scholarly journals Study on the Durability of Concrete under an Underwater Coupling Environment

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Chunhua You ◽  
Gen He
Keyword(s):  
Corrosion Resistance ◽  
Concrete Structure ◽  
Pile Foundation ◽  
Acid Corrosion ◽  
Cementitious Material ◽  
Chloride Diffusion ◽  
Foundation Engineering ◽  
Chloride Diffusion Coefficient ◽  
Cement Ratio ◽  
Water Cement Ratio

The durability of the concrete structure under the coupling effect of underwater corrosion particles has always been one of the hot issues at home and abroad. Aiming at the damage problem of the underground concrete structure in a marine and offshore chloride corrosion environment, based on the pile foundation engineering of the Coastal Industrial Park, the corrosion resistance test of pile foundation concrete is carried out. By preparing 7 kinds of pile foundation concrete samples with different mix proportions, the mechanical properties of concrete with different ages were analyzed under the coupling environment of groundwater. The chloride penetration resistance of concrete was analyzed by the RCM method, and the sulfate corrosion resistance was analyzed by the 17D accelerated simulation test. The test results show that with the decrease of the water-cement ratio and the increase of the cementitious material, the concrete damage is less and the durability is improved. It is suggested that the water-cement ratio of 0.34 and the cementitious material of 480 kg/m3 be selected for the preparation of the pile foundation concrete; when the content of fly ash is 15%, the antisulfuric acid corrosion ability of the concrete cementitious system can be enhanced and the concrete with 40% mineral powder has strong antichloride ion corrosion ability; the results show that the chloride diffusion coefficient of concrete samples with seven mix proportions is less than 6 ∗ 10–12 m2/s, which can meet the durability design requirements and reduce the damage of concrete. The sulfate corrosion resistance of concrete samples with high-efficiency additives is the best.

Effect of Coarse Aggregate Types on the Microstructure of the ITZ and Durability of Concrete

2013 ◽  
Vol 838-841 ◽  
pp. 1801-1805 ◽  
Author(s):  
Li Juan Kong ◽  
Qing Chao Meng ◽  
Yuan Bo Du
Keyword(s):  
Rough Surface ◽  
Coarse Aggregate ◽  
High Water ◽  
Chloride Diffusion ◽  
Concrete Durability ◽  
Chloride Diffusion Coefficient ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Freeze Thaw ◽  
Limestone Aggregate

Influence of aggregate types on the impermeability and frost-resistance of concrete with different water/cement ratios were investigated, as well as the pore structure and hydrates of the ITZ. The results show that, concrete prepared with a high water/cement ratio and using granite aggregate, presents the highest values of chloride diffusion coefficient and the lowest numbers of freeze-thaw cycles. Whereas concrete prepared with a low water/cement ratio and using limestone aggregate, obtains the similar durability results. The limestone aggregate with a rough surface and higher water absorption, has a tight bonding with the cement paste. However, the granite and basalt aggregate that formed by magma eruption, have higher activity. The XRD results demonstrate that more clinkers participate in the hydration of cement, therefore, resulting in a denser ITZ. In order to improve the concrete durability, the basalt aggregate both with higher activity and rough surface is consider optimal.

Experimental Study and Numerical Analysis on Chloride Diffusion Coefficient of Concrete with Various Water-Cement Ratios

2017 ◽  
Vol 726 ◽  
pp. 547-552
Author(s):  
Zheng Ren ◽  
Lian Zhen Xiao ◽  
Wen Chong Shi
Keyword(s):  
Diffusion Coefficient ◽  
Chloride Ion ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Ion Diffusion ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Influence Of Water ◽  
Chloride Ion Diffusion

A rapid chloride ion diffusion coefficient measurement (RCM) was used in this study. The influence of water-cement ratios of 0.30, 0.35 and 0.40 at various ages (3, 7, 14, 28 and 56 days) on chloride ion diffusion coefficient of the concretes and pastes was studied and analyzed. The results show that, with the increase of curing ages, the chloride ion diffusion coefficient of different water-cement ratio of each specimen is decreased. In the early age, the chloride ion diffusion coefficient of the paste with the water-cement ratio of 0.40 is 2~3 times of the paste with water-cement ratio of 0.30 and 0.35, and with the increase of curing age, this difference is gradually decreased. Additionally, the chloride ion diffusion coefficient of the cement paste is 1~2 times of the concrete with same water-cement ratio at different ages. Based on the actual experiment boundary conditions, the process of chloride ions diffusion and permeability was simulated by COMSOL software, and the simulation result was analyzed to predict the permeability of concrete.

Influence of Permeability of HCSA Expansive Agent on High Volume Fly Ash Concrete

2011 ◽  
Vol 477 ◽  
pp. 354-358 ◽  
Author(s):  
Fang Fang Hou ◽  
Juan Hong Liu
Keyword(s):  
Diffusion Coefficient ◽  
Fly Ash ◽  
Rapid Determination ◽  
High Volume ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Experimental Conditions ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Expansive Agent

Based on the rapid determination of chloride diffusion coefficient with NEL method and pore structure analysis, the influence of HCSA expansive agent on chloride diffusion coefficient of concrete has been investigated. Besides, the effects of chloride diffusion coefficient of Water-Cement ratio on HCSA expansive concrete have been also analyzed. The results show that on the condition of 55% mixing amount of fly ash, the chloride diffusion coefficient of concrete of no HCSA is 1.96×10－8cm2/s, which is classified moderate. While the concrete mixing HCSA is about 0.62×10－8cm2/s, the permeability belongs to inferior. The effects of permeability of HCSA mixing amount on concrete is not obviously. The Water-Cement ratio affects the concrete permeability. Under the experimental conditions, the water-cement ratio of 0.4 can achieve better effect of the HCSA expansion; Furthermore, the mercury intrusion further verified that incorporating proper amount of HCSA can make the internal structure dense and improve the density and impermeability of concrete.

scholarly journals Experimental Study on Effective Chloride Diffusion Coefficient of Cement Mortar by Different Electrical Accelerated Measurements

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 240
Author(s):  
Jianlan Chen ◽  
Jiandong Wang ◽  
Rui He ◽  
Huaizhu Shu ◽  
Chuanqing Fu
Keyword(s):  
Diffusion Coefficient ◽  
Cement Mortar ◽  
Early Stage ◽  
Chloride Concentration ◽  
Chloride Diffusion ◽  
Chloride Diffusion Coefficient ◽  
Cement Ratio ◽  
Water To Cement Ratio ◽  
Good Consistency ◽  
Determination Methods

This study investigated the effective chloride diffusion coefficient of cement mortar with different water-to-cement ratio (w/c) under electrical accelerated migration measurement. The cumulative chloride concentration in anode cell solution and the cumulative chloride concentration drop in the cathode cell solution was measured by RCT measurement and the results were further used to calculate the chloride diffusion coefficient by Nordtest Build 355 method and Truc method. The influence of w/c on cement mortar’s chloride coefficient was investigated and the chloride diffusion coefficient under different determination methods were compared with other researchers’ work, a good consistency between this work’s results and literatures’ results was obtained. The results indicated that the increased w/c of cement mortar samples will have a higher chloride diffusion coefficient. The cumulative chloride concentration drop in the cathode cell solution will have deviation in early stage measurement (before 60 h) which will result in overestimation of the effective chloride diffusion coefficient.

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.

Revised Method for Rapid Determination of On-Site Water–Cement Ratio using Microwave Oven

2019 ◽  
Vol 2673 (8) ◽  
pp. 1-10
Author(s):  
Seyednavid Mardmomen ◽  
Hung-Liang (Roger) Chen ◽  
Guadalupe Leon
Keyword(s):  
Coarse Aggregate ◽  
Fresh Concrete ◽  
Rapid Determination ◽  
Microwave Oven ◽  
Cementitious Material ◽  
Percentage Error ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Average Percentage ◽  
Site Water

The water–cement ratio (w/c) of delivered concrete is one of the most important parameters of the material’s quality. In this study, the AASHTO T318-15 guideline was adopted to estimate the water content of fresh concrete mixes and was revised for better precision. The additional step required sieving out the coarse aggregate after drying the sample in a microwave oven, and using it in the calculation of the absorbed water and cementitious material content. The cementitious content was assumed to be proportional to the mix design ratios. Several laboratory batches, as well as on-site water–cementitious material (w/cm) ratio tests, were performed on concrete mixes containing ordinary Portland cement, ground-granulated blast furnace slag, and Class F fly ash. The results of the experiments indicated the accuracy of the revised method was increased to have an average percentage error of about 2.16% from the actual w/cm ratio whereas the method based on AASHTO calculations was 6.2%. For cases with high chemical admixture dosages, washing vinegar was used to wash out the particles around the dried sieved coarse aggregate to calculate the w/cm ratio with a more precise mass for each sample. The correlation between the measured and calculated compressive strength using the measured amount of w/cm ratios provides evidence for the method’s accuracy. Therefore, the revised method can be used as an accurate and practical process of measuring the on-site w/cm ratios of fresh concrete mixes.

Sensitivity Analysis of Durability Parameters of Concrete Structures Corroded by Chloride Ions

2012 ◽  
Vol 594-597 ◽  
pp. 999-1004
Author(s):  
Li Zeng ◽  
Yuan Cheng Guo ◽  
Zhuo Zhao
Keyword(s):  
Concrete Structure ◽  
Diffusion Mechanism ◽  
Limit State ◽  
Concrete Cover ◽  
Chloride Ions ◽  
Chloride Diffusion ◽  
State Function ◽  
Chloride Diffusion Coefficient ◽  
Structural Durability ◽  
Influencing Parameters

For the pre-stressed concrete structure under marine environment，the stochastic characters of structure and environment such as concrete cover depth, initial chloride ions concentration, chloride diffusion coefficient in concrete, critical chloride ions concentration and structural surface chloride ions concentration affect the structural durability in designed service life greatly. Based on the diffusion mechanism of chloride ions, considering the durability failure character of pre-stressed concrete structure, the limit state function of durability failure is established, the sensitivity of durability influencing parameters is analyzed, and the Monte Carlo simulation is carried out based on the stochastic characters of influencing parameters, which will provide method and foundation for the structural durability design, construction and quality control of similar project.

Effects of Water-Cement Ratio on Concrete Sulfate Corrosion Rate

2016 ◽  
Vol 711 ◽  
pp. 295-301 ◽  
Author(s):  
Jian Min Du ◽  
Xiao Li Han ◽  
Zai Ting Li ◽  
Guo Li ◽  
Yong Sheng Ji
Keyword(s):  
Compressive Strength ◽  
Corrosion Resistance ◽  
Corrosion Rate ◽  
Layer Thickness ◽  
Tap Water ◽  
Corrosion Layer ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Development Models ◽  
Concrete Mix

Water-cement (w/c) ratio is an important parameter in concrete mix ratio design, which also plays an important influence on concrete sulfate corrosion rate. In this paper, concrete cubic specimens with w/c of ratio as 0.4, 0.5 and 0.6 were fabricated, respectively, and put into 10% Na2SO4 solution and tap water for 240 days. During the submerging process, superficial corrosion phenomena were observed and concrete cubic strengths were measured periodically. The results showed that the lower the w/c ratio, the stronger the concrete sulfate corrosion resistance is. At the same time, concrete with lower w/c ratio always correspond smaller corrosion layer thickness. Based on the degradation of cubic compressive strength of corroded concrete specimens, the development models of corrosion thickness of each w/c ratio concrete are established as sulfate corrosion goes on

Parameters of Acoustic Emission Signals Obtained During the Setting and Hardening of Concrete Mixtures with Different Water-Cement Ratio

2016 ◽  
Vol 837 ◽  
pp. 152-156 ◽  
Author(s):  
Libor Topolář ◽  
Kristýna Timcakova ◽  
Petr Misak ◽  
Luboš Pazdera
Keyword(s):  
Acoustic Emission ◽  
Concrete Structure ◽  
Building Materials ◽  
Building Structures ◽  
Acoustic Emission Method ◽  
Emission Method ◽  
Destructive Testing ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Concrete Hardening

Concrete hardening and setting processes are the most critical phases during construction work, influencing the properties of concrete structure. For this reason applying non-destructive testing in the early age of concrete lifetime can be useful. Acoustic emission method is a powerful tool for determination of lifetime concrete structures. Nevertheless, its application in civil engineering area is not easy because many building structures are inhomogeneous. This method can describe material changes during concrete lifetime. Acoustic Emission Method monitors concrete structure continuously. Changes in the whole concrete structure are recorded. The acoustic emission phenomenon is directly associated with nucleation of cracks in building materials, therefore the changes result from the volumetric expansion causing formation micro and macro cracking in structure, which we can recognize. Application of Acoustic Emission Method during concrete hardening and setting with different water-cement ratio will be the aim of this article and his influence on parameters of acoustic emission. A comprehension of microstructure-performance relationships is the key to true understanding of material behaviour.

scholarly journals Study on Strength and Ultrasonic Velocity of Air-Entrained Concrete and Plain Concrete in Cold Environment

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Huai-shuai Shang ◽  
Ting-hua Yi ◽  
Xing-xing Guo
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Ultrasonic Velocity ◽  
Concrete Structure ◽  
Plain Concrete ◽  
Cement Ratio ◽  
Water Cement Ratio ◽  
Testing Technology ◽  
The Relationship ◽  
Air Entrained Concrete

Nondestructive testing technology is essential in the quality inspection of repair, alteration, and renovation of the existing engineering, especially for concrete structure in severe environment. The objective of this work is to deal with the behavior of ultrasonic velocity and mechanical properties of plain concrete and air-entrained concrete subjected to freeze-thaw cycles (F-T-C). The ultrasonic velocity and mechanical properties (tensile strength, compressive strength, cubic compressive strength, and splitting strength) of C30 air-entrained concrete and plain concrete with different water-cement ratio (water-cement ratio was 0.55, 0.45, and 0.50, resp.) after F-T cycles were measured. The influences of F-T cycles on ultrasonic velocity and mechanical properties of C30 air-entrained concrete and plain concrete were analyzed. And the relationship between mechanical properties and ultrasonic velocity was established. The experimental results can be useful for the design of new concrete structure, maintenance and life prediction of existing concrete structure such as offshore platform and concrete dock wall.

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