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Lack of understanding of the compaction mechanism, both in the laboratory and field, could result in significant underestimation or overestimation of the roller-compacted concrete pavement (RCCP) performance. The literature (1987 to 2022) depicts that there are numerous techniques to design RCCP in the laboratory; however, which method could closely simulate the field compaction is not fully explored. The present paper critically reviews the fundamental parameters affecting the strength characteristics of RCCP when compacted with different compaction mechanisms in the laboratory and attempts to rank the compaction methods based on the field performance. Also, recommendations are made on how to fabricate the specimens without having much impact on the considered compaction technique. The techniques that have been considered are the vibratory hammer, vibratory table, modified Proctor, gyratory compactor, and special compactors such as California kneading compactor, Marshall hammer, and duplex roller. Based on the present review, future research prospects are outlined to improve the performance of RCCP. Keywords: gyratory compactor; laboratory compaction methods; review; roller-compacted concrete pavement (RCCP); roller-compacted concrete pavement (RCCP) specimen fabrication.

This paper presents the experimental results concerning the mix design and fresh properties of a high-performance fibre-reinforced fine-aggregate concrete for printing concrete. This concrete has been designed to be extruded through a nozzle to build layer-by-layer structural components. The printing process is a novel digitally controlled additive manufacturing method which can build architectural and structural components without formwork, unlike conventional concrete construction methods. The most critical fresh properties are shown to be extrudability and buildability, which have mutual relationships with workability and open time. These properties are significantly influenced by the mix proportions and the presence of superplasticiser, retarder, accelerator and polypropylene fibres. An optimum mix is identified and validated by the full-scale manufacture of a bench component.

The article presents the results of a round-robin test performed by 13 international research groups (representing fifteen institutions) in the framework of the activities of the RILEM Technical Committee 225-SAP \"Applications of Superabsorbent Polymers in Concrete Construction\". Two commercially available SAP materials were used for internal curing of a high-performance, fine-grained concrete in combination with the addition of extra water. The concrete had the same mix composition in all laboratories involved but was composed of local materials. All found a considerable decrease in autogenous shrinkage attributable to internal curing. Also, with regard to the shrinkage-mitigating effect of both particular SAP materials, the results were consistent. This demonstrates that internal curing using SAP is a robust approach, working independently of some variations in the concretes' raw materials, production process, or measuring technique. Furthermore, the effects of internal curing on other properties of concrete in its fresh and hardened states were investigated. These are consistent as well and expand considerably the existing data basis on properties of concrete materials containing SAP. © 2013 RILEM.

Ultra-high performance concrete (UHPC) and ultra-high performance fiber reinforced concrete (UHP-FRC) were introduced in the mid 1990s. Special treatment, such as heat curing, pressure and/or extensive vibration, is often required in order to achieve compressive strengths in excess of 150 MPa (22 ksi). This study focuses on the development of UHP-FRCs without any special treatment and utilizing materials that are commercially available on the US market. Enhanced performance was accomplished by optimizing the packing density of the cementitious matrix, using very high strength steel fibers, tailoring the geometry of the fibers and optimizing the matrix-fiber interface properties. It is shown that addition of 1.5% deformed fibers by volume results in a direct tensile strength of 13 MPa, which is 60% higher than comparable UHP-FRC with smooth steel fibers, and a tensile strain at peak stress of 0.6%, which is about three times that for UHP-FRC with smooth fibers. Compressive strength up to 292 MPa (42 ksi), tensile strength up to 37 MPa (5.4 ksi) and strain at peak stress up to 1.1% were also attained 28 days after casting by using up to 8% volume fraction of high strength steel fibers and infiltrating them with the UHPC matrix.

The capability of processing robust Engineered Cementitious Composites (ECC) materials with consistent mechanical properties is crucial for gaining acceptance of this new construction material in various structural applications. ECC’s tensile strain-hardening behavior and magnitude of tensile strain capacity are closely associated with fiber dispersion uniformity, which determines the fiber bridging strength, complementary energy, critical flaw size and degree of multiple-crack saturation. This study investigates the correlation between the rheological parameters of ECC mortar before adding PVA fibers, dispersion of PVA fibers, and ECC composite tensile properties. The correlation between Marsh cone flow rate and plastic viscosity was established for ECC mortar, justifying the use of the Marsh cone as a simple rheology measurement and control method before fibers are added. An optimal range of Marsh cone flow rate was found that led to improved fiber dispersion uniformity and more consistent tensile strain capacity in the composite. When coupled with the micromechanics based ingredient-tailoring methodology, this rheological control approach serves as an effective ECC fresh property design guide for achieving robust ECC composite hardening properties.

The present study investigates the effects of different compaction methods on the properties of roller-compacted concrete (RCC) used for road pavements. The study focuses on comparing the Proctor compaction method utilizing different compaction efforts and molds (2.5 kg rammer with three layers of 56 blows and 4.5 kg with three and five layers of 56 blows, cylindrical and cube molds) with a slab compactor in static and vibratory setting. The samples produced in a slab compactor were obtained by drilling from the prepared slab. The evaluated properties of the samples included compressive strength and bulk density. The study involved a C25/30 concrete with the intention to be used in low volume roads according to national standards. The study concluded that the utilization of Proctor compaction and slab compactor with vibratory setting provided similar levels of strength performance of the RCC mixture, regardless of the shape of the Proctor compacted samples. In terms of the bulk densities, the main differentiating factor in the case of Proctor compaction was the weight of the rammer. The compressive strength of the samples was also strongly related to their bulk densities.

In this study, the effects of different fiber types on improving the high-temperature performance of roller-compacted concrete (RCC) were comprehensively investigated. For this purpose, 60 mm long steel (S), polypropylene (PP), and environmentally sustainable waste steel (WS) fibers were incorporated into RCC at volumetric ratios of 0%, 0.25%, 0.50%, 0.75%, 1.00%, and 1.25%. The prepared specimens were exposed to controlled conditions at 25 °C (room temperature), 300 °C, 600 °C, and 900 °C, and the influence of thermal exposure on compressive strength and permeability characteristics was thoroughly evaluated. The findings revealed that high temperatures led to significant changes in the physical and mechanical properties of the concrete. Notably, at elevated temperatures such as 600 °C and 900 °C, S and WS fibers were found to reduce strength loss by limiting the propagation of microcracks within the concrete matrix. However, PP fibers were observed to lose their effectiveness at high temperatures due to melting in the range of approximately 160–170 °C, which negatively affected mechanical performance. One of this study’s key findings is that waste steel fibers offer a sustainable alternative while exhibiting comparable performance to conventional steel fibers. These results highlight the potential of recycling industrial waste to reduce environmental impact and lower overall costs.

This research work focuses on the optimization of strength and ductility of ultra high performance fiber reinforced concretes (UHP-FRC) under direct tensile loading. An ultra high performance concrete (UHPC) with a compressive strength of 200 MPa (29 ksi) providing high bond strength between fiber and matrix was developed. In addition to the high strength smooth steel fibers, currently used for typical UHP-FRC, high strength deformed steel fibers were used in this study to enhance the mechanical bond and ductility. The study first shows that, with appropriate high strength steel fibers, a fiber volume fraction of 1% is sufficient to trigger strain hardening behavior accompanied by multiple cracking, a characteristic essential to achieve high ductility. By improving both the matrix and fiber parameters, an UHP-FRC with only 1.5% deformed steel fibers by volume resulted in an average tensile strength of 13 MPa (1.9 ksi) and a maximum post-cracking strain of 0.6%.

The interfacial-bonding, interfacial transition zone (ITZ), and porosity are regarded as the key factors affecting hardened concrete properties. The aim of this study was to experimentally improve the bonding between the rubber aggregate and cement paste by different methodologies including water washing, Na(OH) pre-treatment, and both cement paste and mortar pre-coating. All methods were assessed by determining mechanical and dynamic properties, then correlating this with ITZ porosity and interfacial gap void geometry, along with quantification of the fracture energy during micro crack propagation using fractal analysis. The results indicated that pre-coating the rubber by mortar gave the best results in terms of fracture toughness and energy absorption showing good agreement between observations made at both micro and macro scales.

The strength and shrinkage behaviors of roller-compacted concrete (RCR) with used tire-rubber additive were experimentally investigated by keeping the compressive strengths of all specimens at the level of 40 MPa. Four rubber contents were used: 50, 80, 100, and 120 kg/m 3 . Test results show that the rubber particles homogeneously distributed in RCR, rubber particle emersion was not observed during vibrating for compaction. The workability of RCR was slightly influenced by replacing portion of sand with the same volume of tire rubber particles. RCR specimen exhibited a ductile failure under compression. In comparison with the control concrete, when the compressive strength was kept constant for RCR, the tensile strength, flexural strength, and ultimate tension elongation increased with the increase of rubber content. The incorporation of tire rubber did not help in reducing the drying shrinkage, on the contrary, a little more drying shrinkage developed in RCR than that in the control concrete.