A high strength self-compacting pervious concrete(SCPC) with top-bottom interconnected pores was prepared in this paper. The frost-resisting durability of such SCPC in different deicing salt concentrations(0%, 3%, 5%,...A high strength self-compacting pervious concrete(SCPC) with top-bottom interconnected pores was prepared in this paper. The frost-resisting durability of such SCPC in different deicing salt concentrations(0%, 3%, 5%, 10%, and 20%) was investigated. The mass-loss rate, relative dynamic modulus of elasticity, compressive strength, flexural strength and hydraulic conductivity of SCPC after 300 freeze-thaw cycles were measured to evaluate the frost-resisting durability. In addition, the microstructures of SCPC near the top-bottom interconnected pores after 300 freeze-thaw cycles were observed by SEM. The results show that the high strength SCPC possesses much better frost-resisting durability than traditional pervious concrete(TPC) after 300 freeze-thaw cycles, which can be used in heavy loading roads. The most serious freeze-thaw damage emerges in the SCPC immersed in the 3% of Na Cl solution, while there is no obvious damage in 20% of Na Cl solution. Furthermore, it can be deduced that the high strength SCPC can be used for 100 years in a cold environment.展开更多
Several cracks were found on the surface of the concrete foundations that support the steel towers of the Luohe (漯河)-Huaiyung (淮阳) high-voltage electricity transmission line that is 20 years old and situated i...Several cracks were found on the surface of the concrete foundations that support the steel towers of the Luohe (漯河)-Huaiyung (淮阳) high-voltage electricity transmission line that is 20 years old and situated in an inland salt lake environment in North China. To analyze the deterioration mechanism that led to this condition, field investigations were carried out and several tests were conducted on the soil and the affected concrete, including XRD (X-ray diffraction), electric probe analysis, and chemical analysis. The results show that the concentration of sulfates is very high (0. 39% wt. -0.67% wt. ) in both the surrounding soil and the material around the coarse aggregates inside the concrete. Hence, sulfate attack could be one of the main causes of concrete deterioration. The percentage of sulfates in the surface layer of the concrete was higher than that in the inner layers of the concrete. The sulfates penetrate into the concrete and react with the hydrates of cement to form ettringite (AFt), which leads to increase in the volume and cracking of the concrete.展开更多
On the basis of previous research results, the frost resistance of fully graded concrete and small wet sieving concrete specimens was compared and analyzed, and the characteristics and rules of freeze-thaw damage of h...On the basis of previous research results, the frost resistance of fully graded concrete and small wet sieving concrete specimens was compared and analyzed, and the characteristics and rules of freeze-thaw damage of hydraulic fully graded concrete after freeze-thaw cycles were analyzed through freeze-thaw test, impact-echo test, mechanical test and so on. Meanwhile, the damage characteristics of concrete in the salt and water freezing environment were compared. Through the mechanical test, it is found that the mechanical properties of both fully graded concrete and wet sieving concrete decreased to varying degrees after freeze-thaw cycles. The laws of uniaxial compression and tensile strength of concrete varying with the number of freeze-thaw cycles were obtained. The life of concrete after freeze-thaw cycles was predicted, and it is concluded that the life of concrete in the salt freezing environment was only 0.8 times that in the water freezing environment, proving once again that the damage of concrete in the salt freezing environment was more serious than that in the water freezing environment. Therefore, the grade of frost resistance should be improved appropriately for concrete engineering with salt solution. Finally, based on the damage theory and Lemaitre strain equivalence principle, the freeze-thaw damage evolution equation suitable for fully graded concrete was obtained.展开更多
In recent years,the winter temperature in southern China decreases year by year,and the phenomenon of freeze-thaw damage is also wide-spread in hydraulic buildings.In this paper,the freezing-thawing cycle tests of ful...In recent years,the winter temperature in southern China decreases year by year,and the phenomenon of freeze-thaw damage is also wide-spread in hydraulic buildings.In this paper,the freezing-thawing cycle tests of fully graded concrete specimens and corresponding wet sieving suitable for climate conditions in southern China were carried out,and the effects of freezing-thaw cycles on the appearance,mass loss,relative dynamic elastic modulus,internal temperature and strain of fully graded concrete and wet sieving concrete were studied.The splitting tensile strength test of concrete specimens with specified salt freezing cycles was carried out,and the relationship between the strength reduction of fully graded concrete and wet sieving concrete specimens and the number of freeze-thaw cycles was analyzed.The results show that with the increase of freeze-thaw cycles,the properties of fully graded concrete and wet sieving concrete degraded,and the degradation of compressive strength was the most significant,followed by the splitting tensile strength.In the initial stage of the freeze-thaw cycles,the degradation of each property was not obvious,and the deterioration rate of each property increased significantly after 100 freeze-thaw cycles.Besides,the relationship between the splitting tensile strength of fully graded concrete and wet sieving concrete and the internal wave velocity after freeze-thaw cycles was established.The test results can provide theoretical basis for the design,repair,maintenance and life prediction of dams and offshore platforms in southern China.展开更多
Several action regimes were employed, namely, those exposed to solutions containing single and/or composite chloride and sulfate salts, and under wet-dry cycles and/or flexural loading. The variations in dynamic modul...Several action regimes were employed, namely, those exposed to solutions containing single and/or composite chloride and sulfate salts, and under wet-dry cycles and/or flexural loading. The variations in dynamic modulus of elasticity(Erd values) were monitored, as well as the key factor impacting on the chloride ingress when concrete subjected to multiple action regimes was identified by the method of Grey Relation Analysis(GRA). The changes in micro-structures and mineral products of interior concrete after different action regimes were investigated by means of X-ray diffraction(XRD), mercury intrusion technique(MIP), and scanning electron microscopy(SEM). The test results showed that the cyclic wet-dry accelerated the deterioration of OPC concrete more than the action of 35% flexural loading based on the results of Erd values and the GEA. The analyses from micro-structures could give certain explanations to the change in Erd values under different action regimes.展开更多
The microscopic morphology and pore structure characteristics of concrete with composite admixtures(fly ash and mineral powder) after chlorine salt erosion were analyzed via scanning electron microscopy(SEM) and mercu...The microscopic morphology and pore structure characteristics of concrete with composite admixtures(fly ash and mineral powder) after chlorine salt erosion were analyzed via scanning electron microscopy(SEM) and mercury injection porosimetry(MIP), providing the basis for the design and maintenance of concrete shafts in coal mines. The above-mentioned characteristics were compared with the macroscopic characteristic of concrete fractures under uniaxial compression. The results show that the macroscopic fracture characteristics of concrete under uniaxial compression change from longitudinal split fracture and oblique section shear fracture to conjugate cant fracture, and the degree of breakage increases.Interface cracks, cement paste cracks, spherical surface cracks, and aggregate cracks appear in concrete under uniaxial compression. In the early stages of corrosion, the original cracks which are obvious are repaired. When the corrosion becomes more serious, cement paste cracks appear, and the number of harmful holes increases while the number of harmless holes decreases. This study also reveals the relationship between the macroscopic properties and microscopic structure of concrete under chloride salt erosion. Finally, the paper preliminarily discussed the relationship between the macroscopic properties and mesoscopic characteristics of concrete under chlorine salt erosion.展开更多
To improve watertightness and antibiosis of sewage structure concrete, the antimicrobial watertight admixture was made with fluosilicate salts and antimicrobial compounds. And fresh properties, watertightness, harmles...To improve watertightness and antibiosis of sewage structure concrete, the antimicrobial watertight admixture was made with fluosilicate salts and antimicrobial compounds. And fresh properties, watertightness, harmlessness and antibiosis of concrete were investigated experimentally. As a result, the fresh properties of concrete were similar to those of an ordinary concrete, without setting time delay. Compressive strength and carbonation resistance of concrete were better than those of an ordinary concrete. Finally it was confirmed that the antimicrobial watertight admixture of concrete had an antibiosis inhibiting SOB growth.展开更多
Concrete durability has become a hot research field in civil engineering. Concrete structures suffer salt-erosion damage to different degrees in the semi-arid region of North China. The environmental condition is one ...Concrete durability has become a hot research field in civil engineering. Concrete structures suffer salt-erosion damage to different degrees in the semi-arid region of North China. The environmental condition is one of the important factors affecting the durability of concrete constructions. To realize fully the interaction between various environmental factors, this paper researched concrete durability in the salt environment under combined actions(immersing, freeze–thaw cycles, and wet–dry cycles). According to the laboratory test data, the concrete-durability degradation law under coupling-effect factors was investigated. The results show that concrete's compressive strength decreases with the increase of salt concentration and immersion time. No matter what the environmental conditions were, the compressive strength-loss ratio increased with the test time. The compressive strength-test results indicate that sodium sulfate has the strongest corrosive effect on concrete durability, followed by calcium chloride, with sodium chloride having the weakest corrosion. Compared with the other two environmental factors, the wet–dry cycle is the key factor affecting concrete durability. Therefore, in engineering practice, the influence of environment conditions on the strength and durability of concrete should be taken into full consideration, especially in the wet–dry environment with salt conditions.展开更多
For the sake of understanding the deterioration behavior of concrete in actual railway tunnel structures subjected to aggressive sulfate medium in practice,detailed field investigations and tested analysis on sprayed ...For the sake of understanding the deterioration behavior of concrete in actual railway tunnel structures subjected to aggressive sulfate medium in practice,detailed field investigations and tested analysis on sprayed concrete linings of approximately 40-year-old railway tunnels in environments containing sulfate ion were carried out,respectively.The results show that the deterioration of concretes in the investigated area is serious,which involves complicated physicochemical process between the sulfate salt and concrete.Among them,the secondary sulfateminerals such as gypsum formation under very high concentration sulfate ion condition by accumulating and evaporation process dominate,followed by the crystallization of sulfate salt and formation of thaumasite.展开更多
Reinforcement corrosion directly affects the mechanical behavior of reinforced concrete structures.An electric corrosion test was conducted on a reinforced concrete test specimen,and a finite element model of the rein...Reinforcement corrosion directly affects the mechanical behavior of reinforced concrete structures.An electric corrosion test was conducted on a reinforced concrete test specimen,and a finite element model of the reinforcement corrosion damage was established.In addition,the damage behavior of reinforced concrete under different corrosion sediment distribution characteristics and different corrosion rates was studied.It was noted that when corrosion sediments are in a“semiellipse+semicircle”distribution,the results of numerical calculation are consistent with those obtained experimentally,reflecting the damage characteristics of reinforced concrete test specimens.Further,the results showed that the distribution characteristics of corrosion sediments greatly influence the damage behavior of reinforced concrete.In particular,when the corrosion sediments demonstrate a“semiellipse”distribution,reinforced concrete members may easily suffer from reinforcement damages.In the case of“semiellipse+semicircle”and“circle”distributions,the cohesive force between the reinforcements and concrete decreases:With the same corrosion rate,the damaged area expands with the increase in the number of reinforcements,which indicates a reduction in the cohesive force and thus,a reduction in the damage in the reinforcement area.This paper analyzes in-depth the effects of reinforcement corrosion expansion on the concrete damage behavior,provides references for practical engineering.展开更多
基于青海盐渍土地区埋地钢筋混凝土板现场模型试验,研究了考虑温度影响的盐渍土盐胀作用下钢筋混凝土板内及其表面的应力变化规律,并将其定义为“盐胀应力”。利用钢筋混凝土板内外应变监测结果,通过理论分析得出盐胀应力计算公式。基于...基于青海盐渍土地区埋地钢筋混凝土板现场模型试验,研究了考虑温度影响的盐渍土盐胀作用下钢筋混凝土板内及其表面的应力变化规律,并将其定义为“盐胀应力”。利用钢筋混凝土板内外应变监测结果,通过理论分析得出盐胀应力计算公式。基于Sum of sine函数模型将1年周期内盐胀应力的变化过程以及相对应的盐胀作用划分为发展阶段、稳定阶段、下降阶段3个阶段。其中发展阶段为每年10月至次年2月,温度变化范围为0~10℃,在该温度范围内,随着温度降低,盐胀应力不断增加,说明盐胀现象愈为强烈。对青海盐渍土地区的埋地结构物设计提出了建议,以期最大程度地减少盐渍土对埋地结构物的破坏。展开更多
基金Funded by the National Natural Science Foundation of China(No.51878081).
文摘A high strength self-compacting pervious concrete(SCPC) with top-bottom interconnected pores was prepared in this paper. The frost-resisting durability of such SCPC in different deicing salt concentrations(0%, 3%, 5%, 10%, and 20%) was investigated. The mass-loss rate, relative dynamic modulus of elasticity, compressive strength, flexural strength and hydraulic conductivity of SCPC after 300 freeze-thaw cycles were measured to evaluate the frost-resisting durability. In addition, the microstructures of SCPC near the top-bottom interconnected pores after 300 freeze-thaw cycles were observed by SEM. The results show that the high strength SCPC possesses much better frost-resisting durability than traditional pervious concrete(TPC) after 300 freeze-thaw cycles, which can be used in heavy loading roads. The most serious freeze-thaw damage emerges in the SCPC immersed in the 3% of Na Cl solution, while there is no obvious damage in 20% of Na Cl solution. Furthermore, it can be deduced that the high strength SCPC can be used for 100 years in a cold environment.
基金This paper is supported by China Postdoctoral Science Foundation(No.2005038542)and National"973"Project(No.2001CB610704-3).
文摘Several cracks were found on the surface of the concrete foundations that support the steel towers of the Luohe (漯河)-Huaiyung (淮阳) high-voltage electricity transmission line that is 20 years old and situated in an inland salt lake environment in North China. To analyze the deterioration mechanism that led to this condition, field investigations were carried out and several tests were conducted on the soil and the affected concrete, including XRD (X-ray diffraction), electric probe analysis, and chemical analysis. The results show that the concentration of sulfates is very high (0. 39% wt. -0.67% wt. ) in both the surrounding soil and the material around the coarse aggregates inside the concrete. Hence, sulfate attack could be one of the main causes of concrete deterioration. The percentage of sulfates in the surface layer of the concrete was higher than that in the inner layers of the concrete. The sulfates penetrate into the concrete and react with the hydrates of cement to form ettringite (AFt), which leads to increase in the volume and cracking of the concrete.
文摘On the basis of previous research results, the frost resistance of fully graded concrete and small wet sieving concrete specimens was compared and analyzed, and the characteristics and rules of freeze-thaw damage of hydraulic fully graded concrete after freeze-thaw cycles were analyzed through freeze-thaw test, impact-echo test, mechanical test and so on. Meanwhile, the damage characteristics of concrete in the salt and water freezing environment were compared. Through the mechanical test, it is found that the mechanical properties of both fully graded concrete and wet sieving concrete decreased to varying degrees after freeze-thaw cycles. The laws of uniaxial compression and tensile strength of concrete varying with the number of freeze-thaw cycles were obtained. The life of concrete after freeze-thaw cycles was predicted, and it is concluded that the life of concrete in the salt freezing environment was only 0.8 times that in the water freezing environment, proving once again that the damage of concrete in the salt freezing environment was more serious than that in the water freezing environment. Therefore, the grade of frost resistance should be improved appropriately for concrete engineering with salt solution. Finally, based on the damage theory and Lemaitre strain equivalence principle, the freeze-thaw damage evolution equation suitable for fully graded concrete was obtained.
文摘In recent years,the winter temperature in southern China decreases year by year,and the phenomenon of freeze-thaw damage is also wide-spread in hydraulic buildings.In this paper,the freezing-thawing cycle tests of fully graded concrete specimens and corresponding wet sieving suitable for climate conditions in southern China were carried out,and the effects of freezing-thaw cycles on the appearance,mass loss,relative dynamic elastic modulus,internal temperature and strain of fully graded concrete and wet sieving concrete were studied.The splitting tensile strength test of concrete specimens with specified salt freezing cycles was carried out,and the relationship between the strength reduction of fully graded concrete and wet sieving concrete specimens and the number of freeze-thaw cycles was analyzed.The results show that with the increase of freeze-thaw cycles,the properties of fully graded concrete and wet sieving concrete degraded,and the degradation of compressive strength was the most significant,followed by the splitting tensile strength.In the initial stage of the freeze-thaw cycles,the degradation of each property was not obvious,and the deterioration rate of each property increased significantly after 100 freeze-thaw cycles.Besides,the relationship between the splitting tensile strength of fully graded concrete and wet sieving concrete and the internal wave velocity after freeze-thaw cycles was established.The test results can provide theoretical basis for the design,repair,maintenance and life prediction of dams and offshore platforms in southern China.
基金Funded by the National Natural Science Foundation of China(51578141)the Major State Basic Research Development Program of China(973 Program)(2015CB655102)+1 种基金the Program Most of China(2016YFE0118200)the support of China Scholarship Council
文摘Several action regimes were employed, namely, those exposed to solutions containing single and/or composite chloride and sulfate salts, and under wet-dry cycles and/or flexural loading. The variations in dynamic modulus of elasticity(Erd values) were monitored, as well as the key factor impacting on the chloride ingress when concrete subjected to multiple action regimes was identified by the method of Grey Relation Analysis(GRA). The changes in micro-structures and mineral products of interior concrete after different action regimes were investigated by means of X-ray diffraction(XRD), mercury intrusion technique(MIP), and scanning electron microscopy(SEM). The test results showed that the cyclic wet-dry accelerated the deterioration of OPC concrete more than the action of 35% flexural loading based on the results of Erd values and the GEA. The analyses from micro-structures could give certain explanations to the change in Erd values under different action regimes.
基金The authors gratefully acknowledge the financial support for this work,provided by the Outstanding Youth Science Foundation of China(No.51322401)the Key Project of Chinese National Programs for Fundamental Research and Development of China(No.2015CB251601)+1 种基金the Science and Technology Project of the Chinese Ministry of Housing and Urban-Rural Construction of China(Nos.2013-K4-22 and 2014-K4-042)the General Program of Chinese National Building Materials Industry Technology Innovation Program of China(Nos.2014-M5-1 and 2014-M5-2)
文摘The microscopic morphology and pore structure characteristics of concrete with composite admixtures(fly ash and mineral powder) after chlorine salt erosion were analyzed via scanning electron microscopy(SEM) and mercury injection porosimetry(MIP), providing the basis for the design and maintenance of concrete shafts in coal mines. The above-mentioned characteristics were compared with the macroscopic characteristic of concrete fractures under uniaxial compression. The results show that the macroscopic fracture characteristics of concrete under uniaxial compression change from longitudinal split fracture and oblique section shear fracture to conjugate cant fracture, and the degree of breakage increases.Interface cracks, cement paste cracks, spherical surface cracks, and aggregate cracks appear in concrete under uniaxial compression. In the early stages of corrosion, the original cracks which are obvious are repaired. When the corrosion becomes more serious, cement paste cracks appear, and the number of harmful holes increases while the number of harmless holes decreases. This study also reveals the relationship between the macroscopic properties and microscopic structure of concrete under chloride salt erosion. Finally, the paper preliminarily discussed the relationship between the macroscopic properties and mesoscopic characteristics of concrete under chlorine salt erosion.
基金Brain Korea 2th (BK21) funded by the Korean Government
文摘To improve watertightness and antibiosis of sewage structure concrete, the antimicrobial watertight admixture was made with fluosilicate salts and antimicrobial compounds. And fresh properties, watertightness, harmlessness and antibiosis of concrete were investigated experimentally. As a result, the fresh properties of concrete were similar to those of an ordinary concrete, without setting time delay. Compressive strength and carbonation resistance of concrete were better than those of an ordinary concrete. Finally it was confirmed that the antimicrobial watertight admixture of concrete had an antibiosis inhibiting SOB growth.
基金supported by the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences (QYZDYSSW-DQC015)the funding of the State Key Laboratory of Frozen Soil Engineering (No. SKLFSE-ZT-17)
文摘Concrete durability has become a hot research field in civil engineering. Concrete structures suffer salt-erosion damage to different degrees in the semi-arid region of North China. The environmental condition is one of the important factors affecting the durability of concrete constructions. To realize fully the interaction between various environmental factors, this paper researched concrete durability in the salt environment under combined actions(immersing, freeze–thaw cycles, and wet–dry cycles). According to the laboratory test data, the concrete-durability degradation law under coupling-effect factors was investigated. The results show that concrete's compressive strength decreases with the increase of salt concentration and immersion time. No matter what the environmental conditions were, the compressive strength-loss ratio increased with the test time. The compressive strength-test results indicate that sodium sulfate has the strongest corrosive effect on concrete durability, followed by calcium chloride, with sodium chloride having the weakest corrosion. Compared with the other two environmental factors, the wet–dry cycle is the key factor affecting concrete durability. Therefore, in engineering practice, the influence of environment conditions on the strength and durability of concrete should be taken into full consideration, especially in the wet–dry environment with salt conditions.
基金Project(2008G025-C) supported by the Ministry of Railway of ChinaProject(50708114) supported by the National Natural Science Foundation of China
文摘For the sake of understanding the deterioration behavior of concrete in actual railway tunnel structures subjected to aggressive sulfate medium in practice,detailed field investigations and tested analysis on sprayed concrete linings of approximately 40-year-old railway tunnels in environments containing sulfate ion were carried out,respectively.The results show that the deterioration of concretes in the investigated area is serious,which involves complicated physicochemical process between the sulfate salt and concrete.Among them,the secondary sulfateminerals such as gypsum formation under very high concentration sulfate ion condition by accumulating and evaporation process dominate,followed by the crystallization of sulfate salt and formation of thaumasite.
基金We appreciate the support from National Natural Science Foundation of China Projects(Numbers 11672101,11372099 and 11132003)National Key Research and Development Program Project(Number:2017YFC1502603)Natural Science Foundation of Jiangsu Province(Number:BK20151493).
文摘Reinforcement corrosion directly affects the mechanical behavior of reinforced concrete structures.An electric corrosion test was conducted on a reinforced concrete test specimen,and a finite element model of the reinforcement corrosion damage was established.In addition,the damage behavior of reinforced concrete under different corrosion sediment distribution characteristics and different corrosion rates was studied.It was noted that when corrosion sediments are in a“semiellipse+semicircle”distribution,the results of numerical calculation are consistent with those obtained experimentally,reflecting the damage characteristics of reinforced concrete test specimens.Further,the results showed that the distribution characteristics of corrosion sediments greatly influence the damage behavior of reinforced concrete.In particular,when the corrosion sediments demonstrate a“semiellipse”distribution,reinforced concrete members may easily suffer from reinforcement damages.In the case of“semiellipse+semicircle”and“circle”distributions,the cohesive force between the reinforcements and concrete decreases:With the same corrosion rate,the damaged area expands with the increase in the number of reinforcements,which indicates a reduction in the cohesive force and thus,a reduction in the damage in the reinforcement area.This paper analyzes in-depth the effects of reinforcement corrosion expansion on the concrete damage behavior,provides references for practical engineering.
文摘基于青海盐渍土地区埋地钢筋混凝土板现场模型试验,研究了考虑温度影响的盐渍土盐胀作用下钢筋混凝土板内及其表面的应力变化规律,并将其定义为“盐胀应力”。利用钢筋混凝土板内外应变监测结果,通过理论分析得出盐胀应力计算公式。基于Sum of sine函数模型将1年周期内盐胀应力的变化过程以及相对应的盐胀作用划分为发展阶段、稳定阶段、下降阶段3个阶段。其中发展阶段为每年10月至次年2月,温度变化范围为0~10℃,在该温度范围内,随着温度降低,盐胀应力不断增加,说明盐胀现象愈为强烈。对青海盐渍土地区的埋地结构物设计提出了建议,以期最大程度地减少盐渍土对埋地结构物的破坏。