Increase In Indirect Tensile Strength Research Articles

Optimizing waste management and enhancing asphalt performance: A sustainable approach using discarded baby diapers and face masks

This research introduces an innovative approach to address the management of waste Baby Diapers (BD) and Face Masks (FM) in order to mitigate environmental risks associated with the indiscriminate disposal of BD and FM waste. The study focuses on leveraging the utilization of BD and FM in road pavement hot mix asphalt (HMA) to enhance bitumen and aggregate performance, respectively. The approach involves the direct incorporation of 4% shredded BD during the bitumen melting process, while varying percentages of shredded FM (0%, 0.5%, 1%, and 1.5% relative to aggregate weight) are utilized as aggregate coating through a melting process. The inclusion of BD enhances the modified bitumen’s (MB) resistance to permanent deformations under high temperatures compared to conventional bitumen. Simultaneously, the treatment of FM significantly improves the physical and mechanical attributes of the aggregates. The combination of 4% BD and 1.5% FM results in improved densification, fostering robust bonding between aggregates and asphalt paste. This enhancement leads to a 39% increase in stability, a 18% increase in indirect tensile strength, and a 27% reduction in permanent deformations. Notably, there is a remarkable 53% increase in resistance to rut depth and a 33% increase in resilient modulus. Ultimately, the implementation of 4% BD as a bitumen enhancer and 1.5% FM as an aggregate modifier demonstrates the potential to achieve waste reductions of 36% and 61%, respectively. This approach extends beyond pavement enhancement, contributing to the broader societal mitigation of adverse effects associated with BD and FM waste.

Experimental study on the effects of modification with nanoclay on the properties of an SMA mixture

The modification of bitumens with NM has shown results in the improvement of binder properties, in particular thermal susceptibility. This article aims to present a study to demonstrate the effects of modifying a bituminous mixture (BM) of the Stone Mastic Asphalt (SMA) type with nanoclay. The nanoclay used was of the hydrophilic bentonite type. The modification of the bitumen was carried out by introducing and dispersing in conventional bitumen a 35/50 amount of nanoclay corresponding to 4% of the weight of the modified binder. The bitumens, conventional and nanomodified, were characterized by determining penetration, ring and ball softening temperature and viscosity. In the subsequent BM, to investigate the influence of the nanomodification, tests of permanent deformation (PD), modulus of deformability, resistance to fatigue and sensitivity to water were carried out. The results obtained showed that the nanomodified SMA mixture showed better resistance to fatigue, increase in indirect tensile strength (ITS), less sensitivity to and better resistance to PD.

Marine Geopolymer Concrete—A Hybrid Curable Self-Compacting Sustainable Concrete for Marine Applications

Marine environments are widely addressed as a serious threat to coastal concrete structures due to higher repair and rehabilitation costs. The rising concerns of climate change and related issues also require marine structures to be resilient and sustainable at the same time. Geopolymer concrete has been given more significant consideration as an alternative, reporting better resistance to harsh and hazardous environmental exposure, including sulphate attacks, chloride attacks, and freeze–thaw climates. This study investigated the mechanical properties of fly ash (FA) and ground granulated blast furnace slag (GGBFS)-based self-compacting geopolymer concrete (SCGC), subjected to short term ambient and marine curing conditions. The mechanical performance, inclusive of compressive strength, tensile strength, and modulus of elasticity under three-month marine exposure compared to an ambient environment, indicates that the SCGC mix offered an increase in strength. It is reported that the compressive strength of SCGC increased to the range of 50 MPa after marine exposure in comparison to the 40 MPa strength after 28-day curing. A similar increase in indirect tensile strength and modulus of elasticity were observed for the test specimens, with no signs of leaching of salts under marine exposure. Thus, the current SCGC acts as a sustainable construction material in counteracting the threats of marine degradation in civil structural components.

Cracking resistance of fiber reinforced asphalt concrete at −20 °C

The reinforcing effect of steel fibers in asphalt concrete is investigated through indirect tension tests conducted at −20°C. Control specimens with no fibers, and test series with carbon and polyvinyl alcohol fibers are also carried out for comparison. Cracking resistance, indirect tensile strength, fracture energy, and post-cracking energy are obtained from the tests. The effects of fiber diameter, length, deformed shape, and content of steel fibers are investigated in order to provide fundamental understanding of the reinforcing mechanisms mobilized during fiber pull out and select proper reinforcing fibers. The test results demonstrate that the low temperature cracking resistance of asphalt concrete can be significantly improved by adding the proper type and amount of steel fibers, but that the improvements in mechanical properties are sensitive to fiber length and diameter. The indirect tensile strength and toughness of fiber reinforced asphalt concrete increase with an increase in fiber length within the 0.2–0.4mm diameter range. Mechanical deformations of the fibers, e.g. presence of a hook or twisting, can induce further improvements in post-cracking energy absorption. Compared to unreinforced specimens, fiber reinforced specimens show up to 62.5% increase in indirect tensile strength, and up to 370% and 895% improvements in fracture energy and toughness, respectively. A hypothesis that explains the fiber reinforcing mechanism in asphalt concrete is proposed and critiqued based on the test data.

Evaluation of fatigue behavior of hot mix asphalt mixtures prepared by bentonite modified bitumen

The objective of this research study was to investigate and evaluate effects of bentonite on fatigue properties of hot mix asphalt (HMA) mixtures. The experimental program for this study included use of five percentages of bentonite (10%, 15%, 20%, 25% and 30%) by weight of bitumen for modifying base bitumen. Several tests such as: marshal stability, indirect tensile strength, resilient modulus and fatigue test were conducted. The fatigue tests were based on four-point bending test in strain-controlled mode at 3 microstrain levels (600–800–1000lm/m) with sinusoidal loading. The fatigue life of mixtures has been evaluated based on the 50% reduction of the initial stiffness modulus. The results show that fatigue life of asphalt mixtures prepared with bentonite modified bitumen is longer than conventional HMAs. Also, bentonite leads to relative increase in indirect tensile strength and resilient modulus of asphalt mixtures. Finally, based on experimental results, a model is proposed to describe the fatigue behavior of asphalt mixtures containing bentonite modified bitumen.

Moisture Sensitivity of Bituminous Mixtures with Compound Fly Ash Modifier

Bitumen pavement suffers from moisture damage mainly due to loss of durability and stability in a short span of service life. Filler is known to be capable of increasing the stiffness of bitumen binder, contributing to improvement of moisture sensitivity of bitumen mixture. In this paper a new type of filler named 'Compound Fly Ash Modifier' (CFAM) was introduced in order to enhance the bond strength between acidic aggregate with bitumen. The primary object is to determine the effect of CFAM on the moisture sensitivity of bitumen mixtures prepared by gneiss and granite respectively, which are termed acidic aggregate. Modified Lottman test and fatigue test were conducted. The results show that CFAM improves the resistance of mixes to moisture damage in the increase in indirect tensile strength and the extension of fatigue life. Finally the mechanism of modified effects for CFAM is discussed.

The behaviour of consolidated volcanic tuffs: weathering mechanisms under simulated laboratory conditions

Five volcanic tuffs ranging from dacitic tuffs of Hungary to rhyolite, phonolite and basaltic tuffs of Germany were consolidated under laboratory conditions. Prior to consolidation an anti-hygro, a hydrous consolidant, which reduces the swelling ability of clay minerals, was applied. The three consolidants, a silicic acid ester (SAE), an elastic silicic acid ester (eSAE) and an acrylate resin (PMMA) were applied on test specimens under vacuum. Petrographic characterisation (polarizing microscopy, XRD, SEM) provided data for fabric analyses and the mineral composition of the tuffs. Changes in fabric, effective porosity, density, tensile strength, ultrasonic wave velocity were evaluated after the treatment. Weathering simulation tests such as hygric dilatation and thermal dilatation aimed to prove the effectiveness of consolidation and the durability of consolidated tuff samples. More than 500 samples were analysed. The tests showed that SAE caused the highest increase in indirect tensile strength. The water absorption and the pore size distribution of the tuffs were modified by consolidation. The PMMA reduced the water absorption the most, whereas SAE modified it the least. All the tested consolidants increased the thermal dilatation of the tuffs. The changes in hygric dilatation were not uniform: for most tuffs SAE increased and PMMA decreased the hygric dilatation, although the clay-rich Habichtswald tuff showed the opposite trend. The changes in hygric and thermal behaviour of consolidated tuff require special care when specific consolidants are chosen. These products modify the physical properties of consolidated tuffs and change the behaviour of weathering.

Evaluation of Pyrolisis Polypropylene Modified Asphalt Paving Materials

The main objective of this research study is to investigate the potential use of pyrolisis polypropylene as modifiers in hot mix asphalt paving mixtures. Seven different blends including conventional mix were subjected to binder testing such as rheological tests, as well as to some other tests related to the homogeneity of the system. Optimum asphalt content was obtained by Marshall method and used in all the modified mixes. The engineering properties, including Marshall stability and indirect tensile strength were determined. Research results indicate that modified binders showed higher softening point, keeping the vales of ductility at minimum range of specification of (100cm), and caused a reduction in percent loss of weight due to heat and air (i.e. increase durability of original asphalt). The results indicated that the inclusion of pyrolisis polypropylene with asphaltic concrete mixtures gave a quite satisfactory result in terms of stability and other Marshall properties, and increase in indirect tensile strength).