The effect of hydrophobic impregnation on chloride ingress into cracked concrete

2019 ◽  
Author(s):  
Haris Sohawon ◽  
Hans Beushausen
Keyword(s):  
Service Life ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Water Repellent ◽  
Chloride Ingress ◽  
Chloride Diffusion Coefficient ◽  
Product Lines ◽  
Cracked Concrete ◽  
Cover Depth ◽  
Hydrophobic Silane

<p>Premature concrete degradation due to rebar corrosion has many financial and social implications on a large scale. Direct costs relate to the repair and rehabilitation of existing structures to maintain serviceability while indirect costs include loss in productivity and reduced economic growth. Hydrophobic (silane) impregnation represents a cost-effective way to increase the durability of concrete structures in cases where insufficient design cover quality and depth have been achieved. The water repellent product lines the internal capillary pore structure and provides a water-repellent concrete surface. Thus, the risk of reinforcement corrosion initiation and subsequent deterioration can be reduced as the ingress of water-dissolved aggressive species (chlorides) is minimised or prevented. The purpose of this study was to investigate and quantify the influence of silane impregnation as a remedial measure for poor quality or insufficient cover depth in newly constructed structures and ultimately predict the service life extension possible for specific cover depths. The effectiveness of silane impregnation in cracked concrete was also studied. The results indicate that silane impregnation reduces capillary absorption and conductivity of chloride ions for all the mixes. Chloride ingress in the treated concrete mixes was suppressed and lower chloride surface concentration (C<sub>s</sub> and apparent chloride diffusion coefficient (D<sub>a</sub>) were recorded. A slight decrease in carbonation depth was observed in the w/b 0.60 concrete mixes. The results also suggest that silane impregnation reduces chloride ingress in cracked concrete (up to a crack width of 0.6 mm). A lower rate of chloride ingress was predicted in the silane treated concrete and consequently to achieve the same service life, smaller cover depths are required. The overall results indicate that the service life of concrete with inadequate cover depth and quality, regardless of the binder type, can be effectively extended using hydrophobic (silane) impregnation, assuming proper surface preparation and application methods.</p>

scholarly journals The effect of hydrophobic (silane) treatment on concrete durability characteristics

2018 ◽  
Vol 199 ◽  
pp. 07015
Author(s):  
Haris Sohawon ◽  
Hans Beushausen
Keyword(s):  
Bulk Diffusion ◽  
Cost Effective ◽  
Concrete Surface ◽  
Chloride Ions ◽  
Water Repellent ◽  
Capillary Absorption ◽  
Chloride Ingress ◽  
Concrete Durability ◽  
Product Lines ◽  
Hydrophobic Silane

Hydrophobic (silane) impregnation represents a cost-effective way to increase the durability of concrete structures in cases where insufficient design cover quality and depth have been achieved. The water repellent product lines the internal capillary pore structure and provides a water-repellent concrete surface. Thus, the risk of reinforcement corrosion initiation and subsequent deterioration can be reduced as the ingress of water-dissolved aggressive species (chlorides) is minimised or prevented. The purpose of this study was to investigate the effect of silane impregnation on durability indicators, including penetrability tests and chloride ingress (bulk diffusion). The results indicate that silane impregnation reduces capillary absorption and conductivity of chloride ions. Similarly, chloride ingress in the treated concrete mixes was suppressed.

scholarly journals Chloride Diffusion in Concrete Protected with a Silane-Based Corrosion Inhibitor

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2001 ◽  
Author(s):  
Luigi Coppola ◽  
Denny Coffetti ◽  
Elena Crotti ◽  
Gabriele Gazzaniga ◽  
Tommaso Pastore
Keyword(s):  
Diffusion Coefficient ◽  
Corrosion Inhibitor ◽  
Sharp Decrease ◽  
Chloride Diffusion ◽  
Cement Matrix ◽  
Water Repellent ◽  
Chloride Ingress ◽  
Chloride Diffusion Coefficient ◽  
Apparent Diffusion ◽  
Corrosion Risk

One of the most important parameters concerning durability is undoubtedly represented by cement matrix resistance to chloride diffusion in environments where reinforced concrete structures are exposed to the corrosion risk induced by marine environment or de-icing salts. This paper deals with protection from chloride ingress by a silane-based surface-applied corrosion inhibitor. Results indicated that the corrosion inhibitor (CI) allows to reduce the penetration of chloride significantly compared to untreated specimens, independently of w/c, cement type, and dosage. Reduction of chloride diffusion coefficient (Dnssn) measured by an accelerated test in treated concrete was in the range 30–60%. Natural chloride diffusion test values indicate a sharp decrease in apparent diffusion coefficient (Dapp) equal to about 75% when concrete is protected by CI. Mechanism of action of CI in slowing down the chloride penetration inside the cement matrix is basically due to the water repellent effect as confirmed by data of concrete bulk electrical resistivity.

Concentration Distribution of Chloride Ion in Cracked Concrete

2013 ◽  
Vol 351-352 ◽  
pp. 1581-1584
Author(s):  
Bo Yu ◽  
Zhong Hui Huang ◽  
Ming Wu ◽  
Hui Liang Sun ◽  
Lu Feng Yang ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Concentration Distribution ◽  
Chloride Ion ◽  
Diffusion Path ◽  
Chloride Ions ◽  
Time Dependent ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Cracked Concrete ◽  
Ions Transport

Cracks provide diffusion path for chloride ions transport from the external environment into the concrete, resulting in the durability degradation of concrete structures. In this paper, the boundary condition of cracked concrete and chloride diffusion coefficient in crack were analyzed. The time-dependent chloride diffusion model was established based on the time-dependent chloride diffusion coefficient and the Ficks second law of diffusion. The influence of crack on the concentration distribution of chloride ion in cracked concrete was quantificationally investigated.

Production of High-Performance Composite Concrete Segment and Experimental Investigation of Materials

2010 ◽  
Vol 168-170 ◽  
pp. 1042-1045
Author(s):  
Ying Li Gao ◽  
Bao Guo Ma
Keyword(s):  
Service Life ◽  
Concrete Structure ◽  
High Performance ◽  
Concrete Cover ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Volume Deformation ◽  
Volume Stability ◽  
High Performance Composite ◽  
Structure Layer

Tunnel lining concrete segment is the most critical and important structural member of shield tunneling. This investigation designed and produced high-performance composite concrete segment (HCCS). Some key indexes that affect the properties of segment were tested, such as impermeability, volume stability, mechanical property, etc. The results indicated that the impermeability of HCCS concrete cover was excellent and the chloride diffusion coefficient decreased one order of magnitude compared to that of the ordinary segment concrete cover, while the service-life of HCCS increased more than ten-fold. The volume stability of HCCS concrete cover and concrete structure layer were good and the better compatibility in the volume deformation of the whole structure was shown. Furthermore, the mechanical properties of concrete cover and concrete structure layer met the project requirement perfectly, ensuring the higher durability and longer service-life of HCCS effectively.

scholarly journals Investigation on Durability Performance in Early Aged High-Performance Concrete Containing GGBFS and FA

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Seung-Yup Jang ◽  
Subbiah Karthick ◽  
Seung-Jun Kwon
Keyword(s):  
Diffusion Coefficient ◽  
High Performance ◽  
High Performance Concrete ◽  
Steel Corrosion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Structural Safety ◽  
Concrete Durability ◽  
Chloride Diffusion Coefficient ◽  
Rc Structures

The significance of concrete durability increases since RC (Reinforced Concrete) structures undergo degradation due to aggressive environmental conditions, which affects structural safety and serviceability. Steel corrosion is the major cause for the unexpected failure of RC structures. The main cause for the corrosion initiation is the ingress of chloride ions prevailing in the environment. Hence quantitative evaluation of chloride diffusion becomes very important to obtain a chloride diffusion coefficient and resistance to chloride ion intrusion. In the present investigation, 15 mix proportions with 3 water-to-binder ratios (0.37, 0.42, and 0.47) and 3 replacement ratios (0, 30, and 50%) were prepared for HPC (high-performance concrete) with fly-ash and ground granulated blast furnace slag. Chloride diffusion coefficient was measured under nonstationary condition. In order to evaluate the microstructure characteristics, porosity through MIP was also measured. The results of compressive strength, chloride diffusion, and porosity are compared with electrical charges. This paper deals with the results of the concrete samples exposed for only 2 months, but it is a part of the total test plan for 100 years. From the work, time-dependent diffusion coefficients in HPC and the key parameters for durability design are proposed.

scholarly journals Service Life Prediction of Reinforced Concrete in a Sea-Crossing Railway Bridge in Jiaozhou Bay: A Case Study

2019 ◽  
Vol 9 (17) ◽  
pp. 3570 ◽  
Author(s):  
Zhe Li ◽  
Zuquan Jin ◽  
Tiejun Zhao ◽  
Penggang Wang ◽  
Lixiao Zhao ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Service Life ◽  
Reliability Index ◽  
Life Prediction ◽  
Jiaozhou Bay ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Railway Bridge ◽  
Box Girder ◽  
The Mean

Reinforced bar corrosion induced by chloride ingression is one of the most significant threats to the durability of concrete structures in marine environments. The concrete cover thickness, compressive strength, chloride diffusion coefficient, and surface defects of reinforced concrete in the Jiaozhou Bay sea-crossing railway bridge were measured. The temperature and relative humidity in the concrete and the loading applied onto the reinforced concrete were monitored. Based on the DuraCrete model, a revised model for the service life prediction of concrete structures was established, considering the effects of temperature and loading on the chloride diffusion coefficient. Further, the reliability indexes of the reinforced concrete box girder, pier, and platform, located in the marine and land sections, in relation to service lives lasting various numbers of years, were calculated. The measured and calculated results show that the mean cover thicknesses of concrete piers in the marine and land sections are 52 mm and 36 mm, respectively, and the corresponding standard deviations are 5.21 mm and 3.18 mm, respectively. The mean compressive strengths of concrete in the marine and land sections are 56 MPa and 46 MPa, respectively. The corresponding standard deviations are 2.45 MPa and 2.67 MPa, respectively. The reliability indexes of the reinforced concrete box girder and platform in the marine section, under the condition of a service life of 100 years, are 1.81 and 1.76, respectively. When the corrosion-resistant reinforced bar was used in the pier structure in the marine section, its reliability index increased to 2.01. Furthermore, the reliability index of the reinforced concrete damaged by salt fog in the land section was 1.71.

Corrected Diffusion Model of Chloride in Concrete and its Engineering Application

2011 ◽  
Vol 189-193 ◽  
pp. 1886-1891
Author(s):  
Peng Fei Xue ◽  
Da Ling Mao
Keyword(s):  
Service Life ◽  
Diffusion Model ◽  
Life Prediction ◽  
Engineering Application ◽  
Time Dependent ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Practical Applications ◽  
Environment Variable ◽  
Stochastic Characteristic

A multi-factor diffusion model of chloride in concrete was formulated, in which the hypothesis of Fick’s Law were corrected through parameter definition. The values of the parameters in the model were given for practical applications according to pilot calculation and analysis of mass data. By using this diffusion model, three calculation methods of concrete structure service life were further deduced, it includes definite value method, probability performance based method and time-dependent reliability based method. The service life prediction for the approach bridge of Huang-pu Bridge was carried on by using various prediction approaches mentioned above. The results showed that: time-dependent reliability based method can consider randomness of chloride diffusion coefficient and the depth of concrete covering layer, and the stochastic characteristic of environment variable can be easily taken into account too. By adjusting the target reliability, the prediction results are consistent with those of the other two methods.

Transport of Water and Chloride Ion in Cement Composites Modified with Graphene Nanoplatelet

2014 ◽  
Vol 629-630 ◽  
pp. 162-167 ◽  
Author(s):  
Hong Jian Du ◽  
Sze Dai Pang
Keyword(s):  
Chloride Ion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Cement Composites ◽  
Chloride Diffusion Coefficient ◽  
Barrier Effect ◽  
Graphene Nanoplatelet ◽  
Chloride Migration ◽  
Corrosion Of Steel ◽  
And Diffusion

Cement composites are vulnerable to harsh environments in which the chloride ions can ingress into concrete and thus cause corrosion of steel. In this study, the barrier effect of adding 2-D nanoparticles on the transport properties of cement-based materials was investigated. Graphene nanoplatelet (GNP), which comprises of a few layers of graphene stacked together, is chosen as a candidate in this study due to its impermeability and also its electrical conductivity which can be exploited for self-sensing functionality. Due to the large aspect ratio of the GNP, it is expected that the dispersion of these 2-D nanobarriers can contribute to the reduced permeability and diffusion of harmful agents. Experiments were carried out on cement mortar with 0%, 2.5%, 5.0% and 7.5% of GNP by weight of cement. The water penetration depth, chloride diffusion coefficient and chloride migration coefficient were reduced by 64%, 70% and 31% respectively with the addition of as little as 2.5% of GNP. This reduction can be attributed to the barrier effect of GNP which increases the tortuosity against water and chloride ions penetration, and also the refinement of the capillary pores which was revealed from the MIP tests. At GNP content exceeding 5%, the nanoparticles agglomerate, causing weak pockets which compromises the benefits of adding GNP to impede the ingress of fluids.

Durability Design of Tunnel Concrete Lining under Chloride Attack

2012 ◽  
Vol 594-597 ◽  
pp. 1014-1017
Author(s):  
Lu Feng Yang ◽  
Hong Bin ◽  
Yu Bo
Keyword(s):  
Finite Element ◽  
Element Model ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Concrete Lining ◽  
Chloride Diffusion Coefficient ◽  
Initial Value ◽  
Durability Design ◽  
Chloride Attack ◽  
Finite Element Formulations

Chloride induced corrosion of reinforcing steel is one of major causes of deterioration of tunnel concrete lining under chloride attack. In this paper, a finite element model for chloride ions transport in tunnel concrete lining was proposed based on the Fick’s second law of diffusion. The governing partial differential equation was solved numerically in space as a boundary-value problem and in time as an initial-value problem by means of the finite element formulations. The maximum allowable value of chloride diffusion coefficient of tunnel concrete lining with service life of 100a was achieved and some constructive suggestions for durability design of tunnel concrete lining under chloride attack were also proposed.

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