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Water has a significant impact on the dielectric constant of materials. As a multiphase composite material, the effect of water content must be taken into account when modeling the composite dielectric of cement concrete. Cement concrete traditionally has been thought of as a three-phase mixed material consisting of mortar, aggregate (limestone), and pores (air). Water was used as a constituent material of cement concrete in this paper, and its content was described in terms of water saturation. By abstracting the components of cement concrete into independent medium units and arranging them according to certain rules, the four-phase mixing model of cement concrete can be established. To investigate the effect of water, the dielectric constant of cement concrete was measured using a network analyzer at various water saturation levels. The experimental results show that water significantly can enhance the dielectric constant of cement concrete, and this effect is related to porosity: the higher the water saturation, the faster the dielectric constant increases. According to the established concrete four-phase mixed model, combined with the parallel plate capacitor theory, a composite dielectric model considering water saturation was developed which can improve the prediction accuracy under different water saturation conditions and provide a foundation for the application of ground-penetrating radar (GPR) in the quality inspection of cement concrete pavement. [ABSTRACT FROM AUTHOR]

This research documents the real-world performance of a new pavement product for use in cold regions—steel fiber-reinforced rubberized concrete (SFRRC). During the previous phase of this research, SFRRC underwent laboratory testing as proof of concept. During the current phase, precast slabs of SFRRC was installed on a public road, Abbott Road, in the Municipality of Anchorage, Alaska and monitored in the field using visual inspection, a continuous collection of strain gauge data, deflection measurements, rut depth, skid resistance, and other measures. The current location of the SFRRC is considered a high-traffic urban arterial, which makes it an effective location to study rutting, freeze-thaw resistance, falling weight deflection, skid resistance, and life-cycle cost. A comparative analysis was conducted using the same measuring techniques on hot mix asphalt (HMA) on an adjacent road section built at the same time. The results show that the SFRRC road sections have significantly better rutting resistance compared to the adjacent HMA road section, and the results of the freeze-thaw resistance and deflection field testing validate the results of the laboratory testing performed as part of an earlier phase. Furthermore, comparative life-cycle cost analyses of SFRRC and HMA justifies the use of SFRRC in roadway construction in cold regions in terms of cost effectiveness, enhanced performance, and extended life. The outcome of this research recommends the use of SFRRC for highway intersections and/or test sections on major arterials as the next phase of introducing this material for roadway construction in cold regions. The newly developed material of steel fiber-reinforced rubberized concrete (SFRRC) can be readily utilized in the construction of pavement structures where issues of short pavement life are a concern in northern climates as a result of the use of studded tires. This new material addresses the shortfalls of the use of Portland cement concrete (PCC) pavement under very low temperatures, such as micro-crack development, as a result of the freeze-thaw cycles by utilizing the added rubber in that it is readily able to expand and contract. In addition, the added steel fiber will enhance the resistance of crack development under low temperatures. Furthermore, this new material can be an alternative to Portland cement concrete pavement, where premature failures like joint cracking or raveling can occur. SFRRC is more cost-effective than traditional hot mix asphalt (HMA) pavements as it can prolong the life of the pavement and lead to less pavement maintenance costs over time. [ABSTRACT FROM AUTHOR]

Mixed mode I–II fatigue fracture of concrete is commonly encountered in practical engineering. Accurate prediction of the fatigue crack propagation process and fatigue life is essential to evaluate the safety of concrete structures. In this study, the mixed mode I–II fatigue crack propagation process of the three-point bending (TPB) beam is investigated based on the digital image correlation (DIC) method. The results indicate that the mixed mode I–II crack propagation path under fatigue loading is consistent with that under static loading, and the stress intensity factor (SIF) corresponding to the unstable failure of concrete is constant, regardless of the fatigue load level and specimen size. Based on the experimental results, a unified model for characterizing mixed mode I–II fatigue crack propagation in concrete is developed, where the equivalent SIF amplitude composed of mode-I and mode-II SIF amplitude is introduced into Paris law, and the statistical analysis is conducted to determine the probabilistic distribution of the empirical constant in Paris law. Furthermore, the feasibility of predicting the fatigue life of concrete structures is explored using the proposed model. It is concluded that the fatigue life with different reliability can be obtained when the mixed mode I–II fatigue crack propagation path is determined based on static tests. It is expected that the developed model contributes to the prediction of fatigue life and further safety assessment of concrete structures under fatigue loading. Many concrete structures are subjected to fatigue loads in service, such as concrete pavements and bridge decks suffering from cyclic vehicle loads. Under fatigue loading, the crack gradually propagates, resulting in the fatigue failure of concrete structures. Therefore, it is critical to investigate the fatigue crack propagation process of concrete such that the safety assessment of concrete structures can be conducted. In this study, a prediction model for mixed mode I–II fatigue fracture of concrete is proposed based on the well-known Paris law. When the SIFs at the crack tip are calculated based on the finite-element method, the whole fatigue crack propagation process and fatigue life of concrete structures with different reliability can be reasonably predicted using the proposed model. Furthermore, the stability analysis of fatigue crack and the reinforcement and repair of cracked concrete structures can be conducted timely according to the predicted fatigue crack propagation length and fatigue life. In general, the proposed model is of great significance to guarantee the safety of concrete structures under fatigue loading, e.g., concrete pavements and bridge decks. [ABSTRACT FROM AUTHOR]

Investigations into the dielectric properties of concrete form the basis for concrete quality testing and condition monitoring of internal structures when using ground penetrating radar (GPR). The formula used to describe the quantitative relationship between the dielectric properties of composite materials and the dielectric constant and volumetric ratio of each component is known as a dielectric model. In this study, a new dielectric model was deduced from circuit theory on the basis of structural abstraction to calculate the dielectric permittivities of concrete. To validate the applicability and accuracy of the proposed model, because concrete consists of matrix (cement mortar), aggregates (limestone), and air, the dielectric traits of concrete and its components were acquired using an open-ended coaxial probe. Compared with the Brown model, complex refractive index method (CRIM) model, Looyenga model, and Rayleigh model (i.e., the classical models), the results showed that among overall predictions of concrete dielectric constants, the proposed model has the greatest accuracy, because the theoretical results matched the test results more closely. This indicates that the proposed model can better interpret the dielectric properties of concrete, which lays the groundwork for future research into the application of GPR to the nondestructive testing and evaluation of concrete pavement. [ABSTRACT FROM AUTHOR]

The alkali-silica reaction (ASR) has been recognized as a major distress in concrete for nearly a century. In the US, ASR is a major cause of the deterioration of highway concrete structures (i.e., bridges and pavements). A research study was recently undertaken in the state of Idaho to evaluate the advantages associated with implementing the miniature concrete prism test (MCPT) from current standards for various reactive aggregates. A total of 11 different aggregate materials (both coarse and fine fractions), including a nonreactive reference aggregate, were collected from various sources and tested using the 56-days MCPT as well as the commonly used accelerated mortar bar test (AMBT). In addition, selected aggregate samples were tested using the 1-year long concrete prism test (CPT) and the 6-month accelerated concrete prism test (ACPT). The results demonstrated that the 56-day MCPT method resulted in higher percent expansion compared with the 14-day AMBT and 1-year CPT methods for the fine fractions of the test aggregates. The coarse fractions of the test aggregates, on the other hand, exhibited a lower percent expansion during the 56-day MCPT compared with the 14-day AMBT. Overall, the MCPT test results were found to correlate well with the 14-day AMBT and 1-year CPT test results. In addition, the 6-month ACPT method showed similar results to the ones of the 1-year CPT method, with high correlation between both methods. Recommendations were made based on the findings from this study to facilitate the implementation of the MCPT into practice by state and local highway agencies for better assessment of the ASR potential of aggregates. [ABSTRACT FROM AUTHOR]

Effects of synthetic and neutralized vinsol resin (NVR) air-entraining admixtures (AEAs) were compared through air-content measurements of freshly mixed concrete, hardened cylinders, and cores from field and laboratory concrete, and through a modified foam drainage test. The results show that air bubbles entrained with synthetic AEAs are less likely to survive during concrete sampling procedures than those entrained with NVR-based AEAs, leading to larger discrepancies between air-content measurements using the pressure method and the air content established from pavement cores. These discrepancies in turn can prompt imposition of contractor penalties, delays in construction, and controversy with potential longer-term impacts on concrete pavement longevity. [ABSTRACT FROM AUTHOR]

This paper investigates the potential use of phase change materials (PCM) in concrete pavements to store heat, which can be used to reduce ice formation and snow accumulation on the surface of the concrete pavement. The thermal properties of the PCMs are evaluated using a low-temperature differential scanning calorimeter (LT-DSC) while a longitudinal guarded comparative calorimeter (LGCC) is used to evaluate the thermal response of cementitious mortar containing the PCM. Paraffin oil (petroleum based) and methyl laurate (vegetable based) were selected as PCMs since they have high enthalpies of fusion (~130-170 J=g) and have desirable freezing temperatures (~2-3°C) during the liquid to solid phase transformation. Two approaches were used to place the PCM in the mortar specimens: (1) placing the PCM in lightweight aggregate (LWA) in mortar and (2) placing the PCM in an embedded tube that is placed in mortar. The durability and stability of the PCMs in the cementitious system were studied by monitoring the change in enthalpy of fusion, mass loss, pulse velocity, and compressive strength. When the PCM was placed in the mortar specimen using LWA, the paraffin oil can release a considerable amount of heat during phase transformation, which can be used to melt ice and snow. However, it was observed that the methyl laurate reacts with the cementitious matrix, causing damage to the mortar. Both paraffin oil and methyl laurate showed promising performance to melt ice and snow when the PCM was placed in an embedded tube in the mortar specimen. [ABSTRACT FROM AUTHOR]

This paper presents the results of a testing plan designed to evaluate the effects of macrosynthetic fibers on pervious concrete material properties and durability. The effects of two lengths of fibers (38 and 56 mm) were investigated at three dosage rates (1.5, 3.0, and 4.5 kg/m³) in a single mixture. The unit weight and void content of all samples were controlled to allow determination of the effects caused directly by the fibers. Samples were tested for strength and durability properties. The results indicate that fibers in general reduced permeability and the infiltration rate, while reducing surface abrasion and improving freeze-thaw durability. [ABSTRACT FROM AUTHOR]

In this research, the ability of pervious concrete pavement material to reduce pollutant concentrations and purify water was investigated. This project mainly aims to study the ability of pervious concrete pavement material to reduce pollutant concentrations such as those in diluted sulfuric acid, seawater, and motor oil. The results demonstrated that the ability of pervious concrete pavement material to reduce pollutant concentrations and purify water was effective in diluted sulfuric acid, artificial seawater, and motor oil tests. After flowing through pervious concrete pavement, a diluted sulfuric acid solution (pH value 2.0) could dramatically increase its pH value to approximately 7.0. A pervious concrete pavement system could greatly decrease the content of an artificial seawater solution (salinity 36%) to about 1%, and the oil content of motor oil combined with certain types of water could also be significantly decreased to 1%. The study demonstrates that pervious concrete pavement holds potential for environment conservation and hydrologic consideration. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the minimum paste volume required with an appropriate water-to-cementitious ratio () to achieve required workability, strength, and durability requirements of concrete mixtures for pavements. In this experimental program, 64 concrete mixtures with varying , cementitious content, and binder type were prepared and tested. The fine aggregate-to-total aggregate ratio was held constant for all the mixtures. Fresh and hardened concrete properties of the mixtures were determined at various ages. Test results have shown that approximately 1.5 times more paste by volume is required than voids between the aggregates to achieve a minimum performance in concrete for pavements. For a given , strength is independent of cementitious content after a critical value is provided. When is constant, increasing paste content increased chloride penetrability and air permeability. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the minimum paste volume required with an appropriate water-to-cementitious ratio () to achieve required workability, strength, and durability requirements of concrete mixtures for pavements. In this experimental program, 64 concrete mixtures with varying , cementitious content, and binder type were prepared and tested. The fine aggregate-to-total aggregate ratio was held constant for all the mixtures. Fresh and hardened concrete properties of the mixtures were determined at various ages. Test results have shown that approximately 1.5 times more paste by volume is required than voids between the aggregates to achieve a minimum performance in concrete for pavements. For a given , strength is independent of cementitious content after a critical value is provided. When is constant, increasing paste content increased chloride penetrability and air permeability. [ABSTRACT FROM AUTHOR]

In concrete pavements, steel dowels are exposed to a particularly aggressive environment that leads to depassivation and greatly reduces the corrosion initiation stage. Aggressive agents such as chlorides and CO2 have easy access to the dowels through pavement joints and, consequently, the corrosion performance of the system depends largely on the properties of the steel dowel being used. This study investigates the corrosion performance of several types of steel dowels embedded in concrete and subjected to accelerated corrosion by exposure to 3.5% NaCl solution for 18 months. Seven types of dowels were tested: bare carbon steel, stainless steel clad, grout-filled hollow stainless steel, microcomposite steel, carbon steel coated with bendable epoxy, and carbon steel coated with nonbendable epoxies. Half-cell potential, polarization resistance, visual inspections, and microscopic investigations by scanning electron microscopy were carried out to evaluate their corrosion performance. Results show that microcomposite steel dowels exhibit greater resistance to corrosion propagation than carbon steel dowels, but lesser than stainless clad and stainless hollow bars. In epoxy-coated bars, corrosion occurred at a few localized defective areas, generally at holidays and edges of bar ends. No significant difference was observed between nonbendable and bendable epoxy-coated dowels. [ABSTRACT FROM AUTHOR]

This paper deals with the results of a study on the effect of curing on as-constructed smoothness and subsequent roughness development of portland cement concrete pavements (PCCP) in Kansas. Ten test sections on five newly built PCCP projects on I-70 and I-135 were selected. At each site, one section was cured with a double application of curing compound as opposed to the single application currently specified. A section of equal length with single application was designated as the control section. Some sections were instrumented with thermocouples to collect temperature data at the bottom of the PCCP slab during construction. Large temperature gradients between the top and the bottom of the PCCP slab were observed during concrete placement. Double curing compound application tends to decrease this temperature gradient. Periodic longitudinal profile data was collected with a South Dakota-type profiler on the wheel paths of both driving and passing lanes on each section. From these profile data international roughness index (IRI) statistics were computed for each test section. Analysis of variance was performed to compare mean IRI values with respect to the curing compound application rate. It was found that the single curing compound results in lower as-constructed IRI values, but double application reduces roughness development in the long run, possibly due to lower differential autogenous volume change of concrete. [ABSTRACT FROM AUTHOR]

The temperature profiles in a hydrating concrete slab are produced by a two-dimensional finite-element method software tool, TMAC2 (temperature and moisture analysis for curing concrete), as a function of time and ambient boundary conditions described in this paper. To include the effect of the heat of vaporization, heat flux due to evaporation is included in the boundary condition of heat transfer at the slab surface in addition to the effects of surface humidity, effective curing thickness, and surface moisture emissivity on the rate of evaporation. Thermal conductivity is back-calculated using the data collected from laboratory measurements toward the improvement of the modeling of thermal conductivity. Theoretically, the material properties determined in this manner should facilitate accurate temperature prediction. Thus, temperature prediction in hardening concrete pavements under various conditions can be effectively calibrated by improved material characterization. To this end, this paper provides the basis of a calibration protocol. [ABSTRACT FROM AUTHOR]

This research was conducted to understand the effects of curing compounds and their application methods on concrete properties. In the research, three different curing compounds were selected and applied to lab and field concrete at different times. The curing compounds were applied with two methods—single- and double-layer sprays. Moisture content, electrical conductivity, sorptivity, and strength tests were performed to investigate the effects of curing on concrete properties, especially on the near-surface layer concrete properties. The experimental results indicated that for pavement without curing compound, the properties of the near-surface layer were considerably different from those of the internal layers. By decreasing the differences between the layers through proper curing technique, a pavement would have more uniform properties throughout its depth. Based on the results, the test methods for quantifying concrete curing effectiveness were also evaluated. [ABSTRACT FROM AUTHOR]

In this study the physical and engineering characteristics of various no-fines concrete mixtures are investigated. No-fines concrete mixtures subjected to impact compaction are studied under unconfined compression, indirect tension, and static modulus of elasticity; and the results are interpreted as functions of mixture proportions. The effect of impact-compaction energies, consolidation techniques, mixture proportions, curing types, and testing conditions on physical and engineering properties are presented. The abrasion characteristics and resistance to freezing and thawing of no-fines concrete are also discussed. It was found that the strength of no-fines concrete is strongly related to its mixture proportion and compaction energy. A sealed compressive strength of 20.7 MPa (3,000 psi) can readily be achieved with an aggregate cement ratio of 4.5:1 or less and a minimum compaction energy of 165 J/m 3 (4,303 ft-lb/cu ft). The splitting tensile-compressive relationship followed a pattern similar to that of conventional concrete. No-fines concrete had a lower modulus of elasticity than conventional concrete. The ultimate drying shrinkage of compacted no-fines concrete was found to be approximately 280 × 10 -6 , about half that typically expected in conventional concrete. Air-entrained no-fines concrete exhibited a higher resistance to freezing and thawing than non-air-entrained mixtures. [ABSTRACT FROM AUTHOR]

A study was conducted to evaluate the effect of coefficient of thermal expansion (CTE) test procedures and length-change measuring devices on the measured CTE values. Twenty different coarse aggregate sources were tested using the Texas Department of Transportation (TxDOT) and the American Association of State Highway and Transportation Officials (AASHTO) suggested CTE methods. Two different types of length-change measuring devices, linear variable differential transformers (LVDTs) and differential variable reluctance transducers (DVRTs), were used. No significant effects of length-change measuring devices were observed on the CTE values measured by the TxDOT method. However, the test methods have shown effects on the measured values. The TxDOT method yields higher CTE values than the AASHTO method. Data obtained in this study confirmed that the internal water pressure development during the heating and cooling cycles is one of the potential reasons. Internal water pressure can significantly affect the CTE of concrete. Further investigation is needed to determine the effect of internal water pressure on the CTE, which affects the design and service life of concrete pavements. [ABSTRACT FROM AUTHOR]