Salt Scaling Resistance Of Concrete Research Articles

Effects of Curing Method on Properties and Salt-Scaling Resistance of Concrete under Lab Testing

AbstractThis paper presents a study of the effect of curing on the salt-scaling resistance of concrete containing supplementary cementitious materials (SCMs) under lab conditions. Two curing method...

Validation of sequential pressure method for evaluation of the content of microvoids in air entrained concrete

The suitability of the sequential air pressure method (SAM) to evaluate the quality of air entrainment in concrete mix to support prediction of durability of hardened concrete was studied. The experiments included both laboratory-produced mixes and on-site trials on mixes delivered for highway pavement construction. The fresh air content and the air void distribution was tested using the SAM apparatus. The air content and the air void characteristics in hardened concrete was tested using the microscopic analysis on polished sections. Standard fresh mix properties were also tested and the compressive strength and salt-scaling resistance of concrete was determined. Effects of type and proportion of admixtures, type of crushed aggregate, timing of SAM measurements and the method of mix consolidation were analyzed. The relationship between the SAM number and the air void characteristics in hardened concrete was critically evaluated. The relationship between SAM number and the content of microvoids (A300) is found for the laboratory mixes and confirmed with few field test results. The criterion of SAM number ≤ 0.4 is proposed for the target microvoids content A300 ≥ 1.5% and the enhanced salt scaling resistance of concrete.

Linking air-void system and mechanical properties to salt-scaling resistance of concrete containing slag cement

This paper is focused on correlating salt-scaling resistance to material performance of concrete made with various water-to-cement ratios (w/cm), ternary blends of slag cement and fly ash, and air contents. The fly ash incorporation was kept constant at 20% cement content replacement for all mixes. The material performance of the mixtures was evaluated using air-void system, sorptivity, abrasion, compressive strength, and depth-sensing indentation (DSI) tests.Test results show that effect of concrete properties, i.e., sorptivity, surface hardness, and air content on salt scaling resistance of concrete is relative to mixture proportion. For a w/cm of 0.55 the average total salt scaling after 45 F-T cycles was found about 80% higher than that of mixes made with w/cm of 0.35. The results associated with mixtures made with slag cement were found misleading, since they exhibited improved mechanical properties, while lowered salt-scaling resistance. In addition, 3–6% of air entrainment appeared beneficial for concrete mixtures made with w/cm of 0.55, when subjected to high potential salt scaling environments.

Effect of initial curing conditions on air permeability and de- icing salt scaling resistance of surface concrete

Enhancing the surface quality of concrete is a key to improve the durability of reinforced concrete. Surface concrete can protect steel bars from corrosion due to the migration of gas, water and ion from the surrounding environment. Therefore, the influence of the initial curing on air permeability and the de-icing salt scaling resistance of surface concrete were investigated in this paper. Firstly, existing bridge structures in the cold region of Japan were surveyed with visual rating and non-destructive test (NDT) for the surface quality of concrete. Secondly, the concrete specimens were prepared for different curing conditions and methods including cold weather concreting, heat or non-heat-supply curing, ex- tending demold period and water-retention sheet. These results showed that concrete curing with sheet or permeability formwork was better than curing in air. Especially, utilizing permeability formwork is greatly effective for the attainment of high surface quality of concrete. Simultaneously, focus on cold weather concreting, could evaluate the appropriate curing period combining with the surface air perme- ability and the de-icing salt scaling resistance of concrete. The surface concrete has better de-icing salt frost resistance, when the surface air permeability coefficient is below 1×10-16m2 or the initial curing period is more than three weeks.

Effect of finishing practices on surface structure and salt-scaling resistance of concrete

The impact of three different finishing times on the surface layer properties of concrete containing different contents of ground granulated blast-furnace slag (GGBFS) replacement was evaluated, as well as the relationship between finishing, abrasion resistance of surface layer, and salt-scaling resistance. In addition, a novel method for monitoring the bleeding period of fresh concrete was investigated.Based on the results obtained in this study, choice of finishing time can influence salt scaling resistance by affecting abrasion resistance of concrete mixtures. It was found that lower resistance of slag concrete to salt scaling is not necessarily due to a weaker surface layer. While slag replacement reduced the mixtures’ scaling resistance, up to 40% of slag replacement improved mechanical properties, including surface abrasion resistance.

Water absorption of carbonated reactive MgO concrete and its correlation with the pore structure

Water absorption of concrete is an important indicator of concrete durability, which is closely related to the porosity and pore structure of concrete. This study investigates the water absorption behavior of carbonated concrete specimens containing reactive MgO of 10%, 30%, 50%, 70% and 90%. Meanwhile, the corresponding chemical composition and pore structure of each mix was characterized by XRD, TG/DTA, MIP and SEM. Experimental results reveal that the uniform pore structure of carbonated concrete containing 10%, 50%, 70% and 90% reactive MgO result in either high initial sorptivities or high quantities of absorbed water. The gradually microstructural change of a denser outer layer and less-dense inner layer from the surface to the center of the 50% reactive MgO concrete yields a low initial sorptivity and absorbed water quantity, which may have beneficial improvement on the freeze/thaw resistance and de-icing salt scaling resistance of concrete.

Freeze thaw and deicer salt scaling resistance of concrete prepared with alkali aluminosilicate cement

Concrete materials were prepared with a cement based primarily on the alkali aluminosilicate chemistry. Two aspects of concrete performance were emphasized and compared against those of ordinary Portland cement (OPC) concrete: freeze-thaw durability, and deicer salt scaling resistance. Test results indicated that the concrete prepared with the alkali aluminosilicate cement (AAC) produced excellent freeze-thaw durability; its dicer salt scaling resistance, however, was lower than that provided by the OPC concrete. Efforts were made to improve the deicer salt scaling resistance of the AAC concrete through refinement of the AAC composition. The use of an air-entraining agent was found to enhance the deicer salt scaling resistance of the AAC concrete. Modification of the AAC chemistry with polyethylene glycol, tartaric acid, or a combination of sodium benzoate and triisopropanolamine was found to also improve the AAC concrete resistance to deicer salt scaling with minimal effect on compressive strength.

Effect of Surface Preparation on the Deicing Salt-Scaling Resistance of Concrete With and Without SCM: Laboratory and Field Performance in the Presence of Sodium Chloride Deicing Salt

Abstract Deicing salt scaling is a form of surface deterioration of concrete, which describes the progressive raveling of mortar, sometimes even coarse aggregate, from the surface. This paper presents findings from both laboratory and field studies on the deicing salt-scaling resistance of concrete incorporating various proportions of fly ash (25 % and 50 %) and slag (30 % and 60 %). In the laboratory study, concrete slabs finished with different methods as well as concrete with non-finished surfaces were tested for deicing salt-scaling resistance. For the field study, larger concrete slabs were cast and cured in the laboratory and then placed outdoors. Deicing salt solution was applied on the slabs following each snowfall during the winter seasons to maintain an ice-free condition on the surface of the slabs. The results from the laboratory study indicate that the reduced salt-scaling resistance of concrete incorporating supplementary cementing materials is not solely depended on the mechanical strength of the concrete itself. It is also shown that concrete containing high levels of fly ash and slag maybe more sensitive to finishing techniques.

Effect of entrained air voids on salt scaling resistance of concrete containing a new composite cement

Salt scaling is a major damage problem for concrete pavements in cold environments. Salt scaling is a type of superficial damage caused by freezing and thawing a saline solution on the surface of concrete. Effects of a new composite Portland cement and air void on deicer scaling resistance of concrete were investigated in this paper. Another objective is to investigate effects of compressive strength, tensile strength, abrasion resistance and water penetration on the freeze-thaw deicer salt scaling. Specimens were tested for freeze-thaw deicer salt scaling resistance in accordance with ASTM C672 test method. Surface strengths of concrete play an important role in salt scaling resistance. There is no appropriate relationship between compressive strength and salt scaling resistance, when concrete mixtures are made with various cementitious materials. Results reveal that the mixture containing composite Portland cement with entrained air bubbles has the best performance in salt scaling test.

Effect of New Composite Cement Containing Volcanic Ash and Limestone on Mechanical Properties and Salt Scaling Resistance of Concrete

AbstractSalt scaling is one of the major damage problems for cementitious materials in cold environments. One of the main objectives of this work is to determine effects of air void and a new composite portland cement containing volcanic ash (tuff) and limestone on deicer scaling resistance of concrete. Another objective is to investigate the effects of compressive strength, tensile strength, abrasion resistance, and water penetration on the freeze-thaw deicer salt scaling. The specimens were tested for salt scaling resistance in accordance with standard test methods. The scanner method is used to quantify air void characteristics. In the scanner method, the polished surface is scanned twice on a high-resolution flatbed scanner. The polished surface of concrete sample is scanned in two different conditions; its natural and contrast-enhanced condition. Then the captured images are analyzed by a Visual Basic script. Tensile and surface strengths of concrete play an important role on salt scaling resistance....

Determination of the optimum conditions for de-icing salt scaling resistance of concrete by visual examination and surface scaling

One of the main objectives of this work is to determine the most important parameter that affects the scaling resistance of concrete. Another objective is to investigate combined effects of finishing treatment and air-entrainment on the freeze–thaw scaling of horizontal concrete surfaces subjected to de-icing salt exposure. The parameters studied in this work were; water–cement ratio, cement content, curing condition, the air-entraining admixture, and second finishing treatment. The total number of freeze–thaw cycles was 50. In the experiments, both visual examination according to ASTM C 672 and scaling test methods were considered. The parameters studied were optimized using Taguchi Optimisation Method. It has been shown that the use of de-icing salt on concrete surface causes gradual deterioration from the surface into the inner section. There is a significant positive effect of air-entrainment on the freeze–thaw scaling at horizontal concrete surfaces. It can be concluded that the second finishing treatment has a positive effect on first cycles but loses its effect on the proceeding cycles.

Capillary suction model for characterizing salt scaling resistance of concrete containing GGBFS

Abstract This paper presents a rational method to characterize the freeze–thaw salt scaling performance of concrete based on capillary suction forces. The testing program included evaluating the concrete’s chemical chloride binding capacity, degree of hydration, total porosity, compressive strength, sorptivity and de-icer salt scaling resistance conducted at both, 28 days and 2 years. Mixtures consisted of paste and concrete containing 0–60% GGBFS as cement replacement, and a water-to-binder ratio of 0.31 or 0.38. The proposed capillary suction model was adapted to include the concrete’s chloride binding capacity, pore characteristics, and age. Results from the capillary suction model are found to correlate with experimentally measured ionic sorption coefficients. Results revealed that the capillary suction depth decreases with increasing percentages of GGBFS due to blocking of capillary pores as a result of the chemical interaction between the saline solution and the binder material. A freeze–thaw salt scaling resistance factor (F/T SSRF) is proposed which accounts for the concrete’s degree of hydration, sorptivity and tensile strength and is shown to correlate with the concrete’s cumulative mass loss tested in accordance with MTO LS-412. Accordingly, the salt scaling performance of concrete containing GGBFS is influenced by the combined effect of the concrete’s pore size distribution of the exposed surface, chloride binding capacity, degree of hydration, and tensile strength.

Effect of Clinker Chemistry on Salt Scaling Resistance of Concrete

Work was conducted under a larger experimental program investigating the effects of processing additions on the performance of portland cements in concrete mixtures. One of the findings of this work is that there appears to be a trend that increasing tricalcium aluminate and the alkali content of the cement clinker increases the risk of freeze–thaw damage when tests are done in the laboratory. This trend was observed in mixtures with adequate air void systems and similar compressive strengths. It is possible that this effect is due to the increased osmotic pressures set up by increasing alkali contents in the pore solutions.

Frost salt scaling resistance of concrete containing CFBC fly ash

The possibility for using coal combustion by-products in concrete exposed to frost-salt aggression was investigated. The research was aimed to assess an influence addition of circulating fluidized bed combustion (CFBC) fly ash on frost-salt scaling of air-entrained concrete. For evaluation of the resistance of concrete to frost salt scaling the test called “depth sensing indentation” (DSI) was applied. The DSI test method was implemented on a universal testing frame using a standard Vickers indenter. Experimental tests were performed on cement paste specimens and concrete specimens designed with partial replacement of cement with coal combustion by-products. The mass of scaled material in standard frost salt scaling resistance tests on concrete was inversely proportional to the Vickers hardness of the paste containing CFBC fly ash; the best-fit arithmetic relationship is provided.

Precision of Tests for Assessment of the Deicer Salt Scaling Resistance of Concrete

Abstract Some aspects of the variability of Test Method for Scaling Resistance of Concrete Surfaces Exposed to Deicing Chemicals (ASTM C 672) measurements are discussed in this paper. The influence of the operator's subjectivity on the visual rating is studied. The relationship between the visual rating and the cumulated mass of scaled-off particles is also analyzed. From a statistical analysis of several hundred different concrete mixtures, the variability of the test method is estimated for various types of concrete considering only the cumulated mass of scaled-off particles. Using the same statistical analysis, the precision of ASTM C 672 is finally compared to that of the Canadian brine immersion test (Precast Concrete Paving Blocks, CAN/CSA A231.2 M85) designed to assess the deicer salt scaling resistance of precast concrete elements.

Deicer salt scaling resistance of steel-fiber-reinforced concrete

This project is part of a global research program aimed at studying the durability of steel-fiber-reinforced concrete exposed to severe winter conditions. It was carried out to determine if the use of steel fibers can have a significant influence on the deicer salt scaling resistance of concrete. Sixteen steel-fiber-reinforced concrete mixtures were investigated. The test variables were the water/binder ratio, the use of silica fume, the type of fiber and the quality of the air-void network. The results of the tests show that the fibers have no apparent influence on the deicer salt scaling resistance of concrete. Furthermore, it has been observed that a very small difference in the minimal freezing temperature could have a great influence on the deicer salt scaling resistance.