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Nancy E Karraker - One of the best experts on this subject based on the ideXlab platform.
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road Deicing Salt irreversibly disrupts osmoregulation of salamander egg clutches
Environmental Pollution, 2011Co-Authors: Nancy E Karraker, James P GibbsAbstract:It has been postulated that road Deicing Salts are sufficiently diluted by spring rains to ameliorate any physiological impacts to amphibians breeding in wetlands near roads. We tested this conjecture by exposing clutches of the spotted salamander (Ambystoma maculatum) to three chloride concentrations (1 mg/L, 145 mg/L, 945 mg/L) for nine days, then transferred clutches to control water for nine days, and measured change in mass at three-day intervals. We measured mass change because water uptake by clutches reduces risks to embryos associated with freezing, predation, and disease. Clutches in controls sequestered water asymptotically. Those in the moderate concentrations lost 18% mass initially and regained 14% after transfer to control water. Clutches in high concentration lost 33% mass and then lost an additional 8% after transfer. Our results suggest that spring rains do not ameliorate the effects of Deicing Salts in wetlands with extremely high chloride concentrations.
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effect of road Deicing Salt on the susceptibility of amphibian embryos to infection by water molds
Environmental Research, 2009Co-Authors: Nancy E Karraker, Gregory R RuthigAbstract:Some causative agents of amphibian declines act synergistically to impact individual amphibians and their populations. In particular, pathogenic water molds (aquatic oomycetes) interact with environmental stressors and increase mortality in amphibian embryos. We documented colonization of eggs of three amphibian species, the wood frog (Rana sylvatica), the green frog (Rana clamitans), and the spotted salamander (Ambystoma maculatum), by water molds in the field and examined the interactive effects of road Deicing Salt and water molds, two known sources of mortality for amphibian embryos, on two species, R. clamitans and A. maculatum in the laboratory. We found that exposure to water molds did not affect embryonic survivorship in either A. maculatum or R. clamitans, regardless of the concentration of road Salt to which their eggs were exposed. Road Salt decreased survivorship of A. maculatum, but not R. clamitans, and frequency of malformations increased significantly in both species at the highest salinity concentration. The lack of an effect of water molds on survival of embryos and no interaction between road Salt and water molds indicates that observations of colonization of these eggs by water molds in the field probably represent a secondary invasion of unfertilized eggs or of embryos that had died of other causes. Given increasing salinization of freshwater habitats on several continents and the global distribution of water molds, our results suggest that some amphibian species may not be susceptible to the combined effects of these factors, permitting amphibian decline researchers to devote their attention to other potential causes.
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impacts of road Deicing Salt on the demography of vernal pool breeding amphibians
Ecological Applications, 2008Co-Authors: Nancy E Karraker, James P Gibbs, James R. VoneshAbstract:Deicing agents, primarily road Salt, are applied to roads in 26 states in the United States and in a number of European countries, yet the scale of impacts of road Salt on aquatic organisms remains largely under-studied. The issue is germane to amphibian conservation because both adult and larval amphibians are known to be particularly sensitive to changes in their osmolar environments. In this study, we combined survey, experimental, and demographic modeling approaches to evaluate the possible effects of road Salt on two common vernal-pond-breeding amphibian species, the spotted salamander (Ambystoma maculatum) and the wood frog (Rana sylvatica). We found that in the Adirondack Mountain Region of New York (USA), road Salt traveled up to 172 m from the highway into wetlands. Surveys showed that egg mass densities of spotted salamanders (A. maculatum) and wood frogs (R. sylvatica) were two times higher in forest pools than roadside pools, but this pattern was better explained by road proximity than by incr...
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impacts of road Deicing Salt on the demography of vernal pool breeding amphibians
Ecological Applications, 2008Co-Authors: Nancy E Karraker, James P Gibbs, James R. VoneshAbstract:Deicing agents, primarily road Salt, are applied to roads in 26 states in the United States and in a number of European countries, yet the scale of impacts of road Salt on aquatic organisms remains largely under-studied. The issue is germane to amphibian conservation because both adult and larval amphibians are known to be particularly sensitive to changes in their osmolar environments. In this study, we combined survey, experimental, and demographic modeling approaches to evaluate the possible effects of road Salt on two common vernal-pond-breeding amphibian species, the spotted salamander (Ambystoma maculatum) and the wood frog (Rana sylvatica). We found that in the Adirondack Mountain Region of New York (USA), road Salt traveled up to 172 m from the highway into wetlands. Surveys showed that egg mass densities of spotted salamanders (A. maculatum) and wood frogs (R. sylvatica) were two times higher in forest pools than roadside pools, but this pattern was better explained by road proximity than by increased salinity. Experiments demonstrated that embryonic and larval survival were reduced at moderate (500 muS) and high conductivities (3000 muS) in A. maculatum and at high conductivities in R. sylvatica. Demographic models suggest that such egg and larval stage effects of Salt may have important impacts on populations near roads, particularly in the case of A. maculatum, for which Salt exposure may lead to local extinction. For both species, the effect of road Salt was dependent upon the strength of larval density dependence and declined rapidly with distance from the roadside, with the greatest negative effects being limited to within 50 m. Based on this evidence, we argue that efforts to protect local populations of A. maculatum and R. sylvatica in roadside wetlands should, in part, be aimed at reducing application of road Salt near wetlands with high conductivity levels.
V.m Malhotra - One of the best experts on this subject based on the ideXlab platform.
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mechanical properties and durability of concrete made with high volume fly ash blended cements using a coarse fly ash
Cement and Concrete Research, 2001Co-Authors: N Ouzoubaâ, Min-hong Zhang, V.m MalhotraAbstract:This paper presents a study on the mechanical properties and durability of concrete made with a high-volume fly ash (HVFA) blended cement using a coarse fly ash that does not meet the fineness requirement of ASTM C 618. The results were compared with those of the HVFA concrete in which unground fly ash had been added at the concrete mixer. The properties of the fresh concrete determined included the slump, air content, slump loss, stability of air content, bleeding, and setting time; those of the hardened concrete investigated included the compressive strength, flexural- and splitting-tensile strengths, Young's modulus of elasticity, drying shrinkage, resistance to abrasion, chloride-ion penetration, freezing and thawing cycling, and to Deicing Salt scaling. The results show that except for the resistance of the concrete to the Deicing Salt scaling, the mechanical properties and the durability of concrete made with this blended cement were superior to the concrete in which the unground fly ash and the cement had been added separately at the mixer. The production of HVFA blended cements, therefore, offers an effective way for the utilization of coarse fly ashes that do not otherwise meet the fineness requirements of ASTM C 618.
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Deicing Salt scaling resistance of concrete incorporating supplementary cementing materials canmet research
RILEM PROCEEDINGS 30. FREEZE-THAW DURABILITY OF CONCRETE, 1997Co-Authors: A. Bilodeau, V.m MalhotraAbstract:This paper presents the results of four CANMET investigations dealing with the Deicing Salt scaling resistance of concrete incorporating supplementary cementing materials. The supplementary cementing materials investigated included silica fume, blast-furnace slag and fly ash. The scaling resistance of the superplasticized concrete incorporating high volumes of fly ash was also determined. In general, the incorporation of supplementary cementing materials affected adversely its Deicing Salt scaling resistance. This effect ranged from being very marginal to considerable depending upon the type and percentage of the supplementary cementing materials used. Concretes incorporating 8% silica fume or up to 30% fly ash performed satisfactorily in the ASTM Deicing Salt scaling test C 672. In particular, the performance of fly ash concrete was noticeably improved by the use of membrane curing. The slag concretes showed considerably more scaling than the reference concretes, and in general, their surfaces were rated as moderately scaled. All high-volume fly ash concretes performed relatively poorly in the scaling test. Their poor performance is possibly related to the unsatisfactory quality of their air-void parameters, principally at the surface of the specimens. (A) For the covering abstract see IRRD 887310.
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some aspects of durability of high volume astm class f low calcium fly ash concrete in durability of concrete second international conference august 4 9 1991 montreal canada volume i
DURABILITY OF CONCRETE. SECOND INTERNATIONAL CONFERENCE., 1991Co-Authors: V.m Malhotra, G G Carette, A. BilodeauAbstract:Low-calcium fly ash, ASTM Class F, is being increasingly incorporated into portaldn cement concrete as a partial replacement for cement. The replacements commonly used are 15 to 25 percent by weight of cement. This paper presents data on several aspects of durability of this new type of concrete. The aspects discussed include freezing and thawing cycling, resistance to chloride ion diffusion, Deicing Salt scaling resistance, carbonation, and volume stability. Data on the role of high volumes of fly ash to control alkali-silica reaction in concrete are also presented. It is concluded that, in general, high-volume fly ash concrete has excellent durability characteristics. The only exception is the Deicing Salt scaling tests, in which the above concrete performs poorly.
Jason W Weiss - One of the best experts on this subject based on the ideXlab platform.
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use of fly ash to minimize Deicing Salt damage in concrete pavements
Transportation Research Record, 2017Co-Authors: Prannoy Suraneni, Vahid Jafari Azad, Burkan O Isgor, Jason W WeissAbstract:Premature damage has been observed at the joints in numerous concrete pavements where calcium chloride and magnesium chloride Deicing Salts have been used. This damage results from a reaction between the Deicing Salt and the calcium hydroxide (CH) in the hydrated cement paste. This reaction leads to the formation of an expansive product known as calcium oxychloride (CAOXY). The use of supplementary cementitious materials as a replacement for cement has been proposed to reduce the CH that is available in the mixture to react with the Deicing Salts. Reducing the CH can reduce the amount of CAOXY that forms. In this study, mixtures representative of paving concrete were made with cements and fly ashes from across the country. CH amounts were determined by using thermogravimetric analysis, and CAOXY amounts were determined by using low-temperature differential scanning calorimetry. Various replacement levels of fly ash were used to demonstrate that the main parameter that influences the amounts of CH and CAOX...
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numerical simulation of the freeze thaw behavior of mortar containing Deicing Salt solution
Materials and Structures, 2017Co-Authors: Hadi S Esmaeeli, Yaghoob Farnam, Dale P Bentz, Pablo D Zavattieri, Jason W WeissAbstract:This paper presents a one-dimensional finite difference model that is developed to describe the freeze-thaw behavior of an air-entrained mortar containing Deicing Salt solution. A phenomenological model is used to predict the temperature and the heat flow for mortar specimens during cooling and heating. Phase transformations associated with the freezing/melting of water/ice or transition of the eutectic solution from liquid to solid are included in this phenomenological model. The lever rule is used to calculate the quantity of solution that undergoes the phase transformation, thereby simulating the energy released/absorbed during phase transformation. Undercooling and pore size effects are considered in the numerical model. To investigate the effect of pore size distribution, this distribution is considered using the Gibbs-Thomson equation in a saturated mortar specimen. For an air-entrained mortar, the impact of considering pore size (and curvature) on freezing was relatively insignificant; however the impact of pore size is much more significant during melting. The fluid inside pores smaller than 5 nm (i.e., gel pores) has a relatively small contribution in the macroscopic freeze-thaw behavior of mortar specimens within the temperature range used in this study (i.e., +24 °C to -35 °C), and can therefore be neglected for the macroscopic freeze-thaw simulations. A heat sink term is utilized to simulate the heat dissipation during phase transformations. Data from experiments performed using a low-temperature longitudinal guarded comparative calorimeter (LGCC) on mortar specimens fully saturated with various concentration NaCl solutions or partially saturated with water is compared to the numerical results and a promising agreement is generally obtained.
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performance of carbonated calcium silicate based cement pastes and mortars exposed to nacl and mgcl2 Deicing Salt
Construction and Building Materials, 2016Co-Authors: Yaghoob Farnam, Chiara Villani, Taylor Washington, Mark Spence, Jitendra Jain, Jason W WeissAbstract:Abstract This paper investigates the performance of two cementitious systems exposed to freezing or Deicing Salts. The first cementitious system is made using an ordinary portland cement (OPC) that reacts through hydration. The second cementitious system is made using a calcium silicate cement (CSC) that reacts and gains strength through carbonation (i.e., carbonated calcium silicate based cement (CCSC)). Two experimental techniques were used to evaluate the performance of these materials. The first technique measures the potential reactivity between the concrete paste and the Deicing Salt (NaCl and MgCl 2 ) using a low temperature differential scanning calorimeter. The second technique uses a longitudinal guarded comparative calorimeter equipped with acoustic emission to assess the freeze–thaw performance of mortar samples saturated with water or Deicing solutions. No chemical reaction is observed between CCSC paste and NaCl while a damaging reaction is observed between the OPC paste and NaCl due to the presence of calcium sulfoaluminate phases. A chemical reaction occurs for both the CCSC and OPC paste exposed to MgCl 2 : for the CCSC paste, this appears non-deleterious since relatively no reduction in dynamic elastic modulus is observed; for OPC paste, however, this is a damaging reaction due to formations of magnesium silicate hydrate and calcium/magnesium oxychloride. CCSC mortar sample saturated with water shows freezing in the large pores at approximately −5 °C and smaller pores at approximately −28 °C. Both the OPC and CCSC mortars show similar freeze–thaw performance when the system is water saturated. When the water in the pores of the mortar is replaced with a Salt solution (NaCl and MgCl 2 ), the CCSC mortar shows less freeze–thaw damage (mainly due to possessing a different pore structure) and more resistance to Salt degradation (mainly due to possessing a different chemistry) than the OPC mortar does.
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the influence of Deicing Salt exposure on the gas transport in cementitious materials
Construction and Building Materials, 2014Co-Authors: Chiara Villani, Tommy Nantung, Jason W WeissAbstract:Abstract The gas transport properties of concrete can provide useful information for the prediction of the service life. However, to interpret the transport properties properly, some corrections may be needed to account for the moisture content and the distribution of moisture in the concrete. This paper investigates the influence of Deicing Salts on gas transport. Specifically, oxygen permeability and oxygen diffusion were examined for mortar samples initially saturated with different Deicing Salt solutions and then exposed to drying. The presence of Deicing was found to increase the degree of saturation of mortar samples and as such it decreases permeability and diffusivity. These findings were further confirmed through desorption analysis. This study suggests that care must be taken when performing investigations on concrete previously exposed to Deicing Salts either in situ or when this concrete is extracted and used for laboratory testing.
N De Belie - One of the best experts on this subject based on the ideXlab platform.
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towards an adequate Deicing Salt scaling resistance of high volume fly ash hvfa concrete and concrete with superabsorbent polymers saps
Int. RILEM Conference on Materials Systems and Structures in Civil Engineering - Segment on Frost Action in Concrete, 2016Co-Authors: Didier Snoeck, P Van Den Heede, N De BelieAbstract:The Deicing Salt scaling resistance has been investigated for two types of concrete, i.e., air entrained high-volume fly ash (HVFA) concrete with a 50% cement replacement and non-air entrained concrete containing superabsorbent polymers (SAPs). A full characterization of their air void systems from the moment of casting until the freeze/thaw test was also done. Due to the presence of the highly AEA adsorptive fly ash an increased AEA dosage (7.0 ml/kg binder) was needed to achieve an adequate air void system in terms of air content and spacing factor to keep Salt scaling within acceptable limits. For the novel non-air entrained concrete type with SAPs, which are able to absorb up to 500 times their weight in fluids, the Salt scaling resistance is surprisingly high. The microstructural analysis revealed the formation of macro-pores due to these SAPs, creating an air void system as can be found in air-entrained concrete. Another advantage is that the strength of concrete with SAPs is much higher than for a conventional air-entrained concrete. This substantiates the further use of these SAPs as admixture in precast concrete road elements.
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influence of air entraining agents on Deicing Salt scaling resistance and transport properties of high volume fly ash concrete
Cement & Concrete Composites, 2013Co-Authors: P Van Den Heede, J Furniere, N De BelieAbstract:Abstract Based on laboratory tests, the Deicing Salt scaling resistance of high-volume fly ash (HVFA) concrete is usually reported as less than satisfactory. Therefore, we developed a HVFA composition with an air entraining agent (AEA) that should meet the European Salt scaling criterion (⩽1 kg/m 2 ). This paper presents a full characterization of its air void system from the moment of casting until the freeze/thaw test on cast surfaces, and evaluates the influence of air entrainment on its transport properties. The minimum air content of 6–7% was achieved with 7.0 ml AEA/kg binder (versus 2.0 ml AEA/kg binder for traditional concrete). However, with very fine fly ash (45 μm fineness: 13.2% retained), it was more difficult to maintain an adequate air void system and control the Salt scaling resistance at later age (91 days). With coarser fly ash (45 μm fineness: 26.6% retained), Salt scaling after 28 severe freeze/thaw cycles equaled only 0.5 kg/m 2 . Nevertheless, AEA use increased the water sorption under vacuum and the apparent gas permeability.
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Influence of air entraining agents (AEAs) on Deicing Salt scaling resistance of high-volume fly ash concrete (HVFA concrete)
2011Co-Authors: P Van Den Heede, J Furniere, N De BelieAbstract:It is usually concluded from laboratory tests that Deicing Salt scaling resistance of High-Volume Fly Ash concrete (HVFA concrete) is less than satisfactory. This is mainly attributed to the partial adsorption of the applied air entraining agent (AEA) by the unburnt carbon present in the fly ash. As a consequence, the presence of an adequate air void system in HVFA concrete can not always be garantueed. This explains why the use of HVFA concrete in pavements exposed to freezing and thawing with Deicing Salts, is still not generally accepted. Therefore, we carefully evaluated the air void system of this concrete type in the hardened state. This paper presents a full assessment of this air void system for two HVFA compositions with a total binder content of 450 kg/m³ (50 % cement, 50 % fly ash) and a water-to-binder ratio of 0.35. The two mixtures mutually differed in the type of fly ash used. For both of them, the minimum required air content in the fresh state was achieved with an AEA dosage of 5.0 ml/kg binder. The air void system was evaluated qualitatively using microscopic analysis on thin sections. The air content (≥ 4 %) and spacing factor (≤ 200 μm) were quantified with the Rapidair 457 apparatus. Although these two properties were similar for the two mixtures and they both met the applicable criteria, the air void system still seemed a bit less pronounced under the microscope for one of the mixtures. The Salt scaling resistance of the latter mixture was also found to be significantly less after 28 days of curing and 28 severe freeze/thaw cycles. The mass loss due to Salt scaling was found to be equal to more or less 1 kg/m², the maximum allowed value according to the applicable European standard, while the amount of scaled off material for the other mixture was much less (0.44 kg/m²).
Yaghoob Farnam - One of the best experts on this subject based on the ideXlab platform.
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evaluating the use of supplementary cementitious materials to mitigate damage in cementitious materials exposed to calcium chloride Deicing Salt
Cement & Concrete Composites, 2017Co-Authors: Yaghoob Farnam, Bochen Zhang, Jason WeissAbstract:Abstract This paper discusses the role of supplementary cementitious materials (SCM) in reducing damage caused by calcium oxychloride formation. Calcium oxychloride is a destructive product of a reaction between calcium hydroxide (CH) that exists in a cementitious matrix and CaCl 2 that can enter the pores of the matrix when it is used as a Deicing Salt. Paste samples were prepared where a percentage of ordinary portland cement was replaced with various types of SCM (including fly ash, slag, and silica fume). This paper examined the amount of calcium oxychloride that formed using low-temperature differential scanning calorimetry, and damage development detected using acoustic emission. Thermogravimetric analysis was also performed to determine the relationship between the amount of CH in cementitious materials and the amount of calcium oxychloride formation. The results show that the use of SCM is effective in reducing the calcium oxychloride formation and resulting damage when cementitious materials are exposed to various compositions of solution containing CaCl 2 . The explanation of the benefit of using SCM is that it can reduce the calcium oxychloride formation due to a reduction in the amount of CH in the cementitious materials through pozzolanic reaction and dilution of cement. As a result, cementitious materials with SCM exposed to CaCl 2 may experience less damage and have a longer service life.
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numerical simulation of the freeze thaw behavior of mortar containing Deicing Salt solution
Materials and Structures, 2017Co-Authors: Hadi S Esmaeeli, Yaghoob Farnam, Dale P Bentz, Pablo D Zavattieri, Jason W WeissAbstract:This paper presents a one-dimensional finite difference model that is developed to describe the freeze-thaw behavior of an air-entrained mortar containing Deicing Salt solution. A phenomenological model is used to predict the temperature and the heat flow for mortar specimens during cooling and heating. Phase transformations associated with the freezing/melting of water/ice or transition of the eutectic solution from liquid to solid are included in this phenomenological model. The lever rule is used to calculate the quantity of solution that undergoes the phase transformation, thereby simulating the energy released/absorbed during phase transformation. Undercooling and pore size effects are considered in the numerical model. To investigate the effect of pore size distribution, this distribution is considered using the Gibbs-Thomson equation in a saturated mortar specimen. For an air-entrained mortar, the impact of considering pore size (and curvature) on freezing was relatively insignificant; however the impact of pore size is much more significant during melting. The fluid inside pores smaller than 5 nm (i.e., gel pores) has a relatively small contribution in the macroscopic freeze-thaw behavior of mortar specimens within the temperature range used in this study (i.e., +24 °C to -35 °C), and can therefore be neglected for the macroscopic freeze-thaw simulations. A heat sink term is utilized to simulate the heat dissipation during phase transformations. Data from experiments performed using a low-temperature longitudinal guarded comparative calorimeter (LGCC) on mortar specimens fully saturated with various concentration NaCl solutions or partially saturated with water is compared to the numerical results and a promising agreement is generally obtained.
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performance of carbonated calcium silicate based cement pastes and mortars exposed to nacl and mgcl2 Deicing Salt
Construction and Building Materials, 2016Co-Authors: Yaghoob Farnam, Chiara Villani, Taylor Washington, Mark Spence, Jitendra Jain, Jason W WeissAbstract:Abstract This paper investigates the performance of two cementitious systems exposed to freezing or Deicing Salts. The first cementitious system is made using an ordinary portland cement (OPC) that reacts through hydration. The second cementitious system is made using a calcium silicate cement (CSC) that reacts and gains strength through carbonation (i.e., carbonated calcium silicate based cement (CCSC)). Two experimental techniques were used to evaluate the performance of these materials. The first technique measures the potential reactivity between the concrete paste and the Deicing Salt (NaCl and MgCl 2 ) using a low temperature differential scanning calorimeter. The second technique uses a longitudinal guarded comparative calorimeter equipped with acoustic emission to assess the freeze–thaw performance of mortar samples saturated with water or Deicing solutions. No chemical reaction is observed between CCSC paste and NaCl while a damaging reaction is observed between the OPC paste and NaCl due to the presence of calcium sulfoaluminate phases. A chemical reaction occurs for both the CCSC and OPC paste exposed to MgCl 2 : for the CCSC paste, this appears non-deleterious since relatively no reduction in dynamic elastic modulus is observed; for OPC paste, however, this is a damaging reaction due to formations of magnesium silicate hydrate and calcium/magnesium oxychloride. CCSC mortar sample saturated with water shows freezing in the large pores at approximately −5 °C and smaller pores at approximately −28 °C. Both the OPC and CCSC mortars show similar freeze–thaw performance when the system is water saturated. When the water in the pores of the mortar is replaced with a Salt solution (NaCl and MgCl 2 ), the CCSC mortar shows less freeze–thaw damage (mainly due to possessing a different pore structure) and more resistance to Salt degradation (mainly due to possessing a different chemistry) than the OPC mortar does.
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damage development in cementitious materials exposed to magnesium chloride Deicing Salt
Construction and Building Materials, 2015Co-Authors: Yaghoob Farnam, Andrew Wiese, Dale P Entz, Jeffrey M Davis, Jaso WeissAbstract:Abstract Magnesium chloride (MgCl 2 ) is used in Deicing applications due to its capability to depress freezing temperatures to a lower point than other Salts such as sodium chloride (NaCl). The constituents of concrete (i.e., pores solution, calcium hydroxide, aluminate phases, and calcium silicate hydrate gel) can alter the MgCl 2 –H 2 O phase diagram when it is used to interpret the performance of concrete. Different chemical reactions may concurrently occur between MgCl 2 and cementitious constituents to form brucite, Friedel’s Salts, magnesium silicate hydrate, magnesium oxychloride, and/or secondary calcium oxychloride. In this study, it was observed that MgCl 2 can be entirely consumed in concrete by the chemical reactions and produce CaCl 2 . As such, it was found that MgCl 2 interacts significantly with a cementitious material and it follows a response that is more similar to the Ca(OH) 2 –CaCl 2 –H 2 O phase diagram than that of the MgCl 2 –H 2 O phase diagram. Mortar samples exposed to low concentration MgCl 2 solutions ( 2 and cementitious constituents at room temperature (23 °C). These chemical reactions occurred rapidly (within 5–10 min) and caused a significant decrease in subsequent fluid ingress into exposed concrete.
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measuring freeze and thaw damage in mortars containing Deicing Salt using a low temperature longitudinal guarded comparative calorimeter and acoustic emission
Advances in Civil Engineering Materials, 2014Co-Authors: Yaghoob Farnam, Dale P Bentz, Aaron R Sakulich, Daniel R Flynn, Jason WeissAbstract:Deicing Salts are often applied to the surface of pavements and bridge decks in the winter to melt ice, thereby improving safety for the traveling public. In this paper, the influence of NaCl Deicing Salt on freezing and thawing temperatures of pore solution and corresponding damage of mortar specimens were investigated. A low-temperature longitudinal guarded comparative calorimeter (LGCC) was developed to cool down a mortar sample at a rate of 2°C/h and to re-heat the mortar at a rate of 4°C/h. Heat flux during freezing and thawing cycles was monitored, and the temperatures at which freezing and thawing events occurred were detected. During cooling and heating, acoustic emission (AE) activity was measured to quantify the damage (cracking) caused by aggregate/paste thermal mismatch and/or phase changes. The results show that NaCl solution in a mortar sample freezes at a lower temperature than the value expected from its bulk phase diagram because of under-cooling. Conversely, the frozen solution in mortar melts at the same melting temperature as the bulk frozen NaCl solution. As the Salt concentration increases, the freezing temperature is lowered. For samples containing more highly concentrated solutions, an additional exothermic event is observed whose corresponding temperature is greater than the aqueous NaCl liquidus line in the phase diagram. Damage also begins to occur at this temperature. For mortar samples saturated by solutions with 5 % and 15 % NaCl by mass, greater freeze/thaw damage is observed. The AE calorimeter developed herein is applicable for investigating damage behavior during freezing and thawing of different phases in pore solution (in mortars).