mineralization of vegetal fibres is highly unlikely. Moreover, we observe that the addition of hydrated lime resulted in a reduction in the number of cracks and their depths;Samples (A) and (B) have a rather compact appearance than the case 1% Fibres without lime (material (C)). Furthermore, with lime stabilization, the insulating potential is improved while the thermal inertia has been deteriorated compared to material (C). However, compressive strength decreases with lime, which could be due to the presence of fibres that would inhibit the hardening of the lime. At last, with 3.39% ± 3.07% MPa, 2.27% ± 11.30% MPa for samples (A), (B) respectively, the minimum required by CRATerre-EAG (guide of CDI, 1996) for construction of envelope (walls) of single storey (ground floor) buildings is met.
基金Supported by the National Science and Technology (2006BAE03A11)the National Natural Science Foundation of China(50674062)
文摘The interaction of Si anions with AI sites during the hydration process was observed by NMR, IR and SEM to understand the reaction mechanism of the hydrates formation mixed with oil shale calcined at different temperatures. As the reaction progressed,the coordination of AI (IV, V, and VI) changed almost completely to IV, when mixed with oilshale calcined at 700^(。)C. However, when mixed with oil shale calcined at 400^(。)C, some6-coordination of AI still remained in the hydrates. Under the function of alkaline solutions,which were produced with the hydration of clinker, a certain amount of Si and AI atomsdissolved or hydrolyzed from aluminosilicate, formed geomonomers in solutions, and thenpolycondensed to form networks.
基金Funded by the National Key Technology R&D Program in the12th Five Year Plan of China(No.2011BAE14B06)the National High Technology ResearchDevelopment Program of China(No.2015AA034701)
文摘Main performance of the cement grouting materials made up by Portland cement(PC) and sulphoaluminate cement(SAC) was investigated in this program, a kind of expanding agent(EA) which was mainly constituted by metakaolin and alunite was utilized for the compensation of the shrinkage, the hydration products and micro structure of the grouting materials were researched by X-ray diffraction(XRD) and scanning electron microscopy(SEM). The results showed that a high expansion rate of the grouting materials could be reached as the expanding agent mixed in 6% of PC mass; the addition of SAC in the S2(PC:SAC:EA=34:6:2.25) brought a further improvement of the expansion rate of the grouting materials, the analysis of XRD and SEM showed that due to the reaction of expanding agent and SAC in the grouting materials, more ettringite crystal was generated, which resulted in a higher early strength, the addition of SAC played an expansion and strength reinforcement role in the grouting materials.
文摘In recent years,the incorporation of nanoparticles in the cementitious matrix has been regarded as a prominent strategy in the research effort.This paper reviews the influences of the nanomaterial GO(graphene oxide)in cement bound materials,as GO has become one of the most well-known inclusion nanoparticles in the cementitious matrix in the last few years.This study describes(i)the influences of the GO on enhancing hydration mechanism in the cementitious materials;and(ii)the improved performance of the cementitious materials,which are highly dependent on the functionalizing behavior of the GO.All this improves the properties of the matrix.The paper reports the influences of GO on the workability of the mixtures and the durability enhancement of the cementitious composites.Therefore,it demonstrates promising results of employing GO in the fabrication of novel building materials.However,tremendous progress in utilizing GO in scientific domains like materials technology has achieved a significant level.Remarkable progress has been achieved by applying the GO in different fields such as solar cells and super capacitors.Hence,more intensive research is required to achieve comparable improvement in building materials which constitutes a significant future challenge.