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Mechanical properties of pervious concrete (PC) are highly influenced by the applied compaction; however, the required level of compaction to achieve the desired density and strength in the field is currently unknown. In some cases, compaction is established empirically on costly test panels. In this study, the relationship between the applied compaction force and the hardened porosity (Ø) and compressive strength (fc) was investigated. Three PC mix proportions with varying paste contents were compacted in the laboratory using a lightweight deflectometer (LWD) at four different compaction levels. Porosity and 7-day fc testing were carried out on cylinders cast with each compaction level. In general, the first 15 LWD drops influenced Ø and fc significantly, while the effect of compaction beyond that level was less significant. The applied compaction force recorded by the LWD was used to obtain the required properties of a rotary roller-screed to apply an equivalent compaction force in the field. Then, regression-based models were developed to estimate the 7-day Ø and fc of PC based on the applied compaction force and the paste content. The developed models provide a practical solution to compute the required compaction force in the field to achieve the desired PC mechanical properties. [ABSTRACT FROM AUTHOR]

This paper investigates the development of compressive strength (fc′), flexural strength (fr), and static elastic modulus (Ec) in relation to the dynamic modulus (Ed) for portland concrete cement (PCC) pavement and patch mixtures. The study in this paper was motivated by the need to establish the less commonly known fr−Ed relationship in comparison with the more established fc′−Ed models. A total of 399 cylinders and 144 beams were cast and cured under laboratory (23°C) and cold (7.22°C) regimes. Experiments were conducted at concrete ages ranging from 12 h to 28 days. Cylinder specimens were subjected to fc′ , Ec , and transverse dynamic modulus (EdcT) tests. Beam specimens were subjected to fr , transverse (EdpT), and longitudinal (EdpL) dynamic modulus tests. Early opening to traffic (EOT) concrete strength criteria were accurately predicted as most fc′ and fr estimates fell within 10% of relative error when respectively using EdcT and EdpT. Overall, the normalized development of fc′−EdcT and fr−EdpT relationships reveals distinct growth trends as fr developed at a higher power factor. [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]

Pervious concrete pavements (PCP) are increasingly recognized and used as a best management practice to control stormwater runoff and for low-volume traffic. However, there are limited studies on the structural integrity of the PCP section on performance under vehicular loads. This study investigated the mechanical properties of field samples and the structural integrity of PCP when subjected to traffic loads using the falling weight deflectometer (FWD). The compressive strength for cored samples from the field installation was about 11.5 MPa with an average unit weight of . The deflection of the PCP sections at the load application point was about 1.7 to 4 times of the impervious concrete section, dependent on the subbase characterization. The composition of the PCP subbase materials and the compaction effort of the layers significantly affected the deflection. Back-calculation analysis showed that the loosely compacted subbase layers had lower elastic moduli and exhibited higher deflection responses, which compromised the structural integrity of the PCP systems to traffic loadings. [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]

The work reported in this paper is based on a laboratory study of superplasticized high-volume fly-ash (HVFA) concrete suitable for pavement construction. Three control concrete mixtures having 400 kg/m3 of ordinary portland cement (OPC) and water–cementitious material (w–cm) ratios of 0.30, 0.34, and 0.40 were prepared. Other concrete mixtures were then prepared by substituting 20, 30, 40, 50, and 60% fly ash in all control mixtures. Compressive and flexural strengths at ages of 7, 28, 90, 180, 256, and 365 days, drying shrinkage, and abrasion resistance of concrete were measured for all the mixtures. The laboratory test results showed that HVFA concrete mixtures containing 50–60% fly ash can be designed to fulfill the requirement of strength and workability suitable for cement concrete pavement construction. At all w–cm ratios, the concrete mixture containing 60% OPC and 40% fly ash developed maximum strength at the age of 90 days and beyond. However, a maximum increase in the strength of concrete at 365 days over the 28 days strength was observed in the mixtures containing equal amount of OPC and fly ash. Drying shrinkage of concrete decreased with decreasing w–cm ratio and increasing fly-ash content. Among all the concrete mixtures, the mixture with w–cm ratio of 0.30 and containing 60% fly ash showed least shrinkage. Abrasion resistance of concrete, measured by the sand-blasting method, decreased with increasing fly-ash content and decreasing compressive strength. However, abrasion resistance of HVFA concrete mixture with 60% fly ash at 0.30 w–cm ratio was adequate from concrete-pavement considerations. [ABSTRACT FROM AUTHOR]