The soil construction materials cured with biopolymers are gradually being recognized and widely used in engineering areas,such as roadbeds or foundation fills.The strength of biopolymer-solidified soils(BSS)is easily...The soil construction materials cured with biopolymers are gradually being recognized and widely used in engineering areas,such as roadbeds or foundation fills.The strength of biopolymer-solidified soils(BSS)is easily influenced by the change of internal residual moisture content(RMC),however,the quantitative relationship between them remains unclear.Xanthan gum,as a representative of biopolymer,was used in this study to enhance the mechanical properties of silty sand dredged from the Yellow River under different initial water contents and curing temperatures.The unconfined compressive strength(UCS),curing time,water stability and microscopic properties of BSS were investigated via a series of indoor experiments.Results show that the proposed method for quantitatively evaluating the BSS strength using different RMC values was found to be workable compared to that of the traditional cement-treated method under different curing ages.The curing time required for BSS to reach a certain target strength,i.e.2900 kPa,is reduced to 9.3 h at a higher curing temperature of 90℃.Moreover,BSS exhibits the“self-healing”properties of strength recovery after re-temperature drying,with a strength recovery ratio above 45%.The control raw soil samples completely disintegrate in water within 10 s,and even lower xanthan gum biopolymer dosages,such as 0.5%,improved stability in water by reducing permeability by sealing the internal voids of the soil.SEM results indicate that the initial water content and curing temperature mainly affect the distribution of effective xanthan gum linkages,and thus significantly improve the strength and water stability of BSS.展开更多
In this context,an enzyme-induced magnesia carbonization(EIMC)method was proposed for practical healing of rock weathering cracks in term of bio-cementing sandstone grains.For this,a series of experiments were conduct...In this context,an enzyme-induced magnesia carbonization(EIMC)method was proposed for practical healing of rock weathering cracks in term of bio-cementing sandstone grains.For this,a series of experiments were conducted on EIMC mortar samples,and the physicomechanical properties were obtained.The effects of urea pre-hydrolysis time,mass ratio of liquid solution to magnesia,and urea concentration were analyzed.Experimental results indicated that the urea pre-hydrolysis based EIMC method had a better cementation ability of sandstone grain and greater crack surface bonding performance of sandstone than the existing microbial-induced magnesia carbonization(MIMC)method.The optimal bio-cementation conditions were of pre-hydrolysis time of 24 h,mass ratio of liquid solution to magnesia of 1.75,and urea concentration of 1 mol/L.Under these conditions,the peak tensile stress of EIMC mortar samples reached up to 948.45 kPa,and interfacial peak tensile stress of EIMC-sandstone samples reached 608.57 kPa.These values were 118.6%(799.97 kPa)and 123.2%(493.19 kPa)of those of samples bio-cemented by the MIMC method,respectively.The improved bio-cementation performance can be attributed to the pre-hydrolysis of urea,ensuring an adequate supply of CO_(3)^(2-) ions and promoting the magnesia hydration and the brucite carbonization.The increased production of hydrated magnesium carbonates,coupled with formation of the amorphous brucite facilitated by biomolecules,established a denser structure,enhancing the physicomechanical properties.Microcrack development near the interfacial zone of mortar and sandstone was an important factor in the reduced biocementation performance of the MIMC method.The EIMC method is a practical bio-healing method for rock weathering cracks due to the availability of urease and its good cementation properties.展开更多
This study proposed an improved bio-carbonation of reactive magnesia cement(RMC)method for dredged sludge stabilization using the urea pre-hydrolysis strategy.Based on unconfined compression strength(UCS),pickling-dra...This study proposed an improved bio-carbonation of reactive magnesia cement(RMC)method for dredged sludge stabilization using the urea pre-hydrolysis strategy.Based on unconfined compression strength(UCS),pickling-drainage,and scanning electron microscopy(SEM)tests,the effects of prehydrolysis duration(T),urease activity(UA)and curing age(CA)on the mechanical properties and microstructural characteristics of bio-carbonized samples were systematically investigated and analyzed.The results demonstrated that the proposed method could significantly enhance urea hydrolysis and RMC bio-carbonation to achieve efficient stabilization of dredged sludge with 80%high water content.A significant strength increment of up to about 1063.36 kPa was obtained for the bio-carbonized samples after just 7 d of curing,which was 2.64 times higher than that of the 28-day cured ordinary Portland cement-reinforced samples.Both elevated T and UA could notably increase urea utilization ratio and carbonate ion yield,but the resulting surge in supersaturation also affected the precipitation patterns of hydrated magnesia carbonates(HMCs),which weakened the cementation effect of HMCs on soil particles and further inhibited strength enhancement of bio-carbonized samples.The optimum formula was determined to be the case of T?24 h and UA?10 U/mL for dredged sludge stabilization.A 7-day CA was enough for bio-carbonized samples to obtain stable strength,albeit slightly affected by UA.The benefits of high efficiency and water stability presented the potential of this method in achieving dredged sludge stabilization and resource utilization.This investigation provides informative ideas and valuable insights on implementing advanced bio-geotechnical techniques to achieve efficient stabilization of soft soil,such as dredged sludge.展开更多
基金support provided by the Major science and technology program of Inner Mongolia,China(Grant No.2021ZD0007)National Natural Science Foundation of China(Grant Nos.51979267 and 52074143).
文摘The soil construction materials cured with biopolymers are gradually being recognized and widely used in engineering areas,such as roadbeds or foundation fills.The strength of biopolymer-solidified soils(BSS)is easily influenced by the change of internal residual moisture content(RMC),however,the quantitative relationship between them remains unclear.Xanthan gum,as a representative of biopolymer,was used in this study to enhance the mechanical properties of silty sand dredged from the Yellow River under different initial water contents and curing temperatures.The unconfined compressive strength(UCS),curing time,water stability and microscopic properties of BSS were investigated via a series of indoor experiments.Results show that the proposed method for quantitatively evaluating the BSS strength using different RMC values was found to be workable compared to that of the traditional cement-treated method under different curing ages.The curing time required for BSS to reach a certain target strength,i.e.2900 kPa,is reduced to 9.3 h at a higher curing temperature of 90℃.Moreover,BSS exhibits the“self-healing”properties of strength recovery after re-temperature drying,with a strength recovery ratio above 45%.The control raw soil samples completely disintegrate in water within 10 s,and even lower xanthan gum biopolymer dosages,such as 0.5%,improved stability in water by reducing permeability by sealing the internal voids of the soil.SEM results indicate that the initial water content and curing temperature mainly affect the distribution of effective xanthan gum linkages,and thus significantly improve the strength and water stability of BSS.
基金supported by the State Key Laboratory for Geo-Mechanics and Deep Underground Engineering,China University of Mining&Technology/China University of Mining&Technology,Beijing(Grant No.SKLGDUEK2214)the National Natural Science Foundation of China(Grant No.42477188)National Key Research and Development Program of China(Grant No.2023YFC3007102).
文摘In this context,an enzyme-induced magnesia carbonization(EIMC)method was proposed for practical healing of rock weathering cracks in term of bio-cementing sandstone grains.For this,a series of experiments were conducted on EIMC mortar samples,and the physicomechanical properties were obtained.The effects of urea pre-hydrolysis time,mass ratio of liquid solution to magnesia,and urea concentration were analyzed.Experimental results indicated that the urea pre-hydrolysis based EIMC method had a better cementation ability of sandstone grain and greater crack surface bonding performance of sandstone than the existing microbial-induced magnesia carbonization(MIMC)method.The optimal bio-cementation conditions were of pre-hydrolysis time of 24 h,mass ratio of liquid solution to magnesia of 1.75,and urea concentration of 1 mol/L.Under these conditions,the peak tensile stress of EIMC mortar samples reached up to 948.45 kPa,and interfacial peak tensile stress of EIMC-sandstone samples reached 608.57 kPa.These values were 118.6%(799.97 kPa)and 123.2%(493.19 kPa)of those of samples bio-cemented by the MIMC method,respectively.The improved bio-cementation performance can be attributed to the pre-hydrolysis of urea,ensuring an adequate supply of CO_(3)^(2-) ions and promoting the magnesia hydration and the brucite carbonization.The increased production of hydrated magnesium carbonates,coupled with formation of the amorphous brucite facilitated by biomolecules,established a denser structure,enhancing the physicomechanical properties.Microcrack development near the interfacial zone of mortar and sandstone was an important factor in the reduced biocementation performance of the MIMC method.The EIMC method is a practical bio-healing method for rock weathering cracks due to the availability of urease and its good cementation properties.
基金supported by the National Natural Science Foundation of China(Grant Nos.41925012 and 42230710)the Key Laboratory Cooperation Special Project of Western Cross Team of Western Light,CAS(Grant No.xbzg-zdsys-202107).
文摘This study proposed an improved bio-carbonation of reactive magnesia cement(RMC)method for dredged sludge stabilization using the urea pre-hydrolysis strategy.Based on unconfined compression strength(UCS),pickling-drainage,and scanning electron microscopy(SEM)tests,the effects of prehydrolysis duration(T),urease activity(UA)and curing age(CA)on the mechanical properties and microstructural characteristics of bio-carbonized samples were systematically investigated and analyzed.The results demonstrated that the proposed method could significantly enhance urea hydrolysis and RMC bio-carbonation to achieve efficient stabilization of dredged sludge with 80%high water content.A significant strength increment of up to about 1063.36 kPa was obtained for the bio-carbonized samples after just 7 d of curing,which was 2.64 times higher than that of the 28-day cured ordinary Portland cement-reinforced samples.Both elevated T and UA could notably increase urea utilization ratio and carbonate ion yield,but the resulting surge in supersaturation also affected the precipitation patterns of hydrated magnesia carbonates(HMCs),which weakened the cementation effect of HMCs on soil particles and further inhibited strength enhancement of bio-carbonized samples.The optimum formula was determined to be the case of T?24 h and UA?10 U/mL for dredged sludge stabilization.A 7-day CA was enough for bio-carbonized samples to obtain stable strength,albeit slightly affected by UA.The benefits of high efficiency and water stability presented the potential of this method in achieving dredged sludge stabilization and resource utilization.This investigation provides informative ideas and valuable insights on implementing advanced bio-geotechnical techniques to achieve efficient stabilization of soft soil,such as dredged sludge.
