Durability Model of Exposed Concrete On-Site Based on Dual Coupling Factors

Yong Fu,Hongxia Qiao,Chenggong Lu,Theogene Hakuzweyezu,Fei Guo 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.1

Aiming at the problem that the reliability analysis of the outdoor exposed concrete structure under the action of a single factor is not consistent with the actual service environment, a reliability analysis based on the Copula function describing multiple degradation factors is proposed. According to the actual data collected on-site, the relative quality evaluation parameters (RQEP) and relative dynamic elastic modulus evaluation parameters (RDEMEP) was selected as the key degradation indicators, and the Aperture Information Criterion (AIC) was used to determine the optimal marginal distribution function in different degradation trajectories, and obtain the most optimal edge distribution function under a single factor. Optimize the edge distributions reliability curve, establish the relationship between the edge distributions through the Copula function, and couple the edge distributions of the remaining life of the concrete to obtain the joint reliability function of the concrete under the action of the coupling factors. The results show that the selection of two degradation indicators, RQEP and RDEMEP, is helpful in establishing the concrete life prediction model in the field exposure environment, and the RDEMEP are more sensitive to the field exposure environment than the RQEP. The Gumbel Copula distribution function can reasonably predict the reliability of exposed concrete on-site under dual coupling factors. The service life of C40 and C50 exposed concrete on site is about 400 and 550 months, respectively.

Accelerated life testing of concrete based on stochastic approach and assessment

Binrong Zhu,Hongxia Qiao,Qiong Feng,Chenggong Lu 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.1

This study aimed to design the accelerated life testing (ALT) of concrete, which stimulating the special natural environment maximumly. Its evaluation indexes, such as dynamic elastic modulus, mass and ultrasonic velocity were measured, and the variation of relative mass and relative dynamic elastic modulus of concrete were studied. Meanwhile, the microanalysis method was used. Moreover, an exploratory application of the stochastic approach, the Weibull distribution and the lognormal distribution, were made to assess the durability of concrete structures. The results show that the ALT for simulating natural environment is more close to the service process of concrete structure under actual conditions; The relative dynamic elastic modulus can be used as the dominant durability evaluation parameters, because it is more sensitive to the environmental factors compared with the relative quality evaluation parameters; In the course of the concrete deterioration, the destruction of the salt freezing cycle is the dominant factor, supplemented by other factors; Both of those two stochastic approaches can be used to evaluate the reliability of concrete specimens under the condition of ALT; By comparison, The lognormal distribution method is better to describe the reliability process.

Visual Analysis of the Protective Effect of Asphalt Coating on MOCC against Steel Corrosion and Rust Crack Formation

Penghui Wang,Hongxia Qiao,Qiong Feng,Cuizhen Xue 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.2

The constant current energization accelerated test was carried out to study the effect of asphalt coating on delaying reinforcement corrosion and rust-induced cracks in coated reinforced magnesium oxychloride cement concrete (CRMOCC). CRMOCC with different degrees of damage was scanned by adopting X-ray computed tomography (X-CT) technology, and the spatial information of rust and rust-induced cracks were analyzed visually and quantitatively. In addition, Scanning Electron Microscope (SEM) was used to analyze the non-uniformity of rust-induced crack formation. The results showed that the corrosion amount of coated reinforcement after energization was only 81.6% of that of uncoated reinforcement. Besides, no crack no cracking was observed on CRMOCC after 480h’s energization, while the rust-induced crack of reinforced magnesium oxychloride cement concrete (RMOCC) was 0.11 mm. The coating reduced the potential of rust-induced crack formation such that only three areas in CRMOCC were cracked, while RMOCC had cracks in eight areas. This study also found that interface transition zone (ITZ) played a dominant role in the formation of rust-induced cracks. The surface crack width in CRMOCC had an exponential relation with the crack volume and it had a linear relation with the volume of corrosion products. Further, there was an exponential relation between the volume loss of the reinforcement and the formation of rust-induced cracks. The correlation between surface crack width, corrosion products volume, rust-induced cracks volume and steel volume can be described by quadric surface. Results by SEM analysis indicated that in the ITZ of CRMOCC, Mg and O elements were the two main elements in the hydration products that were loose and needle-like. Furthermore, Si and O elements were the dominant materials in the non-interface transition zone (NITZ), resulting in relatively dense hydration products.

Life Prediction and Long-Term Durability of Coated Steel Bars in Magnesium Oxychloride Concrete

Penghui Wang,Hongxia Qiao,Kefan Chen,Yuanke Li,Qiong Feng 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.7

The solution to the problem of corrosion of the steel bars in magnesium oxychloride cement concrete (MOCC) is to apply a coating that protects the steel. To investigate the coating’s long-term protective effect on the steel, a solution immersion accelerated corrosion test was carried out on coated reinforced MOCC for up to 2,160 days. Electrochemical tests were conducted every 90 days to measure the polarization curve and AC impedance during the steel bars’ corrosion process. Then, the corrosion current density that characterizes the corrosion of a coated steel bar was used as a degradation index, and the time to the coated steel bar’s corrosion was predicted based on the Wiener function. It was concluded that after 2,160 days of solution immersion, the coated steel bars’ corrosion current density was 0.063 μA·cm−2, indicating that the coating protected the steel bars in MOCC from corrosion well. Thdroughout the immersion process, the specimen’s corrosion current density showed a steady and increasing trend, and its polarization impedance showed a volatile growth trend. The degradation of the coated steel bars also obeyed the Wiener degradation process, and the bars reached a severely rusted state at 21,800d with a corrosion time of R0.6(t) is 10,650d.

Prediction of steel corrosion in magnesium cement concrete based on two dimensional Copula function

Qiong Feng,Hongxia Qiao,Penghui Wang,Wei Gong 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.2

In order to solve the life prediction problem of damaged coating steel bar in magnesium cement concrete, this study tries to establish the marginal distribution function by using the corrosion current density as a single degradation factor. Representing the degree of steel corrosion, the corrosion current density were tested in electrochemical workstation. Then based on the Copula function, the joint distribution function of the damaged coating was established. Therefore, it is indicated that the corrosion current density of the bare steel and coated steel bar can be used as the boundary element to establish the marginal distribution function. By using the Frank-Copula function of Copula Archimedean function family, the joint distribution function of the damaged coating steel bar was successfully established. Finally, the life of the damaged coating steel bar has been lost in 7320d. As a new method for the corrosion of steel bar under the multi-dimensional factors, the two-dimensional Copula function has certain practical significance by putting forward some new ideas.

Life Prediction Model of Nano-CaCO3 Modified Concrete in Sulfate Environment

Theogene Hakuzweyezu,Hongxia Qiao,Chenggong Lu,Bo Yang,Kan Li 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.8

In the saline soil environment, the salts corrode the ordinary cement concrete seriously, and concrete structures deteriorate gradually until it fails, which impedes the practical application of ordinary Portland cement concrete in this area. Aiming at the durability problems of concrete in a harsh environment, this paper selects the coefficient of compressive strength, coefficient of flexural strength, relative dynamic elastic modulus, and relative mass to jointly evaluate the resistance of nano-CaCO3 modified concrete to sulfate corrosion. More importantly, the Wiener process for modeling the degradation process of concrete specimens was used to obtain the remaining life's reliability function. The results indicated that adding 1% nano-CaCO3 (Nano Calcium Carbonate) can enhance the resistance of concrete to sulfate corrosion, and the service life of concrete will increase significantly. The Random Wiener process can effectively predict the durability deterioration process of concrete specimens. By integrating the deterioration process's life data, this method's reliability function may directly reflect the concrete's life.

Accelerated Life Testing of Concrete based on Three-parameter Weibull Stochastic Approach

Xiangke Guo,Hongxia Qiao,Binrong Zhu,Penghui Wang,Shaoyong Wen 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.4

Due to the time-varying characteristics of the durability of a concrete structure, a long duration of exposure and monitoring in natural conditions is required. The present research provided the indoor accelerated life testing of concrete, which simulated the special natural environments in the Xining area, including solar radiation, dry-wet circulation, freeze-thaw cycle, and salt corrosion. The measured dynamic modulus was taken as an evaluation index for the durability of concrete, and the change of the relative dynamic modulus of the specimen was studied. Meanwhile, a two-parameter Weibull distribution and three-parameter Weibull distribution were proposed based on the stochastic analysis method in order to assess the durability of concrete structure. It has been observed that the indoor accelerated life testing of concrete can make up for the shortcomings of long-term exposure under natural conditions. The variation of the relative dynamic modulus can effectively reflect the durability of the concrete degradation process. By contrasting two methods of stochastic analysis, the three-parameter Weibull distribution method is better to fit the accelerated lifedata of concrete specimens and to evaluate the durability of concrete structures during service.

Research on Enhancing the Corrosion Resistance of Concrete In a MgSO 4 Corrosive Environment Using CTF Synergist

Xi Wang,Hongxia Qiao,Yunsheng Zhang,Wenhua Zhang,Cuizhen Xue,Mubita Majory Mundia,Lei Zhang 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.4

Concrete structure is easy to be damaged by corrosion in natural environment. In order to find a new way to improve the corrosion resistance of concrete. In this paper, the effect of Coal Tar Fuel (CTF) synergist on the corrosion resistance of concrete was analyzed by using MgSO4solution with concentration of 5% as corrosion medium. The change rule of concrete pore structure was studied. And the performance of concrete interfacial transition zone (ITZ) is studied. Finally, the effect of CTF synergist on hydration reaction of cementitious materials was revealed. The results show that the addition of 0.7% CTF synergist can significantly enhance the corrosion resistance of concrete, even with 10% reduction in cement dosage. After 28 days of being cured under this dosage, there is 13.54% increase in the proportion of pores with a diameter less than 100 μm and a 5.36% decrease in the proportion of pores with a diameter greater than 600 μm. Meanwhile, the microhardness of ITZ increases by 41.14%, while the width of ITZ decreases by 12.5%. Additionally, there is a reduction in the maximum crack width at the interface between ITZ and aggregate by 1.8 μm. The exothermic reaction of the cementitious material during hydration is more pronounced when the hydration time exceeds one hour.

Age quadratically affects intestinal calcium and phosphorus transporter gene expression in broiler chickens

Lv, Xianliang,Hao, Junfang,Wu, Lihua,Liu, Mengyuan,He, Lei,Qiao, Yingying,Cui, Yanyan,Wang, Guan,Zhang, Chunmei,Qu, Hongxia,Han, Jincheng Asian Australasian Association of Animal Productio 2022 Animal Bioscience Vol.35 No.12

Objective: This research aimed to evaluate the effects of age on growth, tibia development, and intestinal calcium (Ca) and phosphorus (P) transporter gene expressions in broiler chickens. Methods: A total of 224 male Arbor Acres broilers were fed with nutrient-adequate diets and reared in eight cages (28 broilers per cage). Eight broilers (one broiler per cage) were selected and killed at 5, 10, 15, 20, 25, 30, 35, and 40 days of age, respectively. Results: Body weight continuously increased with age of broiler chickens from 5 to 40 days. The bone weight, ash weight, diameter, and length of the tibia also increased with broiler age. By contrast, the tibia ash, Ca, and P percentages quadratically changed with age (p<0.001), and the highest values of mineral contents were observed at 20, 25, and 25 days of age, respectively. The mRNA abundances of calcium-binding protein 28-kDa (CaBP-D28k), sodium-calcium exchanger 1 (NCX1), and plasma membrane ATPase 1b (PMCA1b) increased from 5 to 25 days and then decreased up to 40 days. Similar results were noted in the mRNA abundances of IIb sodium-phosphate cotransporter (NaPi-IIb), inorganic phosphate transporter 1 (PiT-1), inorganic phosphate transporter 2 (PiT-2), nuclear vitamin D receptor (nVDR), and membrane vitamin D receptor (mVDR). The mRNA abundances of Ca and P transporters and VDRs were the highest at 25 days of age. Conclusion: These data indicate that age quadratically affects intestinal Ca and P transporter gene expression and mineral absorption capacity in broiler chickens.

Intestinal segment and vitamin D3 concentration affect gene expression levels of calcium and phosphorus transporters in broiler chickens

Jincheng Han,Lihua Wu,Xianliang Lv,Mengyuan Liu,Yan Zhang,Lei He,Junfang Hao,Li Xi,Hongxia Qu,Chuanxin Shi,Zhiqiang Li,Zhixiang Wang,Fei Tang,Yingying Qiao 한국축산학회 2023 한국축산학회지 Vol.65 No.2

Two experiments were conducted in this research. Experiment 1 investigated the spatial expression characteristics of calcium (Ca) and phosphorus (P) transporters in the duodenum, jejunum, and ileum of 21-day-old broilers provided with adequate nutrient feed. Experiment 2 evaluated the effects of dietary vitamin D3 (VD3) concentration (0, 125, 250, 500, 1,000, and 2,000 IU/kg) on growth performance, bone development, and gene expression levels of intestinal Ca and P transporters in 1–21-day-old broilers provided with the negative control diet without supplemental VD3. Results in experiment 1 showed that the mRNA levels of calcium- binding protein 28-kDa (CaBP-D28k), sodium-calcium exchanger 1 (NCX1), plasma membrane calcium ATPase 1b (PMCA1b), and IIb sodium-phosphate cotransporter (NaPi-IIb) were the highest in the broiler duodenum. By contrast, the mRNA levels of inorganic phosphate transporter 1 (PiT-1) and 2 (PiT-2) were the highest in the ileum. Results in experiment 2 showed that adding 125 IU/kg VD3 increased body weight gain (BWG), feed intake (FI), bone weight, and percentage and weight of Ca and P in the tibia and femur of 1–21-day-old broilers compared with the negative control diet (p < 0.05). The rise in dietary VD3 levels from 125 to 1,000 IU/kg further increased the BWG, FI, and weights of the bone, ash, Ca, and P (p < 0.05). No difference in growth rate and leg bone quality was noted in the broilers provided with 1,000 and 2,000 IU/kg VD3 (p > 0.05). Supplementation with 125–2,000 IU/kg VD3 increased the mRNA abundances of intestinal Ca and P transporters to varying degrees. The mRNA level of CaBP-D28k increased by 536, 1,161, and 28 folds in the duodenum, jejunum, and ileum, respectively, after adding 1,000 IU/kg VD3. The mRNA levels of other Ca and P transporters (PMCA1b, NCX1, NaPi-IIb, PiT-1, and PiT-2) increased by 0.57–1.74 folds by adding 1,000–2,000 IU/kg VD3. These data suggest that intestinal Ca and P transporters are mainly expressed in the duodenum of broilers. Moreover, the addition of VD3 stimulates the two mineral transporter transcription in broiler intestines.