1,721,018 research outputs found
A Preliminary Laboratory Evaluation on the Use of Shredded Cigarette Filters as Stabilizing Fibers for Stone Mastic Asphalts
Full text linkCigarette butts can be considered as one of the most common contemporary sources of waste, considering the large consumption of cigarettes all over the world. Despite the fact that different solutions have been developed and tested in the recent years aiming to recycle them, cigarette butts are currently landfilled and incinerated. Following the circular economy principles, the experimental application proposed in this paper is an exploratory investigation on the use of shredded cigarette filters as sustainable alternative to the addition of fibers into Stone Mastic Asphalts (SMAs). This represents the preliminary step for a wider research project, aiming to find a possible recycling solution for cigarette butts as fibers in bituminous materials. The use of fibers is a common and well-established solution for the production of high bitumen content mixtures. The fibers have a double function: acting, generally, as a stabilizing agent and, where possible, improving the mechanical performance of the bituminous mixtures. In the present research, two different SMAs were produced and tested aiming to analyze the effects given by the addition of the shredded cigarette filters. The first asphalt concrete, produced with traditional cellulose fibers was taken as a reference mixture, while the experimental mixture was produced with the shredded cigarette filters. The data highlight interesting and promising results for future development, making the use of waste cigarette filters a potential eco-friendly alternative to common cellulose fibers for SMAs
Ultra-thin sealing surface treatments for solar radiation screening on asphalt facing dams
Full text linkBituminous materials are widely used in a large range of hydraulic applications due their
excellent waterproofing properties. More than 300 asphalt facing reservoirs were built in the last
century, presenting higher mechanical and hydraulic performance when compared with other
facing alternatives, such as cement concrete or steel membranes. On the other hand, the dark
colour of bitumen may lead to high temperatures inside asphalt paved system, affecting long term
ageing of binder and jeopardizing the quality of the impervious layer. Recently, multifunctional
ultra-thin surface treatments are becoming an alternative to demolition-reconstruction of the
impervious layer, significantly abating the quantity of energy and raw materials required for
maintenance. High-reflective surface treatments may represent also an effective solution to
reduce the temperature of asphalt layers, extending the service life of the dam embankment and
reducing the need of maintenance. In fact, there is a lack of literature concerning the assessment
of thermal impact on asphalt dams. In the light of above, a number of different combinations of
sealing surface treatments were investigated in this study. An ad hoc testing equipment and
procedure were designed to perform an artificial solar irradiance test. A complete colorimetry
analysis was performed and the outcomes were compared with temperature data, making use of a
thermal camera and of embedded sensors for surface and base temperature measurements,
respectively. Major results and their relationships have been commented in-depth along with
proposed further research activities
An efficient approach to identifying optimum dosages of the two-component synchronous rejuvenator composite for rejuvenating the aged SBS-modified asphalt
No full textReconnecting fractured styrene-butadiene-styrene (SBS) polymer chains and rebalancing unstable colloidal
structures of aged pure asphalt using two-component synchronous rejuvenator composite (SRC) are essential for
recycling waste SBS-modified asphalt (SBSMA) mixtures. This research develops an efficient approach to identify
the optimum dosages of SRC through the restoration of FTIR peak area ratios. Based on the FTIR analysis of aged
SBSMA rejuvenated by triallyl isocyanurate (TAIC) (SBS repair agent) and aromatic oil (pure asphalt component
regulation agent), the optimum dosage of TAIC was identified at which the FTIR peak area ratio loss at 968 cm-1
was completely compensated by the new peak area ratios at 1022 cm-1 and 1112 cm-1, while the optimum dosage
of aromatic oil was defined at which the loss of FTIR peak area ratios at 1376 cm-1 and 1600 cm-1 was fully
restored. In line with this principle, seven types of aged SBSMA were prepared and rejuvenated with different
dosages of TAIC and aromatic oil incorporated. Through analyzing the FTIR peak area ratios of the prepared aged
SBSMAs before and after synchronous rejuvenation, a good linear relationship was found between the optimum
TAIC/aromatic oil dosage and the required restoration peak area ratio. The fitting equations of
yTAIC=1.7852x+0.0229 (R2= 0.9616) and yAromatic oil=2.2809x-0.0109 (R2 = 0.9395) were developed for
determining the optimum dosages of two-component SRC, respectively. After adding the theoretically derived
optimum dosages of TAIC and aromatic oil into three aged SBSMAs, their physical-rheological-microscopic
performance was found to be restored around 90 % of the virgin ones, validating the efficiency of the newly
proposed approach
Regeneration mechanisms of aged bitumen by rejuvenators: Insights from interfacial diffusion and structural deagglomeration
No full textTo realize the efficient recycling of aged bitumen, it is of great significance to reveal the regeneration mechanisms
of aged bitumen for the selection and design of rejuvenators. First, the physical properties and microstructure
of mineral rejuvenators and biomass rejuvenators were investigated. Then, the diffusion behavior at the
interface between the rejuvenator and aged bitumen and the deagglomeration behavior of the rejuvenator on the
agglomerates of aged bitumen were quantitatively characterized based on mechanical properties and structural
characteristics of recycled bitumen. Finally, the regeneration mechanisms of rejuvenators on aged bitumen were
analyzed based on molecular dynamics simulations of colloidal interfacial diffusion behavior and colloidal
structural deagglomeration behavior. The results showed that mineral rejuvenators demonstrated better ability
to accelerate the diffusion at the colloidal interface of aged bitumen and virgin bitumen due to their small
molecular weight and non-polar properties. However, the deagglomeration of aged bitumen colloid structure was
limited, mainly because the small moleculars could only fill the free volume of aged bitumen, but could not
effectively achieve the deagglomeration of asphaltene nanoclusters. Biomass rejuvenators exhibited weak
diffusion performance due to their macromolecular structure. However, they could effectively exert the steric
hindrance effect to realize the deagglomeration of asphaltene nanoclusters, which was attributed to the fact that
the functional group branched chain of biomass rejuvenators could exert pullout and intercalation effect to
deagglomerate the asphaltene nanoclusters. The regeneration efficiency of aged bitumen is jointly determined by
the diffusion rate and the deagglomeration effectiveness of the base oil in rejuvenator. Therefore, balancing both
diffusion capability and deagglomeration performance constitutes a critical consideration in the design and
development of high-performance rejuvenators
Laboratory surface texture analysis of road pavements using a mobile phone camera based close-range photogrammetry technique
Full text linkThe wearing course conditions strongly affect road pavements quality in terms of traffic safety and overall functionality. Surface texture can be considered a very strategic aspect to assess road pavement status, in order to predict its degradation and to define an effective maintenance program. Nowadays, common texture assessment approaches are mainly empirical and based on in-situ and/or laboratory direct measurements, thus the quantity and quality of the obtainable information are limited. On the other hand, advanced contactless techniques require expensive and often complicated equipment that can be hardly used in common applications. In this regard, a low budget close-range photogrammetry technique for road pavements 3D surface texture analysis is here proposed. 14 areal texture parameters including depth, volume, distribution and feature indicators have been determined by analysing the 3D models. The outcomes have been compared with those found with the traditional volumetric patch and pendulum tests, and a complete pairwise correlation matrix has been obtained. Volume patch test exhibits a high relationship with different volume and height surface texture parameters, while low-correlations have been found comparing pendulum test with the intrinsic and statistical indicators. The results and their relationships have been commented in-depth along with proposed further research activities
Surface treatment of waste tire rubber via oxidation and alkalization for enhanced compatibility with bitumen
Full text linkThe accumulation of waste tires poses critical environmental and engineering challenges. Incorporating waste crumb rubber (WCR) into asphalt pavements enhances recycling and pavement performance, yet limited compatibility between WCR and bitumen remains a constraint. This study explores surface treatments using hydrogen peroxide (H2O2) and sodium hydroxide (NaOH) under varying intensities. Microscopic analysis (scanning electron microscopy (SEM), specific surface area (SSA), contact angle, and Fourier transform infrared (FTIR) spectroscopy) and macroscopic evaluations (striping rates by modified boiling test) on coarse WCR, and storage stability test on rubberized binders reveal that both treatments enhance interfacial adhesion and compatibility through surface etching and polar group incorporation. Within 2 mol/L, H2O2 treatment becomes increasingly effective with higher concentration and temperature, whereas NaOH solutions exceeding 15 % at elevated temperatures cause excessive corrosion without further interfacial improvement. Unexpectedly, both treatments may induce the micro-swelling effect, modifying WCR viscoelasticity, with NaOH exhibiting a more pronounced impact
Preliminary Evaluation of Geopolymer Mix Design Applying the Design of Experiments Method
Full text linkThe use of waste materials in road construction is becoming widely spread due to
economic and environmental needs. Construction and demolition waste materials and mining
residues have been studied for a long time. However, the use of fine materials, mainly from mine
tailing and mining residue, is still complex, as they can be used as inert materials into the mix or can
become a reactive agent in geopolymer mixes. In the present paper, an experimental application of
basalt powder is proposed in the geopolymerisation reaction to produce artificial aggregates. In
order to understand the input and output variables’ interactions used in the mix design, a statistical
method called Design of Experiments was applied. With this design approach, it was possible to
optimize the mix design of the experimental geopolymer mortars. The study evaluated several
mixes with respect to their workability, compressive strength, and success rate of aggregates
production. Finally, a model for predicting compressive strength is proposed and evaluated
The use of fibres in asphalt mixtures: A state of the art review
Full text linkThe various acknowledged benefits given by the use of fibre for construction materials made this component
essential for specific applications, including asphalt pavements. Fibres in asphalt mixtures usually play two
important roles: acting as an asphalt stabilizer to decrease the drain-down effect; and as a reinforcing additive to
enhance the mechanical performance of asphalt mixtures. To better understand their use, this paper aims to
review the various uses of different types of fibres in asphalt pavements. The main variables that influence the
effectiveness of fibres and the reinforcing mechanism of using fibres are discussed. Furthermore, a state-of-the-art
of the combined use of fibres and other additives, such as crumb rubber, polymer modifiers, and nano-size
modifiers, is presented. Results from relevant studies confirmed the effectiveness of using fibres in asphalt
pavements and the significance of optimizing the mixing method, size and dosage of fibres to achieve more
suitable performance. Additionally, the latest research findings and experimental applications are discussed, with
a specific focus on waste and recycled materials. Exploring feasible recycled alternatives to natural and traditional
fibres, optimizing the use of fibres from wastes, and combining the use of fibres with other sustainable
technologies, could maximize the environmental benefits of using fibres in asphalt pavements
Thermally Treated Waste Silt as Geopolymer Grouting Material and Filler for Semiflexible Pavements
Full text linkConsidering the future shortage of natural aggregates, various researchers have promoted the recycling of by-products into various asphalt pavement types. This paper promoted a double-recycling technique, where thermally treated waste silt was used as a filler for the bituminous skeleton and grouting material of a geopolymer-based semiflexible pavement. Semiflexible pavements (SFP) inherit the flexibility of common asphalt pavements and simultaneously benefit from the rigidity of cement concrete pavements. For this purpose, waste silt obtained from a local asphalt plant was thermally treated at 750 °C and was used as the filler to produce the porous skeleton. Two different materials, including conventional cement-based and a geopolymer-based cement, were used as the grouting material. The geopolymer grout was produced by mixing metakaolin (MK), potassium-based liquid hardener and calcined silt as filler. The porous and grouted samples were characterized in terms of indirect tensile strength (ITS), the indirect tensile strength modulus (ITSM) and moisture sensitivity. The use of thermally treated waste silt as filler in porous asphalt demonstrated promising results and was comparable to the control samples produced with limestone as the filler. However, the control samples grouted with cement-based material outperformed the geopolymer grout in all aspects. Moreover, the addition of calcined silt improved the low-temperature fatigue performance of porous and grouted asphalt pavements
Mixture Optimization of Concrete Paving Blocks Containing Waste Silt
Full text linkMost of the waste materials recycled for the production of new construction materials are
by-products of various manufacturing processes, such as the aggregate washing process. Recycling
such materials is of paramount importance since it could reduce the adverse environmental impacts
resulting from landfilling. Various studies have attempted to recycle different types of waste materials
and by-products into concrete paving blocks. However, the availability of literature on concrete
paving blocks containing waste silt is quite scarce. Thus, the current paper focuses on mix design
optimization and production of concrete paving blocks containing high amounts of waste silt resulting
from the aggregate production process. Using the mixture Design of Experiments (DOE), 12 sets of
concrete paving blocks with different aggregate blends were produced to optimize the mix design.
Once the final mix design was achieved, the physical and mechanical properties of the concrete paving
blocks were investigated following the EN 1338 standard. Shape and dimension measurements and
various tests, including water absorption, tensile splitting strength, abrasion resistance, and slip/skid
resistance were conducted on the experimental concrete paving samples. Overall, the produced
concrete paving blocks showed promising properties for future applications in pedestrian walking
paths
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