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The present study investigated the performance characteristics of concrete paver block (CPB) mixes with incorporated reclaimed asphalt pavement (RAP) aggregates under different curing regimes, namely, continuous water curing (WC), air curing (AC1 and AC2), intermittent water and air curing (WAC), water spray curing (WSC) and heat curing (HC). Seven CPB mixes were formulated by volumetrically replacing virgin coarse and fine aggregates partially and in combination with coarse RAP, fine RAP, and combined RAP fractions. For better refinement of agglomerated particles present in the RAP and to achieve a dense microstructure, the block specimens were fabricated using a design methodology that included a staged mixing approach and time-controlled compaction simultaneously with a vibratory hammer and table vibrator. Hardened CPB specimens were tested to assess mechanical (compressive, flexural, and tensile splitting strength) and durability (water absorption, porosity, and carbonation) properties of the concrete. CPBs fabricated from the considered RAP-inclusive concrete mixes manifested great potential to be used for pavement applications having medium to very heavy traffic when cured with the WC, WAC, WSC, and AC2 curing regimes. Curing regimes WAC and WSC, which involved a combination of water and air curing, were found to be the most effective for the RAP CPB mixes, resulting in superior strength properties. The presence of carbonation was detected in all the RAP CPB mixes when exposed to air curing (AC2) for a prolonged period of time. [ABSTRACT FROM AUTHOR]

Although roller-compacted concrete pavement (RCCP) has been considered the most popular among its counterparts, it has not been widely used due to a number of reasons. The most dominant reason is the variability in mixture proportioning methods and material selection considering its unique behavior compared to conventional concrete mixes. Therefore, the present paper focuses on the above-mentioned parameters by critically reviewing the literature over the past four decades (1984–2021). Initially, the influence of conventional and recycled waste materials on the fresh & hardened state behavior of RCCP is reviewed in detail. Subsequently, the potential applications of various mineral & chemical admixtures and the different types of synthetic and metallic fibers for performance improvement are discussed. In addition, this study has critically appraised various mixture proportioning methods ranging from conventional concrete approaches to empirical, semi-empirical, and theoretical methods for RCCP. The study concludes by noting that all considered materials (alternative aggregates, chemical & mineral admixtures, and fibers) could be used to produce high-quality RCCP; however, an optimal proportion must be prudently selected. Consequently, RCCP could be effectively proportioned by adopting solid suspension, optimal paste volume, and gyratory compaction methods. In addition, it is observed that the strength of the RCCP is related to the aggregate-cement ratio (A/C), water-cement ratio (W/C), and coarse-sand ratio (C/S); the A/C ratio shows an inverse relationship with strength, whereas a mixed behavior between W/C and strength was found. Nevertheless, RCCPs having a vebe time, A/C ratio, and C/S ratio in the ranges of 30–50 s , 5–8 , and 1–1.4 , respectively, could be used for the surface course application of pavements. [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]

Due to greater durability and lower maintenance costs, concrete pavements are more competitive than asphalt pavements in areas where rigid pavements are required. To ensure the surface skid resistance of concrete pavement for driving safety, appropriate textures must be created on the concrete pavement surface. Common surface texturing treatments in Germany include exposed aggregate, grinding and grooving, and sealing methods. To investigate the influence of different surface texturing methods on the wearing resistance of concrete pavement, concrete pavement samples with six different surface textures were manufactured in this study. The advanced Aachen Polishing Machine (APM) was used to simulate the different polishing states on the extracted samples with 0, 16, 33, 100, 200, and 300 min of real-tire polishing effect. After each polishing stage, a series of surface characteristic tests was conducted to evaluate the wearing characteristics of pavement samples. The test results showed that different surface textures have different long-term polishing resistances. Of the texturing methods investigated, the exposed aggregate and sealing treatments provide the best long-term polishing resistance for plastic and hardened concrete, respectively. This research provided a comprehensive evaluation of and significant guidance on the selection of surface treatment methods for new construction of cement pavement and surface maintenance of hardened concrete pavement. [ABSTRACT FROM AUTHOR]

Foamed asphalt cold-recycled mixtures have been increasingly used in China. However, the interlayer shear performance between the foamed asphalt cold-recycled layer and its top and bottom layers is still not clear. In this study, we explored factors affecting the interlayer shear performance of foamed asphalt cold-recycled layers (FACRL). Regarding the interlayer performance between the foamed asphalt cold-recycled layer and cement-treated base (CTB), the optimal content of the prime coat asphalt was 0.8 kg/m2 , and the prime coat asphalt was recommended to be applied on the surface of the base as soon as the base was paved. Styrene-butadiene-styrene (SBS)-rubber modified asphalt with a content of 2.3 kg/m2 and aggregates with a size range of 4.74–9.5 mm was recommended for use in the seal coats. The aggregates used in the seal coat were recommended to be premixed with a 0.3% asphalt binder to improve the adhesion and to be paved with a spreading area of 65%. Regarding the interlayer performance between the foamed asphalt cold-recycled layer and top hot-mix asphalt (HMA), the interlayer shear strength and fracture energy increased and then decreased with the added tack coat asphalt. The shear strength and fracture energy of the interlayer at 50°C was only 20% and 8% of that at 25°C, respectively. The optimum usage percent of the tack coat binder is 0.4 kg/m2. [ABSTRACT FROM AUTHOR]

This study discusses the effect of utilizing coarse reclaimed asphalt pavement (RAP) aggregates as a replacement to natural coarse aggregates (NCAs) for the production of pervious concrete pavement (PCP) mixes. Coarse RAP (RC) aggregates were utilized in proportions of 0%, 25%, 50%, 75%, and 100%, respectively. It was observed that the porosity and permeability coefficient of the PCP mixes increases considerably as the RAP replacement level increases. Meanwhile, the incorporation of RC was also found to negatively affect the mechanical properties of the PCP mixes. However, the compressive and flexural strength values were noted to be well within the prescribed limits (5–25 MPa and 1–3.2 MPa) required for a PCP mixture. On the other hand, the incorporation of RC was observed to reduce the hardened density, resistance to abrasion, and resistance against aggressive environment of chlorides and sulfates. Therefore, in order to prepare a PCP mixture such that there exists a fine balance in various properties, it is recommended that RC up to 50% may be utilized as a replacement to NCA. In view of achieving maximum sustainability, RC up to 100% may be completely utilized for the production of PCP mixes provided a binary gradation is adopted. Utilization of RAP in preparation of pervious concrete pavement mix will not only resolve the issues related to clearance of an enormous amount of RAP dumps, but would go a long way in dealing with various other environmental and ecological impacts. [ABSTRACT FROM AUTHOR]

The findings of an extensive literature review on the permeability of hot-mix asphalt concrete are detailed in a state-of-the-art report on the measurement and interpretation of asphalt concrete permeability data. The permeability of asphalt concrete is affected by a range of factors with various levels of importance, which are reviewed along with their impact on the coefficient of permeability. Many theoretical, empirical, semiempirical, and numerical models have been developed to predict permeability, using a range of indicators. Some of these models are reviewed and their advantages and shortcomings discussed. Recent advances in X-ray tomography studies are also summarized. The review reveals that field permeability measurements are not reported to match numerically well with laboratory measurements, though there is some correlation. The reviewed test methods for permeability all rely on an assumption of laminar flow that is unlikely in more porous mixtures. Attempts to measure connected air voids improve the chances of obtaining more meaningful correlations between permeability and air voids, regardless of the mathematical model used to link the two quantities. The lift-thickness to nominal maximum aggregate size (NMAS) ratio and/or changes in the binder content has a less significant effect on permeability than changes in the porosity and/or mix gradation. Air void gradients and distributions in compacted asphalt concrete mixtures can now be assessed with X-ray techniques: the distribution of air voids appears to be nonuniform in laboratory-prepared specimens. [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]