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In this investigation, four types of sands as alternatives to river sand, namely, crushed sand (CS), marine sand, fine recycled concrete aggregate (FRCA), and fine reclaimed asphalt pavement (FRAP), were studied for their potential for cement-concrete pavement applications. Initially, the physicochemical and morphological characteristics of these sands were understood and later linked to the hydration kinetics and the behavior of cement-mortar systems in both the fresh and hardened states. Due to their evenly graded particle size distribution, CS and FRCA exhibited higher packing densities despite having more gradient angularity, whereas the interlocking capacity of FRAP was found to be affected by the agglomerated particles. Morphology, fineness modulus, and chemical composition of the sands were observed to be the dominating parameters affecting the hydration kinetics and thus the performance of the mortar mixes. Improving these parameters, especially the grain size distribution, could help in enhancing the potential of these sands for pavement applications. [ABSTRACT FROM AUTHOR]

The development of new functional pavement materials and the application of sustainable concepts in road construction have led to a dramatic change in functional roads. Pouring semiflexible pavement (SFP) has superior advantages over traditional concrete and asphalt pavements in terms of road performance and convenient construction. The purpose of this research is to investigate the feasibility of SFP in terms of healing capacity, noise reduction, and electrical conductivity. First, the self-healing properties of the cement-asphalt-aggregate (C-AS-A) interface are analyzed by pull-out test, and the cracking characteristics and crack-healing capacity of SFP are investigated by semicircular bending (SCB) test and X-ray computed tomography (CT), respectively. Subsequently, the noise reduction performance of SFP, asphalt mixture, and cement concrete are compared by tire vertical drop test. Finally, different conductive SFP materials including graphite powder, carbon fiber, and steel fiber are prepared and their resistivity and road performance are analyzed. The results show that the C-AS-A interface has a significant self-healing ability; the cracks in SFP mainly occur at the C-AS-A interface (accounting for 53.12%) at −10°C. Moreover, when heated with microwave radiation, the heating-healing ratio of the SFP specimen increases by 63.33% with the addition of steel fiber. Besides, the noise reduction capability of SFP material is between that of asphalt mixture and cement concrete. By combining graphite powder and carbon fiber, the electrical conductivity and road performances of SFP are significantly improved. The results provide references for further design and development of SFP with heating healing capacity, noise reduction ability, and electrical conductivity. [ABSTRACT FROM AUTHOR]

Geogrid reinforcement effectively controls the rutting of pavements under traffic loads, especially when constructed over soft subgrades. In this study, extensive large-scale model pavement experiments (LSMPEs) were performed to quantify the rut depths of flexible pavements. In all, 20 LSMPEs were performed on pavement sections overlying subgrades of different strengths with California bearing ratio (CBR) values varying from 1% to 5%. Three geogrid types were considered to study the effects of material type [polypropylene (PP) and polyester (PET)] and tensile strengths (30–60 kN/m) on the rutting behavior of flexible pavements. LSMPEs were first performed under monotonic loading to obtain the optimum depth of reinforcement within the base layer of flexible pavement. Thereafter, a series of repetitive load (haversine loading) was applied on paved sections of reinforced flexible pavements using a high-end, linear, double-acting actuator system. Rut deformations were measured at both the surface and the subgrade levels of the model pavements. The rut deformations were found to distinctly vary in accordance with the condition of the subgrade, the thickness of the pavement layers, and the type of geogrid used. The rut depth reduction (RDR) at the pavement surface was found to range from 22% to 69% for PP- and PET-geogrid reinforced base layers. Geogrid reinforcement significantly reduced the rut depths at the subgrade level (as high as 90%) compared to unreinforced sections. In addition, the model pavements were instrumented with the earth pressure cells to measure the vertical pressures transferred to the subgrade due to surface loading. The ability of geogrid reinforcement to distribute loads to wider areas was quantified in terms of the vertical stress distribution angle, αmax , at the end of the load cycles (N=100,000 cycles). The αmax maximum values for geogrid (GG1/GG2/GG3)-reinforced pavements built over weak subgrade (CBR=1%) varied from 28.4° to 32.2°, while it was 25.7° for unreinforced pavements. Likewise, αmax values for geogrid-reinforced pavements overlying a relatively fair subgrade (CBR=5%) varied from 34.5° to 43.6° against 30.4° for an unreinforced case. [ABSTRACT FROM AUTHOR]

A series of spectral analyses of surface waves (SASW) tests were conducted on a cement concrete pavement by dropping steel balls of four different values of diameter () varying between 25.4 and 76.2 mm. These tests were performed (1) by using different combinations of source to nearest receiver distance () and receiver spacing (), and (2) for two different heights () of fall, namely, 0.25 and 0.50 m. The values of the maximum wavelength () and minimum wavelength () associated with the combined dispersion curve, corresponding to a particular combination of and , were noted to increase almost linearly with an increase in the magnitude of the input source energy (). A continuous increase in strength and duration of the signals was noted to occur with an increase in the magnitude of . Based on statistical analysis, two regression equations have been proposed to determine and for different values of source energy. It is concluded that the SASW technique is capable of producing nearly a unique dispersion curve irrespective of (1) diameters and heights of fall of the dropping masses used for producing the vibration, and (2) the spacing between different receivers. The results presented in this paper can be used to provide guidelines for deciding about the input source energy based on the required exploration zone of the pavement. [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]

Pervious concrete is becoming more common as a storm-water management tool in freeze-thaw climates. One of the main concerns or obstacles preventing a more widespread application is the aspect of freeze-thaw durability, whether perceived or actual. This paper describes a series of tests designed to determine the specific role coarse aggregate has on the freeze-thaw durability of pervious concrete using the ASTM C666A procedure. 17 different coarse aggregate samples were obtained from locations across the United States and Canada. Pervious concrete mixtures were placed using a mixture proportion previously determined as freeze-thaw durable. The range of durable aggregate gradations clearly defined a gradation specification and suggestions are made for optimizing the gradation with a small portion of sand. Mixtures with excellent freeze-thaw performance contained either granite or highly durable river gravel. The impact of aggregate angularity on mixture proportions and ultimate yield is also discussed. [ABSTRACT FROM AUTHOR]

A numerical study on the fracture behavior of steel fiber-reinforced concrete (SFRC) slabs on grade for industrial pavements is presented. Finite element analyses have been carried out by using a commercial finite element code where user subroutines based on nonlinear fracture mechanics have been implemented to describe the progressive cracking behavior of SFRC. The model is capable of simulating both primary and secondary cracks when they occur in concrete and it has been validated by comparing numerical predictions with experimental observations of full-scale tests on slabs on elastic subgrade under point loads in different positions. A real pavement with contraction or construction joints has been numerically simulated to investigate the stress and the strain fields for the most significant positions of point loads. [ABSTRACT FROM AUTHOR]

This study presents the findings from a research investigation conducted to characterize the toughness/abrasion resistance and soundness of aggregates from 23 sources using the micro-Deval, Los Angeles (LA) abrasion, sodium sulfate soundness, and magnesium sulfate soundness tests. Correlations between the results of micro-Deval test and other tests were explored, and the NCHRP 4-19 study recommendation of maximum loss of 18% in micro-Deval test to characterize good versus poor aggregates was evaluated against the field performance of the aggregate. Also, the effect of aggregate gradation on the loss observed in micro-Deval and LA abrasion tests was studied. Based on the results from this study, the recommendations from the NCHRP 04-19 study appear to be valid for the aggregates evaluated. Also, a high degree of correlation was observed between the size of the aggregate evaluated and the micro-Deval loss, with smaller sized aggregates yielding larger loss. Good correlation was observed between results of sodium sulfate and magnesium sulfate soundness tests, however, no significant correlation was observed between the losses observed in micro-Deval test and either of the two sulfate soundness tests or the LA abrasion test. [ABSTRACT FROM AUTHOR]

Cementitious stabilization is a common method of ground improvement when weak foundation soils are encountered in practice, and marginal or nonstandard materials such as recycled aggregates are used in civil engineering construction. Long-term durability of stabilized materials becomes an issue, especially when it involves one or more recycled materials with unknown and often questionable properties. The study presented herein investigates the fatigue durability, endurance limit, and damage accumulation process in recycled crushed concrete aggregate stabilized with cement–fly ash mixtures. Results show that the 2 million cycles fatigue endurance limit for the stabilized recycled aggregate was nearly 53% of the static modulus of rupture, indicating that the fatigue strength of this material is quite similar to or better than other traditional cementitious composites. It was also found that the accumulated permanent deformation and the expended fatigue life can be related by a nonlinear power law, and the fatigue damage in this material approximately follows Miner’s rule for cumulative damage. Finally, the importance of developing innovative testing methods for durability assessment are highlighted, which include coupled mechanical and environmental loadings to simulate the most damaging field conditions, and accelerated aging and life prediction processes using the Arrhenius time–temperature superposition methods. [ABSTRACT FROM AUTHOR]

The nonlinear models of pavement base and subgrade were briefly reviewed. Subroutines of the three-dimensional finite-element analysis in the ABAQUS package were developed for nonlinear behavior of a coarse-grained base and subgrade. The programs were validated by comparing them with the theoretical-solution-based program BISAR and the 2D finite-element program ILLI-PAVE. Significant discrepancy was found between the 3D analysis and the 2D axisymmetric analysis, especially for the deformation results. It was also found that the stiffness matrices of the nonlinear materials were not symmetrical, which causes accuracy problems in those programs based on 2D axisymmetry formulations. The results of nonlinear analysis and linear analysis were also compared. It was concluded that the determinations of the resilient modulus for the linear models is critical to interpret the behaviors of nonlinear materials. [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]