The high strength concrete (HSC) was produced by partially replacing the normal portland cement with special ground granulated blast-furnace slag ( GGBS) ranging up to 60% . The effects of the GGBS on the flowabilitya...The high strength concrete (HSC) was produced by partially replacing the normal portland cement with special ground granulated blast-furnace slag ( GGBS) ranging up to 60% . The effects of the GGBS on the flowabilityand mechanical properties of HSC were studied. The hydration process and microstructure characteristics were investigated by X-ray diffraction ( XRD) and scanning electron microscopy ( SEM), respectively. The test results indicate that the GGBS has especially supplementary effect on water reducing and excellent property of better control of lump loss. The concrete flowability increases remarkably with the increase of GGBS fineness and the replacement level in the range of 20% to 50% . The compressiae and splitting tensile strengths of HSC containing GGBS are higher than the corresponding strength of the control concrete at all ages .展开更多
The effect of carbonation on fatigue performance of ground granulated blast-furnace slag concrete was investigated. Based on the static compression tests of carbonated GGBS-concrete, the correlation between carbonatio...The effect of carbonation on fatigue performance of ground granulated blast-furnace slag concrete was investigated. Based on the static compression tests of carbonated GGBS-concrete, the correlation between carbonation depth and compressive strength was analyzed and an equation between carbonation depth and compressive strength was put forward. Meanwhile, fatigue S-N curves of various carbonation depths were fitted, and the infl uence of carbonation on fatigue life and strength was studied. Carbonation has a dual effect on the fatigue behavior of GGBS-concrete. A fatigue equation based on the depth of carbonation was established. Also, the probabilistic distribution of fatigue life of carbonated concrete at a given stress level was modeled by the two-parameter Weibull distribution.展开更多
The effect of ground granulated blast-furnace slag(GGBFS) and silica fume(SF) on the chloride migration through concrete subjected to repeated loading was examined.Portland cement was replaced by 20%,30%,40% GGBFS and...The effect of ground granulated blast-furnace slag(GGBFS) and silica fume(SF) on the chloride migration through concrete subjected to repeated loading was examined.Portland cement was replaced by 20%,30%,40% GGBFS and 5%,10% SF,respectively.Five times repeated loadings were applied to specimens,the maximum loadings were 40% and 80% of the axial cylinder compressive strength(f′c),respectively.Chloride migration through concretes was evaluated using the rapid chloride migration test and the chloride concentration in the anode chamber was measured.The results indicate that the transport number of chloride through concrete containing 20% and 30% GGBFS replacements and 5% and 10% SF replacements is lower than that of the control concrete,but 40% GGBFS replacement increases the transport number of chloride.Five loadings at 40% f′cor 80% f′c increase the transport number of chloride for all mixes investigated in this study.5% SF replacement has a very close effect on the chloride permeability of concrete with 20% GGBFS when concrete is subjected to 40% f′cor 80% f′c.展开更多
A new hydraulic cementitious binder was developed by mainly utilizing industrial byproducts phosphogypsum(PG)and ground granulated blast furnace slag(GGBFS)with small addition of ordinary portland cement(OPC).The hydr...A new hydraulic cementitious binder was developed by mainly utilizing industrial byproducts phosphogypsum(PG)and ground granulated blast furnace slag(GGBFS)with small addition of ordinary portland cement(OPC).The hydration process and microstructure were studied by X-ray diffraction(XRD) and scanning electronic microscopy(SEM).OPC hydrated first at early age to form primarily C-S-H gel,ettringite and calcium hydroxide(CH).GGBFS activated by CH and sulfate ions hydrated continuously at later age,producing more and more hydration products,C-S-H gel and ettringite.Thus the paste developed a denser microstructure and its strength increased.The 28 d compressive strength of the mixture of 50%PG,46% GGBFS and 4%OPC exceeded 45 MPa.The setting time was faster and 3 d and 7 d strength were higher when the proportion of OPC increased.But the 28 d strength decreased when OPC exceeded 4%due to large amount of ettringite formed at late hydration age which damaged the microstructure.展开更多
Tensile strength of concrete were examined on its partial replacement of cement and sand using ground granulated blast furnace and quarry dust.The study examines its behaviour at different dimensions.This is to monito...Tensile strength of concrete were examined on its partial replacement of cement and sand using ground granulated blast furnace and quarry dust.The study examines its behaviour at different dimensions.This is to monitor the variation effect of these parameters on the growth rates of tensile to the optimum curing age.These include non linear conditions of tensile state,non-elastic and its brittle behaviour at all times as it express zero conditions in tension.This means that it has the ability to with stand pull force.It also reflects its weak ability to handle shear stress thus tends to cause deformation in material as it has poor elasticity.The reflection of its brittle influence the rate of tensile behaviour from concrete ductility.These are known to be a material on modern mechanics of concrete.These are also considered as quasi brittle material.This behaviour was reflected as the system considered evaluating the growth rate of tensile strength that replaced cement and sand with these locally sourced addictives.The developed model monitor other reflected influential parameters such as variation of concrete porosity due it compaction in placements,tensile behaviour reflects these effect that subject it to mechanical properties of concrete.The study expressed the reaction of these parameters in the simulation,the evaluation of these affected the details variation of tensile growth rate at different water cement ratios and curing age.The tensile behaviour that was monitored are based on these factors in the study.The derived model were validated with the a researcher results[24],and both parameters developed best fits correlation.The study is imperative because the system expressed the behaviour of tensile strength from concrete at different dimensions.Experts can applied these concept to monitor tensile behaviour considering these parameters in its growth rates.展开更多
Dredged marine soils(DMS)have poor engineering properties,which limit their usage in construction projects.This research examines the application of reactive magnesia(rMgO)containing supplementary cementitious materia...Dredged marine soils(DMS)have poor engineering properties,which limit their usage in construction projects.This research examines the application of reactive magnesia(rMgO)containing supplementary cementitious materials(SCMs)to stabilize DMS under ambient and carbon dioxide(CO_(2))curing conditions.Several proprietary experimental tests were conducted to investigate the stabilized DMS.Furthermore,the carbonation-induced mineralogical,thermal,and microstructural properties change of the samples were explored.The findings show that the compressive strength of the stabilized DMS fulfilled the 7-d requirement(0.7-2.1 MPa)for pavement and building foundations.Replacing rMgO with SCMs such as biochar or ground granulated blast-furnace slag(GGBS)altered the engineering properties and particle packing of the stabilized soils,thus influencing their performances.Biochar increased the porosity of the samples,facilitating higher CO_(2) uptake and improved ductility,while GGBS decreased porosity and increased the dry density of the samples,resulting in higher strength.The addition of SCMs also enhanced the water retention capacity and modified the pH of the samples.Microstructural analysis revealed that the hydrated magnesium carbonates precipitated in the carbonated samples provided better cementation effects than brucite formed during rMgO hydration.Moreover,incorporating SCMs reduced the overall global warming potential and energy demand of the rMgO-based systems.The biochar mixes demonstrated lower toxicity and energy consumption.Ultimately,the rMgO and biochar blend can serve as an environmentally friendly additive for soft soil stabilization and permanent fixation of significant amounts of CO_(2) in soils through mineral carbonation,potentially reducing environmental pollution while meeting urbanization needs.展开更多
This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na<sub>2</sub>...This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>): the soundness, sulfate resistance, alkali-silica reactivity and efflorescence factors are considered. Results of tests show that such mortars are resistant to alkali-silica expansion. Mortars are also sulfate-resistant when the amount of HCFA in the complex binder is within a limit of 10 wt%. The fineness of fly ash determines its’ ability to activate GGBFS hydration, and influence soundness of the binder, early strength development, sulfate resistance and efflorescence behavior. The present article is a continuation of authors’ work, previously published in MSA, Vol. 14, 240-254.展开更多
High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace sla...High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace slag (GGBFS). Substitution of 10% - 30% of GGBFS by HCFA and premixing of 1% - 3% Na2CO3 to this dry binary binder was discovered to give mortar compression strength of 10 - 30 to 30 - 45 MPa at 7 and 28 days when moist cured at ambient temperature. High-calcium fly ash produced from low-temperature combustion of fuel, like in circulating fluidized bed technology, reacts with water readily and is itself a good hardening activator for GGBFS, so introduction of Na<sub>2</sub>CO<sub>3</sub> into such mix has no noticeable effect on the mortar strength. However, low-temperature HCFA has higher water demand, and the strength of mortar is compromised by this factor. As of today, our research is still ongoing, and we expect to publish more data on different aspects of durability of proposed GGBFS-HCFA binder later.展开更多
The effect of the ground granulated blast-furnace slag （GGBFS） addition, the modulus n （ mole ratio of SiO2 to Na2O） and the concentration of sodium silicate solution on the compressive strength of the material, i...The effect of the ground granulated blast-furnace slag （GGBFS） addition, the modulus n （ mole ratio of SiO2 to Na2O） and the concentration of sodium silicate solution on the compressive strength of the material, i e alkali-activated carbonatite cementitious material （AACCM for short） was investigated. In addition, it is found that barium chloride has a satisfactory retarding effect on the setting of AACCM in which more than 20% （by mass） ground carbonatite was replaced by GGBFS. As a result, a cementitious material, in which ground carbonatite rock served as dominative starting material, with 3-day and 28-day compressive strength greater than 30 MPa and 60 MPa and with continuous strength gain beyond 90 days was obtained.展开更多
To provide basic data for the reasonable mixing design of the alkali-activated (AA) foamed concrete as a thermal insulation material for a floor heating system, 9 concrete mixes with a targeted dry density less than 4...To provide basic data for the reasonable mixing design of the alkali-activated (AA) foamed concrete as a thermal insulation material for a floor heating system, 9 concrete mixes with a targeted dry density less than 400 kg/m3 were tested. Ground granulated blast-furnace slag (GGBS) as a source material was activated by the following two types of alkali activators: 10% Ca(OH)2 and 4% Mg(NO3)2, and 2.5% Ca(OH)2 and 6.5% Na2SiO3. The main test parameters were water-to-binder (W/B) ratio and the substitution level (RFA) of fly ash (FA) for GGBS. Test results revealed that the dry density of AA GGBS foamed concrete was independent of the W/B ratio an RFA, whereas the compressive strength increased with the decrease in W/B ratio and with the increase in RFA up to 15%, beyond which it decreased. With the increase in the W/B ratio, the amount of macro capillaries and artificial air pores increased, which resulted in the decrease of compressive strength. The magnitude of the environmental loads of the AA GGBS foamed concrete is independent of the W/B ratio and RFA. The largest reduction percentage was found in the photochemical oxidation potential, being more than 99%. The reduction percentage was 87% - 93% for the global warming potential, 81% - 84% for abiotic depletion, 79% - 84% for acidification potential, 77% - 85% for eutrophication potential, and 73% - 83% for human toxicity potential. Ultimately, this study proved that the developed AA GGBS foamed concrete has a considerable promise as a sustainable construction material for nonstructural element.展开更多
Lime and Portland cement are the most widely used binders in soil stabilization projects.However,due to the high carbon emission in cement production,research on soil stabilization by the use of more environmentally-f...Lime and Portland cement are the most widely used binders in soil stabilization projects.However,due to the high carbon emission in cement production,research on soil stabilization by the use of more environmentally-friendly binders with lower carbon footprint has attracted much attention in recent years.This research investigated the potential of using alkali-activated ground granulated blast furnace slag(GGBS)and volcanic ash(VA)as green binders in clayey soil stabilization projects,which has not been studied before.The effects of different combinations of VA with GGBS,various liquid/solid ratios,different curing conditions,and different curing periods(i.e.7 d,28 d and 90 d)were investigated.Compressive strength and durability of specimens against wet-dry and freeze-thaw cycles were then studied through the use of mechanical and microstructural tests.The results demonstrated that the coexistence of GGBS and VA in geopolymerization process was more effective due to the synergic formation of N-A-S-H and C-(A)-S-H gels.Moreover,although VA needs heat curing to become activated and develop strength,its partial replacement with GGBS made the binder suitable for application at ambient temperature and resulted in a remarkably superior resistance against wet-dry and freeze-thaw cycles.The carbon embodied of the mixtures was also evaluated,and the results confirmed the low carbon footprints of the alkali-activated mixtures.Finally,it was concluded that the alkali-activated GGBS/VA could be promisingly used in clayey soil stabilization projects instead of conventional binders.展开更多
In the present study,compressive strength,pore structure,thermal behavior and microstructure characteristics of concrete containing ground granulated blast furnace slag and TiO2 nanoparticles as binder were investigat...In the present study,compressive strength,pore structure,thermal behavior and microstructure characteristics of concrete containing ground granulated blast furnace slag and TiO2 nanoparticles as binder were investigated.Portland cement was replaced by different amounts of ground granulated blast furnace slag and the properties of concrete specimens were investigated.Although it negatively impacts the properties of concrete at early ages,ground granulated blast furnace slag up to 45 wt% was found to improve the physical and mechanical properties of concrete at later ages.TiO2 nanoparticles with the average particle size of 15 nm were partially added to concrete with the optimum content of ground granulated blast furnace slag and physical and mechanical properties of the specimens were measured.TiO2 nanoparticle as a partial replacement of cement up to 3 wt% could accelerate C-S-H gel formation as a result of increased crystalline Ca(OH)2 amount at the early age of hydration and hence increase compressive strength of concrete.The increased TiO2 nanoparticles' content of more than 3 wt% may cause reduced compressive strength because of the decreased crystalline Ca(OH)2 content required for C-S-H gel formation and unsuitable dispersed nanoparticles in the concrete matrix.TiO2 nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and less-harm pores.展开更多
In this work,strength assessments and percentage of water absorption of self compacting concrete containing ground granu-lated blast furnace slag (GGBFS) and Al2O3 nanoparticles as binder have been investigated.Portla...In this work,strength assessments and percentage of water absorption of self compacting concrete containing ground granu-lated blast furnace slag (GGBFS) and Al2O3 nanoparticles as binder have been investigated.Portland cement was replaced by different amounts of GGBFS and the properties of concrete specimens were investigated.Although it negatively impacts the physical and mechanical properties of concrete at early ages of curing,GGBFS was found to improve the physical and me-chanical properties of concrete up to 45 wt% at later ages.Al2O3 nanoparticles with the average particle size of 15 nm were added partially to concrete with the optimum content of GGBFS and physical and mechanical properties of the specimens were measured.Al2O3 nanoparticle as a partial replacement of cement up to 3.0 wt% could accelerate C-S-H gel formation as a re-sult of increased crystalline Ca(OH)2 amount at the early ages and hence increase strength and improve the resistance to water permeability of concrete specimens.The increase of the Al2O3 nanoparticles’ content by more than 3.0 wt% would cause the reduction of the strength because of the decreased crystalline Ca(OH)2 content required for C-S-H gel formation.Several em-pirical relationships have been presented to predict flexural and split tensile strength of the specimens by means of the corre-sponding compressive strength at a certain age of curing.Accelerated peak appearance in conduction calorimetry tests,more weight loss in thermogravimetric analysis and more rapid appearance of the peaks related to hydrated products in X-ray dif-fraction results,all indicate that Al2O3 nanoparticles could improve mechanical and physical properties of the concrete speci-mens.展开更多
Properties and mechanism were investigated on flexural fatigue of concrete containing polypropylene fibers and ground granulated blast furnace slag(GGBFS).Four polypropylene fibers’volume fractions and five slag prop...Properties and mechanism were investigated on flexural fatigue of concrete containing polypropylene fibers and ground granulated blast furnace slag(GGBFS).Four polypropylene fibers’volume fractions and five slag proportions were considered.An experiment was conducted to obtain the fatigue lives at three stress levels in 20 Hz frequency and at a constant stress level of 0.59 in four frequency respectively.Mechanism and evaluation were investigated based on the experimental data.Fatigue life span models were established.The results show that the addition of polypropylene fibers improves the flexural fatigue cumulative strength and fatigue life span.It is proposed that the slag particles and hydrated products improve Interfacial Transition Zone(ITZ)structure and benefit flexural fatigue performance.A composite reinforce effect is found with the incorporation of slag and polypropylene fibers.The optimum mixture contents 55%slag with 0.6%polypropylene fiber for the cumulative fatigue stress.Fatigue properties are decreased as the stress level increasing,the higher frequency reduces the fatigue strength more than lower frequency at a constant stress level.展开更多
The workability and durability of a type of sustainable concrete made with steel slag powder were investigated. The hydrated products of cement paste with ground granulated blast furnace slag(GGBFS) alone or with a co...The workability and durability of a type of sustainable concrete made with steel slag powder were investigated. The hydrated products of cement paste with ground granulated blast furnace slag(GGBFS) alone or with a combined admixture of GGBFS-steel slag powder were investigated by X-ray diffraction(XRD). Furthermore, the mechanism of chemically activated steel slag powder was also studied. The experimental results showed that when steel slag powder was added to concrete, the slumps through the same time were lower. The initial and fi nal setting times were slightly retarded. The dry shrinkages were lower, and the abrasion resistance was better. The chemically activated steel slag powder could improve compressive strengths, resistance to chloride permeation and water permeation, as well as carbonization resistance. XRD patterns indicated that the activators enhanced the formation of calcium silicate hydrate(C-S-H) gel and ettringite(AFt). This research contributes to sustainable disposal of wastes and has the potential to provide several important environmental benefi ts.展开更多
In this experimental study,the impact of Portland cement replacement by ground granulated blast furnace slag(GGBFS)and micronized rubber powder(MRP)on the compressive,flexural,tensile strengths,and rapid chloride migr...In this experimental study,the impact of Portland cement replacement by ground granulated blast furnace slag(GGBFS)and micronized rubber powder(MRP)on the compressive,flexural,tensile strengths,and rapid chloride migration test(RCMT)of concrete were assessed.In this study,samples with different binder content and water to binder ratios,including the MRP with the substitution levels of 0%,2.5%and 5%,and the GGBFS with the substitution ratios of 0%,20%and 40%by weight of Portland cement were made.According to the results,in the samples containing slag and rubber powder in the early ages,on average,a 12.2%decrease in the mechanical characteristics of concrete was observed,nonetheless with raising the age of the samples,the impact of slag on reducing the porosity of concrete lowered the negative impact of rubber powder.Regarding durability characteristics,the RCMT results of the samples were enhanced by using rubber powder because of its insulation impact.Moreover,adding slag into the MRP-included mixtures results in a 23%reduction in the migration rate of the chloride ion averagely.At last,four mathematical statements were derived for the mechanical and durability of concrete containing the MRP and GGBFS utilizing the genetic programming method.展开更多
基金Funded by Natural Science Foundation of China (No. 59908007).
文摘The high strength concrete (HSC) was produced by partially replacing the normal portland cement with special ground granulated blast-furnace slag ( GGBS) ranging up to 60% . The effects of the GGBS on the flowabilityand mechanical properties of HSC were studied. The hydration process and microstructure characteristics were investigated by X-ray diffraction ( XRD) and scanning electron microscopy ( SEM), respectively. The test results indicate that the GGBS has especially supplementary effect on water reducing and excellent property of better control of lump loss. The concrete flowability increases remarkably with the increase of GGBS fineness and the replacement level in the range of 20% to 50% . The compressiae and splitting tensile strengths of HSC containing GGBS are higher than the corresponding strength of the control concrete at all ages .
基金Funded by the National Natural Science Foundation of China(No.51278167)the Research and Innovation Project for College Graduates of Jiangsu Province(No.CXZZ12_0238)the Natural Science Foundation of Jiangsu Province,China(No.BK.20131374)
文摘The effect of carbonation on fatigue performance of ground granulated blast-furnace slag concrete was investigated. Based on the static compression tests of carbonated GGBS-concrete, the correlation between carbonation depth and compressive strength was analyzed and an equation between carbonation depth and compressive strength was put forward. Meanwhile, fatigue S-N curves of various carbonation depths were fitted, and the infl uence of carbonation on fatigue life and strength was studied. Carbonation has a dual effect on the fatigue behavior of GGBS-concrete. A fatigue equation based on the depth of carbonation was established. Also, the probabilistic distribution of fatigue life of carbonated concrete at a given stress level was modeled by the two-parameter Weibull distribution.
基金supported by the National Natural Science Foundation of China (Grant No.50808045)Natural Science Foundation of Beijing(Grant No.2112024)Fok Ying Tung Education Foundation (GrantNo.132016)
文摘The effect of ground granulated blast-furnace slag(GGBFS) and silica fume(SF) on the chloride migration through concrete subjected to repeated loading was examined.Portland cement was replaced by 20%,30%,40% GGBFS and 5%,10% SF,respectively.Five times repeated loadings were applied to specimens,the maximum loadings were 40% and 80% of the axial cylinder compressive strength(f′c),respectively.Chloride migration through concretes was evaluated using the rapid chloride migration test and the chloride concentration in the anode chamber was measured.The results indicate that the transport number of chloride through concrete containing 20% and 30% GGBFS replacements and 5% and 10% SF replacements is lower than that of the control concrete,but 40% GGBFS replacement increases the transport number of chloride.Five loadings at 40% f′cor 80% f′c increase the transport number of chloride for all mixes investigated in this study.5% SF replacement has a very close effect on the chloride permeability of concrete with 20% GGBFS when concrete is subjected to 40% f′cor 80% f′c.
文摘A new hydraulic cementitious binder was developed by mainly utilizing industrial byproducts phosphogypsum(PG)and ground granulated blast furnace slag(GGBFS)with small addition of ordinary portland cement(OPC).The hydration process and microstructure were studied by X-ray diffraction(XRD) and scanning electronic microscopy(SEM).OPC hydrated first at early age to form primarily C-S-H gel,ettringite and calcium hydroxide(CH).GGBFS activated by CH and sulfate ions hydrated continuously at later age,producing more and more hydration products,C-S-H gel and ettringite.Thus the paste developed a denser microstructure and its strength increased.The 28 d compressive strength of the mixture of 50%PG,46% GGBFS and 4%OPC exceeded 45 MPa.The setting time was faster and 3 d and 7 d strength were higher when the proportion of OPC increased.But the 28 d strength decreased when OPC exceeded 4%due to large amount of ettringite formed at late hydration age which damaged the microstructure.
文摘Tensile strength of concrete were examined on its partial replacement of cement and sand using ground granulated blast furnace and quarry dust.The study examines its behaviour at different dimensions.This is to monitor the variation effect of these parameters on the growth rates of tensile to the optimum curing age.These include non linear conditions of tensile state,non-elastic and its brittle behaviour at all times as it express zero conditions in tension.This means that it has the ability to with stand pull force.It also reflects its weak ability to handle shear stress thus tends to cause deformation in material as it has poor elasticity.The reflection of its brittle influence the rate of tensile behaviour from concrete ductility.These are known to be a material on modern mechanics of concrete.These are also considered as quasi brittle material.This behaviour was reflected as the system considered evaluating the growth rate of tensile strength that replaced cement and sand with these locally sourced addictives.The developed model monitor other reflected influential parameters such as variation of concrete porosity due it compaction in placements,tensile behaviour reflects these effect that subject it to mechanical properties of concrete.The study expressed the reaction of these parameters in the simulation,the evaluation of these affected the details variation of tensile growth rate at different water cement ratios and curing age.The tensile behaviour that was monitored are based on these factors in the study.The derived model were validated with the a researcher results[24],and both parameters developed best fits correlation.The study is imperative because the system expressed the behaviour of tensile strength from concrete at different dimensions.Experts can applied these concept to monitor tensile behaviour considering these parameters in its growth rates.
基金This work was supported by the Creative Groups of Natural Science Foundation of Hubei Province(Grant No.2021CFA030).Onyekwena Chikezie Chimere is an awardee for the ANSO Scholarship 2020-PhD.Ishrat Hameed Alvi is a recipient of the 2021 PhD ANSO Scholarship.
文摘Dredged marine soils(DMS)have poor engineering properties,which limit their usage in construction projects.This research examines the application of reactive magnesia(rMgO)containing supplementary cementitious materials(SCMs)to stabilize DMS under ambient and carbon dioxide(CO_(2))curing conditions.Several proprietary experimental tests were conducted to investigate the stabilized DMS.Furthermore,the carbonation-induced mineralogical,thermal,and microstructural properties change of the samples were explored.The findings show that the compressive strength of the stabilized DMS fulfilled the 7-d requirement(0.7-2.1 MPa)for pavement and building foundations.Replacing rMgO with SCMs such as biochar or ground granulated blast-furnace slag(GGBS)altered the engineering properties and particle packing of the stabilized soils,thus influencing their performances.Biochar increased the porosity of the samples,facilitating higher CO_(2) uptake and improved ductility,while GGBS decreased porosity and increased the dry density of the samples,resulting in higher strength.The addition of SCMs also enhanced the water retention capacity and modified the pH of the samples.Microstructural analysis revealed that the hydrated magnesium carbonates precipitated in the carbonated samples provided better cementation effects than brucite formed during rMgO hydration.Moreover,incorporating SCMs reduced the overall global warming potential and energy demand of the rMgO-based systems.The biochar mixes demonstrated lower toxicity and energy consumption.Ultimately,the rMgO and biochar blend can serve as an environmentally friendly additive for soft soil stabilization and permanent fixation of significant amounts of CO_(2) in soils through mineral carbonation,potentially reducing environmental pollution while meeting urbanization needs.
文摘This work investigates durability of cement-free mortars with a binder comprised of ground granulated blast furnace slag (GGBFS) activated by high-calcium fly ash (HCFA) and sodium carbonate (Na<sub>2</sub>CO<sub>3</sub>): the soundness, sulfate resistance, alkali-silica reactivity and efflorescence factors are considered. Results of tests show that such mortars are resistant to alkali-silica expansion. Mortars are also sulfate-resistant when the amount of HCFA in the complex binder is within a limit of 10 wt%. The fineness of fly ash determines its’ ability to activate GGBFS hydration, and influence soundness of the binder, early strength development, sulfate resistance and efflorescence behavior. The present article is a continuation of authors’ work, previously published in MSA, Vol. 14, 240-254.
文摘High-calcium fly ash (HCFA)—a residue of high-temperature coal combustion at thermal power plants, in combination with sodium carbonate presents an effective hardening activator of ground granulated blast-furnace slag (GGBFS). Substitution of 10% - 30% of GGBFS by HCFA and premixing of 1% - 3% Na2CO3 to this dry binary binder was discovered to give mortar compression strength of 10 - 30 to 30 - 45 MPa at 7 and 28 days when moist cured at ambient temperature. High-calcium fly ash produced from low-temperature combustion of fuel, like in circulating fluidized bed technology, reacts with water readily and is itself a good hardening activator for GGBFS, so introduction of Na<sub>2</sub>CO<sub>3</sub> into such mix has no noticeable effect on the mortar strength. However, low-temperature HCFA has higher water demand, and the strength of mortar is compromised by this factor. As of today, our research is still ongoing, and we expect to publish more data on different aspects of durability of proposed GGBFS-HCFA binder later.
基金Supported by the National "863"Research Project of China(No.2002AA335050) ,the National Natural Science Foundation ofChina( No.50409011) and the High-level University ConstructionProject of South China University of Technology (No.B09-224)
文摘The effect of the ground granulated blast-furnace slag （GGBFS） addition, the modulus n （ mole ratio of SiO2 to Na2O） and the concentration of sodium silicate solution on the compressive strength of the material, i e alkali-activated carbonatite cementitious material （AACCM for short） was investigated. In addition, it is found that barium chloride has a satisfactory retarding effect on the setting of AACCM in which more than 20% （by mass） ground carbonatite was replaced by GGBFS. As a result, a cementitious material, in which ground carbonatite rock served as dominative starting material, with 3-day and 28-day compressive strength greater than 30 MPa and 60 MPa and with continuous strength gain beyond 90 days was obtained.
文摘To provide basic data for the reasonable mixing design of the alkali-activated (AA) foamed concrete as a thermal insulation material for a floor heating system, 9 concrete mixes with a targeted dry density less than 400 kg/m3 were tested. Ground granulated blast-furnace slag (GGBS) as a source material was activated by the following two types of alkali activators: 10% Ca(OH)2 and 4% Mg(NO3)2, and 2.5% Ca(OH)2 and 6.5% Na2SiO3. The main test parameters were water-to-binder (W/B) ratio and the substitution level (RFA) of fly ash (FA) for GGBS. Test results revealed that the dry density of AA GGBS foamed concrete was independent of the W/B ratio an RFA, whereas the compressive strength increased with the decrease in W/B ratio and with the increase in RFA up to 15%, beyond which it decreased. With the increase in the W/B ratio, the amount of macro capillaries and artificial air pores increased, which resulted in the decrease of compressive strength. The magnitude of the environmental loads of the AA GGBS foamed concrete is independent of the W/B ratio and RFA. The largest reduction percentage was found in the photochemical oxidation potential, being more than 99%. The reduction percentage was 87% - 93% for the global warming potential, 81% - 84% for abiotic depletion, 79% - 84% for acidification potential, 77% - 85% for eutrophication potential, and 73% - 83% for human toxicity potential. Ultimately, this study proved that the developed AA GGBS foamed concrete has a considerable promise as a sustainable construction material for nonstructural element.
基金supported by Chem Concrete Pty.Ltd.Australia,Abadgaran Negin Jonoobshargh Company(ANJ Co.),Iran(Grant No.118/3C-1399)。
文摘Lime and Portland cement are the most widely used binders in soil stabilization projects.However,due to the high carbon emission in cement production,research on soil stabilization by the use of more environmentally-friendly binders with lower carbon footprint has attracted much attention in recent years.This research investigated the potential of using alkali-activated ground granulated blast furnace slag(GGBS)and volcanic ash(VA)as green binders in clayey soil stabilization projects,which has not been studied before.The effects of different combinations of VA with GGBS,various liquid/solid ratios,different curing conditions,and different curing periods(i.e.7 d,28 d and 90 d)were investigated.Compressive strength and durability of specimens against wet-dry and freeze-thaw cycles were then studied through the use of mechanical and microstructural tests.The results demonstrated that the coexistence of GGBS and VA in geopolymerization process was more effective due to the synergic formation of N-A-S-H and C-(A)-S-H gels.Moreover,although VA needs heat curing to become activated and develop strength,its partial replacement with GGBS made the binder suitable for application at ambient temperature and resulted in a remarkably superior resistance against wet-dry and freeze-thaw cycles.The carbon embodied of the mixtures was also evaluated,and the results confirmed the low carbon footprints of the alkali-activated mixtures.Finally,it was concluded that the alkali-activated GGBS/VA could be promisingly used in clayey soil stabilization projects instead of conventional binders.
文摘In the present study,compressive strength,pore structure,thermal behavior and microstructure characteristics of concrete containing ground granulated blast furnace slag and TiO2 nanoparticles as binder were investigated.Portland cement was replaced by different amounts of ground granulated blast furnace slag and the properties of concrete specimens were investigated.Although it negatively impacts the properties of concrete at early ages,ground granulated blast furnace slag up to 45 wt% was found to improve the physical and mechanical properties of concrete at later ages.TiO2 nanoparticles with the average particle size of 15 nm were partially added to concrete with the optimum content of ground granulated blast furnace slag and physical and mechanical properties of the specimens were measured.TiO2 nanoparticle as a partial replacement of cement up to 3 wt% could accelerate C-S-H gel formation as a result of increased crystalline Ca(OH)2 amount at the early age of hydration and hence increase compressive strength of concrete.The increased TiO2 nanoparticles' content of more than 3 wt% may cause reduced compressive strength because of the decreased crystalline Ca(OH)2 content required for C-S-H gel formation and unsuitable dispersed nanoparticles in the concrete matrix.TiO2 nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and less-harm pores.
文摘In this work,strength assessments and percentage of water absorption of self compacting concrete containing ground granu-lated blast furnace slag (GGBFS) and Al2O3 nanoparticles as binder have been investigated.Portland cement was replaced by different amounts of GGBFS and the properties of concrete specimens were investigated.Although it negatively impacts the physical and mechanical properties of concrete at early ages of curing,GGBFS was found to improve the physical and me-chanical properties of concrete up to 45 wt% at later ages.Al2O3 nanoparticles with the average particle size of 15 nm were added partially to concrete with the optimum content of GGBFS and physical and mechanical properties of the specimens were measured.Al2O3 nanoparticle as a partial replacement of cement up to 3.0 wt% could accelerate C-S-H gel formation as a re-sult of increased crystalline Ca(OH)2 amount at the early ages and hence increase strength and improve the resistance to water permeability of concrete specimens.The increase of the Al2O3 nanoparticles’ content by more than 3.0 wt% would cause the reduction of the strength because of the decreased crystalline Ca(OH)2 content required for C-S-H gel formation.Several em-pirical relationships have been presented to predict flexural and split tensile strength of the specimens by means of the corre-sponding compressive strength at a certain age of curing.Accelerated peak appearance in conduction calorimetry tests,more weight loss in thermogravimetric analysis and more rapid appearance of the peaks related to hydrated products in X-ray dif-fraction results,all indicate that Al2O3 nanoparticles could improve mechanical and physical properties of the concrete speci-mens.
基金Funded by the National Science and Technology Support Plan (No.2006BAD11B03)Shaanxi Provincial Natural Science Foundation(No.SJ08E111)
文摘Properties and mechanism were investigated on flexural fatigue of concrete containing polypropylene fibers and ground granulated blast furnace slag(GGBFS).Four polypropylene fibers’volume fractions and five slag proportions were considered.An experiment was conducted to obtain the fatigue lives at three stress levels in 20 Hz frequency and at a constant stress level of 0.59 in four frequency respectively.Mechanism and evaluation were investigated based on the experimental data.Fatigue life span models were established.The results show that the addition of polypropylene fibers improves the flexural fatigue cumulative strength and fatigue life span.It is proposed that the slag particles and hydrated products improve Interfacial Transition Zone(ITZ)structure and benefit flexural fatigue performance.A composite reinforce effect is found with the incorporation of slag and polypropylene fibers.The optimum mixture contents 55%slag with 0.6%polypropylene fiber for the cumulative fatigue stress.Fatigue properties are decreased as the stress level increasing,the higher frequency reduces the fatigue strength more than lower frequency at a constant stress level.
基金Funded by the National Natural Science Foundation of China(Nos.51208370,51172164)the Fundamental Research Funds for the Central Universities(No.0500219170)
文摘The workability and durability of a type of sustainable concrete made with steel slag powder were investigated. The hydrated products of cement paste with ground granulated blast furnace slag(GGBFS) alone or with a combined admixture of GGBFS-steel slag powder were investigated by X-ray diffraction(XRD). Furthermore, the mechanism of chemically activated steel slag powder was also studied. The experimental results showed that when steel slag powder was added to concrete, the slumps through the same time were lower. The initial and fi nal setting times were slightly retarded. The dry shrinkages were lower, and the abrasion resistance was better. The chemically activated steel slag powder could improve compressive strengths, resistance to chloride permeation and water permeation, as well as carbonization resistance. XRD patterns indicated that the activators enhanced the formation of calcium silicate hydrate(C-S-H) gel and ettringite(AFt). This research contributes to sustainable disposal of wastes and has the potential to provide several important environmental benefi ts.
文摘In this experimental study,the impact of Portland cement replacement by ground granulated blast furnace slag(GGBFS)and micronized rubber powder(MRP)on the compressive,flexural,tensile strengths,and rapid chloride migration test(RCMT)of concrete were assessed.In this study,samples with different binder content and water to binder ratios,including the MRP with the substitution levels of 0%,2.5%and 5%,and the GGBFS with the substitution ratios of 0%,20%and 40%by weight of Portland cement were made.According to the results,in the samples containing slag and rubber powder in the early ages,on average,a 12.2%decrease in the mechanical characteristics of concrete was observed,nonetheless with raising the age of the samples,the impact of slag on reducing the porosity of concrete lowered the negative impact of rubber powder.Regarding durability characteristics,the RCMT results of the samples were enhanced by using rubber powder because of its insulation impact.Moreover,adding slag into the MRP-included mixtures results in a 23%reduction in the migration rate of the chloride ion averagely.At last,four mathematical statements were derived for the mechanical and durability of concrete containing the MRP and GGBFS utilizing the genetic programming method.
