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This article outlines the combined effects of saltwater and water flow on deterioration of concrete under freezing and thawing cycles. In order to simulate the real freezing situation that concrete usually undergoes, four sets of experimental exposure conditions were designed. These exposure conditions include plain flowing water, flowing saltwater...
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... the pore is connected to the surface through pores in which the pore solution freezes at a higher temperature than the actual one. The salt concentration may be increased locally owing to segregation of salt ions. The next step in the formation of ice is redistribution of pore solution when the temperature ranges between À 5°C and minimum temperature of the frost cycle (Kaufmann 2004). Local supercooling occurs if large pores or whole pore regions are connected to the ice front through smaller “ neck ” pores only. Especially, highly porous border zones around aggregates and porous non-frost-resistant aggregates might be separated from the ice front through smaller cement matrix pores leading to high hydrostatic pressure (Fagerlund 1997) when reached by the ice front. The thermodynamic equilibrium in the pore solution is disturbed by the ice formation (Scherer 1999). Because of the lower chemical potential, unfrozen pore solution, mostly in smaller pores or locally supercooled pore regions, flows toward the existing ice in the larger pores and freezes there. Liquid transport is also induced by a higher salt concentration ahead of the ice front (osmosis). This redistribution may induce internal shrinkage and additional hydrostatic pressures (Kaufmann 1999). Empty pore space, resulting from the bigger thermal contraction of ice than of the matrix, is refilled. At heating, the ice will expand more than the surrounding matrix, which induces additional tension. The lower the minimal temperature of the frost cycle, the stronger the tension. Additional tension also depends on the efficiency of the redistribution of the liquid (Kaufmann 2004). Water flow exists in the vicinity of many concrete structures during winter. When the temperature reaches 0°C, water flow does not allow the ice to form on the surface of concrete. According to the ice-formation procedure, freezing is mostly initiated from preexisting ice. As a result, it seems that water flow can slow down the formation of ice in concrete pores during the freezing cycle. This research aims to simulate the real freeze thaw exposure conditions that concrete usually undergoes. The effects of water flow on durability of concrete under freeze – thaw cycles, especially the combined effects of water flow and saltwater, are going to be examined. Usually, water flow exists in the vicinity of many concrete structures. In addition, deicing salt is commonly used for melting the frost and snow in cold regions. To simulate the water flow and the presence of saltwater, four sets of freezing and thawing exposure conditions were designed. These conditions include still plain water, flowing plain water, still saltwater, and flowing saltwater. Therefore, the damaging effects of water flow and saltwater, especially their combined effects, were examined. Two types of concrete with different water – cement ratio were prepared and submerged in each freeze – thaw condition. Weight change and compressive strength change of each sample were measured during the cycles. The concrete samples were prepared according to ACI 211.3R [American Concrete Institute (ACI) 2002]. Coarse aggregates were crushed stones (diameter ranging from 5 mm to 20 mm), and fine aggregates were natural river sand (fineness modulus of 2.6). Two types of concrete were prepared with water – cement ratios of 0.4 and 0.45 and a fine aggregate percentage of 0.45. Table 1 shows the major parameters of the mixtures. These ingredients were mixed for approximately 1 min and then water was added. Finally, the ingredients were mixed for approximately 2 – 3 min. Beams were cast in three approximately equal layers. Each layer was vibrated by using a vibrating table. The vibration was carried out until the bubbles stopped coming to the top. Lower water – cement ratio concrete samples were vibrated longer. For each concrete type, three beams with the dimensions of 70 × 10 × 10 cm were cast. All concrete samples were submerged in water and cured for 28 days. Because of the space limitations, 35 cores were drilled out of each concrete specimen with a diameter of 5 cm. Finally, 96 cylindrical samples with the dimensions of 5 × 10 cm were placed in four different freeze – thaw exposure conditions. In each exposure condition, 24 samples were submerged. After each seven cycles, weight changes in all the samples were measured. In addition, for measuring the compressive strength loss, three samples of each concrete type were tested after each seven cycles. To simulate the real freeze thaw conditions that occur in cold regions, four sets of experiments were designed. These include flowing plain water, still plain water, flowing saltwater, and still saltwater. Water flow was produced by an electromotor with a propeller. The motor rotated 2.4 times per second, providing slow water flow (0 : 2 m = s) to simulate the effects of flowing water in freezing – thawing cycles. Fig. 1 shows the set of the electromotor with the propeller, and Fig. 2 shows a schematic freeze – thaw cycle. In this research, 3% sodium chloride solution was used and samples were submerged in the solution during the freeze – thaw cycles. Because of the wide use of deicing salt for melting the snow or as a major component of seawater, salt is mostly available in freezing and thawing cycles. The samples were put in the freeze – thaw chamber that was planned to provide varying temperature ranging from þ 4 : 4°C to À 17 : 8°C. Both the freezing and thawing of the samples were conducted in water. The length of the cycles was considered as 24 h because the presence of deicing salt and water flow slows down the ice formation. This cycle length limited the practical number of freeze – thaw cycles, and 28 cycles were completed. Weight and compressive strength of the samples were measured before, during, and after the tests. Visual observation of the freezing condition and concrete deterioration was per- formed for each cycle. The comparison of the still plain water and flowing plain water showed that the most common deterioration in plain water was cracking, but the depth and number of concrete cracks in flowing plain water were significantly more than still plain water. In still plain water, the water surface freezes when the temperature reaches 0°C, and gradually, the depth of ice increases, but in flowing plain water, the water flow does not allow ice formation when the temperature reaches 0°C. In this situation, small ice particles form at the places in which the water flow is at the lowest level. Gradually, the ice formation continues forward to the highest water flow area. Finally, the ice stops the electromotor and a thin layer of ice forms on the surface. As the freezing cycles continue, the depth of this layer increases. The use of 3% sodium chloride in still saltwater showed that the deterio- rating effects of saltwater are more aggressive than water flow. In addition to cracking, samples underwent surface scaling, crumbling, and erosion. Freezing and thawing in flowing saltwater showed that the combined effects of saltwater and water flow are significantly more than other freeze – thaw conditions. Early deterioration of concrete occurred because of severe cracking and scaling. After four freeze – thaw cycles, many of the samples underwent great deterioration, and after seven cycles, complete deterioration of some of the samples happened. Furthermore, great chemical reaction occurred between concrete materials and saltwater. After four cycles, a white deposit of calcium carbonate sediment appeared because of rapid chemical reactions. The presence of water flow increases the rate and speed of chemical reactions. As a result, the rate of deterioration is more severe and faster under freezing and thawing cycles in the flowing saltwater exposure condition. Fig. 3 illustrates the formation of ice in flowing plain water, and Fig. 4 shows a white deposit because of chemical reactions between concrete materials and saltwater. Fig. 5 shows schematic types of samples ’ deterioration and their relative severity in different freezing conditions. Saturated surface dry (SSD) weight loss of concrete samples was measured as an important factor. After every seven cycles, samples were taken out of the container for weight measurement. At first, the samples were placed in a tub of tap water, and loose particles on the samples were removed gently by hand. Then, the samples were laid on a paper towel to dry, and if the sample was not too friable, it was blotted with paper towels. Samples were rotated periodically to facilitate drying of all faces. After 15 – 20 min, samples were weighed precisely. Figs. 6 and 7 illus- trate the weight change in types A and B concrete under different freeze – thaw conditions. As shown in Fig. 6, type A concrete with a water – cement ratio of 0.4 remained intact under freeze – thaw cycles in still plain water, flowing plain water, and still saltwater, but underwent 10% weight loss after 14 cycles in flowing saltwater and 100% weight loss after 28 cycles because of severe cracking and scaling. According to Fig. 7, Type B concrete with a water – cement ratio of 0.45 remained intact in still plain water, whereas it underwent a 24.37% weight loss because of severe cracking and scaling in flowing plain water. In addition, it lost 4.03% of its weight after seven cycles in still saltwater, 38.21% after 14 cycles, and 51.59% after 21 cycles. whereas it lost 78.37% of its weight just after seven cycles in flowing saltwater and 100% after 14 cycles. The comparison of Type A and B concrete samples shows that the lowering of the water – cement ratio has great influences on durability of concrete under freeze – thaw cycles. Results indicated that the presence of water flow or saltwater increases the deterioration of concrete, but the deteriorative effects of saltwater are considerably more than water flow on deterioration of concrete. The combined effects of ...
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... Concrete in the marine environment is exposed to composite degradation factors due to the environmental impact of the sea and high solar irradiation [5]. In the marine environment, the influence of saltwater can be considered the most representative factor [6,7]. Concrete absorbs water, and structures adjacent to the sea are exposed to large amounts of saltwater. ...
Concrete structures in marine environments are prone to deterioration and damage due to chloride ion penetration, freezing and thawing, and chemical erosion. Ultra-high-performance concrete (UHPC) mixed with steel fibers has been proposed as a solution to enhance the durability and mechanical properties of concrete in marine environments. Although several studies have been conducted in this regard, they have yet to focus on addressing errors that may be caused during the construction of offshore piers. Therefore, this study proposes a modular system to control horizontal and vertical errors during construction using a new connecting core type. UHPC with a fiber content of 0.75% was considered the optimum mix proportion because this met the tensile and compressive strength requirements and the chloride attack resistibility requirements of marine structures. The structural performance of a specimen constructed using modular technology was evaluated. The results of the lateral load resistance experiments showed minimal deformation in the girder and pier. Additionally, both the precast and cast-in-place types met the criterion of load resistance. This study contributes to the advancement of construction technology in marine environments by considering both material performance and construction conditions.
... To evaluate the state of concrete structures and determine their carrying capacities, it is possible to make use of several of the structures' mechanical and physical attributes. The researcher carried out a static truckload test on a recently built bridge to determine how the bridge reacted when a truck drove over it [1][2][3][4]. The weight and compressive strength of the samples were evaluated both before and after the freeze-thaw cycles, and the findings were analyzed. ...
To evaluate the state of the building's structure and determine whether it is structurally sound, forensic construction is required. The purpose of this study is to highlight some of the research that has been conducted on impacted concrete structures in various building types where destructive testing and non-destructive tests have been conducted. The structural integrity can be evaluated based on the extent of the deterioration from the experimental results. For instance, the cause of the corrode reinforcements was due to inadequate concrete cover, whereas the failure of the concrete wall was due to structures under design, which led to the collapse of the wall. This can be seen in the example of the corroded reinforcements.
... Diao et al. [11] found that when subjected to the freeze-thaw cycles and mixed corrosion, the loading capacity of reinforced concrete beams decreased by 4%. Amini and Tehrani [12] developed quantitative damage models to predict the mass loss and the compressive strength loss due to the combined effect of saltwater and water flow on the deterioration of concrete subjected to freeze-thaw cycles. Richardson et al. [13] found that rubber crumb was effective in providing freeze-thaw protection. ...
This study aims to investigate the effects of two freeze–thaw environments (i.e., maintenance freeze-thaw (MFT) environment and immersion freeze-thaw (IFT) environment) on the durability performance, deterioration rules, and mechanisms of concrete. In MFT, the concrete specimens were firstly cured in the standard curing environment (temperature, 20 ± 3, humidity, not less than 95%, and ages, 28 d) and then were carried out in freeze–thaw environment, while in IFT, the concrete specimens were firstly cured in the salt (NaHCO3, NaCl, and Na2SO4) immersion environment for 90 d and then were carried out in freeze–thaw environment. In this study, the damage features, relative dynamic elastic modulus, mass changes, and erosion-resistance coefficient of concrete have been measured. Thereafter, using the scanning electron microscopy (SEM) and the mercury intrusion porosimetry (MIP), the air-void structure parameters and the microstructures have been measured, respectively. The results show that the relative dynamic elastic modulus and the erosion-resistance coefficient of the compressive strength of the concrete in the IFT environment are, respectively, 14.3% and 21.0% higher than those of the concrete in the MFT environment. In addition, the results of the microstructure analyses show that the corrosion damages of the concrete are mainly caused by the combined action of the corrosion products of ettringite and freeze–thaw environment. However, the damage to the concrete in the MFT environment is more serious than that in the IFT environment. The results of the MIP analysis show that the harmful pore value for the concrete in the MFT environment is almost two times larger than that for the concrete in the IFT environment.
... 。 部分学者通过实验量化混凝土冻融损伤，并建 立冻融损伤和不同影响因素之间的关系。Penttala 等在盐溶液中采用 CIF/CDF 试验，建立冻融损伤 程度 D 和水灰比 r、 含气量 A 以及养护时间 B 的关 系[37] 。 Wloss、抗压强度损失∆σ与冻融循环次数 N， 水灰比 W 和与盐溶液浓度相关变量 S 之间的关系[38] 。 ...
The durability of the concrete under salt-freezing environment is rapidly degraded due to the coupling effect. In this review, the research results of chloride transport under freeze-thaw cycles were summarized according to the mechanical behavior, the diffusivity of chloride and several protective measurements. In freeze-thaw action, the concrete damage could be divided into two stages, and the two-stage damage theory was proposed to describe the initial and diffusion of damage, respectively. Some experimental methods were used to quantitatively investigate the damage degree of concrete. The relationships between damage degree and diffusion coefficient were established to deal with the acceleration effect of freeze-thaw cycle on chloride transport. The influence of influencing factors on the chloride transport under freeze-thaw cycle was investigated. The existing studies are mostly obtained from lab-scale experiments, thus restricting the quantitative evaluation of the life of actual concrete structures. A series of protective measures, such as surface treatment, electrochemical rehabilitation/protection and addition of admixture were proposed, and a future research direction in this field was discussed based on three aspects, i.e., experiment, theory and modelling.
... The carbonation depth is a decreasing function of the compressive strength and its coefficient depends on the porosity of cover concrete [6]. Carbonation shrinkage significantly reduced the elastic modulus and rather favorable with respect to the elastic modulus and tensile strength of ordinary Portland cement paste [7]. The chemical attack of H + and SO 4 2À caused the compressive strength of concrete decreased by reacting with the CaO in the concrete, and then the fragility of the concrete increased but the ductility reduced [8,9]. ...
Experimental investigations were taken for the degradation of concrete under coupling effects of hydrochloric acid mist and mixed salt mist consisting of chlorine and sulfate and carbon dioxide according to coal mine environment. Concrete specimens were subjected to four different deterioration time from 45 days to 180 days, with an interval of 45 days. The results showed that the carbonization depth of concrete increased speedy at first, then gently and then rapidly again with the change of fragility. The compressive strength of concrete increased at the initial stage of deterioration, and then decreased until the time of 135 days when they came to the second ascension of small quantity and then entered the decline trend under the coupling effect of carbonization and acid-salt attack. The elastic modulus changed slightly with the deterioration, meanwhile the fragility and ductility changed significantly before and after deterioration time of 180 days, which was identical to the failure modes.
... Sulfate attack and frost damage are two of the most common durability damages in concrete, and many scholars have conducted studies on these damages and achieved abundant research results [1][2][3][4]. However, in many cases, these two failure modes are coupled together and produce new damages on concrete [5][6][7][8]. ...
Rapid freeze–thaw cycle experiments were carried out on concrete specimens with 0.4, 0.5, and 0.6 water–cement (w/c) ratio in 0% (tap water), 1%, and 5% Na2SO4 solutions, respectively, to study the performance of ordinary concrete resistance to sulfate freeze–thaw cycle. The specimens underwent visual inspection, and mass losses and relative dynamic elastic modulus (RDEM) were measured regularly. Scanning electron microscope observation and X-ray diffraction analysis were conducted on partial specimens after the freeze–thaw cycle experiment. Research results show that due to the coupling effects of freeze–thaw cycle and sulfate corrosion, freeze–thaw cycles of concrete in Na2SO4 solution caused more damages than in tap water. Higher Na2SO4 concentration produced severe damages. Concrete with different w/c ratios exhibit different sulfate freeze–thaw cycle resistances, and concrete with lower w/c ratio usually produces stronger resistance. RDEM loss is considered the control index to determine concrete failure. The corrosion products in Na2SO4 solution freeze–thaw cycle are mainly ettringite and gypsum. With the increase in Na2SO4 concentration, ettringite formation gradually decreases and gypsum formation gradually increases.
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... Besides the experimental investigations on the damage behaviors of concrete, many researchers also proposed some damage prediction models for plain concrete under the single effect of freeze-thaw cycle [19][20][21][22][23], the coupling effect of freeze-thaw cycle and other factors (e.g., salts attack [19,24], carbonation [25], and salts attack and water flow [5]), and the coupling effect of flexural load and other factors (e.g., chemical attack [26] and water freezethaw [27]). ...
... According to Eqs. (5) and (7), the damage degree could be rewritten, as shown in Eq. (8). ...
In this paper, the workability, mechanical properties and damage behaviors of self-compacting concrete (SCC) under coupling effect of salt freeze-thaw and flexural load were experimentally investigated. The results showed that the workability of fresh SCC and mechanical properties could be influenced by fly ash, blast furnace slag and silica fume added in the mixture. Salt freeze-thaw had small influences on the surface erosion and relative dynamic elastic modulus of the SCC used in this study. Under coupling effect of salt freeze-thaw and flexural load, different levels of flexural load were applied on the SCC specimens. The results showed that with increasing salt freeze-thaw cycles, the weight loss increased and the relative dynamic elastic modulus declined. The coupling effect had a slight influence on the surface erosion, while it had a significant influence on the occurrence of brittle fracture. Higher stress levels always caused earlier and more occurrences of brittle fracture. A prediction model of the damage degree of SCC was proposed by incorporating the test results achieved in the paper. The comparison results showed that the prediction values had good consistencies with the experimental values. The model is expected to be used to predict the damage degree of SCC under coupling effect of salt freeze-thaw and flexural load.
... Studies on the performance of concrete that is subjected to salt solution freeze-thaw cycles have been conducted and significant conclusions have been presented [3][4][5][6]. Mu et al. reported that various salt solutions have different effects on the frost resistance of concrete [7]. They also argued that NaCl solution causes no change in the failure mechanism of concrete freeze-thaw cycles, whereas Na 2 SO 4 solution can cause freeze-thaw damage and sulfate attack at the same time. ...
... Li et al. suggested that 1 rapid freezethaw cycle for concrete in the laboratory is nearly equal to 12 freeze-thaw cycles for concrete in the natural environment [20]. Moreover, the relationship between the predicted service life of concrete T and the maximum number of rapid freezethaw cycles N F can be calculated using the following equation: (4) where B is the coefficient of rapid freeze-thaw experiment, namely, the number of 1 rapid freeze-thaw cycle equivalent to the natural freeze-thaw cycles, which is generally set at 12; k is the safety factor for concrete structure design, which is commonly set at 1.5; and M is the annual average number of freezing and thawing cycles of concrete structures in the natural environment. According to [20], the value of M in the northwest region of China can be set at 118. ...
To investigate the resistance of normal concrete to sulfate solution frost, concrete specimens with different water/cement (w/c) ratios, mineral admixture types, replacement ratios, and air contents were fabricated. Then, these specimens were frozen and thawed cyclically in 5% concentration Na 2 SO 4 solution. As the freezing and thawing cycles proceeding, the appearance morphology, mass loss, and dynamic elastic modulus (DEM) of the specimens were observed. The service life of concrete that is subjected to the freeze–thaw cycles in Na 2 SO 4 solution was calculated based on specimens' DEM losses. Results indicated that the appearance damage and mass loss of concrete along with the freeze–thaw cycles were unnoticeable until failure, and DEM losses played a controlling role in determining specimens' failure. In addition, a sudden fracture failure in the middle occurred easily in specimens with low w/c ratio. Decreasing concrete w/c ratio can slightly increase the concrete resistance to the freeze–thaw cycles in Na 2 SO 4 solution, whereas incorporating fly ash or slag has almost no effect. Moreover, higher replacement ratio of fly ash or slag increases the adverse effects on concrete. Adding an air-entraining agent to concrete can significantly improve its resistance to the freeze–thaw cycles. Air content at 4.6% and 5.7% can extend the service life of concrete under the freeze–thaw cycles in Na 2 SO 4 solution by more than 5 times its ordinary life span.
... The work concludes that efflorescence is more of an aesthetic defect and has little or no effect on the concrete structural properties and can be minimized by reducing the cyclic welting and drying of river water on concrete to avoid the crystallization of sulphate salts. Cement content is not a factor in terms of protecting concrete against saltwater effects [3] but ambient pressure has accelerated effects on the deterioration of concrete in deep river water environment [13] also, water flow accelerates the deterioration of concrete and that the combined effects of salt water and water flow are more severe and cause rapid deterioration [14]. There has been a recommendation that a rich mix other than 1:3:6 and 1:3:5 be strictly enforced on construction sites for concrete under saline attack [15]. ...
This paper presents a comparison of seawater and laboratory brine on concrete using experimental methods. The seawater employed was obtained from Escravos in the coast of Atlantic Ocean in Nigeria. A concrete mix of 1:2:4and water/cement ratio of 0.6 was adopted. The cube samples measured 150mmx150mmx150mm. The samples were cured in potable water for a period of 7, 14, 21 and 28 days at 240C.The seawater and laboratory simulated saltwater contained an equal amount of salt ion concentration. The laboratory saltwater was prepared with an analytical grade sodium chloride salt. The concrete cubes cast with potable water had a 28 days compressive strength of 33.48 N/mm2, concrete cubes cast with the seawater had a compressive strength of 31.04N/mm2, while the laboratory brined concrete cubes had a compressive strength of 25.26N/mm2. The results showed that the laboratory prepared salt water samples had the least compressive strength. Compared with the control samples, there was a strength reduction of 7.29% and 24.55% in the compressive strength of the seawater and laboratory saltwater samples respectively. Comparing the concrete cubes made with seawater with that of laboratory brined samples revealed a reduction of 18.62% in compressive strength of the laboratory brined concrete. Seawater therefore has a lesser reducing effect on the compressive strength of concrete than brine. Seawater is currently in use for mixing structural concrete in the Niger Delta region of Nigeria where portable water is not easily available.http://dx.doi.org/10.4314/njt.v34i3.6
... Breysse et al. [5] described the various aims of NDT methods such as to detect the condition of RC structures, rank the structures according to present condition, and compare the different Sanayei et al. [6] performed static truck load test on a newly constructed bridge, to capture the response of bridge when a truck traveled across it. Amini and Tehrani [7] designed experimentally four sets of exposure conditions, weight and compressive strength of the samples had been measured before and after the freeze thaw cycles, and the results were analyzed. Loizos and Papavasiliou [8] performed a comprehensive monitoring and data analysis research study by using Falling Weight deflectometer (FWD) for in situ evaluation of recycled pavements. ...
An engineering assessment was performed on concrete cubes casted from M25 concrete for checking the efficiency of non-destructive testing methods namely Schmidt’s rebound hammer test and Ultra Sonic Pulse Velocity test. The study was aimed at checking the viability of these above named non-destructive tests. Firstly, in the case of undamaged concrete structures and later on in the case of concrete structures damaged by fire, and then to compare the results to find out the efficiency of non-destructive testing methods. It is assumed that in the case of an undamaged structure the concrete is a homogenous mixture with equal strength at all depths. Hence, the non-destructive tests even if they are able to measure the surface strength like in case of the rebound hammer test may give a pretty accurate value when compared to the compressive tests performed in the laboratory. In the case of a structure, which has been damaged by fire, the concrete may no longer be homogenous at all depths and there might be considerable changes in its internal structure. Hence, this study is an attempt to carry out non-destructive tests on such concrete samples, which have been damaged by fire and then find out the viability and accuracy of the results when compared to the compressive tests performed in the laboratory.
