Chloride Permeability Of Concrete Research Articles

Designing a novel waterproof thin-layer based on silicon-modified polyacrylate grafted 2D-graphene nanosheets for chloride-induced corrosion protection of rebar in concrete structures

BackgroundRebar plays a critical role in reinforcing concrete structures by providing tensile strength and improving their resistance to various loads. The chloride-induced corrosion of rebar is a major concern in the construction industry, as it can lead to significant structural damage and compromise the safety and integrity of concrete structures. For the first time in this work, a thin hydrophobic layer based on polyisocyanate functionalized graphene oxide (PIF-GO) was synthesized by modifying graphene oxide (GO) nanosheets with a silicon-modified polyacrylate through covalent grafting with polyisocyanate (PI) bridges to diminish water and chloride permeability of concrete. MethodsThe characterization of the synthesized nanomaterials was done by FT-IR, TGA, Raman spectroscopy, FE-SEM, and EDS analyses. Corrosion measurements were done by EIS and the waterproof properties of the applied thin film were investigated by contact angle and Capillary tests. Significant findingsCharacterization techniques exhibited that PI and silicon-modified polyacrylate were successfully grafted on GO. The PIF-GO dispersion was sprayed on the concrete surface. The water contact angle of GO increased significantly from 43° to 102° after modification. Capillary water absorption of concrete covered with the PIF-GO thin layer (60.4 g.cm−2.h−1/2) showed excellent waterproofing performance compared to GO (684.8 g.cm−2.h−1/2). EIS was used to scrutinize the corrosion behavior of rebar in concrete immersed in a saline solution for 71 days, revealing a significant diminish in the chloride and water penetration into the concrete.

Effect of mixed basalt fiber and calcium sulfate whisker on chloride permeability of concrete

Rapid chloride migration (RCM) test was used to determine the non-steady-state chloride migration coefficient (DRCM) of concrete mixed with calcium sulfate whisker (CSW) and basalt fiber (BF). Meanwhile, the microscopic morphology of CSW and BF in concrete was observed through scanning electron microscope (SEM), and the microstructural parameters were determined by the nuclear magnetic resonance (NMR) method. Results show that mixes with 3.0 kg/m3 CSW or BF alone outperformed in terms of chloride penetration reduction. However, by considering the strength factors comprehensively, the effect of enhancing concrete strength and chloride permeability resistance is better when 3.0 kg/m3 CSW and 4.5 kg/m3 BF are mixed. Binary problem optimal analysis results show that the optimal admixture dosage for improving the chloride impermeability and the optimum admixture dosage for enhancing the compressive strength (fc) of concrete are not consistent. According to SEM results, CSW is evenly distributed in the matrix and BF is wrapped by concrete matrix. The addition of BF and CSW to concrete reduced its porosity according to NMR tests. Increasing the content of BF would increase the contributive porosity (φ) of macro pores in concrete, while CSW could reduce the φ of macro pores. The DRCM has the strongest correlation with φ with a pore size of 100–1000 nm, followed by porosity.

Effect of recycled aggregate and supplementary cementitious material on mechanical properties and chloride permeability of concrete

With impending demand for sustainable development, construction wastes as recycled aggregate (RA) to produce recycled aggregate concrete (RAC) is inevitable. However, RA makes adverse effect on performance of RAC. To enhance its performance, the supplementary cementitious materials (SCM), including ground granulated blast furnace slag, red mud, and glass powder, were used to partially substitute cement. In this investigation, the plain cement concrete and mineral-admixture concrete with four replacement ratios of RA were poured. For each mixture, the compressive strength, dynamic elastic modulus, and resistivity were determined; Besides, chloride penetration test was conducted in a tidal cycling simulation device, in which specimens with dimension of 100 × 100 × 400 mm3 were used to explore the effect of drying-wetting time ratios RD/W on chloride diffusion. It was found concrete with 50% RA exhibits improved compressive strength and equivalent chloride resistance through 25% SCM addition. Concrete containing 100% RA achieves equivalent or even superior chloride resistance to control group as SCM added by 45%. With the increase of RD/W, the diffusion of chloride is more serious. Considering the inhomogeneity of concrete pores, a double-porosity transport model solution was derived based on Fick's second law. Combined with test results, a time-dependent model was then established to predict chloride concentration in concrete containing RA and SCM. Furthermore, an analytical solution of cumulative chloride content diffused into concrete was derived to quantify chloride permeability. Subsequently, a linear correlation between chloride permeability and resistivity is confirmed. This investigation will encourage the use of RA in marine engineering, thereby leading to a more sustainable and cleaner production.

Near-Surface and Chloride Permeability of Concrete Using Pozzolanic Materials and Manufactured Sand as Partial Replacement of Fine Aggregate

The overuse level of cement and natural sand for civil industry has several undesirable social and ecological consequences. As an answer for this, industrial wastes called by-products (pozzolanic materials) like fly ash, GGBFS, silica fume and metakaolin can be used to interchange partially cement and natural fine aggregate by manufacturing sand (M-sand). Thus, the present research work reported in this article deals with the feasibility study of using manufactured sand as sand replacement and pozzolana as cement replacement materials in concrete. So this will solve two problems simultaneously, viz. the bulk utilization of pozzolanic materials and saving the natural quarries of sand. Thus, the research work presented here specifically dealt with the potential utility of manufactured sand as sand replacement and pozzolana as cement replacement material and its effect on the durability and microstructure properties. Thus, the main objective of this experimental investigation is to find out the durability properties of concrete produced by replacing natural sand by manufactured sand in varying percentages like 0%, 10%, 20%, 30%, 40%, 50%, 60% 70%, 80%, 90% and 100%, and 20% cement replacing with pozzolanic materials. In this experimentation, natural fine aggregate was partially replaced by M-sand in various percentages 0–100% with 10% interval, water–cement ratio of 0.45, and cement was partially substituted by 20% of pozzolanic materials. M30 concrete grade proportions were considered as per IS 10262:2009 guidelines. The durability properties like water absorption, sorptivity and chloride permeability results were checked for the different concrete mix proportions and compared with conventional concrete. From this research work, it can be concluded that for replacement of 60% natural fine aggregate by manufactured sand (M-sand) and 20% cement by silica fume yields minimum water absorption, sorptivity, chloride permeability and denser microstructure than conventional concrete.

Pozzolanic reactivity of natural pozzolans, ground glasses and coal bottom ashes and implication of their incorporation on the chloride permeability of concrete

It is well understood that the partial replacement of portland cement with pozzolans in sufficient proportions results in improved long-term performance of concrete. However, dwindling availability of the most widely used pozzolan in the construction industry, fly ash, is forecast due to the termination of coal-fired electricity power stations around the world, necessitating the exploration of alternative pozzolans. Experimental investigations are conducted to study the performance of traditional pozzolans such as fly ash, silica fume and natural pozzolans (metakaolin, pumice, perlite and lassenite) together with novel pozzolans, including ground glasses (high-alkali and low-alkali), and ground bottom ash. Twenty-one concrete mixtures are examined for compressive strength, electrical conductivity, electrical resistivity, chloride permeability, and chloride migration coefficient. The reactivity of pozzolans studied is also determined in terms of compressive strength in lime-pozzolan mortar using a modified lime-reactivity test method. Many of the materials tested demonstrate the potential to be used in place of fly ash. However, a wide variation in the performance of these materials is evident which highlights the need for a reliable test to determine the level of reactivity of a pozzolan. The results indicate that the 7-day strength in the modified lime-reactivity test provides a good indication of the pozzolanic reactivity of the material and of how the material can be expected to contribute to the strength and permeability of concrete. The use of electrical resistivity as an indicator of the performance of pozzolans in terms of strength development and chloride penetration resistance when used to partially replace portland cement in concrete is also discussed.

Application of granulated copper slag in massive concrete under saline soil environment

The present study aimed to utilize granulated copper slag (GCS) as a mineral admixture for massive concrete in the saline-soil environment, then analyze the feasibility through the experiment. A contrastive analysis was conducted on the hydration heat in paste mixtures with a partial replacement of Ordinary Portland cement (OPC) by GCS and FA at different temperatures (25 °C and 50 °C). Results showed that the properties of cement blended with GCS were similar to that of FA, which can effectively reduce the hydration heat. The GCS influence on the fluidity, rheological performance, compressive strength, and chloride permeability of concrete was investigated. Results showed that utilizing GCS to replace cement can improve workability while reducing the yield stress, plastic viscosity, mechanical strength, and chloride permeability of concrete. By adjusting the w/b ratio and the GCS amount, three groups of concrete samples (C-0.40, G35-0.35, G40-0.32) with similar workability, compressive strength, and chloride permeability were selected for adiabatic temperature rise testing. A detailed analysis was conducted on the compressive strength, splitting tensile strength, chloride ion permeability, and sulfate attack resistance of concrete under the temperature match curing (TMC) condition. Results showed that the concrete sample containing GCS can reduce the adiabatic temperature rise, while slightly increasing the compressive strength, splitting tensile strength, chloride permeability, and sulfate attack resistance. The present study provided a theoretical basis for the application of GCS to the massive concrete.

Effects of Coal Bottom Ash as Cementitious Material on Compressive Strength and Chloride Permeability of Concrete

Coal Bottom Ash (CBA) is the waste material produced by coal-based power plants, particularly in Malaysia around 1.7 million tons of CBA was produced annually, which is major environmental concern. Therefore, the use of CBA as a partial replacement of cement in concrete is a possible solution for that pollution; this approach also creates a new corridor in the field of concrete production. However, this study aims to evaluate the effects of CBA as cementitious material on the concrete properties. This study incorporated 10% CBA as a cement replacement by weight method in concrete. However, concrete samples were prepared with and without CBA and immersed in water for 7, 28, 56 and 90 days. Next, the performances of concrete with and without CBA were evaluated in terms of workability, compressive strength, and rapid chloride permeability test. It was found that due to presence of CBA in concrete, workability reduces; no substantial growth in compressive strength at the early ages but substantial rise in strength was noticed after 56 days. Almost 4.7% higher strength was recorded than the control specimens at 90 days. Besides that, concrete containing CBA has lower chloride penetration as compared to the control specimen, which shows its better durability performance. It can be concluded that CBA has an enormous potential to be utilized as a cementitious material in durable concrete production.

Effect of different types of Cement in Concrete Chloride Permeability

Effect of different types of Cement in Concrete Chloride Permeability

Effects of High Temperature and Cooling Pattern on the Chloride Permeability of Concrete

Concrete structure is frequently subjected to the fire attack, whereas the permeability of concrete with fire-damage has received little consideration. This paper aims to investigate the chloride permeability of plain concrete and recycled aggregate concrete (RAC) with fire-damage, and the effects of various cooling patterns and recuring treatment on the chloride permeability are also studied. The results manifest that the elevated temperatures result in an increase in the fire-damage and chloride permeability of concrete, and that the increase becomes more obvious with the temperature above 400°C. Attributing to the water-cooling which provides a recuring environment, the chloride permeability after water-cooling is lower than that after air-cooling when the temperature is 200°C. Whereas when the temperature is above 400°C, the chloride permeability after water-cooling becomes higher than that after air-cooling, due to an extra damage that the water-cooling produces. The recuring treatment can reduce the chloride permeability of concrete with fire-damage, and the reduction becomes more significant when the concrete suffers a serious fire-damage. Exposing to the same condition of high temperature, the addition of recycled aggregate (RA) further boosts the fire-damage and chloride permeability of concrete. Particularly, the chloride permeability increases with the increasing of RA replacement ratios, linearly, and the increased temperatures further lead to an increase in the slope of the fitting straight line.

The Effect of Superplasticizer on Strength and Chloride Permeability of Concrete Containing GGBFS

The effect of superplasticizer on the mechanical property and chloride permeability of concrete containing GGBFS is investigated in this paper. Compressive and rapid chloride-ion diffusion tests were conducted to determine the axial compressive and chloride-ion diffusion coefficients of GGBFS modified concrete. The tests result indicated that the compressive strength of GGBFS modified concrete with the addition of 2wt. % superplasticizer are further improved at 14 and 28 days. Superplasticizer can significantly enhance the resistance to chloride ion penetration of concrete containing GGBFS with a reasonable additive content at long-term age. The optimum content of superplasticizer is suggested to be 1wt. % to 2wt. % of the cementitous materials.

Effect of Pore Structure on the Chloride Permeability of Concrete with Mineral Admixture

In this paper, the effect of pore structure on the chloride ions ingress into concrete was investigated. The most probable diameter was measured by Mercury intrusion porosimetry (MIP) and the total porosity was measured by evaporative water method (EWM). The results indicate that the most probable diameter by MIP has better linear relationship with chloride diffusion coefficient than the total porosity by EWM, the most probable diameter has significant influence on chloride diffusivity, and the smaller most probable diameter will lead to higher chloride penetration resistance.

STRENGTH, CHLORIDE PERMEABILITY AND CORROSION OF COARSE FLY ASH CONCRETE WITH BAGASSE-RICE HUSK-WOOD ASH ADDITIVE

This study studied the utilization of Bagasse-Rice Husk-Wood Ash (BRWA) as an additive for improving the strength and durability of coarse Fly Ash (FA) concrete. The ground BRWA was used as an additive for maintaining the consistent slump of FA concrete. The strength, chloride permeability and corrosion resistance were investigated. The chloride permeability of concrete was evaluated using the measurement of coulomb charge as per ASTM C1202 and the corrosion resistance was detected using the Accelerated Corrosion test by Impressed Voltage (ACTIV). The test indicated that the incorporation of ground BRWA as an additive in FA concrete improved potentially both the strength and corrosion resistance, particularly the concrete containing up to 40% FA. While the 60% FA concrete with ground BRWA additive improved significantly in strength, the resistance to corrosion was insignificantly improved. The results showed that the use of ground BRWA as an additive was one approach for its utilization in concrete beyond use as pozzolan. The increase in the use of BRWA in concrete could reduce costs and minimize the environmental problems as well.

Corrosion behaviour of reinforcing steel embedded in a concrete surface treated by in situ synthesised super-absorbent resin

A concrete surface was treated by in situ synthesised super-absorbent resin (SAR) of poly(acrylic acid-co-acrylamide). Experiments aimed at determining the resistance to carbonation and the chloride permeability of SAR-treated concrete compared with control concrete specimens were conducted. The corrosion risk and corrosion rate for the rebar embedded in SAR-treated and control concrete specimens at various periods of carbonation were evaluated through the accelerated corrosion test, wherein the rebar was subjected to 3·5% sodium chloride solution. The results show that the resistance to carbonation and chloride permeability of SAR-treated concrete is higher than that of control concrete, and that the corrosion risk and corrosion rate of steel embedded in SAR-treated concrete is smaller than that of steel in control concrete. Lighter carbonation can effectively decrease the chloride permeability of concrete, but serious carbonation is harmful to the long-term maintenance of the passive film of steel in concrete.

Evaluation of Relationship between Innitial Current, Conductance, Chloride Diffusion Coefficient and Charge Passed of Concrete

In this study, plain and mineral admixture (slag, fly ash and silica fume) modified concrete prisms were made with three water-to-binder ratios (w/b), and four test methods (Rapid Chloride Permeability Test-ASTM C1202-91, AC Conductance Test, 150-days Ponding Test, Alternate Wetting and Drying Test by cyclic loading with salt solution and drying) were employed to measure the concrete prisms’ chloride penetrability. The effects of mineral admixtures on the concrete chloride permeability were discussed, and the correlation of results separately obtained from the four test methods were analyzed. The experiment results indicate that blending concrete is beneficial with regard to the resistance against chloride ion penetration, and good linear ralationship between charge passed and innitial current, charge passed and conductance, charge passed and chloride diffusion coefficients by 150-days Ponding Test, charge passed and diffusion coefficients by Alternate Wetting and Drying Test were obtained.

Effect of Mineral Admixtures and Water/Binder Ratios on the Resistance to the Chloride Ions Penetration into Concrete

In this study, concrete prisms were made with three mineral admixtures: fly ash, blast furnace slag or silica fume and with three water-to-binder ratios(w/b). Chloride penetration was measured by the rapid chloride permeability test (RCPT)-ASTM C1202, 150-days ponding test and alternate wetting and drying test by cyclic loading with salt solution and oven drying, and the results by the three test methods were compared. This paper discussed the effects of mineral admixtures and w/b on the concrete chloride permeability. Blending concrete with blast furnace slag, fly ash or silica fume was beneficial with regard to the resistance against chloride ion penetration. Concrete specimens with lower w/b showed lower chloride permeability.

Effects of Mineral Admixtures on the Chloride Permeability of Hydraulic Concrete

The chloride permeability of concrete with slag or (20wt%, 30wt%, and 40wt% of binder) and binary slag and fly ash (the ratio of slag and fly ash 5:5, 4:6 and 6:4) was investigated in this study. The results show that the chloride permeability of concrete decreases firstly and increases latterly with the increasing of fly ash content. However, the permeability of concrete with slag decreases sharply with the slag content increases. Especially the content of slag is 40 wt%, the permeability is only 15.4% of the control concrete. The permeability of concrete using binary admixture of slag and fly ash is less than that of fly ash concrete and more than that of slag concrete.

Effect of cement type on the resistance of concrete against chloride penetration

In chloride containing environment, chloride permeability of concrete is an important parameter affecting the service life of concrete structures. The primary objective of this experimental study was to study the effect of cement types on the resistance of concrete against chloride penetration for given compressive strength classes. These cements included two different types of granulated blast-furnace slag cement (CEM III/A 32.5N and CEM III/A 42.5N), a sulfate resisting cement (SRC 32.5), and a Portland cement blended with fly ash; all of which compared to an ordinary Portland cement (CEM I 42.5R). For each binder type, four concretes at different strength classes were produced and as a result 20 mixtures were obtained. Rapid chloride ion penetration tests according to ASTM C 1202 were conducted. In addition, electrical resistivity and capillary water absorption tests were carried out. In order to characterize the concrete quality, compressive strength of the specimens were also obtained. The test results clearly demonstrated that the blast-furnace slag cements have the highest resistance against chloride penetration, while the pure Portland cement and sulfate resisting cement have the lowest resistance. Concretes produced with the sulfate resisting cement had substantially higher capillary sorption compared to other mixtures. Test results confirmed the strong relationship between the chloride permeability and electrical resistivity.

Pore structure and chloride permeability of concrete containing nano-particles for pavement

Pore structure and chloride permeability of concrete containing nano-particles (TiO 2 and SiO 2) for pavement are experimentally studied and compared with that of plain concrete, concrete containing polypropylene (PP) fibers and concrete containing both nano-TiO 2 and PP fibers. The test results indicate that the addition of nano-particles refines the pore structure of concrete and enhances the resistance to chloride penetration of concrete. The refined extent of pore structure and the enhanced extent of the resistance to chloride penetration of concrete are increased with the decreasing content of nano-particles. The pore structure and the resistance to chloride penetration of concrete containing nano-TiO 2 are superior to that of concrete containing the same amount of nano-SiO 2. However, for the concrete containing PP fibers, the pore structure is coarsened and the resistance to chloride penetration is reduced. The larger the content of PP fibers, the coarser the pore structure of concrete, and the lower the resistance to chloride penetration. For the concrete containing both nano-TiO 2 and PP fibers, the pore structure is coarser and the resistance to chloride penetration is lower than that of concrete containing the same amount of PP fibers only. A hyperbolic relationship between chloride permeability and compressive strength of concrete is exhibited. There is an obvious linear relationship between chloride permeability and pore structure of concrete.

Chloride Permeability and Microstructure of Portland Cement Mortars Incorporating Nanomaterials

Chloride permeability of concrete has been recognized as a critical intrinsic property affecting the durability of reinforced concrete. An experimental study was done, designed to examine the chloride permeability and microstructure of portland cement mortar with nanomaterials admixed at 1% by weight of cement. The electromigration test showed that, for cement mortars of the same mix design, the incorporation of nanoparticles (Fe2 O3, Al2O3, TiO2, and SiO2) and nanoclays (montmorillonite) improved the chloride penetration resistance of the mortar, as indicated by the reduced apparent diffusion coefficients of chloride anion. The nanomaterials also reduced the general ionic permeability of the mortar, as indicated by the reduced electric charge passing through. Such improvements were especially significant when using nano-SiO2 and nanoclays. The electrochemical impedance spectroscopy test indicated that incorporation of nanomaterials in cement mortar significantly increased its ionic transport resistance and decreased its electric capacitance, and again such effects were especially significant when using nano-SiO2 and nanoclays. The field emission scanning electron microscopy test revealed that the admixing of nanomaterials not only led to denser cement mortar but also changed the morphology of cement hydration products. Mechanisms are proposed to explain the physicochemical changes induced by the nanomaterials and the specific surface area of nanomaterials is demonstrated as one of the key factors. Considering the low cost of nanoclays, their use in concrete to reduce chloride permeability and to improve other properties of concrete is promising.

A parametric study of concrete permeability

Permeability plays a key role in concrete performance. Concrete permeability requirements are dependent upon concrete applications. Functional requirements of concrete permeability may lead to environmental concerns. Most concrete permeability tests are very time consuming. Rapid chloride permeability test is a desirable surrogate test for measuring the permeability of concrete. This paper presents findings of a parametric chloride permeability study. The methodology included a stepwise regression analysis, which pointed out the relative importance of various variables and their combined effects on chloride permeability of concrete. The results indicate that the following variables influence the chloride permeability of concrete: water to cement ratio, air content, coarse aggregate absorption, concrete cure method, and cure time. The most important feature of this paper is that relative effect of these variables on concrete permeability can be quantified by using the models presented.