Scaling Resistance Of Concrete Research Articles

Evaluations of frost and scaling resistance of fly ash concrete in terms of changes in water absorption and pore structure under the accelerated carbonation conditions

In this study, the frost and scaling resistance of concrete with various fly ash (FA) replacement ratios exposure to air and accelerated carbonation conditions were investigated. The changes in water absorption were measured by RILEM / CIF test and in pore structure were measured by the Archimedes method and the mercury intrusion porosimetry method due to carbonation. Results show that the influence of FA and carbonation on the frost and scaling resistance of concrete can be ignored due to air bubbles by air entraining (AE) admixture in case of AE FA concrete. For Non-AE FA concrete, carbonation of FA concrete does not change the gel porosity/capillary porosity ratio, which is the reason for the frost resistance is not influenced by carbonation of FA concrete. Additionally, it is noteworthy to note that the scaling resistance is strongly connected to the pore volume above 75 nm, and that when exposed to carbonation, the scaling resistance tends to rise as a result of the increase in pore volume above 75 nm that occurs as a result of carbonation. Because of the addition of FA and carbonation, the frost and scaling resistance are far more reliant on the changes in pore structure than they are on the water absorption.

Effect of Timing of Curing Compound Application on Scaling Resistance of Concrete

Effect of Timing of Curing Compound Application on Scaling Resistance of Concrete

A Study on Assessment Method and Scaling Resistance of Concrete by the Different Type of Deicing Agents and Treatment of Concrete Surface Hardener

A Study on Assessment Method and Scaling Resistance of Concrete by the Different Type of Deicing Agents and Treatment of Concrete Surface Hardener

Durability of steam-cured concrete with slag under the combined deterioration of freeze-thaw cycles and de-icing chemicals

In previous studies on the durability of slag-mixed concrete against the combined impacts of deicing chemicals and freeze-thaw cycles, scaling resistance of concrete was improved using replacement amounts of slag from 25% to 35% of the total cement content. However, the resistance decreased rapidly when the amount of slag replacement increased above 40% of cement content. Furthermore, in these studies, only normal cured concrete products were used rather than steam-cured ones. Thus, the research on the scaling resistance of steam-cured concrete products with slag replacement has not been studied enough. In this study, the durability characteristics of slag-replaced steam-cured concrete against the impacts of concrete deicing chemicals and freeze-thaw cycles were investigated with the aim of improving the quality of precast concrete products. Scaling, chloride ion penetration, pull-off strength, and relative dynamic modulus of elasticity were evaluated for both the pouring and bottom sides of the specimens. This was done because it was expected that the concrete pouring side would suffer more degradation than the bottom side owing to weakened concrete strength caused by bleeding effects.

Prediction of Scaling Resistance of Concrete Modified with High-calcium Fly Ash Using Classification Methods

The goal of the study was applying machine learning methods to create rules for prediction of the surface scaling resistance of concrete modified with high-calcium fly ash. To determine the scaling durability the Boras method, according to European Standard procedure (PKN- CEN/TS 12390-9:2007), was used. The results of numeral experiments were utilized as a training set to generate rules indicating the relation between material composition and the scaling resistance. The classifier generated by BFT algorithm from the WEKA workbench can be used as a tool for adequate classification of plain concretes and concretes modified with high-calcium fly ash as materials resistant or not resistant to the surface scaling.

Effects of Deicing Salts on the Scaling Resistance of Concrete

The scaling resistance of concrete with strength grades of 30 MPa (C30) and 50 MPa (C50) subjected to different types (A and B) and concentrations (3, 5, and 20%) of deicing salt solution were studied using an accelerated freezing-thawing test. Deicing Salt A was composed of about 80% sodium chloride and 20% calcium chloride, B was composed of 70% sodium chloride, 25% magnesium chloride and 5% calcium chloride. The changes in strength, mass loss and relative dynamic modulus of elasticity of concrete were examined during the testing. The results showed that the salt scaling resistance of C50 was better than that of C30. The former could pass 160 freezing-thawing cycles while the latter could pass only 95 cycles. Specimens showed the largest deterioration when subjected to 5% solution, and the smallest deterioration when subjected to 20% solution after 200 cycles. Deicing salts with a higher percentage of NaCl and CaCl2 demonstrated a more obvious deterioration effect on concrete. The incorporation of 5% silica fume (by the mass of binder) or 1% high-efficiency air entraining agent significantly improved the salt scaling resistance of the concrete, even no visible deterioration was observed after 200 cycles. The main scaling deterioration features of concrete include surface spalling and cracking. Microstructural examinations indicated that formation of Friedel’s salt resulting from chemical reaction between NaCl or CaCl2 and calcium aluminate hydrates could lead to the deterioration of concrete during salt scaling testing.

Effect of Water-Binder Ratio and Mineral Admixture on Frost Scaling Resistance of Concrete

In order to increase freeze-salt scaling resistance of concrete, effect of water-binder ratio, fly ash, slag and silica fume on freeze-salt scaling resistance are researched according to the CDF method. The results show that the scaled mass and the dynamic modulus of elasticity loss rate of the concrete are reduced with decreasement of water-binder ratio. When mineral admixture compound is added into concrete the scaled mass and the dynamic modulus of elasticity loss rate are also reduced. Compared with fly ash and slag the trend is more obvious as result of fume and slag added. The scaled mass and the loss rate of dynamic elasticity modulus are slightly reduced with decreasement of fly ash and slag. But the scaled mass and the loss rate of dynamic elasticity modulus are obviously reduced with increasement of silica fume and slag.

Frost Scaling Resistance and Improvement of Concrete

In order to increase freeze-salt scaling resistance of concrete, improvement of fly ash, slag and air entraining agent on freeze-salt scaling resistance are researched according to the CDF method. The results show that the scaled mass and the dynamic modulus of elasticity loss rate of concrete are reduced by 20% to 36 % and 4 % to 55 %. The microstructure was more denser compared with the control concrete after 28 cycles as a result of adding mineral admixture and air entraining agent into concrete. The freeze-salt scaling resistance of concrete is improved. The freeze-salt resistance of concrete mixed with ground slag is superior to fly ash concrete. The damage of concrete is mainly surface scaling during salts frost.

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.

Freeze–Thaw Durability and Salt Scaling Resistance Assessment of Portland Cement Concrete Composite Pavement

The SHRP 2 R21 project on composite pavement investigated the durability of various mixtures of portland cement concrete (PCC) used in the construction of a two-layer composite PCC pavement. Project consultants in Europe, where composite PCC over PCC pavement was more common than in the United States, advised the R21 research team to consider using the CIF (capillary suction, internal damage, and freeze–thaw) standard of the International Union of Laboratories and Experts in Construction Materials, Systems, and Structures (RILEM), Paris, rather than the familiar ASTM standards. As a result, the R21 project adopted the RILEM CIF standard to evaluate the freeze–thaw durability and salt scaling resistance of concretes. The research also explored a modified RILEM CIF test (using pure water instead of a sodium chloride solution in scaling tests) alongside the standard RILEM CIF tests. The paper describes this experience to expose other institutions and agencies in the United States to the RILEM standards for the freeze–thaw durability and salt scaling resistance testing of concretes.

Effect of Curing Condition on Structure and Scaling Resistance of Specified Density Concrete

Influence of curing condition on internal relative humidity (IRH) of specified density concrete with different w/b ratios, pore structure of cement paste, hydrated product as well as scaling resistance of concrete were investigated. The results show that, as for concrete with w/b ratio of 0.31, water and standard curing can stop or slow up the migration of internal water, and the structure of cement paste is dense due to good hydrated environment, so the scaling resistance of concrete is best; as for concrete with w/b ratio of 0.47, the IRH of concrete under natural curing condition at 28 days is still 90%, there is sufficient water for the hydration of cement, and internal water content of concrete is lower as compared to concrete under water and standard curing conditions which makes it less easy to saturate, so natural curing concrete has better scaling resistance.

Analysis of the representativeness and relative severity of ASTM C672 and NQ 2621-900 standard procedures in evaluating concrete scaling resistance

The aim of this study is to gain an understanding of the representativeness and relative severity of ASTM C672 and NQ 2621-900 standard test procedures in evaluating the scaling resistance of concrete incorporating various proportions of fly ash (25% and 35%), slag (25% and 35%), and silica fume (1% and 2%). Length of curing and presaturation of samples were varied before starting the freeze–thaw tests. Laboratory durability of tested concrete was compared with that of similar concrete after 4 years of service life. Results show that the length of the moist pretreatment period is a key parameter in scaling resistance of laboratory-tested concrete. A 28-day period of moist curing appears to be optimal and leads to more realistic assessment of the actual scaling resistance of concrete. The use of a draining-bottom mold had no significant effect on the scaling resistance of the concretes in this study.

Proposed Behavioral Model for Deicer Scaling Resistance of Slag Cement Concrete

This study was performed to define and evaluate specific mechanisms that control deicer scaling (freeze-thaw) resistance in slag cement concrete. Modified ASTM C672 procedures were used to measure the deicer scaling resistance of concrete made with grade 120 slag cement substituted for ordinary portland cement at equal mass replacement levels of 30 and 50%. Two types of coarse aggregate, two Type I portland cement brands, and several curing methods were studied. The effects of carbonation were found to be a main cause of reduced scaling resistance in slag cement concrete, as supported by trends among curing methods and by variations in the chemical composition of portland cement. For concrete cured under ambient and low-carbonation conditions, increased carbonation is correlated with an increase in the concrete's scaling loss. These experimental results supported a proposed behavioral model linking cement hydration, concrete carbonation, and deicer scaling resistance. Decreased scaling resistance in concrete cured under moist conditions did not correlate with carbonation, but was likely caused by other factors related to continuous moisture present during curing.

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.

Surface microstructure and scaling resistance of concrete

Three different types of surfaces were tested to investigate the influence of the microstructure of the surface layers on the resistance of concrete to freezing in the presence of deicer salts: troweled surfaces prepared in two different ways, and sawed surfaces. In order to perform the investigation on various types of concrete, six different mixtures were prepared using two ordinary portland cements and one fly ash. The water to binder ratio was fixed at 0,40, and the replacement level of cement by fly ash was 20% and 40% (by mass). The scanning electron microscope observations carried out clearly indicate that the first millimeters below the surface of troweled laboratory concrete specimens can have a microstructure different than that of the bulk of the concrete. In all concretes tested, an extremely porous layer (i.e. with a very high water/binder ratio) was observed at the surface. The scaling test results show that the higher porosity of the surface layers tends to markedly reduce the deicer salt scaling durability of wood troweled laboratory samples during the first cycles of freezing and thawing. The use of fly ash was found to increase the thickness and the porosity of the surface layer.