1,720,969 research outputs found
Investigation on the effects of mix water temperature on High-Early strength cement concrete properties – An experimental work and a case study
No full textConsidering the cold weather concreting techniques, using concrete additives and High Early strength cement (Type HE) are by far the most commonly prescribed approaches as well as heating the components. However, the optimum temperatures for heated components and in particular the temperature of mixing water is under skepticism. In this respect many experimental research works and field data showed difficulties in this regards. To address the reported controversies, the present study examined the effects of mix-water temperature on some of the performance and mechanical properties of concrete made with High-Early strength cement. The experimental program included the tests for both fresh (or plastic) and hardened concrete with various water temperature in the range of 5–90 °C. Based on the experimental results and field-practices’ observations it could be concluded that the optimum mixing water temperature range is 50 ± 5 °C when using High-Early strength cement. In addition to the examined compressive strength, bleeding and optimum slump of mixtures were observed within the same temperature range. The higher temperature of mixing water out of this range resulted in higher bleeding, segregation, and further relative failures in this study
A comparison study on low-temperature properties of Stone Mastic Asphalts modified with PmBs or modified fibres
No full textA research was conducted to assess the effectiveness of different kinds of Modified Fibres (MF) on the thermal cracking performance of a Stone Mastic Asphalt (SMA) compared to the conventional SMA mixtures modified with SBS Polymer modified Bitumen (PmB). In addition, the capability of rubberised fibres to alleviate the thermal cracking sensitivity was investigated. Besides the main scope, a series of the same SMAs were also produced containing 25% of Reclaimed Asphalt Pavement (RAP) to investigate the effects of RAP on the low-temperature performance of the mixtures, which were modified either with MF or PmB. The experimental plan included both binder and mixture characterisation by means of Bending Beam Rheometer (BBR) test and Thermal Stress Restrained Specimen Test (TSRST). Binder-scale test results showed that the stiffness of all bituminous compounds is increased by the addition of fibres and rubber improves the elasticity of both neat and PmB compounds. In the mixture scale, TSRST results showed no significant difference between the mixtures. However it is noteworthy that, in addition, better low-temperature performance was recorded for virgin mixtures compared to to RAP containing ones. The overall results may confirm the feasibility of modified fibres in the modification of mixtures at low temperatures
Recycled and rubberized SMA modified mixtures: A comparison between polymer modified bitumen and modified fibres
No full textIn the presented research a series of Stone Mastic Asphalt (SMA) mixtures with and without Reclaimed Asphalt Pavement (RAP) and rejuvenating agent modified with SBS Polymer modified Binder (PmB) or composite Modified Fibres (MF) were optimized and investigated. In addition, beyond the common wet and dry methods of using waste tire rubber for producing asphalt mixtures, the rubber was added to the fibres with and without containing a plastomer polymer as a modifier. A comprehensive experimental programme including mechanical and performance tests were considered for evaluating the properties of the mixtures modified with PmB or MF with and without rubber and RAP. According to the test results, the SMA mixtures modified with MF were comparable with those of modified with PmB in most of the cases, however, the superiority of PmB mixtures were apparent in some cases. In the case of RAP addition, while it increased the tensile properties of corresponding mixtures observed by ITS and ITSM tests, it intensified the low-temperature sensitivity and reduced the fatigue life of mixtures containing rubberized fibres. Finally, the performance tests, moisture susceptibility and bitumen/aggregate, showed no significant difference between the tested mixtures in terms of moisture susceptibility and effectiveness of rubberized-fibres in bitumen binder's adhesion properties
A complete study on an asphalt concrete modified with graphene and recycled hard-plastics: A case study
Full text linkTo date, many asphalt modifiers have been introduced and tested in the road pavement industry aiming at improving the properties of asphalt concrete and consequently its service life. In this context, also considering the environmental and circular economy principles, recently waste plastics, as a source of plastomeric polymers, have gotten more attention. This paper presents a complete case study on an asphalt pavement containing an asphalt concrete modifier composed of recycled hard plastics and graphene nanoplatelets that is compared with its counterpart made of SBS Polymer-modified Bitumen (PmB). The study aimed at providing a complete knowledge on a real-scale job and practical issues using such modifier that has not been well-reported within the current literature. This paper is divided into I) mix design and pre-qualification, 2) post-production tests, and 3) two years of monitoring of the trial section. Based on the results, the mixtures modified with recycled-plastic additives showed higher stiffness and tenacity and as expected though, a higher resistance to permanent deformation in line with the literature. As far as the fatigue is concerned, a similar fatigue endurance was observed for both of the studied asphalt concretes. In addition, the pavement condition survey carried out by pavement experts did not reveal any distress or failure for both of the executed pavements
Fundamental properties of bitumen binders containing novel cellulose-based poly-functional fibres
No full textA series of Fibre-added bitumen compounds were subjected to conventional and rheological tests for investigating the effectiveness of modified fibres in improving the characteristics of bituminous binders. The studied fibres were novel composite cellulose-based poly-functional fibres with and without a plastomeric polymer and crumb rubber content, which blended with neat bitumen or SBS Polymer modified Bitumen (PmB). The test program included a primary stage of microscopic analysis by means of Scanning Electron Microscopy (SEM), for observing these composite fibres’ microstructure as well as the empirical test methods, and dynamic rheological analyses using Dynamic Shear Rheometer (DSR). According to the conventional test results, the addition of fibres increased the softening point and viscosity and reduced the penetration. From another perspective, while the addition of rubber decreased the softening point and viscosity, it increased the penetration of compounds in comparison to those containing fibres without rubber content. From the results obtained by Multiple-Stress Creep-Recovery (MSCR) and Frequency Sweep (FS) test, the isochronal graphs of complex modulus and creep-recovery curves showed the same trends in terms of increased stiffness. In addition, the phase angle curves confirm that the presence of rubber decreased the stiffness and increased the elasticity for PmB compounds in comparison to those of reference mixtures containing non-rubberized fibres
Recycling asphalt pavement and tire rubber: A full laboratory and field scale study
No full textThe present research deals with the influence of fine Crumb Rubber (CR) incorporation on the mechanical and performance characteristics of dense graded asphalt mixtures including 30% Reclaimed Asphalt Pavements (RAP) by means of both laboratory-scale and in situ tests. In the laboratory phase, the mixtures were evaluated in terms of Indirect Tensile Strength (ITS), moisture sensitivity, Indirect Tensile Stiffness Modulus (ITSM) and Repeated Load Axial Test (RLAT). Experimental tests indicated that while the difference of RLAT results were insignificant, the ITS values and the ITSM modulus changed in an effective way. On the other hand, the in-situ investigations on texture by means of sand patch and British pendulum provided testimonies to the effectiveness of CR in recycled dense graded mixtures. Finally, the tire/pavement noise emission measurements of the trial sections by means of Close Proximity (CPX) showed no significant difference between the tested pavements with and without rubber
Fatigue resistance of waste plastic-modified asphalt
No full textRecycling of waste plastic is the only truly sustainable solution for today’s environmental
concerns as it represents the most concrete action to reduce the impacts of such
material (Milios et al., 2018). However, due to the inherent complexity and variability
of its nature, there are still significant challenges related to the management of different
waste plastics. The development of new industrial technologies for the collection,
distribution, and reprocessing of waste plastic are leading to new solutions for its
recycling, including their use in pavements.
The recycling sector today constitutes one of the most dynamic areas in the plastics
industry (Hopewell et al., 2009). Very different recycling processes and methods have
been investigated and an ever-increasing number of experimental applications of recycled
plastic waste have been evaluated. Researchers are exploring alternative methods
and materials to repurpose waste plastics that can be utilized in civil infrastructures,
such as wood–plastic composites, concrete blocks, and mortars. Also, incorporating
plastic waste into asphalt pavements is today a possible and sustainable practice.
Several studies have verified that specific polymers and plastics can effectively improve
the performance and the durability of the road pavements if adequately blended with
bitumen according to certain construction and service conditions.
Generally, the integration of polymers and modifiers of various nature in asphalt
concrete can be either performed according to the so-called “wet” or the “dry” methods.
In the first one, the modifier is added at a high temperature to the bitumen, which is accordingly referred to as polymer-modified Bitumen (PmB). Instead, according to the
second one, the modifiers are added during the mixing phase of the asphalt concrete,
together with aggregates and bitumen; the final product is therefore referred to as
Polymer-modified Asphalt (PmA).
While PmB has become common practice (e.g., styrene-butadiene-styrene (SBS)
and styrene-butadiene rubber), taking advantage of waste plastics in asphalt pavements
(which are usually added through the dry method, PmA) is an interesting but still
challenging task for researchers and practitioners. On one hand, the adoption of various
types of waste materials should be pursued to reduce the environmental impacts
and save raw materials. On the other hand, researchers must prove that the use of
recycled materials in large amounts allows achieving similar or improved performances
when compared to traditional bituminous mixtures. Overall, the goal is to balance the
environmental benefits given by the adoption of the recycled materials with the impact
on the performance of the bituminous mixtures, making the most of the physical,
and mechanical contributions of the incorporated recycled materials. This chapter
investigates the state-of-the-art of waste plastic in bituminous mixtures for pavements
with a specific focus on the effects on fatigue resistance
A complete laboratory assessment of crumb rubber porous asphalt
No full textBesides the many advantages of porous asphalt (PA), the permanent deformation resistance, fatigue strength, stripping and moisture susceptibility are not as good as for dense graded mixtures. In this research, the effectiveness of adding crumb rubber (CR) by dry method to PA mixtures was assessed. Rubberized porous asphalt (RPA) mixtures manufactured incorporating CR into SBS modified asphalt concrete were produced and compared with a control mixture by means of Indirect Tensile Strength (ITS), Indirect Tensile Stiffness Modulus (ITSM), moisture susceptibility, permeability, Cantabro, rolling bottle, draindown and creep tests. Results proved that although the application of CR reduces the vertical permeability and permanent deformation resistance, it improves the bitumen/aggregate affinity and it controls the draindown rate without adding fibres. On the other hand, the use of CR decreased the ITSM value at low temperature, which represents a lower susceptibility to thermal cracking. Other complementary test results in this research support the effectiveness of RPA mixtures
Experimental application of waste glass powder filler in recycled dense-graded asphalt mixtures
Full text linkThis paper presents laboratory study results, including both bituminous mastics and mixtures tests, to assess the use of glass powder (GP) as possible surrogate to limestone filler in recycled dense-graded asphalt mixtures. To achieve a comprehensive approach, the analysis has been divided into three parts including filler, mastics and mixture characterisation. The GP has been completely studied with chemical and physical tests to compare the fundamental characteristics to the commonly used limestone filler. In the second part, rheological tests using the Dynamic Shear Rheometer has been implemented to evaluate fillers interaction with not modified and modified bitumen. Finally, the mechanical properties of the asphalt mixtures containing GP filler were investigated in terms of indirect tensile strength, indirect tensile stiffness modulus and creep characteristics. According to the obtained results, GP filler provided comparable values to limestone filler within both mastic and mixture study. It is noteworthy that from the permanent deformation analysis, both MSCR and RLAT tests confirmed the improvement of rutting resistance with using GP filler
1H-NMR Spectroscopy: A Possible Approach to Advanced Bitumen Characterization for Industrial and Paving Applications
Full text linkBitumen has unique chemo-mechanical properties, and for this reason, it is today one of the main constituents of many industrial products beside its common use in highway pavements construction. While the excellent rheological properties of bitumens have been investigated by means of different techniques, much remains to be known about the intrinsic properties of this complex material. It is therefore important to investigate its structure and properties from a closer point of view, towards possible useful modifications of the neat material. The present research developed a technique to investigate the composition of bitumens using Thin Layer Chromatography (TLC) to separate the different fractions, and Nuclear Magnetic Resonance (NMR) spectroscopy to assess and quantify the aliphatic hydrogen part with respect to the aromatic part. To achieve a comprehensive understanding of the chemical composition of the materials, Proton Nuclear Magnetic Resonance (1H-NMR) analysis was conducted in solution, using CCl4 as solvent, on three different neat bitumens and on their asphaltene and maltene fractions. The combined application of TLC and 1H-NMR spectroscopy enables the advanced characterization of bitumens supplied from different sources or obtained from different processes. This further allows addressing the use of specific modifications according to the bitumen final applications
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