Using Acoustic Emission to Quantify Freeze–Thaw Damage of Mortar Saturated with NaCl Solutions

Mortar samples were saturated with NaCl solutions of various concentrations and subjected to freeze– thaw cycles. Passive and active acoustic emission (AE) testing was conducted. The freezing temperature of the NaCl solutions in mortar corresponded with the sudden observation of passive AE events. The acoustic energy and damage parameter were calculated to evaluate the extent of freeze–thaw damage. The influence of the NaCl solution concentration and whether the solution freezes on freeze–thaw damage are discussed

Reducing Damage Due to Chemical Reactions in Concrete Exposed to Sodium Chloride: Quantification of a Deleterious Chemical Phase Change Formation

It has been shown that sodium chloride can react with the tricalcium aluminate (C3A) and its hydrates, leading to a formation of a deleterious chemical phase change during thermal cycling. It is believed that this chemical phase change is implicated in the premature deterioration of concrete pavements in the cold regions. This work examines the potential formation of the deleterious chemical phase change in several cementitious pastes made using different types of portland cement and supplementary cementitious materials (SCMs). The amount of the chemical phase change was quantified using a low-temperature differential scanning calorimetry. The results indicated that the formation of the chemical phase change can be reduced by using cements with low C3A content. The addition of SCMs showed different effects on the chemical phase change formation. Slag and Class F fly ash could reduce the amount of the chemical phase change due to only the dilution effect whereas silica fume could significantly reduce the amount of the chemical phase change due to the dilution effect as well as pozzolanic reactions. Adversely, the addition of Class C fly ash showed a negative effect through increasing the formation of the chemical phase change

Early Detection of Joint Distress in Portland Cement Concrete Pavements

INDOT (as well as several surrounding states) have observed that certain concrete pavements may show a susceptibility to joint deterioration. Unfortunately, by the time that this joint deterioration is observed it is often too late and costly partial depth repairs are needed. The deterioration is generally occurring in the joint behind the backer rod and joint sealant; as such, it is difficult to detect even if one is standing directly above the joint. This project investigated the use of electrical resistivity and ground penetrating radar as two techniques to detect premature joint deterioration. The thought process was that if the joint deterioration is determined at an early stage, low cost corrective actions can be taken to extend the life of the concrete. The electrical response was measured for mortars subjected to a temperature cycle from 23 °C to -35 °C, with varying degrees of saturation, and varying salt concentrations. The resistivity increased as the degree of saturation was reduced due to the reduction in the volume of the conductive medium and increase in tortuosity. Changes in resistivity were detected when cracking occurred in the sample. The magnitude of these changes was similar to that detected using changes in the ultrasonic wave speed. Ground penetrating radar (GPR) was used effectively to detect fluid accumulation in the saw-cut joint behind the joint sealant. The typical GPR waveforms are however difficult and time consuming to interpret. A signal processing approach called, referred to as the CID, was used to obtain a single number that reflects the potential for fluid in the joint. Scalar waveform features and the computed CID can be used to estimate which joints may contain fluid thereby providing insights into which joint sealant sections may need to be repaired or when a sufficient number of joints may contain fluid suggesting a larger joint maintenance effort be performed to seal the joints or the concrete

Evaluation of Sealers and Waterproofers for Extending the Life Cycle of Concrete

Concrete pavements represent a large portion of the transportation infrastructure. While the vast majority of concrete pavements provide excellent long-term performance, a portion of these pavements have recently shown premature joint deterioration. Substantial interest has developed in understanding why premature joint deterioration is being observed in jointed portland cement concrete pavements (PCCP). While some have attributed this damage to insufficient air void systems, poor mixture design, or chemical reaction between the salt and the paste, it is the hypothesis of this work that a component of this damage can be attributed to fluid absorption at the joints and chemical reactions between the salt and chemistry of the matrix. This paper discusses the role of soy methyl ester - polystyrene blends (SME-PS) as a potential method to extend the service life of concrete pavements by limiting the ingress of salt solutions. The report discusses field application of the SME-PS blends for field investigation in Lafayette and Fishers. Low temperature-differential scanning calorimetry (LT-DSC) techniques identified noticeable differences between plain mortar samples and mortar treated with SME-PS. The report also discusses the development of a test to assess chloride solution ingress during temperature cycling. The aim of this work is to provide background on some aspects that can lead to joint deterioration and provide early documentation showing that sealers may help to reduce the impact of deicers on joint damage, thereby extending the life of the concrete pavement. It should be noted that these sites as well as others are still ongoing and should be monitored for long term performance. Application procedure for SME-PS should follow manufacturer’s recommendation

An Overview of Joint Deterioration in Concrete Pavement: Mechanisms, Solution Properties, and Sealers

Concrete pavements represent a large portion of the transportation infrastructure. While the vast majority of concrete pavements provide excellent long-term performance, a portion of these pavements have recently shown premature joint deterioration. Substantial interest has developed in understanding why premature joint deterioration is being observed in jointed portland cement concrete pavements (PCCP). While some have attributed this damage to insufficient air void systems, poor mixture design, or chemical reaction between the salt and the paste, it is the hypothesis of this work that a component of this damage can be attributed to fluid absorption at the joints. This report begins by discussing the importance of the level of concrete saturation on freeze-thaw damage. Second, this report describes the influence of deicing salt solutions on drying and wetting of concrete. Third, the report describes some observations from field studies. Fourth, the report discusses soy methyl esters polystyrene blends (SME-PS) as a potential method to extend the service life of concrete pavements by limiting the ingress of salt solutions. The report also discusses field application of the SME-PS blends for field investigation. Finally, the report discusses the development of a test to assess chloride solution ingress during temperature cycling. The aim of this work is to provide background on some aspects that can lead to joint deterioration and to provide the pavement community alternatives on how sealers and deicers may be able to be used more efficiently to reduce joint damage

Performance of Concrete Pavement in the Presence of Deicing Salts and Deicing Salt Cocktails

Deicing salts are widely used for anti-icing and de-icing operations in pavements. While historically sodium chloride may have been the deicer most commonly used, a wide range of deicing salts have begun to be used to operate at lower temperatures, to stick to the road better and to improve other aspects of performance such as environmental impact or corrosion resistance. It has been observed that some chloride based deicing salts can react with the calcium hydroxide in the mixture resulting in the formation of calcium oxychloride an expansive phase that can damage concrete pavements, especially at the joints. This report describes the two main objectives of this work. First, the report documents the development a standardized approach to use low temperature differential scanning calorimetry (LT-DSC) to assess the influence of cementitious binder composition on the potential for calcium oxychloride formation. Second, this work will assess the influence of blended salt cocktails on the formation of calcium oxychloride

Damage development, phase changes, transport properties, and freeze-thaw performance of cementitious materials exposed to chloride based salts

Recently, there has been a dramatic increase in premature deterioration in concrete pavements and flat works that are exposed to chloride based salts. Chloride based salts can cause damage and deterioration in concrete due to the combination of factors which include: increased saturation, ice formation, salt crystallization, osmotic pressure, corrosion in steel reinforcement, and/or deleterious chemical reactions. This thesis discusses how chloride based salts interact with cementitious materials to (1) develop damage in concrete, (2) create new chemical phases in concrete, (3) alter transport properties of concrete, and (4) change the concrete freeze-thaw performance. A longitudinal guarded comparative calorimeter (LGCC) was developed to simultaneously measure heat flow, damage development, and phase changes in mortar samples exposed to sodium chloride (NaCl), calcium chloride (CaCl 2), and magnesium chloride (MgCl2) under thermal cycling. Acoustic emission and electrical resistivity measurements were used in conjunction with the LGCC to assess damage development and electrical response of mortar samples during cooling and heating. A low-temperature differential scanning calorimetry (LT-DSC) was used to evaluate the chemical interaction that occurs between the constituents of cementitious materials (i.e., pore solution, calcium hydroxide, and hydrated cement paste) and salts. Salts were observed to alter the classical phase diagram for a salt-water system which has been conventionally used to interpret the freeze-thaw behavior in concrete. An additional chemical phase change was observed for a concrete-salt-water system resulting in severe damage in cementitious materials. In a cementitious system exposed to NaCl, the chemical phase change occurs at a temperature range between -6 °C and 8 °C due to the presence of calcium sulfoaluminate phases in concrete. As a result, concrete exposed to NaCl can experience additional freeze-thaw cycles due to the chemical phase change creating cracks and damage to concrete under freezing and thawing. In a cementitious system exposed to CaCl2, the chemical phase change is mainly due to the presence of calcium hydroxide (CH) in concrete. Calcium hydroxide can react with CaCl2 solution producing calcium oxychloride. Calcium oxychloride forms at room temperature (i.e., 23 °C) for CaCl 2 salt concentrations at or above ~ 12 % by mass in the solution creating expansion and degradation in concrete. In a cementitious system exposed to MgCl2, it was observed that MgCl2 can be entirely consumed in concrete by reacting with CH and produce CaCl2. As such, it followed a response that is more similar to the concrete-CaCl2-water system than that of the MgCl2-water phase diagram. Formation of calcium/magnesium oxychloride is most likely the main source of the chemical phase change (which can cause damage) in concrete exposed to MgCl2. During the LGCC testing for CaCl2 and MgCl2 salts, it was found that the chemical reactions occur rapidly (~ 10 min) and can cause a significant decrease in subsequent fluid ingress into exposed concrete in comparison to NaCl. Isothermal calorimetry, fluid absorption, oxygen permeability, oxygen diffusivity, and X-ray fluorescence testing showed that the formation of calcium oxychloride in concrete exposed to CaCl2 and MgCl 2 can block or fill in the concrete pores on the surface of the specimen; thereby decreasing the CaCl2 and MgCl2 fluid ingress into the concrete. To mitigate the damage and degradation due to the chemical phase transition, two approaches were evaluated: (1) use of a cementitious binder that does not react with salts, and (2) use of a new practical technology to melt ice and snow, thereby decreasing the demand for deicing salt usage. For the first approach, carbonated calcium silicate based cement (CCSC) was used and the CCSC mortar showed a promising performance and resistance to salt degradation than an ordinary portland mortar does. For the second approach, phase change materials (PCM), including paraffin oil and methyl laurate, were used to store heat in concrete elements and release the stored heat during cooling to reduce ice formation and snow accumulation on the surface of concrete. PCM approach also showed a promising performance in melting ice and snow, thereby decreasing the demand for salt usage

The Influence of Calcium Chloride Salt Solution on the Transport Properties of Cementitious Materials

The chemical interaction between calcium chloride (CaCl2) and cementitious binder may alter the transport properties of concrete which are important in predicting the service life of infrastructure elements. This paper presents a series of fluid and gas transport measurements made on cementitious mortars before and after exposure to various solutions with concentrations ranging from 0% to 29.8% CaCl2 by mass. Fluid absorption, oxygen diffusivity, and oxygen permeability were measured on mortar samples prepared using Type I and Type V cements. Three primary factors influence the transport properties of mortar exposed to CaCl2: (1) changes in the degree of saturation, (2) calcium hydroxide leaching, and (3) formation of chemical reaction products (i.e., Friedel’s salt, Kuzel’s salt, and calcium oxychloride). It is shown that an increase in the degree of saturation decreases oxygen permeability. At lower concentrations (<~12% CaCl2 at room temperature), the addition of CaCl2 can increase calcium hydroxide leaching, thereby increasing mortar porosity (this is offset by the formation of Friedel’s salt and Kuzel’s salt that can block the pores). At higher concentrations (>~12%), the formation of chemical reaction products (mainly calcium oxychloride) is a dominant factor decreasing the fluid and gas transport in concrete

Engineering particle size distribution of sintered lightweight aggregates manufactured from waste coal combustion ash

Converting waste coal combustion ash (W-CCA) from power plants into novelty lightweight aggregates (LWA) is a viable and sustainable solution. Utilizing this waste material to produce a useful product for the concrete industry requires that the manufactured LWA adhere to industrial material regulations. This study focuses on engineering laboratory manufactured LWA to achieve aggregate gradation that meets the ASTM C330 standard. A systematic study that manipulates the degree of saturation during W-CCA paste preparation was adopted to understand the effect of moisture on LWA gradation. The degree of saturation was assessed based on the liquid (water) to solid ratio required to manufacture W-CCA paste. The investigation only alters the amount of water and recorded the gradation for fine LWA (FLWA), coarse LWA (CLWA), and combined coarse and fine LWA. L/S ratio of 0.33 achieved ASTM C330 required gradation for FLWA. A combination of L/S ratio of 0.33 and 0.34 achieved ASTM C330 required gradation for combined coarse and fine LWA. Engineering the gradation of LWA to meet ASTM required standard will allow the production of LWA from W-CCA a more attainable and practical product for the construction industry

Deterioration in concrete exposed to sodium chloride and heat-cool cycling

Many infrastructure domains required material research as an initial phase of project development life cycle. One such futuristic domain is bridge engineering, where there is a critical need of study of environmental impact and material strength. This paper focuses on the premature deterioration of concrete infrastructures exposed to sodium chloride (NaCl) salts in the presence of thermal cycling. NaCl salts can cause damage and rapid deterioration of concrete due to physical and chemical aspects, including salt scaling, corrosion of rebars, ice and salt crystallizations and/or deleterious chemical reactions. This paper discusses how NaCl solutions can cause damage in concrete in the presence of thermal cycling and how such damage can be mitigated. This paper at-tempts to provide an advanced thermo-chemo-physical understanding of NaCl salt damage in concrete. This paper also discusses specific structural and chemical alterations during thermal cycling that are caused by NaCl to develop damage to concrete. Results indicates that the heat-cool cycling induces the formation of mirabilite (Na2SO4.10H2O) in concrete exposed to high concentrations of NaCl solution. The mirabilite formation is found to be due to the release of sulfate ions from the concrete matrix