scholarly journals Influence of Crack Width on Chloride Penetration in Concrete Subjected to Alternating Wetting–Drying Cycles

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3801
Author(s):  
Jun Lai ◽  
Jian Cai ◽  
Qing-Jun Chen ◽  
An He ◽  
Mu-Yang Wei
Keyword(s):  
Crack Width ◽  
Chloride Concentration ◽  
Rc Beam ◽  
Rc Beams ◽  
Cross Sectional ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Steel Bar ◽  
Steel Bars ◽  
Average Loss

To investigate the durability of reinforced concrete (RC) beams under the combined actions of transverse cracks and corrosion, corrosion tests were conducted on a total of eight RC beams with different water–cement ratios and cracking states. The effects of the transverse crack width, water–cement ratio, and the length of the wetting–drying cycle on the distribution of the free chloride concentration, the cross-sectional loss of the tensile steel bars, and the chloride diffusion coefficient are analyzed. The results show that the widths of the transverse crack and the water–cement ratio of concrete greatly affected the chloride profile and content of the RC beam specimens. Specifically, the chloride contents in all the cracked RC beams at the depth of the steel bar exceeded the threshold value of 0.15%. As the width of the cracks increased, the chloride concentration and penetration of the cracked concrete beam increased. However, the chloride concentration at the reinforcement position did not seem to be obviously affected by increasing the wetting–drying cycles from 182 days to 364 days. Moreover, the decrease of the water–cement ratio effectively inhibited the penetration of chloride ions in the RC beam specimens. In terms of the cross-sectional loss of the steel bars, the average loss of the steel bar increases with increasing crack width for the beams with 182-day cycles, while the effect of crack width on the average loss is not as noticeable for the beams with 364-day cycles. Finally, a model is proposed to predict the relationship between the crack width influence coefficient, μ, and the crack width, w, and this model shows good agreement with the experimental results.

Influence of Corrosion Distribution on Estimation of Flexural Loading Capacity of Corroded RC Beams

2017 ◽  
Vol 12 (3) ◽  
pp. 478-486
Author(s):  
Takashi Yamamoto ◽  
◽  
Satoshi Takaya ◽  
Toyo Miyagawa ◽  
Keyword(s):  
Estimation Method ◽  
Rc Beam ◽  
Loading Capacity ◽  
Kriging Method ◽  
Flexural Capacity ◽  
Cross Sectional ◽  
Flexural Loading ◽  
Load Carrying ◽  
Steel Bars ◽  
Inspection Data

A load carrying capacity of the reinforced concrete (RC) member is degraded by the corrosion of reinforcing steel bars due to chloride ion ingress. A lot of researches on the effect of corrosion in the longitudinal tensile reinforcing steel bars on the load carrying behavior have been available up to now. Accurate and quantitative estimation of capacity, however, is often difficult, because of the non-uniformity of corrosion in the member. Thus, a relationship between the spatial distribution of corrosion in the reinforcement including its scatter and the flexural loading capacity of RC member with such distribution of corrosion should be clarified so that the flexural capacity of corroded RC member can be estimated accurately. On the other hand, in case of the practical RC member under the corrosive environment, it should be considered that the flexural capacity often have to be derived from not a large number of inspection data on cross sectional areas of corroded reinforcements. So, in this study, a flexural loading test was performed by using RC beam specimens with the corroded tensile reinforcements provided the distribution of sectional areas. An estimation method of the flexural capacity of corroded RC beam was also shown, considering the distribution and its scatter in sectional areas of corroded reinforcements under the limited inspection data. Furthermore, the estimation of the longitudinal distribution of the cross sectional area of corroded reinforcement was performed by the spatial interpolation using Kriging method. Test results showed the yield and maximum load capacity in the corroded RC beam decreased as the corrosion rate increased. The failure mode of rupture in the reinforcement was shown in the large corrosion. The proposed estimation method was able to lead the safe evaluation of those experimental flexural capacities, determining the appropriate longitudinal characteristic value of the cross sectional area of corroded reinforcement. The flexural capacity can be also safely calculated using the characteristic value of diameters estimated by the corrosion crack width on the surface of the concrete, while the ratio of the experimental flexural capacity to the estimated one decreased as the corrosion loss increased. The distribution of bar diameters in the corroded reinforcement was able to be roughly estimated by using Kriging method. However, it was suggested that the measurement points close to the minimum bar diameter should be included to estimate the flexural capacity on the safe side.

EFFECT OF CORROSION LONGITUDINAL STEEL BARS ON THE FLEXURAL STRENGTH OF RC BEAMS

2021 ◽  
Vol 28 (2) ◽  
pp. 44-53
Author(s):  
Noor Mahmood ◽  
Assim Lateef
Keyword(s):  
Concrete Beams ◽  
Concrete Strength ◽  
Corrosion Process ◽  
Rc Beams ◽  
Cross Sectional ◽  
Flexural Failure ◽  
Steel Bars ◽  
Major Parameter ◽  
Mode Of Failure ◽  
Concentrated Loading

The main objective of this research is to investigate the effect of corroded steel bars on the ultimate flexural capacity of reinforcement concrete beams. The experimental work consists of four RC beams with dimensions (150×200×1200) mm tested under two-point concentrated loading. The major parameter of the current research is corrosion period (5,10,20) days. The amount of longitudinal and transverse reinforcement, concrete strength and, the other parameters were kept constant for all samples. The comparisons between specimens are based on the visual cracking loads, ultimate loads, deflection, cracks pattern and mode of failure. Results showed that visual first cracking load, and ultimate loads of corroded RC beams were decreased with increase corrosion durations relative to the control beam as a result of the corrosion process. The mode of failure was flexural failure for all specimens. Corrosion caused decreasing percentage in weight of steel bars and cross-sectional area of longitudinal steel bars. This percent increased as exposure time to corrosion process increased by 8.5% and 28.39% for 20 days respectively.

Analysis of Shear Capacity of Stirrup Corroded RC Beam Based on the Truss-Arch Theory

2012 ◽  
Vol 204-208 ◽  
pp. 2865-2873
Author(s):  
Ke Bo Zhang ◽  
Zhi Zhang ◽  
Jian Ren Zhang ◽  
Bin Liu
Keyword(s):  
Strength Criterion ◽  
Shear Capacity ◽  
Control Group ◽  
Rc Beam ◽  
Arch Model ◽  
Rc Beams ◽  
Diagonal Reinforcement ◽  
Steel Bars ◽  
Shear Bearing Capacity ◽  
Crucial Parameter

On the basis of truss-and-arch model and the concrete softening strength criterion under ultimate state, a formula for shear capacity of reinforced concrete (RC) beam with diagonal reinforcement was established and verified. Accordingly, six RC beams with diagonal reinforcement and corroded stirrup were tested along with control group, the tested results were analyzed by liner regression to modify the formula given. Hence a formula for inclined section shear capacity of stirrups corroded RC beam with diagonal reinforcement was proposed and compared with a preceding formula without a consideration of diagonal reinforcement in corroded RC beam .The results showed that the existence of diagonal reinforcing steel bars enhanced the behavior of vertical compression web member in truss institutions, therefore increasing the shear force shared by truss mechanism. The inclination of diagonal web member is a crucial parameter of truss model. As the stirrup corrosion aggravating, the shear bearing capacity of such RC beams does not decrease drastically.

Corrosion-Induced Concrete Cracking, Steel-Concrete Bond Loss, and Mechanical Degradation of Steel Bars

2014 ◽  
Vol 919-921 ◽  
pp. 1760-1770 ◽  
Author(s):  
Fu Jian Tang ◽  
Gen Da Chen ◽  
Wei Jian Yi
Keyword(s):  
Cross Section ◽  
Crack Width ◽  
Surface Profile ◽  
Concrete Surface ◽  
Cross Sectional Area ◽  
Mechanical Degradation ◽  
Sectional Area ◽  
Cross Sectional ◽  
Steel Bars ◽  
The Cross

This study experimentally investigated corrosion-induced deterioration in reinforced concrete (RC) structures: concrete cover cracking, steel-concrete bond loss, and mechanical degradation of corroded steel bars. Pullout and RC beam specimens were prepared, subjected to accelerated corrosion in a wet sand bath, and tested under loading. A 3D laser scan was employed to measure the surface profile of corroded steel bars and determine the corrosion effect on the distribution of residual cross section area. The crack width on the concrete surface was sampled randomly and analyzed statistically. Corrosion reduced the bond strength between steel bars and concrete, particularly in the form of corrosion-induced number and width of cracks. Both the yield and ultimate strengths depended upon the critical cross sectional area of steel bars, whereas the elongation changed with the cross section distribution over the length of the steel bars. Corrosion also changed the distribution of the cross sectional area of steel bars. The crack width on the concrete surface can be well represented by a normal distribution regardless of corrosion levels.

scholarly journals Study on the Permeability of Recycled Aggregate Pervious Concrete with Fibers

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 321 ◽  
Author(s):  
Haitang Zhu ◽  
Chengcheng Wen ◽  
Zhanqiao Wang ◽  
Lan Li
Keyword(s):  
Compressive Strength ◽  
Permeability Coefficient ◽  
Polypropylene Fiber ◽  
Volumetric Analysis ◽  
Pervious Concrete ◽  
Recycled Aggregate ◽  
Fiber Types ◽  
Cross Sectional ◽  
Cement Ratio ◽  
Water Cement Ratio

Pervious concrete is considered to be porous concrete because of its pore structure and excellent permeability. In general, larger porosity will increase the permeability coefficient, but will significantly decrease the compressive strength. The effects of water-cement ratio, fiber types, and fiber content on the permeability coefficient, porosity, compressive strength, and flexural strength were investigated. The pore tortuosity of the pervious concrete was determined by volumetric analysis and two-dimensional cross-sectional image analysis. The concept and calculation method of porosity tortuosity were further proposed. Results show that the permeability coefficient of the pervious concrete is the most suitable with a water-cement ratio of 0.30; the water permeability of the pervious concrete is influenced by fiber diameter. The permeability coefficient of pervious concrete with polypropylene thick fiber (PPTF) is greater than that with copper coated steel fiber (CCF) and the polypropylene fiber (PPF). The permeability coefficient is related to tortuosity and porosity, but when porosity is the same, the permeability coefficient may be different. Finally, general relations between the permeability coefficient and porosity tortuosity are constructed.

Study on Mechanical Property of Reinforced Concrete (RC) Beams under Sea Water

2013 ◽  
Vol 351-352 ◽  
pp. 355-358
Author(s):  
Xi Kang Yan ◽  
Xiang Shang Chen ◽  
Pei Chen
Keyword(s):  
Mechanical Property ◽  
Bearing Capacity ◽  
Sea Water ◽  
Vertical Section ◽  
Rc Beam ◽  
Rc Beams ◽  
Cement Ratio ◽  
Normal Section ◽  
Initial Strength ◽  
Pressure Test

By way of the soaking and drying cycle test on the different mix proportions vertical section of 10 pieces of RC beams suffered artificial sea water (ASW) corrosion under0,35,70,105,140 times of dry-wet cycles, the compared result of exerting pressure test of these beams under simply supporting were investigated. The law was as follows: The resistibility to ASW corrosion for the concrete specimens with various water cement ratio (various initial strength) are different;The characters of normal section failure for RC beams attacked by sea water are about the same as that for ordinary RC beam; Along with the extension of the time for seawater attack, the bearing capacity for normal section of RC beams varies wave upon wave. The specimens attacked by seawater for about 35 times of corrosion cycle achieve minimum bearing capacity.

Effect of Water-Cement Ratio on Carbonation and Steel-Corrosion Resistance of Recycled Concrete

2012 ◽  
Vol 174-177 ◽  
pp. 1552-1557 ◽  
Author(s):  
Ya Li Sun ◽  
Jin Song Zhu
Keyword(s):  
Compressive Strength ◽  
Concrete Strength ◽  
Steel Corrosion ◽  
Recycled Concrete ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Ordinary Concrete ◽  
Steel Bar ◽  
Steel Corrosion Resistance ◽  
Concrete Cube

This paper studies the effects of different water-cement ratio on recycled concrete strength, anti-carbonation capability, and protecting reinforce steel bar capability. Select the water-cement ratio 0.6,0.55,0.5,0.45,0.4 five cases of the pilot study.It shows that: recycled concrete cube compressive strength, anti-carbonation capacity and protecting reinforce steel bar capability are less than ordinary concrete.

A Study on Flexural Performance of RC Beam Strengthened with UHTCC for Improved Durability

2008 ◽  
Vol 400-402 ◽  
pp. 43-54
Author(s):  
Shi Lang Xu ◽  
Xiu Fang Zhang ◽  
Christopher K.Y. Leung
Keyword(s):  
Composite Beam ◽  
Crack Width ◽  
Tensile Strain ◽  
Experimental Results ◽  
Rc Beam ◽  
Rc Beams ◽  
Strain Capacity ◽  
Flexural Performance ◽  
High Toughness ◽  
Tensile Strain Capacity

Ultra-high toughness cementitious composite (UHTCC) exhibits the pseudo-hardening feature when subjected to tensile load and has high tensile strain capacity of normally up to 3%. Also, UHTCC has a unique cracking behavior. From cracking up to ultimate tensile strain capacity, the crack width in UHTCC could be still kept below 100m. This paper presents the utilization of UHTCC to replace a layer of concrete surrounding the main flexural reinforcement in ordinary RC beam to improve flexural performance especially beam durability as UHTCC displays high toughness and shows multiple fine cracks. Analytical closed-form formulae for flexural capacity, curvature and deformation of UHTCC/RC composite beam derived based on the elastic beam theory is presented first. Subsequently, experimental results of two groups of different reinforcement ratios of UHTCC/RC beams and control RC beams tested under flexural loading to verify the feasibility of analytical formulae as well as to examine the performance improvement of UHTCC/RC composite beam over the control beam is presented. Moment-curvature curves and load-mid span displacement curves for the tested beams are compared with the theoretical analysis. A good agreement between experimental and analytical results is found. The experimental results show that the use of a layer of UHTCC in RC beams can enhance both flexural capacity and ductility. The improvement is not significant with the increase in reinforcement ratio; however, the maximum crack width under service load even in the case of lightly reinforced beams can be limited within 0.1mm.

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