Calcium Oxychloride Research Articles

Long-Term Performance of Soybean-Based Concrete Surface Protectant under Laboratory Accelerated Aging Conditions

Soy methyl ester-polystyrene (SME-PS) is an organic material derived from soybeans, which has proven to be an effective protectant for concrete surfaces. This study investigated the long-term performance of cement paste samples treated with SME-PS under laboratory accelerated aging conditions (AAC). The specimens were subjected to cyclic conditions: 8 h of UVA radiation (simulating solar radiation), followed by 6 h of darkness with water condensation and a high temperature of 40°C for 28 days. After the AAC exposure, the samples were immersed in a deicing salt solution, specifically a 29.8 wt. % calcium chloride solution, for 7 days. To evaluate the long-term behavior of SME-PS, a series of experiments, including visual observation, thermogravimetric analysis (TGA), and low-temperature differential scanning calorimetry (LT-DSC) was conducted. Visual observations revealed slight damage in SME-PS-treated samples after AAC exposure, while control samples experienced microcrack formations. SME-PS chemical compositions remained unaffected by AAC, in contrast to the control samples where a decrease in the quantity of calcium hydroxide and an increase in calcium carbonate content were observed as a result of carbonation during AAC exposure. LT-DSC results indicated that SME-PS-treated samples showed a significant reduction in the enthalpy of fusion associated with calcium oxychloride (CAOXY) formation, indicating that the SME-PS remained effective after AAC exposure, while control samples exhibited higher CAOXY enthalpy of fusion.

Mitigating calcium oxychloride formation in cementitious paste using alternative supplementary cementitious materials

Supplementary cementitious materials (SCMs) are known to reduce calcium oxychloride (CAOXY) contents in cementitious pastes. However, when availability or cost precludes the use of traditional SCMs, such as fly ash, mitigation could be provided through alternative materials. Fly ash (FA), rice husk ash (RHA), bottom ash (BA), limestone filler (LS), nepheline syenite filler (NS), sandstone filler (SS), and silica flour (SFL) were evaluated for CAOXY mitigation in cementitious paste using low-temperature differential scanning calorimetry, reactivity testing, thermogravimetric analysis, and compressive strength testing. The order of CAOXY mitigation from least to most effective is SS, LS, SFL, NS, BA, FA, and RHA.

Utilizing Nano Silica to Reduce Calcium Oxychloride Formation in Cementitious Materials

This paper examines the use of two nano silica (NS) materials as an additive that can reduce the susceptibility of concrete to deicing salt damage. The motivation for this research is to evaluate whether NS can be used to improve resistance to calcium oxychloride formation because of deicing salts. Deicing salts, like calcium chloride and magnesium chloride, can react with water and calcium hydroxide in concrete to form an expansive product called calcium oxychloride. This work builds on previous observations that supplementary cementitious materials (SCMs), such as Class F fly ash, slag, and silica fumes, can reduce calcium oxychloride formation through dilution of the cement, which results in a reduction in calcium hydroxide and the pozzolanic reaction, which further reduces calcium hydroxide through chemical reaction. This paper investigates whether NS additions during the mixing process can provide similar results to other SCMs. Both NSs had the same particle size distribution and specific surface area, but NS2 had alumina on the surface while NS1 did not. Toward this end, the calcium hydroxide content and calcium oxychloride were measured using thermal gravimetric analysis and low-temperature differential scanning calorimetry, respectively. The addition of NS to a mixture was found to reduce the calcium oxychloride at lower dosages as compared to Class F fly ash.

The influence of air voids and fluid absorption on salt-induced calcium oxychloride damage

Calcium and magnesium deicing salts may damage concrete due to calcium oxychloride formation (CaOXY). Previous work has shown that replacing a portion of the cement in a mixture with supplementary cementitious materials reduce CaOXY formation. AASHTO PP-84 was developed to help specify damage-resistant mixtures by limiting the CaOXY amount in paste. This limit was established based on empirical observations; however, this did not consider other aspects of the mixture such as paste volume or air content. This paper investigates how fluid absorption, paste volume, and air content are all key parameters in determining damage from CaOXY. Concrete with a higher paste volume has more CaOXY and is more susceptible to damage. Concrete with a higher air content is less susceptible to damage as the voids provide space for fluid absorption and CaOXY formation; however this only occurs for mixtures with a specific range of calcium hydroxide (Ca(OH)2) (between 7 and 12 g Ca(OH)2/100 g paste). This paper incorporates these factors to provide a more comprehensive explanation for CaOXY-induced damage in concrete.

Durability of concretes exposed to high concentrations of CaCl2 and MgCl2.

In cold regions, calcium and magnesium chloride deicing salts damage concrete pavements due to the formation of certain deleterious chemical phases, including calcium oxychloride. While there is much research at a cement paste-scale, damage in concrete has been less studied. In this study, we evaluate concrete damage due to calcium and magnesium chloride and explain the roles of supplementary cementitious materials (SCM) replacement level, air entrainment, salt type, and exposure conditions in damage development. Various non-destructive test methods including bulk resistivity, mass change, and visual damage assessment were used to monitor the damage over time. Damage was reduced as the SCM replacement level and air content increased, regardless of exposure conditions. Bulk resistivity and visual assessment were promising indicators of damage. The product of 91-day bulk resistivity and the air content predicted concrete performance when exposed to concentrated deicing salts. Based on several criteria, mixtures with 20% fly ash replacement level or 35% slag mitigated damage significantly when the air content was greater than 5% by concrete volume. Damage mitigation mechanisms of SCM and air are discussed.Supplementary InformationThe online version contains supplementary material available at 10.1617/s11527-022-01992-y.

Durability of Mortars Manufactured with Low-Carbon Binders Exposed to Calcium Chloride-Based De-Icing Salts

Calcium chloride is one of the main de-icing salts for removing snow and ice from roads, infrastructures and service areas. It is well known that reinforced concrete structures, if exposed to calcium chloride, can suffer from severe damages due to both corrosion of steel reinforcement and chemical attack of the cement paste. This paper aims at evaluating the resistance to chemical attack of mortars manufactured with different low-carbon binders (alkali activated slag cements, calcium sulphoaluminate cement-based blends, high volume ultrafine fly ashes cements) in presence of CaCl2-based de-icing salts in cold weather (temperature about 4°C). Results indicated that alkali activated slag-based mortars are quasi-immune to calcium chloride attack due to their mineralogical composition. On the contrary, calcium sulphoaluminate-based blends show the total loss of binding capacity, especially when calcium sulphoaluminate cement is used with gypsum and Portland cement. Finally, the partial substitution of Portland cement with ultrafine fly ash strongly reduces the mass change and the strength loss of mortars submerged in 30 wt.% CaCl2 solutions due to the strong reduction of calcium hydroxide responsible for the calcium oxychloride formation in the cement paste.

Effect of presowing seed treatments on teak (Tectona grandis L. F) drupes dormancy and germination

Poor seed germination is a major issue in teak (Tectona grandis) propagation. Teak seed dormancy is thought to be the reason for delayed germination. So far, specific dormancy mechanisms have not yet been identified. In order to study the influence of presowing treatments on germination, seedling vigour, and biochemical attributes of fresh teak drupes collected from the seed production area of Top Slip in Tamil Nadu. The collected drupes were subjected to different presowing treatments viz., T1 - control, T2 - soaking and drying for 6 days, T3 – T18 (soaking and drying for 5 days + soaking in different concentrations of thiourea, potassium nitrate, hydrogen peroxide and calcium oxychloride for 12 hours). Treated drupes were placed for germination in earthen pots and kept in open sunlight. In parallel, true seeds extracted from untreated drupes were also subjected to germination under in vitro conditions as a check. A higher percentage of germination (40%) was recorded in true seeds under in vitro conditions when compared to the treated and untreated drupes under in vivo conditions. Among the treated drupes sown under in vivo conditions, the drupes given soaking + drying for 5 days + soaking in 2% calcium oxychloride (CaOCl2) recorded higher germination (17.16) with better seedling vigour. Analysis of teak true seeds and mesocarp extract in high-performance liquid chromatography showed that gibberellic acid was found only in true seeds, whereas the other compounds, viz., indole-3-acetic acid, indole butyric acid, abscisic acid and coumarin, were not present in the true seed or mesocarp.

Effectiveness of Soy Methyl Ester-Polystyrene as a Concrete Protectant on Mitigating the Chemical Interaction between Cement Paste and Calcium Chloride

Concrete pavements and bridge decks suffer from severe deterioration caused by the application of chloride-based deicing salts (i.e., NaCl, CaCl2, and MgCl2) during winter. One of them is the formation of a destructive calcium oxychloride (CAOXY) phase caused by the chemical interaction between cement paste and CaCl2/MgCl2. By simulating the practical service conditions, this work investigated the formed CAOXY phase in cement paste exposed to CaCl2 solution and evaluated the performance of soy methyl ester-polystyrene (SME-PS) blend as a promising concrete protectant in mitigating the formation of CAOXY. With the surface treatment of SME-PS, cement paste showed less than 10% of the formed CAOXY phase in control cement paste after being exposed to CaCl2 solution for 28 days. In control cement paste, the amount of formed CAOXY at the exposed surface increased with the exposure time and some of the CAOXY phase formed in the cement paste exhibited a higher phase changing temperature. Moreover, a modified model based on Fick’s second Law was developed for predicting the CAOXY content in concrete with respect to the depth of the exposed surface. This model was verified by the comparison between the predicted values and the data obtained from a low-temperature differential scanning calorimetry (LT-DSC) test.

Investigating concrete deterioration due to calcium oxychloride formation

Calcium oxychloride is a serious deterioration mechanism affecting concrete pavements. In order to mitigate calcium oxychloride deterioration in concrete, fly ash is used as partial cement replacement in conjunction with entrained air. Concrete specimens were stored in a 30% calcium chloride solution at 5 °C for 202 days. Following storage, specimens were evaluated through compressive and flexural strength loss along with mass change, length change, and chloride penetration. Results indicate that a partial cement replacement with 15% fly ash mitigates deterioration in concrete specimens when tested for flexural strength loss; however, 30% or more fly ash is needed for similar mitigation based on compressive strength. Further, results indicate that specimens cast with 5% entrained air outperform those without air entrainment. Class C fly ash generally mitigated strength loss to a greater extent than Class F fly ash.

Synergistic effects of air content and supplementary cementitious materials in reducing damage caused by calcium oxychloride formation in concrete

Pavement damage occurs in cold-region concrete exposed to high concentrations of calcium chloride (CaCl2). The damage is caused by a combination of conventional freeze-thaw damage and the formation of a deleterious phase known as calcium oxychloride from a reaction between CaCl2 and calcium hydroxide in the concrete. Much research has focused on calcium oxychloride mitigation in cement pastes, but not on concrete damage due to calcium oxychloride. In this study, the synergistic roles of air and supplementary cementitious materials (SCMs) in reducing damage in concrete exposed to high concentrations of CaCl2 and freeze-thaw conditions is studied. Concrete mixtures were made with different SCM replacement levels and air contents and immersed in 25% CaCl2 solutions and subject to freeze-thaw cycles (−8 °C–25 °C) for 600 days. Bulk resistivity and visual assessment of damage were excellent descriptors of the damage progression. Damage was reduced as the SCM content and air content were increased. Mixtures which had 20% SCM and 8% air and mixtures which had 35% SCM and more than 4% air showed strong durability against calcium oxychloride damage.

Quantification of Calcium Oxychloride by Differential Scanning Calorimetry: Validation and Optimization of the Testing Procedure

Abstract The American Association of State Highway and Transportation Officials (AASHTO) T 365 standard, Standard Method of Test for Quantifying Calcium Oxychloride Formation Potential of Cementitious Pastes Exposed to Deicing Salts, describes a test methodology that uses low-temperature differential scanning calorimetry (LTDSC) to quantify the formation of calcium oxychloride in cementitious systems exposed to concentrated calcium chloride solutions. AASHTO T 365 is included in AASHTO PP 84, Standard Practice for Developing Performance Engineered Concrete Pavement Mixtures, as a performance indicator for mixtures at risk of calcium oxychloride formation. During the test, the sample temperature is first dropped to −90°C, looped through a brief thermal cycle, then slowly increased to a maximum of 50°C, at a constant heating rate of 0.25°C/minute (min), for a total testing time of approximately 11 hours. The objective of this work is to modify the test to reduce its duration to facilitate wide adoption among practitioners. It is found that by increasing the minimum conditioning temperature from −90°C to −5°C, as well as by increasing the heating rate from 0.25°C/min up to 1°C/min, the test duration can be reduced from approximately 10.7 hours to approximately 1.6 hours without any statistically significant difference in the numerical test results, although an offset of the melting peak and a change in its shape were observed. This change can provide valuable savings in terms of time and energy/gas consumption and make AASHTO T 365 more competitive with other available tests for the estimation of calcium oxychloride formation, such as thermogravimetric analysis (TGA). TGA and LTDSC are compared to each other in terms of mixture classification for susceptibility to calcium oxychloride formation. It is shown that the two tests show good agreement, with 85 % of cases (out of 30 tested) receiving the same classification.

Using compressive strength and mass change to verify the calcium oxychloride threshold in cementitious pastes with fly ash

Calcium oxychloride (CAOXY) formation is a deterioration mechanism known to cause joint damage in concrete pavements. The accepted CAOXY mitigation threshold in paste is 15 g/100 g paste; however, this limit was developed using flexural strength testing of pastes. This investigation seeks to verify this threshold using compressive strength and mass change testing. Cementitious pastes were cast with portland cement and fly ash (up to 50% mass). Specimens were stored in a 30% mass CaCl2 at 5 °C to accelerate deterioration. Visual observations, thermogravimetric analysis, low-temperature differential scanning calorimetry, mass change, and compressive strength results were recorded. Partial replacement of cement with fly ash reduces the Ca(OH)2, CAOXY, and damage levels. Using mass change, a threshold at which no damage occurs is established at 20 g/100 g paste, indicating that the current threshold is conservative. For compressive strength, while increasing the amount of fly ash reduces damage, damage is noted in all specimens tested; however, strength loss noted in this work is similar to the research which established the current threshold. Therefore, the compressive strength results generally validate the CAOXY threshold level of 15 g/100 g paste. Careful correlations between paste and concrete damage are needed in order to further verify the threshold value.

Petrographic analysis of in-service cementitious mortar subject to freeze-thaw cycles and deicers

Chloride-based deicers, especially CaCl2 and MgCl2, can damage cementitious materials due to the formation of mineral phases such as calcium oxychloride and brucite. However, there are only limited direct observations of calcium oxychloride formed in cementitious materials in the field. This paper uses petrographic methods to evaluate damage of an in-service cementitious mortar substrate subject to freeze-thaw cycles and deicers for six years. The amount of calcium hydroxide in the mortar was quantified using thermogravimetric analysis. Changes in hydration products and microstructure were characterized by optical microscopy. Scanning electron microscopy coupled with energy dispersive X-ray spectroscopy was used to examine the morphology and elemental composition of secondary deposits related to the deicer damage. The mortar with less than 3% air exhibits horizontal cracks and microcracks cutting around aggregate particles. The cracks and microcracks are partially filled with calcium oxychloride due to the application of CaCl2. A densified crust of brucite and calcite, likely associated with the usage of MgCl2, covers the top surface of the damaged mortar. The deicer exposure results in leaching of calcium hydroxide mainly due to the formation of calcium oxychloride. Calcium leaching increases the apparent paste porosity in the damaged mortar, which likely weakens the physicomechanical properties of the mortar and accelerates the ingress of external deicer solutions. Moreover, the deicer application results in air-void-filling by calcium oxychloride and secondary ettringite, which may reduce the space available to release the internal stresses associated with ice formation and thus compromises the freeze-thaw durability.

Chlorine dioxide, peroxyacetic acid, and calcium oxychloride for post-harvest decontamination of citrus fruit against Xanthomonas citri subsp. citri, causal agent of citrus canker

After a new regulation on the control of citrus canker (Xanthomonas citri subsp. citri) came into force in Brazil in 2017, the post-harvest sanitization of citrus fruit became mandatory to prevent dissemination of the causal pathogen and enable the commercial trade of citrus to other states and countries. Although several sanitizers are available worldwide for decontamination of fresh produce, only sodium hypochlorite is legally required by the country for decontamination of citrus fruit traded with other states and countries against X. citri in the packing house. Thus, the objectives of this study were to assess the efficiency of chlorine dioxide, peracetic acid, and calcium oxychloride as alternative sanitizers and exposure times of 1 and 2 min for the post-harvest decontamination of citrus fruit against X. citri. Sodium hypochlorite, the legally required standard, was used as control. The sanitizers were evaluated regarding the capacity to eliminate live X. citri in solution immediately or 1 h after exposure to the products and the efficiency in disinfesting artificially and naturally contaminated lime fruit. An additional assessment was carried out to determine the infective potential of X. citri suspensions at different concentrations in order to evaluate the risk of disease dissemination by the remaining bacterial population on the fruit following treatment. All the assessed sanitizers were able to completely eliminate X. citri in suspension immediately after treatment. In artificially and naturally contaminated fruit, the sanitizers promoted a significant reduction of 2.4–2.8 and 1.1 to 1.5 log10 cfu/mL, respectively, in the population of live bacteria when compared to the untreated control. In these experiments, the amount of X. citri that remained on the fruit ranged from 0.5 to 1.0 and 0.1 to 0.3 log10 cfu/mL, respectively, regardless of the exposure time. The labeled concentrations and treatment periods assessed effectively decontaminated fruit with X. citri and demonstrated little or no risk of pathogen spread from treated fruit.

Halogenation for improvement of seed yield and quality in chilli (Capsicum annuum L.)

Freshly harvested seeds of chilli variety Anugraha were treated with halogens namely Calcium oxy chloride (CaOCl2) and Iodine crystal (I2) indirectly through a carrier Calcium carbonate (CaCO3). The treatments included Control (Untreated), CaOCl2 + CaCO3 (2g each/kg seed), CaOCl2 + CaCO3 (4g each/kg seed), Iodine crystal + CaCO3 (50mg each/kg seed) and Iodine crystal + CaCO3 (100mg each/kg seed). Seed treatment with CaOCl2 + CaCO3 @2g each/kg seed registered significantly higher values for fruits per plant, fruit weight, seed yield per plant and hundred seed weight followed by CaOCl2 + CaCO3 @4g each/kg seed. The treatments, CaOCl2 + CaCO3 @2 g each/kg seed and Iodine crystal + CaCO3 @100mg each/kg seed performed superior in seed quality with higher seedling vigour and lower electrical conductivity of seed leachates over other treatments, while untreated control recorded least seedling vigour indices and highest electrical conductivity.

Petrographically quantifying the damage to field and lab-cast mortars subject to freeze-thaw cycles and deicer application

Although calcium oxychloride (Ca-Oxy) is known to damage cementitious materials exposed to calcium chloride (CaCl2) deicers, there is little direct observation of Ca-Oxy in the field due to its instability. This paper uses optical microscopy (OM) and scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM-EDX) to detect the formed Ca-Oxy and quantify its associated damage in a field mortar subject to freeze-thaw cycles and deicer application. The characterized damage in the field mortar is compared to that in lab-cast portland cement paste and mortar which are submerged in a CaCl2 solution of 25 wt.% under freeze-thaw cycles (− 8 to 25 °C). The field and lab-cast mortars show similar cracking patterns that are parallel to the exposure surface with a variation of 30–45° in the preferred orientation due to the constraints of sand particles. During each lab-controlled freeze-thaw cycle, the high CaCl2 concentration of 25 wt.% stabilizes the formed Ca-Oxy, which continually damages the mortar and eventually results in 3–4 times higher crack density compared to that in the field mortar. SEM-EDX analysis confirms the presence of secondary deposits including Friedel’s salt, ettringite and Ca-Oxy. Image analysis on thin section photomicrographs shows a reduction of 86.4% in calcium hydroxide (Ca(OH)2) content in the damaged field mortar compared to the undamaged field mortar, suggesting significant leaching of Ca(OH)2 to form Ca-Oxy due to the deicer application.

Calcium oxychloride: A critical review of the literature surrounding the formation, deterioration, testing procedures, and recommended mitigation techniques

Deicing salts have long been known to cause deterioration in concrete pavements. Freeze/thaw, surface scaling, and reinforcement corrosion are well documented deterioration mechanisms. However, another mechanism exists causing severe concrete damage that is much less understood. This deterioration is due to the formation of calcium oxychloride, from chemical interactions between the cementitious paste and certain chloride-based deicing salts. The basic chemical structure of calcium oxychloride, with slight variations, has been reported in deteriorated samples. Ideas have been postulated about failure mechanisms associated with the formation of calcium oxychloride. Further, testing techniques such as thermogravimetric analysis, low-temperature differential scanning calorimetry, and volume change measurements have been successfully utilized to better understand/quantify calcium oxychloride. Mitigation techniques to minimize the impact of calcium oxychloride include reducing cement content through the use of supplementary cementitious materials or other means, the use of adequate air entrainment, preferential carbonation, and the use of concrete sealants. This review of the literature highlights the current understanding of calcium oxychloride, provides best practice guidance and identifies new areas of research needed in order to effectively mitigate calcium oxychloride damage in concrete pavements.

The Durability of One-Part Alkali-Activated Slag-Based Mortars in Different Environments

The paper assesses the durability of one-part alkali-activated slag-based mortars (AAS) in different aggressive environments, such as calcium chloride- and magnesium sulphate-rich solutions, in comparison with traditional cementitious mortars at equal water to binder ratio. Moreover, the freezing and thawing resistance was evaluated on mortars manufactured with and without air entraining admixture (AEA). Experimental results indicate that the alkali content is a key parameter for durability of AAS: the higher the alkali content, the higher the resistance in severe conditions. In particular, high-alkali content AAS mortars are characterized by freeze–thaw resistances similar to that of blast furnace cement-based mixtures, but lower than that of Portland cement-mortars while AAS with low activators dosages evidence a very limited resistance in cold environment. The effectiveness of AEA in enhancement of freeze–thaw resistance is confirmed also for AAS mortars. Moreover, AAS mixtures are quasi-immune to expansive calcium oxychloride formation in presence of CaCl2-based deicing salts, but they are very vulnerable to magnesium sulphate attack due to decalcification of C-S-H gel and gypsum formation.

Material characterization to assess effectiveness of surface treatment to prevent joint deterioration from oxychloride formation mechanism

Joints in a rigid pavement can act as local reservoirs trapping deicing salts and moisture. Such a harsh micro-environment can impact the durability of sawn joint surfaces, resulting in premature distress even in cases where the bulk of pavement exhibits sufficient durability against frost action and chemical attack by deicing salts. A comprehensive experimental program was undertaken in this study to elucidate the mechanisms of deterioration of concrete exposed to de-icing salts. Plain cement paste samples cast with water-to-cement ratio of 0.40 were exposed to salt solutions prepared with 4% and 20% concentrations of CaCl2 and MgCl2 at 4 °C. A second series of paste specimens, treated with a wide range of sealers representing various generic types, were also exposed to the aforementioned salt solutions. Mechanisms of deterioration and formation of chemical compositions and phases were monitored at different exposure periods using X-ray diffraction (XRD), and differential scanning calorimetry (DSC). Moreover, concrete specimens were cast and treated with the same sealers to expand the fundamental observations from paste to concrete phase.Data obtained from plain cement paste specimens indicated no sign of calcium or magnesium oxychloride formation when exposed to 4% concentration of salt solutions, while oxychloride formation was detected at 20% concentrations. Potential for calcium oxychloride formation in sealed samples correlated well with paste expansion and visual concrete deterioration rates. Results indicated that an expansion threshold of 0.20 mm corresponded to the recommended threshold of oxychloride formation potential of 15 g per 100 g of paste (gOXY/gPaste).

Chloride binding of cement pastes with fly ash exposed to CaCl2 solutions at 5 and 23 °C

In cementitious materials exposed to solutions containing chloride, chloride binding typically results from the chemical reactions between chloride ions and aluminate phases to form Friedel's salt, and the interaction between chloride ions and calcium silicate hydrates (CSH). Calcium oxychloride can also form when Ca(OH)2 in cementitious materials reacts with CaCl2 solutions. This paper examines the chloride binding of hydrated cement pastes containing fly ash exposed to CaCl2 solutions of varying concentrations at 5 and 23 °C. Thermogravimetric analysis was used to quantify the chloride binding associated with Friedel's salt and calcium oxychloride. The amount of bound chloride by Friedel's salt is relatively independent of the exposure temperature, and as the chloride concentration [Cl−] increases, it increases until a plateau is reached at [Cl−] greater than 2 M. The addition of fly ash results in an increase in the chloride binding due to Friedel's salt. A lower exposure temperature leads to a greater amount of bound chloride associated with calcium oxychloride. In this study, no chloride binding associated with calcium oxychloride was observed in the cement pastes with 40% and 60% fly ash. The temperature-dependent chloride binding associated with CSH is a significant portion of the total chloride binding (19.8 %–70.8%) when cement pastes are exposed to CaCl2 solutions. As the replacement level of fly ash increases, the chloride binding by CSH increases first and then decreases. The amount of bound chloride by CSH increases linearly as the pH of the exposure solution decreases.