One of the ways of overcoming the cost of irrigation is through in-situ water harvesting at the plant roots. Super absorbent polymer (SAP) can facilitate water harvesting at the plant roots. This study attempted to as...One of the ways of overcoming the cost of irrigation is through in-situ water harvesting at the plant roots. Super absorbent polymer (SAP) can facilitate water harvesting at the plant roots. This study attempted to assess the effect of SAP on plant available water (PAW) of different soils. In this study, SAP was sequentially added at the rate of 0.2%, 0.3% and 0.5% of the soil weight and its impact assessed in clay, sandy clay and sandy loam soils. The moisture retention characteristics of the original and SAP treated soils were studied using soil water retention curves (SWRC) and results modelled using Gardner model. PAW was estimated from SWRC as the difference between moisture content at 1.5 and 3 bar in all soils. The difference in PAW between original and treated soils was assessed at 5% level of significance. The WRC of all the samples was adequately found to be described by the Gardner model (Coefficient of determination R<sup>2</sup> ≥ 98% and residual standard error (RSE) ≤ 0.04). SWRC changed with increase in SAP percentage in clay, sandy clay and sandy loam soils. Clay had a higher change in water retention then sandy clay and lastly sandy loam. Plant available water content (PAW) in all soils increased. In clay soil it increased with increase in SAP from 0.3291 at zero SAP to 0.6223 at 0.5% SAP. Sandy clay soil increased in PAW from 0.2721 at zero SAP to 0.5335 at 0.5% SAP and Sandy loam soils from 0.1691 at zero SAP to 0.3461 at 0.5% SAP. Hence, from the study SAP can be used to conserve irrigation water in the plant roots and therefore reducing the cost since PAW has been increased.展开更多
This paper studies the microstructure variation induced by super-absorbent polymer(SAP)to understand the mechanism of macroscopic strength improvement of stabilized soil.The fabric changes of cement elime stabilized s...This paper studies the microstructure variation induced by super-absorbent polymer(SAP)to understand the mechanism of macroscopic strength improvement of stabilized soil.The fabric changes of cement elime stabilized soil were analyzed with respect to the variation of SAP content,water content,lime content and curing time,using mercury intrusion porosimetry(MIP)tests.It can be observed that the delimitation pore diameter between inter-and intra-aggregate pores was 0.2 mm for the studied soil,determined through the intrusion/extrusion cycles.Experimental results showed that fabric in both inter-and intra-aggregate pores varied significantly with SAP content,lime content,water content and curing time.Two main changes in fabric due to SAP are identified as:(1)an increase in intra-aggregate pores(<0.2 mm)due to the closer soilecementelime cluster space at higher SAP content;and(2)a decrease in inter-aggregate pores represented by a reduction in small-pores(0.2e2 mm)due to the lower pore volume of soil mixture after water absorption by SAP,and a slight increase in large-pores(>2 mm)due to the shrinkage of SAP particle during the freezeedry process of MIP test.Accordingly,the strength gain due to SAP for cementelime stabilized soil was mainly due to a denser fabric with less interaggregate pores.The cementitious products gradually developed over time,leading to an increase in intra-aggregate pores with an increasing proportion of micro-pores(0.006e0.2 mm).Meanwhile,the inter-aggregate pores were filled by cementitious products,resulting in a decrease in total void ratio.Hence,the strength development over time is attributable to the enhancement of cementation bonding and the refinement of fabric due to the increasing cementitious compounds.展开更多
A super-absorbent polymer is prepared by graft polymerizing acrylamide (AM) onto potato starch using eerie ammonium nitrate (CAN) and N, N'-methylene-bis-acrylamide (bisAM) as an initiator and cross-linking agent ...A super-absorbent polymer is prepared by graft polymerizing acrylamide (AM) onto potato starch using eerie ammonium nitrate (CAN) and N, N'-methylene-bis-acrylamide (bisAM) as an initiator and cross-linking agent respectively, and then subjecting the potato starch- poly(acrylamide) (PAM) graft copolymer (SPAM) to alkaline saponification. The water absorbency (WA) of the sample is nearly 5000 g H2O/g for dry sample in 24 h at room temperature and is far larger than that of reported in the literature([1]). The variables affecting the WA were investigated and optimiz;ed, they were: concentrations of potato starch, AM, CAN and bisAM were 26.3 g/L, 1.14 mol/L, 10.3 mmol/L and 0.53 mmol/L, respectively. The amount of sodium hydroxide was 15 g and the temperatures of graft copolymerization and saponification reactions were 60 degrees C and 95 degrees C. The time of graft copolymerization and saponification reactions was 2 h, respectively.展开更多
Super-absorbent polymers(SAPs)are widely used chemical water-saving materials,which play an active role in the accumulation of soil water and the improvement of soil structure.Little is known about their performance w...Super-absorbent polymers(SAPs)are widely used chemical water-saving materials,which play an active role in the accumulation of soil water and the improvement of soil structure.Little is known about their performance with repeated usage or about factors influencing their efficiency under alternate wetting and drying cycles.In this study,various concentrations of SAP(0,0.1,0.2 and 0.3%)in soil following three continuous wetting and drying cycles(T1,T2 and T3),were studied to determine effects on soil structure stability and hydro-physical properties.The results indicated that the SAP improved soil water supply capacity under conditions of mild drought(T2)and sufficient irrigation(T3)at concentrations of 0.2 and 0.3%,but a reduction was observed under severe drought conditions(T1),which was negatively correlated with the SAP concentration.The physical adsorption of the SAP by soil and the chemical connection between the SAP and soil mineral colloids as Si-O-Si bonds,-OH bonds and different crystalline silica were the important factors that directly lead to the reduction of water retention capacities of the SAP with alternating wet and dry conditions.Compared with the control,the soil liquid phase ratios of the SAP treatments were increased by8.8-202.7%in the T1 and T2 cycles,which would have led to a decrease in the soil air phase ratios.After repeated wetting and drying cycles,the SAP treatments increased the amount of>0.25 mm soil aggregates and the contents of water-stable macro-aggregate(R_(0.25)),and decreased the amount of<0.053 mm soil aggregates,especially with higher concentrations of the SAP.Increases in mean weight diameter(MWD)and geometric mean diameter(GMD),and declines in fractal dimension(D)and unstable aggregates index(E_(LT))were all observed with the SAP treatments,which indicated an improvement in soil stability and structure.It was concluded that the distribution and stability of soil aggregates and soil water supply capacity was closely related to SAP concentration,soil moisture condition and the interaction between the SAP and soil particles.展开更多
In this paper, the addition of admixed superabsorbent polymer (SAP) improved the microstructure and durability-related properties in a cement-based system with supplementary materials. This is an important issue in re...In this paper, the addition of admixed superabsorbent polymer (SAP) improved the microstructure and durability-related properties in a cement-based system with supplementary materials. This is an important issue in real construction projects when good durability properties are required. This study investigates the effect of SAP on the systems using cement replacement by fly ash and silica fume considering the strength properties and durability properties of paste under sulfate attack of cement-based system. The replacement considered in the study was of 10% silica fume and 20% fly ash in each case, the dosage of SAP was 0.25% of the total amount of cementitious material. The results showed that the addition of SAP in the cement-based system improved the compressive strength and reduced expansion to sulfate attack. Scanning electron micrographs showed that utilization of fly ash with silica fume and silica fume with SAP resulted in a much denser microstructure, thereby, leading to an increase in compressive strength and lower expansion under sulfate attack.展开更多
In order to improve the tensile property, flexuralproperty and drying shrinkage of strain-hardening cementitiouscomposites （SHCC）, mixtures quantitatively modified withsuperabsorbent polymer （SAP） were investigate...In order to improve the tensile property, flexuralproperty and drying shrinkage of strain-hardening cementitiouscomposites （SHCC）, mixtures quantitatively modified withsuperabsorbent polymer （SAP） were investigated. Theuniaxial tensile test, the four-point bending test, thecompressive test, the drying shrinkage test and theenvironmental scanning electron microscope （ESEM） wereemployed to investigate the tensile strain capacity, flexuraldeformation capacity, compressive strength, drying shrinkage,crack width and self-healing of SHCC. The experimentalresults show that SHCC modified with SAP particles exhibitsexcellent ductility and deformability, and the tensile strain isup to about 4.5% and the average crack width is controlledaround 40 μm. Meanwhile, the drying shrinkage of SHCCmodified with SAP particles can reduce by about 60%.Furthermore, the self-healing behavior is observed in thecracks of specimen after three cycles of high-low relativehumidity curing, and the self-healing products can completelyfill the cracks of SHCC specimens modified with SAPparticles. It is, therefore, feasible to produce SHCC materialmodified with SAP particles, while simultaneously retaininghigher material ductility.展开更多
In order to improve the self-healing behavior and the recovery of mechanical properties of engineered cementitious composites(ECC),the approach of incorporating superabsorbent polymer(SAP)in mixtures is investigated.T...In order to improve the self-healing behavior and the recovery of mechanical properties of engineered cementitious composites(ECC),the approach of incorporating superabsorbent polymer(SAP)in mixtures is investigated.The rapid water penetration test and four-point bending test were conducted to evaluate the effects of self-healing on the water permeability and mechanical properties of pre-damaged ECC.The self-healing process and self-healing products were observed by the environment scanning electron microscope(ESEM)and energy dispersive X-ray spectroscopy(EDS).The experimental results show that all ECC mixtures exhibit excellent flexural capacity,meanwhile maintaining a crack width below 50μm.The incorporation of SAP particles in ECC can apparently improve the mechanical recovery of ECC mixtures after 10 healing curing cycles,such as flexural deformation and flexural stiffness.The flexural stiffness of ECC containing 4%SAP particles after self-healing can be recovered to 80%.The self-healing test results show that when the water permeability of ECC mixtures incorporating SAP particles is close to zero,only three healing cycles are needed.When ECC incorpora ting more SAP particles,the accelerated self-healing process can be finished in the first three cycles,and self-healing product is mixed Ca(OH)2/CaCO 3 with CaCO 3 being a major component in the later stage.It is,therefore,feasible to produce ECC materials incorporating SAP particles,while simultaneously maintaining higher material ductility and self-healing behavior.展开更多
The effectiveness of a superabsorbent polymer of sodium polyacrylate was studied, with emphasis on water management, i.e., absorption, retention and desorption in the soil. The polymer was applied in plots with a sand...The effectiveness of a superabsorbent polymer of sodium polyacrylate was studied, with emphasis on water management, i.e., absorption, retention and desorption in the soil. The polymer was applied in plots with a sandy soil near Grandola (southern Portugal). Characterization of the most relevant physical and chemical properties of the polymer was made, namely, its specific gravity, particle diameter, capacity of water absorption and desorption. In the plots with and without the polymer, soil moisture was continuously monitored, and grassland biomass samples were collected and weighed. The results reflected the effective role of the polymer both in the improvement of the water regime in the soil and in the substantial increment of grassland productivity.展开更多
文摘One of the ways of overcoming the cost of irrigation is through in-situ water harvesting at the plant roots. Super absorbent polymer (SAP) can facilitate water harvesting at the plant roots. This study attempted to assess the effect of SAP on plant available water (PAW) of different soils. In this study, SAP was sequentially added at the rate of 0.2%, 0.3% and 0.5% of the soil weight and its impact assessed in clay, sandy clay and sandy loam soils. The moisture retention characteristics of the original and SAP treated soils were studied using soil water retention curves (SWRC) and results modelled using Gardner model. PAW was estimated from SWRC as the difference between moisture content at 1.5 and 3 bar in all soils. The difference in PAW between original and treated soils was assessed at 5% level of significance. The WRC of all the samples was adequately found to be described by the Gardner model (Coefficient of determination R<sup>2</sup> ≥ 98% and residual standard error (RSE) ≤ 0.04). SWRC changed with increase in SAP percentage in clay, sandy clay and sandy loam soils. Clay had a higher change in water retention then sandy clay and lastly sandy loam. Plant available water content (PAW) in all soils increased. In clay soil it increased with increase in SAP from 0.3291 at zero SAP to 0.6223 at 0.5% SAP. Sandy clay soil increased in PAW from 0.2721 at zero SAP to 0.5335 at 0.5% SAP and Sandy loam soils from 0.1691 at zero SAP to 0.3461 at 0.5% SAP. Hence, from the study SAP can be used to conserve irrigation water in the plant roots and therefore reducing the cost since PAW has been increased.
基金the China Postdoctoral Science Foundation(Grant Nos.2016M600396 and 2017T100355)the Fundamental Research Funds for the Central Universities of China(Grant No.B200204001)Jiangsu Natural Resources Science and Technology Fund(Grant No.KJXM2019025)are also acknowledged.
文摘This paper studies the microstructure variation induced by super-absorbent polymer(SAP)to understand the mechanism of macroscopic strength improvement of stabilized soil.The fabric changes of cement elime stabilized soil were analyzed with respect to the variation of SAP content,water content,lime content and curing time,using mercury intrusion porosimetry(MIP)tests.It can be observed that the delimitation pore diameter between inter-and intra-aggregate pores was 0.2 mm for the studied soil,determined through the intrusion/extrusion cycles.Experimental results showed that fabric in both inter-and intra-aggregate pores varied significantly with SAP content,lime content,water content and curing time.Two main changes in fabric due to SAP are identified as:(1)an increase in intra-aggregate pores(<0.2 mm)due to the closer soilecementelime cluster space at higher SAP content;and(2)a decrease in inter-aggregate pores represented by a reduction in small-pores(0.2e2 mm)due to the lower pore volume of soil mixture after water absorption by SAP,and a slight increase in large-pores(>2 mm)due to the shrinkage of SAP particle during the freezeedry process of MIP test.Accordingly,the strength gain due to SAP for cementelime stabilized soil was mainly due to a denser fabric with less interaggregate pores.The cementitious products gradually developed over time,leading to an increase in intra-aggregate pores with an increasing proportion of micro-pores(0.006e0.2 mm).Meanwhile,the inter-aggregate pores were filled by cementitious products,resulting in a decrease in total void ratio.Hence,the strength development over time is attributable to the enhancement of cementation bonding and the refinement of fabric due to the increasing cementitious compounds.
文摘A super-absorbent polymer is prepared by graft polymerizing acrylamide (AM) onto potato starch using eerie ammonium nitrate (CAN) and N, N'-methylene-bis-acrylamide (bisAM) as an initiator and cross-linking agent respectively, and then subjecting the potato starch- poly(acrylamide) (PAM) graft copolymer (SPAM) to alkaline saponification. The water absorbency (WA) of the sample is nearly 5000 g H2O/g for dry sample in 24 h at room temperature and is far larger than that of reported in the literature([1]). The variables affecting the WA were investigated and optimiz;ed, they were: concentrations of potato starch, AM, CAN and bisAM were 26.3 g/L, 1.14 mol/L, 10.3 mmol/L and 0.53 mmol/L, respectively. The amount of sodium hydroxide was 15 g and the temperatures of graft copolymerization and saponification reactions were 60 degrees C and 95 degrees C. The time of graft copolymerization and saponification reactions was 2 h, respectively.
基金supported by the National Natural Science Foundation of China(41601226)the Agricultural Science and Technology Innovation Project of the Chinese Academy of Agricultural Sciences。
文摘Super-absorbent polymers(SAPs)are widely used chemical water-saving materials,which play an active role in the accumulation of soil water and the improvement of soil structure.Little is known about their performance with repeated usage or about factors influencing their efficiency under alternate wetting and drying cycles.In this study,various concentrations of SAP(0,0.1,0.2 and 0.3%)in soil following three continuous wetting and drying cycles(T1,T2 and T3),were studied to determine effects on soil structure stability and hydro-physical properties.The results indicated that the SAP improved soil water supply capacity under conditions of mild drought(T2)and sufficient irrigation(T3)at concentrations of 0.2 and 0.3%,but a reduction was observed under severe drought conditions(T1),which was negatively correlated with the SAP concentration.The physical adsorption of the SAP by soil and the chemical connection between the SAP and soil mineral colloids as Si-O-Si bonds,-OH bonds and different crystalline silica were the important factors that directly lead to the reduction of water retention capacities of the SAP with alternating wet and dry conditions.Compared with the control,the soil liquid phase ratios of the SAP treatments were increased by8.8-202.7%in the T1 and T2 cycles,which would have led to a decrease in the soil air phase ratios.After repeated wetting and drying cycles,the SAP treatments increased the amount of>0.25 mm soil aggregates and the contents of water-stable macro-aggregate(R_(0.25)),and decreased the amount of<0.053 mm soil aggregates,especially with higher concentrations of the SAP.Increases in mean weight diameter(MWD)and geometric mean diameter(GMD),and declines in fractal dimension(D)and unstable aggregates index(E_(LT))were all observed with the SAP treatments,which indicated an improvement in soil stability and structure.It was concluded that the distribution and stability of soil aggregates and soil water supply capacity was closely related to SAP concentration,soil moisture condition and the interaction between the SAP and soil particles.
文摘In this paper, the addition of admixed superabsorbent polymer (SAP) improved the microstructure and durability-related properties in a cement-based system with supplementary materials. This is an important issue in real construction projects when good durability properties are required. This study investigates the effect of SAP on the systems using cement replacement by fly ash and silica fume considering the strength properties and durability properties of paste under sulfate attack of cement-based system. The replacement considered in the study was of 10% silica fume and 20% fly ash in each case, the dosage of SAP was 0.25% of the total amount of cementitious material. The results showed that the addition of SAP in the cement-based system improved the compressive strength and reduced expansion to sulfate attack. Scanning electron micrographs showed that utilization of fly ash with silica fume and silica fume with SAP resulted in a much denser microstructure, thereby, leading to an increase in compressive strength and lower expansion under sulfate attack.
基金The National Natural Science Foundation of China(No.51278097)Start-up Grant provided by Nanyang Technological University(No.M4081208)
文摘In order to improve the tensile property, flexuralproperty and drying shrinkage of strain-hardening cementitiouscomposites （SHCC）, mixtures quantitatively modified withsuperabsorbent polymer （SAP） were investigated. Theuniaxial tensile test, the four-point bending test, thecompressive test, the drying shrinkage test and theenvironmental scanning electron microscope （ESEM） wereemployed to investigate the tensile strain capacity, flexuraldeformation capacity, compressive strength, drying shrinkage,crack width and self-healing of SHCC. The experimentalresults show that SHCC modified with SAP particles exhibitsexcellent ductility and deformability, and the tensile strain isup to about 4.5% and the average crack width is controlledaround 40 μm. Meanwhile, the drying shrinkage of SHCCmodified with SAP particles can reduce by about 60%.Furthermore, the self-healing behavior is observed in thecracks of specimen after three cycles of high-low relativehumidity curing, and the self-healing products can completelyfill the cracks of SHCC specimens modified with SAPparticles. It is, therefore, feasible to produce SHCC materialmodified with SAP particles, while simultaneously retaininghigher material ductility.
基金The National Natural Science Foundation of China(No.51278097)Start-up Grant Provided by Nanyang Technological University(No.M4081208)
文摘In order to improve the self-healing behavior and the recovery of mechanical properties of engineered cementitious composites(ECC),the approach of incorporating superabsorbent polymer(SAP)in mixtures is investigated.The rapid water penetration test and four-point bending test were conducted to evaluate the effects of self-healing on the water permeability and mechanical properties of pre-damaged ECC.The self-healing process and self-healing products were observed by the environment scanning electron microscope(ESEM)and energy dispersive X-ray spectroscopy(EDS).The experimental results show that all ECC mixtures exhibit excellent flexural capacity,meanwhile maintaining a crack width below 50μm.The incorporation of SAP particles in ECC can apparently improve the mechanical recovery of ECC mixtures after 10 healing curing cycles,such as flexural deformation and flexural stiffness.The flexural stiffness of ECC containing 4%SAP particles after self-healing can be recovered to 80%.The self-healing test results show that when the water permeability of ECC mixtures incorporating SAP particles is close to zero,only three healing cycles are needed.When ECC incorpora ting more SAP particles,the accelerated self-healing process can be finished in the first three cycles,and self-healing product is mixed Ca(OH)2/CaCO 3 with CaCO 3 being a major component in the later stage.It is,therefore,feasible to produce ECC materials incorporating SAP particles,while simultaneously maintaining higher material ductility and self-healing behavior.
文摘The effectiveness of a superabsorbent polymer of sodium polyacrylate was studied, with emphasis on water management, i.e., absorption, retention and desorption in the soil. The polymer was applied in plots with a sandy soil near Grandola (southern Portugal). Characterization of the most relevant physical and chemical properties of the polymer was made, namely, its specific gravity, particle diameter, capacity of water absorption and desorption. In the plots with and without the polymer, soil moisture was continuously monitored, and grassland biomass samples were collected and weighed. The results reflected the effective role of the polymer both in the improvement of the water regime in the soil and in the substantial increment of grassland productivity.
