Freeze Thaw Durability of Internally Cured Concrete Made Using Superabsorbent Polymers

The use of superabsorbent polymers (SAPs) to produce internally cured concrete has been shown to be effective in reducing the potential for restrained shrinkage cracking of high performance concrete mixtures. However, not much is known regarding the freeze–thaw durability of concrete mixtures that incorporate SAPs for internal curing (IC). When SAP particles desorb (or partially desorb) the “water” (pore fluid) they contain for the purposes of IC, some believe that the void space created by these particles can provide enough empty voids to accommodate the additional volume caused by water expansion upon freezing. This paper investigates the freeze–thaw durability of internally cured concrete by the use of SAPs. It has been shown that internally cured concretes made using SAP demonstrate good freeze–thaw performance when the concrete is air entrained. When the SAP was used in concrete without air entrainment it did not provide sufficient freeze–thaw durability

Performance of Portland Limestone Cements: Cements Designed to Be More Sustainable That Include up to 15% Limestone Addition

In 2009, ASTM and AASHTO permitted the use of up to 5% interground limestone in ordinary portland cement (OPC) as a part of ASTM C150/AASHTO M85. When this project was initiated a new proposal was being discussed that would enable up to 15% interground limestone to be considered in ASTM C595/AASHTO M234 cement. This project was initiated to provide rapid feedback to INDOT for use in discussions regarding these specifications (this has become ASTM C595/AASHTO M240). PLC is designed to enable more sustainable construction which may significantly reduce the CO2 that is embodied in the built infrastructure while extending the life of cement quarries. The physical and chemical properties of the cementitious materials used in this study were examined. PLC is typically a finer cement (10 to 30% Blaine fineness) with a reduction in the coarse clinker particles (\u3e20µm) and an increase in fine particles which are primarily limestone. Isothermal calorimetry and chemical shrinkage results imply that these PLC materials have a similar or slight greater reaction and would be able to be used interchangeably with OPC in practice as it relates to the rate of reaction. The PLC mortars exhibited relatively similar activation energies compared to the corresponding OPCs allowing the maturity method to be used by INDOT for both the PLC and OPC systems. The mechanical properties of OPC and PLC were generally similar with the PLC typically having slightly higher early age strengths but similar 28 day strengths. No significant change in drying shrinkage or restrained shrinkage cracking was observed for the PLC when compared with OPC (Barrett et al. 2013). The PLC has similar volumes of permeable voids as the OPC. The chloride diffusion coefficients in the PLC systems may range from 0 to 30% higher than the OPCs. The PLC showed synergistic benefits when paired with fly ash. Based on the available literature and available testing results INDOT could consider PLC, as specified in accordance with ASTM C-595/AASHTO M 240, to be a suitable option for use in INDOT concrete applications

Quantifying Asphalt Emulsion-Based Chip Seal Curing Times Using Electrical Resistance Measurements

Chip sealing typically consists of covering a pavement surface with asphalt emulsion into which aggregate chips are embedded. The asphalt emulsion cures through the evaporation of water, thus providing mechanical strength to adhere to the pavement while keeping the aggregate chips in place. The curing time for the chip seal depends on many factors, such as the asphalt emulsion and aggregate types, aggregate moisture content, emulsion and aggregate application rates, and environmental conditions (e.g., temperature, wind speed, relative humidity, and solar radiation). Currently, no field technique is available to quantify when sufficient mechanical strength has developed in the binder to allow traffic on a newly sealed roadway or to remove the surplus aggregate from a fresh chip seal through brooming. Instead such decisions are made by empirical factors that rely on the experience of field personnel. This study investigated the use of electrical resistance measurements to develop a quantitative method for determining the optimum curing time for chip seals. First, full frequency, two-point, uniaxial electrical impedance spectroscopy was used to characterize the electrical properties of asphalt emulsions and various asphalt emulsion-aggregate combinations. The laboratory test results suggest a relationship between the changes in the electrical resistance of an asphalt emulsion and the amount of curing that has occurred in the system. Additionally, standardized mechanical strength tests and full-scale field trials were conducted using a variety of materials. The electrical properties of the fresh seals were quantified using a handheld electrical device with a two-point probe to measure resistance. The findings suggest that chip seal systems gain significant mechanical strength when the initial electrical resistance measurement increases by a factor of 10. Finally, the implementation of the methodology for five full-scale chip seal projects in Indiana indicates that curing times for the chip seals range from 3.5 to 4.0 hours

Documentation of the INDOT Experience and Construction of the Bridge Decks Containing Internal Curing in 2013

The Indiana Department of Transportation (INDOT) constructed four bridge decks utilizing internally cured, high performance concrete (IC HPC) during the summer of 2013. These decks implement research findings from the research presented in the FHWA/IN/JTRP-2010/10 report where internal curing was proposed as one method to reduce the potential for shrinkage cracking, leading to improved durability. The objective of this research was to document the construction of the four IC HPC bridge decks that were constructed in Indiana during 2013 and quantify the properties and performance of these decks. This report contains documentation of the production and construction of IC HPC concrete for the four bridge decks in this study. In addition, samples of the IC HPC used in construction were compared with a reference high performance concrete (HPC) which did not utilize internal curing. These samples were transported to the laboratory where the mechanical properties, resistance to chloride migration, and potential for shrinkage and cracking was assessed. Using experimental results and mixture proportions, the diffusion based service life of the bridge decks was able to be estimated. Collectively, the results indicate that the IC HPC mixtures that were produced as a part of this study exhibit the potential to more than triple the service life of the typical bridge deck in Indiana while reducing the early age autogenous shrinkage by more than 80% compared to non-internally cured concretes

Implementing Rapid Durability Measure for Concrete Using Resistivity and Formation Factor

The durability of in-place concrete is a high priority issue for concrete pavements and bridges. Several studies have been conducted by INDOT to use electrical resistivity as a measure of fluid transport properties. Resistivity is dependent on the chemistry of the cement and supplementary cementitious system used, as such it has been recommended that rather than specifying resistivity it may be more general to specify the formation factor. Samples were tested to establish the current levels of performance for concrete pavements in the state of Indiana. Temperature and moisture corrections are presented and acceptable accelerated aging procedure is presented. A standardized testing procedure was developed (AASHTO TP 119–Option A) resulting in part from this study that provides specific sample conditioning approaches to address pore solution composition, moisture conditioning, and testing procedures. An accelerated aging procedure is discussed to obtain later age properties (91 days) after only 28 days

Influence of Warping on Stress for Restrained Concrete Slabs: For Application to CRCP

Continuously-reinforced concrete pavement (CRCP) is widely used in transportation system because of its low maintenance requirement. However, the need for large volumes of steel creates a high cost for new construction. The Illinois Tollway is preparing to substantially renovate highways in and around Chicago and this work seeks to understand how concretes of varying mixture designs can be made thinner by reducing the amount of built-in stress. The experiment examines warping in beams subjected to various degrees of restraint, in an effort to assess effectiveness at reducing warping in continuously reinforced concrete pavements. Value added methodologies such as internal curing with fine lightweight aggregate and topically-applied shrinkage-reducing admixture (SRA) were applied to a controlled concrete mixture design. The experimental program examines the warping of a composite concrete-steel beam with differing degrees of restraint, accomplished through using a 1/4 and ½” steel plate with a 2.5 concrete section . Each beam undergoes seven days of uni-axial warping, subjected to a controlled temperature and humidity environment (23+/-2C and 50 +/- 2 % RH), with a linear variable differential transformer to monitor endpoint deflection. Results indicate that as degree of restraint increases, the associated, or built-in , stress increases too; however, the deflection decreases by as much as a factor of two between unrestrained and 1/2 restraint. These findings potentially serve as a solution for effectively reducing the amount of concrete necessary for sustained loading associated with CRCP while mitigating warping and stresses associated

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