To achieve higher strength and better durability,ultra-high performance concrete(UHPC)typically employs a relatively small water-binder ratio.However,this generally leads to an undesired increase in the paste viscosit...To achieve higher strength and better durability,ultra-high performance concrete(UHPC)typically employs a relatively small water-binder ratio.However,this generally leads to an undesired increase in the paste viscosity.In this study,the effects of liquid and powder polycarboxylate superplasticizers(PCE)on UHPC are compared and critically discussed.Moreover,the following influential factors are considered:air-entraining agents(AE),slump retaining agents(SA),and defoaming agents(DF)and the resulting flow characteristics,mechanical properties,and hydration properties are evaluated assuming UHPC containing 8‰powder PCE(PCE-based UHPC).It is found that the spread diameter of powder PCE is 5%higher than that of liquid PCE.Among the chemical admixtures studied,AEs have the best effect on improving UHPC workability,while DFs have the worst effect.When the addition of AE and SA is 1.25‰and 14.7%of PCE,paste viscosity reduces by 35%and 19%,respectively compared to the paste with only 8‰PCE.A low AE dosage(1.25‰)decreases compressive strength by 4.1%,while SA(8.1%)increases UHPC compressive strength by 9.1%.Both AE and SA significantly delay the UHPC hydration process,reducing the hydration heat release peaks by 76%and 27%,respectively.展开更多
A solution polymerization method has been used to synthesize a polyacrylic-type superabsorbent polymer(SAP).The influence of various influential factors,such as the temperature,neutralization degree,cross-linking agen...A solution polymerization method has been used to synthesize a polyacrylic-type superabsorbent polymer(SAP).The influence of various influential factors,such as the temperature,neutralization degree,cross-linking agent,and initiator,on the water absorption capacity of SAP has been investigated.The results show that the absorption can display a non-monotonic behavior depending on the synthesis conditions.The absorption can also change according to the pH,ion types and ion concentration.As the pH value increases,the water absorption capacity decreases significantly.It also decreases if the N^(a+)concentration becomes higher and becomes particularly low in solutions containing Mg^(2+).With the addition of SAP,the compressive strength of cement mortar decreases;the internal relative humidity can be maintained at 96%within 200 hours;and autogenous shrinkage can be reduced by nearly 69%.展开更多
The presence of impurities in phosphogypsum has long impeded its effective utilization,highlighting the need for energy-efficient and sustainable purification methods.This study proposes a novel purification strategy ...The presence of impurities in phosphogypsum has long impeded its effective utilization,highlighting the need for energy-efficient and sustainable purification methods.This study proposes a novel purification strategy that synergistically combines pH regulation and micelle-assisted treatment to create an optimized microenvironment for impurity removal.Under mechanical grinding conditions,this approach enhances the rheological properties of the phosphogypsumslurries and facilitates the dissolution and removal of impurity ions.Experimental results demonstrate that the synergistic method achieves a remarkable 64.01%increase in whiteness while significantly reducing soluble phosphorus and fluoride content in a single-step process.This technique not only achieves high purification efficiency but also offers a practical pathway for the high-value utilization of phosphogypsum.These findings suggest that this method has substantial potential for enhancing sustainable resource management and enabling broader industrial applications of purified phosphogypsum.展开更多
Styrene-butadiene-styrene(SBS)modified asphalt(SA)has long found effective applications in road construction materials.When combined with fillers,SBS-modified asphalt has demonstrated promising resistance to fatigue c...Styrene-butadiene-styrene(SBS)modified asphalt(SA)has long found effective applications in road construction materials.When combined with fillers,SBS-modified asphalt has demonstrated promising resistance to fatigue cracking caused by temperature fluctuations and aging.In this study,molybdenum disulfide(MoS_(2))and polyphosphoric acid(PPA)were ground in naphthenic oil(NO)and subjected to mechanical activation to create PPAmodified MoS_(2),referred to as OMS-PPA.By blending various ratios of OMS-PPA with SBS-modified asphalt,composite-modified asphalts were successfully developed to enhance their overall properties.To assess the mechanical characteristics and stability of these modified asphalts,various methods were employed,including penetration factor,flow activation energy,fluorescence microscopy,and dynamic shear rheology.Additionally,the short-term aging performance was evaluated using Fourier transform infrared(FTIR)spectroscopy and nanoindentation tests.The results revealed a 3.7%decrease in the penetration-temperature coefficient for SAOMS compared to SA,while 1-SA-OMS-PPA showed an even greater reduction of 7.1%.Furthermore,after short-term aging,carboxyl group generation in SA increased by 5.93%,while SA-OMS exhibited a smaller rise of 1.36%,and 1-SA-OMS-PPA saw an increase of just 0.93%.The study also highlighted significant improvements in the hardness of these materials.The hardness change ratio for SA-OMS decreased by 43.08%,while the ratio for 1-SA-OMS-PPA saw a notable reduction of 65.16% compared to unmodified SA.These findings suggest that OMS-PPA contributed to improvements in temperature sensitivity,particle dispersibility,and resistance to shortterm aging in asphalts.The results hold significant promise for the future development of advanced asphalt-based materials with potential high-value applications in flexible pavements for highways.展开更多
Phosphate tailings are usually used as backfill material in order to recycle tailings resources.This study considers the effect of the mix proportions of clinker-free binders on the fluidity,compressive strength and o...Phosphate tailings are usually used as backfill material in order to recycle tailings resources.This study considers the effect of the mix proportions of clinker-free binders on the fluidity,compressive strength and other key performances of cementitious backfill materials based on phosphate tailings.In particular,three solid wastes,phosphogypsum(PG),semi-aqueous phosphogypsum(HPG)and calcium carbide slag(CS),were selected to activate wet ground granulated blast furnace slag(WGGBS)and three different phosphate tailings backfill materials were prepared.Fluidity,rheology,settling ratio,compressive strength,water resistance and ion leaching behavior of backfill materials were determined.According to the results,when either PG or HPG is used as the sole activator,the fluidity properties of the materials are enhanced.Phosphate tailings backfill material activated with PG present the largest fluidity and the lowest yield stress.Furthermore,the backfill material’s compressive strength is considerably increased to 2.9 MPa at 28 days after WGGBS activation using a mix of HPG and CS,all with a settling ratio of only 1.15 percent.Additionally,all the three ratios of binder have obvious solidification effects on heavy metal ions Cu and Zn,and P in phosphate tailings.展开更多
Wet-milling in liquid-solid system can achieve ultra-fine mechanical dissociation of solid wastes with low energy consumption,thereby efficiently improving the potential pozzolanic reactivity.However,the wet-milling k...Wet-milling in liquid-solid system can achieve ultra-fine mechanical dissociation of solid wastes with low energy consumption,thereby efficiently improving the potential pozzolanic reactivity.However,the wet-milling kinetics of ultrafine dissociation in liquid-solid system has not been fully investigated.This paper systematically investigates the wet-milling kinetics of fly ash(FA).Results showed that before wet-milling of FA for 360 min,no agglomeration effect was observed.The particle dissociation of FA during wet-milling can be divided into three stages:rapid dissociation,slow dissociation and stabilization.The evolution process of particle size distribution during wet-milling is consistent with the Rosin-Rammler-Bennet distribution.Both the particle uniformity coefficient and fractal dimension showed highly positive linear correlation with the strength activity index of wet-milled FA.The grey correlation analysis showed that FA particles between 1.1 and 3.1μm had the greatest impact on both the early and late strength activity index.Simultaneously,D10 of wet-milled FA has the largest impact on strength activity index at each age,while D100 has the least impact.Therefore,D10 and proportion of particles in 1.1–3.1μm can be an important basis for judging the reactivity of wet-milled FA as ultrafine supplementary cementitious materials.展开更多
基金Key Research and Development Program of Hubei Province(2022BCA082 and 2022BCA077).
文摘To achieve higher strength and better durability,ultra-high performance concrete(UHPC)typically employs a relatively small water-binder ratio.However,this generally leads to an undesired increase in the paste viscosity.In this study,the effects of liquid and powder polycarboxylate superplasticizers(PCE)on UHPC are compared and critically discussed.Moreover,the following influential factors are considered:air-entraining agents(AE),slump retaining agents(SA),and defoaming agents(DF)and the resulting flow characteristics,mechanical properties,and hydration properties are evaluated assuming UHPC containing 8‰powder PCE(PCE-based UHPC).It is found that the spread diameter of powder PCE is 5%higher than that of liquid PCE.Among the chemical admixtures studied,AEs have the best effect on improving UHPC workability,while DFs have the worst effect.When the addition of AE and SA is 1.25‰and 14.7%of PCE,paste viscosity reduces by 35%and 19%,respectively compared to the paste with only 8‰PCE.A low AE dosage(1.25‰)decreases compressive strength by 4.1%,while SA(8.1%)increases UHPC compressive strength by 9.1%.Both AE and SA significantly delay the UHPC hydration process,reducing the hydration heat release peaks by 76%and 27%,respectively.
基金The authors would like to acknowledge the National Natural Science Foundation of China(51902095).
文摘A solution polymerization method has been used to synthesize a polyacrylic-type superabsorbent polymer(SAP).The influence of various influential factors,such as the temperature,neutralization degree,cross-linking agent,and initiator,on the water absorption capacity of SAP has been investigated.The results show that the absorption can display a non-monotonic behavior depending on the synthesis conditions.The absorption can also change according to the pH,ion types and ion concentration.As the pH value increases,the water absorption capacity decreases significantly.It also decreases if the N^(a+)concentration becomes higher and becomes particularly low in solutions containing Mg^(2+).With the addition of SAP,the compressive strength of cement mortar decreases;the internal relative humidity can be maintained at 96%within 200 hours;and autogenous shrinkage can be reduced by nearly 69%.
基金financially supported by the Key Research and Development Program of Hubei Province(No.2022BCA082 and No.2022BEC013).
文摘The presence of impurities in phosphogypsum has long impeded its effective utilization,highlighting the need for energy-efficient and sustainable purification methods.This study proposes a novel purification strategy that synergistically combines pH regulation and micelle-assisted treatment to create an optimized microenvironment for impurity removal.Under mechanical grinding conditions,this approach enhances the rheological properties of the phosphogypsumslurries and facilitates the dissolution and removal of impurity ions.Experimental results demonstrate that the synergistic method achieves a remarkable 64.01%increase in whiteness while significantly reducing soluble phosphorus and fluoride content in a single-step process.This technique not only achieves high purification efficiency but also offers a practical pathway for the high-value utilization of phosphogypsum.These findings suggest that this method has substantial potential for enhancing sustainable resource management and enabling broader industrial applications of purified phosphogypsum.
基金financially supported by the Key Research and Development Program of Hubei Province(Nos.2022BCA077 and 2022BCA082).
文摘Styrene-butadiene-styrene(SBS)modified asphalt(SA)has long found effective applications in road construction materials.When combined with fillers,SBS-modified asphalt has demonstrated promising resistance to fatigue cracking caused by temperature fluctuations and aging.In this study,molybdenum disulfide(MoS_(2))and polyphosphoric acid(PPA)were ground in naphthenic oil(NO)and subjected to mechanical activation to create PPAmodified MoS_(2),referred to as OMS-PPA.By blending various ratios of OMS-PPA with SBS-modified asphalt,composite-modified asphalts were successfully developed to enhance their overall properties.To assess the mechanical characteristics and stability of these modified asphalts,various methods were employed,including penetration factor,flow activation energy,fluorescence microscopy,and dynamic shear rheology.Additionally,the short-term aging performance was evaluated using Fourier transform infrared(FTIR)spectroscopy and nanoindentation tests.The results revealed a 3.7%decrease in the penetration-temperature coefficient for SAOMS compared to SA,while 1-SA-OMS-PPA showed an even greater reduction of 7.1%.Furthermore,after short-term aging,carboxyl group generation in SA increased by 5.93%,while SA-OMS exhibited a smaller rise of 1.36%,and 1-SA-OMS-PPA saw an increase of just 0.93%.The study also highlighted significant improvements in the hardness of these materials.The hardness change ratio for SA-OMS decreased by 43.08%,while the ratio for 1-SA-OMS-PPA saw a notable reduction of 65.16% compared to unmodified SA.These findings suggest that OMS-PPA contributed to improvements in temperature sensitivity,particle dispersibility,and resistance to shortterm aging in asphalts.The results hold significant promise for the future development of advanced asphalt-based materials with potential high-value applications in flexible pavements for highways.
基金the Key Research and Development Program of Hubei Province(2022BCA071)the Wuhan Science and Technology Bureau(2022020801020269).
文摘Phosphate tailings are usually used as backfill material in order to recycle tailings resources.This study considers the effect of the mix proportions of clinker-free binders on the fluidity,compressive strength and other key performances of cementitious backfill materials based on phosphate tailings.In particular,three solid wastes,phosphogypsum(PG),semi-aqueous phosphogypsum(HPG)and calcium carbide slag(CS),were selected to activate wet ground granulated blast furnace slag(WGGBS)and three different phosphate tailings backfill materials were prepared.Fluidity,rheology,settling ratio,compressive strength,water resistance and ion leaching behavior of backfill materials were determined.According to the results,when either PG or HPG is used as the sole activator,the fluidity properties of the materials are enhanced.Phosphate tailings backfill material activated with PG present the largest fluidity and the lowest yield stress.Furthermore,the backfill material’s compressive strength is considerably increased to 2.9 MPa at 28 days after WGGBS activation using a mix of HPG and CS,all with a settling ratio of only 1.15 percent.Additionally,all the three ratios of binder have obvious solidification effects on heavy metal ions Cu and Zn,and P in phosphate tailings.
基金supports from the National Natural Science Foundation of China(grant Nos.U23A20560,52172017)the Key Research and Development Program of Hubei Province(grant No.2022BCA071)the Wuhan Science and Technology Bureau(grant No.2022020801020269).
文摘Wet-milling in liquid-solid system can achieve ultra-fine mechanical dissociation of solid wastes with low energy consumption,thereby efficiently improving the potential pozzolanic reactivity.However,the wet-milling kinetics of ultrafine dissociation in liquid-solid system has not been fully investigated.This paper systematically investigates the wet-milling kinetics of fly ash(FA).Results showed that before wet-milling of FA for 360 min,no agglomeration effect was observed.The particle dissociation of FA during wet-milling can be divided into three stages:rapid dissociation,slow dissociation and stabilization.The evolution process of particle size distribution during wet-milling is consistent with the Rosin-Rammler-Bennet distribution.Both the particle uniformity coefficient and fractal dimension showed highly positive linear correlation with the strength activity index of wet-milled FA.The grey correlation analysis showed that FA particles between 1.1 and 3.1μm had the greatest impact on both the early and late strength activity index.Simultaneously,D10 of wet-milled FA has the largest impact on strength activity index at each age,while D100 has the least impact.Therefore,D10 and proportion of particles in 1.1–3.1μm can be an important basis for judging the reactivity of wet-milled FA as ultrafine supplementary cementitious materials.
