Indirect Tensile Strength Test Research Articles

Influence of Sustainable Grout Material on the Moisture Damage of Semi-flexible Pavement

Semi-flexible pavement (SFP), also known as grouted pavement, is a type of pavement structure consisting of a porous asphalt skeleton with air voids between 25 and 35% injected with cementitious grout materials. The special skeleton of SFP provided enhanced durability and resilience, making it a promising option for the construction of road surfaces in high-traffic areas and severe conditions. The main aim of the current research is to investigate the rutting behavior and moisture resilience of SFP-containing sustainable grout using ceramic waste powder (CWP). This research introduced the use of CWP as a replacement for conventional grout (cement) in SFP for the first time. CWP partially replaced cement at ratios of 15, 20, 30, 40, and 50% of the cement weight. Indirect Tensile Strength (ITS) and Hamburg Wheel Tracking Tests (HWTT) were used to evaluate the performance of SFP to reduce the detrimental effect of moisture. The grout modified with CWP shows excellent results in the ITS and Tensile Strength Ratio (TSR), and all modified SFP mixtures give higher values in these tests compared with Control Mix (CM). In the HWTT, the minimum rut depth of the modified SFP was 2.8 mm and 3.10 mm. Compared to CM, rutting decreased by 73%–76% for CWP mixes with 20% and 30% replacement. This indicates the high fluidity of CWP, which enabled it to penetrate all voids in the porous pavement (PA) and form a dense microstructure due to its excellent pozzolanic interaction, making it a strong structure capable of bearing rutting.

Impact of Nonrecyclable Plastics on Asphalt Binders and Mixtures

Low-density polyethylene (LDPE) and polystyrene (PS) were evaluated for incorporation as binder additives to enhance the potential performance of asphalt concrete (AC) mixtures, as well as addressing global rising concerns over nonrecyclable plastics accumulation. Incorporation of LDPE and PS in asphalt binder resulted in an increase in its complex moduli over a range of temperatures and frequencies, as determined using frequency sweep (FS) and linear amplitude sweep (LAS) tests. AC performance tests were conducted, including the Hamburg wheel-tracking test (HWTT) to assess potential rutting, the Illinois flexibility index test (I-FIT) to determine cracking potential, the indirect tensile strength test (ITS) to assess moisture susceptibility, and the dynamic modulus for structural capacity. Two control AC mixes were designed, utilizing aggregates from different sources. For each AC mix, the aggregate blend and binder content were kept constant, with only the binder type changed. LDPE and PS were added through a wet process in one mix. Dry and wet processes were used in the other mix. Waste plastics–modified AC mixes, in both wet and dry processes, exhibited reduced rutting potential. However, the cracking potential and moisture damage susceptibility varied, depending on the modified AC mix. The addition of waste plastics had no impact on AC dynamic modulus. The results for waste plastics–modified AC mixes were compared with those for styrene-butadiene-styrene (SBS)–modified AC mixes. While waste plastics modification provided improvement over the control mixes, the performance fell short of that of the double-pump SBS-modified mix.

EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES OF MODIFIED PERVIOUS CONCRETE AS A RIGID PAVEMENT FOR LOW VOLUME TRAFFIC

The previous concrete which is also known as No-fines concrete is a mixture of cement, water and a particular sized coarse aggregate combined to form a porous structural material. Application of pervious concrete in pavements mainly focuses on storm water control mostly in urban areas where scarcity of land is high. Permeable pavement allows water from precipitation and other sources to pass through it and therefore reduces the runoff from a site, which results in the recharge of ground water and increases the level. In this view it is necessary to study the behavior of pervious concrete by enhancing its mechanical properties by maintaining required permeability. The main objective of this investigation is to develop a strong pervious concrete mix using with waste tyre rubber powder. In addition, it is also aimed to compare the mechanical properties of these modified mixes with pervious concrete. The properties such as compressive strength, indirect tensile strength, flexural strength and permeability tests are performed to determine the suitability. From the study it is concluded that using of fine aggregate and waste tyre rubber powder as partial replacement material in coarse aggregate shows significant improvement in the mechanical properties (i.e. compressive strength, indirect tensile strength and flexural strength) with maintaining required permeability. Among all the considered modified mixes, MPC-4 (i.e. 10% waste tyre rubber powder as partial replacement material in coarse aggregate) performs better.

Aging Resistance Evaluation of an Asphalt Mixture Modified with Zinc Oxide

The phenomenon of the oxidation and aging of asphalt binders affects the strength and durability of asphalt mixtures in pavements. Several studies are trying to improve the resistance to this phenomenon by modifying the properties of the binders with nano-particles. One material that shows promise in this field is zinc oxide (ZnO), especially in improving ultraviolet (UV) aging resistance. Few studies have evaluated the effect of these nano-particles on the thermo-oxidative resistance of asphalt binders, and, on hot-mix asphalt (HMA), studies are even more scarce and limited. Therefore, in the present study, the resistance to thermo-oxidative aging of an HMA manufactured with an asphalt binder modified with ZnO was evaluated. An asphalt cement (AC 60–70) was initially modified with 0, 1, 3, 5, 7.5, and 10% ZnO (percentage by weight of asphalt binder; ZnO/AC in wt%), and then exposed to aging in Rolling Thin-Film Oven tests (RTFOT) and a Pressure Aging Vessel (PAV). Penetration, viscosity, and softening point tests were performed on these binders, and aging indices were calculated and evaluated. Samples of HMAs were then manufactured using these binders and designed by the Marshall method, determining the optimum asphalt binder content (OAC) and the optimum ZnO/AC ratio. Control (unmodified) and modified HMA were subjected to short-term oven aging (STOA) and long-term oven aging (LTOA) procedures. Marshall, Indirect Tensile Strength (ITS), and resilient modulus (RM) tests were performed on these mixtures. LTOA/STOA results of the parameters measured in these tests were used as aging indices. In this study, ZnO was shown to increase the thermo-oxidative aging resistance of the asphalt binder and HMA. It also contributed to an increase in the resistance under monotonic loading in the Marshall and ITS tests, and under repeated loading in RM test. Likewise, it contributed to a slightly increasing resistance to moisture damage. The best performance is achieved using ZnO/AC = 5 wt%.

Using Biopolymers as Anti-Washout Admixtures under Water Concreting

In this study, we investigate the use of natural additives (biopolymers) resistant to scouring. To this end, three natural substances, Kathira, sodium alginate, and guar gum, have been utilized as additives resistant to scouring, and we examine their mechanical performance, resistance to scouring, and the properties of fresh concrete including slump test, setting time, and ultimately shrinkage test. For this purpose, a total of 12 cylindrical specimens with dimensions of 15 by 30 cm were prepared for 28-day compressive strength test, and 12 cylindrical specimens with dimensions of 15 by 30 cm were prepared for 28-day indirect tensile strength test. Additionally, 12 concrete beams with dimensions of 10 by 10 by 35 cm were fabricated for a 28-day flexural strength test. All laboratory specimens were submerged in lime-saturated water for hydration for a period of 28 days for maintenance and preservation. The results indicate that all three biopolymers improve resistance to scouring, and, two substances enhance compressive, tensile, and flexural strength. Furthermore, all of them lead to a reduction in concrete shrinkage.

Assessing Recycled Binder Availability, Activity, and Contribution at Different Temperatures

Recycled binder availability (RBA), degree of activity (DoA), and recycled binder contribution (RBC) are distinct properties often used interchangeably in the literature. This study aims to clarify the distinctions among these terms and assess how they vary with temperature, as well as their interrelationships. To achieve this, a reclaimed asphalt pavement (RAP) sieve analysis approach, indirect tensile strength testing of 100% RAP specimens, and tracer-based microscopy are employed to measure RBA, DoA, and RBC, respectively. Three RAP sources are evaluated, and each property is measured at multiple temperatures. Sieve analysis and microscopy measurements indicate that only partial RBA and RBC, respectively, are achieved, and that these properties display minimal susceptibility to changes in temperature. In contrast, DoA significantly increased as the temperature rose from 100°C to 140°C, reaching 100%, and then plateaued from 140°C to 155°C. In most of the cases, the laboratory-mixed asphalt mixture samples evaluated exhibited RBC values comparable to the RBA measurements for the respective RAP source, suggesting that RBC becomes equivalent to RBA when the DoA reaches 100%.

Effect of wet-dry history on performances of dense asphalt mixture: Experimental investigation and predicting model

Asphalt pavement experiences various wet-dry histories in the service stage. However, the influence of wet-dry history on asphalt mixture is unknown. Therefore, to clarify the performance degradation mechanism and predict the performance of asphalt mixture under the action of wet-dry history, the creep-recovery test, indirect tensile stiffness modulus test and indirect tensile strength test were conducted at different temperatures. The finite element method was adopted to analyze the moisture diffusing profile inside the specimen after wet-dry cycles. A moisture damage model considering the soaking time and repeated characteristics was developed to predict the damaged properties. Results show that wet-dry cycles cause a slight mass loss of asphalt mixture. Wet-dry cycling action leads to the increment in high-temperature deformation, and reductions in stiffness modulus and tensile strength. The increase of high-temperature deformation is primarily caused by viscoplastic component. Even if the soaking time is short, high moisture damage occurs while the wet-dry cycle is sufficient. Numerical simulations show that the moisture concentration profiles inside asphalt mixture vary under different wet-dry histories, leading to variations in the damage zone. The degree of damage is also closely related to the acting time of moisture. The critical immersion time of the dense asphalt mixture (about 43 hours) was determined in this study. When the immersion period is shorter than the critical immersion time, the strength loss is greater than the modulus. On the contrary, the degree of modulus damage is higher than that of strength. Considering the actual rainfall climate in China, the strength damage of the on-site asphalt mixture in the field predominates. The proposed model could reflect the weakening trends of modulus and strength. It has good universal applicability in predicting the damaged Marshall stability, modulus, and strength at different temperatures.

Evaluation of Asphalt Binder and Mixture Properties Utilizing Fish Scale Powder as a Biomodifier

Fish represent an abundant and underutilized waste product from the fishing industry. This study investigated the effects of incorporating fish scale powder (FSP) at various dosages (3%, 6%, 9%, and 12%) on the properties of asphalt binder and mixtures. Conventional tests, viscosity, storage stability, Fourier transform infrared spectroscopy, and multiple stress creep recovery tests were conducted on the binder. Mix design, wheel tracking, indirect tensile strength, fatigue, and ultrasonic pulse velocity tests were evaluated for the asphalt mixtures. The results showed that FSP increased binder stiffness and reduced temperature susceptibility but compromised low-temperature performance and workability regardless of dose. The storage stability test results showed improved high-temperature storage stability. In the mixtures, the permanent deformation resistance increased with increasing FSP content, decreasing the rut depth from 4.3mm for the control to 2.9mm at 12% FSP. The moisture damage resistance, indicated by the tensile strength ratio, increased from 90% for the control to 94.1% at 12% FSP. However, the fatigue life decreased from 14,010 cycles for the control sample to 11,190 cycles at 12% FSP. The dynamic and elastic modulus values before conditioning increased with higher FSP dosages, and this increasing trend was also observed after conditioning, signifying greater stiffness retention and moisture resistance of the asphalt mixtures containing higher amounts of FSP. Numerically, the 6-9% FSP range offered the optimum balance, enhancing the rutting resistance by 18% and moisture resistance by 3.2% compared to those of the control, while limiting the fatigue life to 12% and maintaining the workability. Overall, fish scale powder has potential for use as an asphalt biomodifier by transforming an environmental liability into a value-added sustainable paving material.

Utilisation of Waste Sludge from Drinking Water Treatment as a Filler Material in Hot Mix Asphalt.

This research investigated the suitability of using sludge from the treatment of drinking water in hot mix asphalt (HMA) as a filler material. The storage and environmental impact of sludge is an enormous problem, especially for countries with large populations. Two different types of sludges, ferric chloride (FC) and aluminium sulphate (AS), were used as a filler material in HMA. The Hamburg Wheel Tracking (HWT) test, which correlates with rutting, and the Indirect Tensile Strength (ITS) test, which indicates the moisture sensitivity of HMA, were carried out at the optimum bitumen content of the mixes to investigate the usability of sludge in HMA. The test results indicate the usability of FC and AS in HMA compared to the reference mixes. However, the AS type of sludge has better rutting resistance than the FC type. Although the results support the usability of both sludges in HMA, it should be noted that the increased cost of the mix containing sludges due to the combustion process and the increased bitumen content during application should be considered.

Macroscopic and Microscopic Investigation of Gypsum Slag Cement-Stabilized Recycled Aggregate Base Layers.

The purpose of this study is to investigate the macro and micro properties of stabilized recycled aggregate base layers using gypsum slag cement (GSC) and compare them with ordinary Portland cement (OPC). To achieve this, four levels of recycled aggregate content (0%, 50%, 60%, 70%) and three levels of binder materials (3.5%, 4.5%, 5.5%) were designed, where the binding materials included OPC and GSC. When GSC is used as the binding material with 0% recycled content, two scenarios for the ratio of slag to activator are considered: 4:1 and 4:2. For recycled content of 50%, 60%, and 70%, only the 4:1 ratio is considered. The macro-mechanical properties of the composite material were studied through compaction tests, unconfined compressive strength tests, and indirect tensile strength tests. Microscopic properties were investigated through X-ray diffraction (XRD) and scanning electron microscopy (SEM). Macroscopic test results indicate that, at an equal binder content, GSC exhibits a higher moisture content and maximum dry density compared to OPC. Moreover, the unconfined compressive strength and indirect tensile strength of GSC are higher than those of OPC. Microscopic test results reveal that the hydration products of both binding materials are essentially similar; however, under identical curing conditions, the hydration products of GSC are more abundant than those of OPC.

Assessment of indirect tensile stress and tensile–strength ratio and creep compliance in HMA mixes with micro-silica and PMB

Abstract This study aims to ascertain the effects of polymer-modified bitumen (PMB) and to utilize mineral filler with micro-silica (MS) on various properties of hot-mix asphalt (HMA). In this work, three specimens of an asphalt-concrete mixture were prepared. The first specimen represents a control mixture, the second specimen contains MS at rates 15, 30, and 45% by the total weight of the total aggregate as filler, and the third specimen contains MS and PMB with 4% novolac by the weight of bitumen and 15% hexamine by the weight of the novolac. The properties of designed mixes were evaluated using the indirect tensile strength test, tensile–strength ratio, and creep compliance. The test results showed an increase in the resistance of asphalt concrete to moisture damage, a reduction influence of water on asphalt concrete properties, creep compliance values indicating growing stiffness for asphalt mixture, and enhanced fatigue life. In conclusion, using 45% MS and PMB improved the properties of HMA and provided long-lasting mixtures for highway construction.

Development and Evaluation of Vegetable Resin Bio-Binders as Technological Alternatives to Bitumen

Recently, the feasibility of using bio-materials to reduce or completely replace the use of bitumen in asphalt mixture has gained increasing attention. Amongst others, an interesting solution is represented by the use of wood co-products with mineral or vegetable oils. This research focuses on the development of bio-binders using vegetable resin (VR) in unmodified form and waste olive oil (WOO) as the main components; in order to optimize the rheological properties of the blends, crumb rubber from end-of-life tyres (CR), Styrene-Butadiene-Styrene (SBS) and polyethylene waxes (PEW) are used as additives. In particular, this investigation focuses on studying different oil/rosin ratios and polymer contents to provide a clear framework on this bio-binder solution; conventional bituminous binders are taken as a reference. The alternative binders are characterized in terms of conventional properties such as penetration depth and softening point, as well as rheological response. Finally, two of the bio-binders studied are selected with the aim of assessing the mechanical properties of the resulting sustainable asphalt mixture using the Marshall Stability test and the Indirect Tensile Strength test, comparing the results with the threshold values set by an Italian road agency. Thus, this research represents a preliminary analysis of the potential application of bio-binder mixtures within the specification limits imposed by road agencies. Although this research represents a first attempt, the results are promising and prove to be worthy of further investigations.

Effect of RAP fractionation and dosage on design and mechanical behaviour of cold asphalt mixes

This study examines the effect of reclaimed asphalt pavement (RAP) material dosage and incorporation method on the mechanical characteristics of Cold Asphalt Mix (CAM). The RAP materials were fractionated into fine and coarse in addition to the unfractionated method. Four levels of RAP dosage (25, 50, 75, and 100%) were considered for each category. The mix design parameters, such as total fluid and emulsion content, were evaluated using the Indirect Tensile Strength (ITS) test. Overall, 455 specimens were prepared for mix design. The Optimum Emulsion Content (OEC) is the design emulsion content determined at peak value of ITS test. ITS, Indirect Tensile Stiffness Modulus (ITSM), and moisture susceptibility tests were conducted. Incorporating RAP in CAM increased the average tensile strength predominantly by 34% in coarse mixes, 28% in unfractionated, and < 10% in fine mixes. The average ITSM of the mixture increased by 30%, 60%, and 80% for fine, coarse, and unfractionated RAP. Further, emulsion demand was reduced by 53%, 43%, and 79% for fine, coarse, and unfractionated RAP, which showed that the RAP incorporation method profoundly influenced OEC. However, regardless of fractionation, CAM mixes showed lower cracking resistance and higher moisture susceptibility with increased RAP dosage. Two different conditioning protocols were used to capture the variation in moisture susceptibility for all 13 mix combinations. Coarse and unfractionated RAP mixes significantly differed in ITS, moisture susceptibility, cracking tolerance index, and ITSM. VIseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR) approach was selected to rank the outperforming combination. The overall ranking of RAP incorporation showed that the coarse RAP mixes outperformed fine and unfractionated RAP mix characteristics. The study recommends restricting RAP usage by up to 75% to ensure the required performance of CAM mixtures.

Performance evaluation of grouted porous asphalt concrete

Abstract Semiflexible pavement (SFP) is considered a composite mixture, as it consists mainly of a porous asphalt mixture with high air voids grouted with highly flowed cementitious grout. Numerous benefits have been attributed to this technology, including exceptional slip resistance, a high static bearing capacity, and rutting resistance. In this study, two different types of semiflexible paving mix were produced by using two different types of grouting materials (GMs). There is a discrepancy between the compressive strengths of the two GMs used, as the compressive strength of the first mixture, which consisted of 96% cement and 4% silica fume (SF), was approximately twice the compressive strength of the second mixture, which consisted of 75% cement and 25% sand. The mechanical and durable properties of the two SFPs were studied, in addition to the effect of variation in the compressive strengths of the two GMs and their effect on the final performance of the pavement. The results of Marshall and rutting tests show that the SFP material exhibits good high-temperature stability. The effect of the variation in the compressive strength of the two mixtures was evident in the results of the tests compared with the sand mixture at a strength of 20.8 MPa, the SF at a strength of 48.1 MPa witnessed a 39.54% increase in the Marshall stability at 28-day curing age. Also, the composite material (CM) showed better rutting performance than traditional asphalt mixtures, which did not exceed 2 mm. The results of the indirect tensile strength (ITS) test showed a discrepancy between the two types of CM, as the ITS value of the grouting material of SF (GMSF) mixture increased by 14.91% compared with the grouting material of sand (GMSN) for the curing age of 28 days for unconditioned samples and by 20.22% for the conditioned samples for the same curing age, while the durability of two types of CM was measured by Cantabro abrasion loss and tensile strength ratio. The results were acceptable and within the specification limits. With a variation for the two types of CM, the GMSF mixture showed an increase in the value of Cantabro loss by 11.52% over the GMSN mixture for ageing samples and 6.59% for non-aging samples of 28 days of curing age.

The Effect of Nano-Hydrated Lime on the Durability of Hot Mix Asphalt

Recently, some of Iraq's newly constructed asphalt concrete pavements showed premature failures with significant negative impacts on roadway safety and the economy. Using Nano hydrated lime (NHL) in pavement construction could be one of the possible steps to improve pavement durability. This article discusses how NHL affects the durability of hot mix asphalt. NHL was added in two methods to the asphalt concrete mixture for the wearing course. The first is the dry method, i.e., on the aggregate, whereas the second is the wet addition method, i.e., to the bitumen. The percentages were tried for each additional method; 1, 2, and 3% by weight of aggregate for the dry method and 0.5, 1, and 1.5% by weight of asphalt concrete for the wet method. The optimum asphalt cement contents were evaluated using the Marshall procedure. Asphalt concrete mixes were prepared at their optimum asphalt content and then tested to evaluate their durability properties, including moisture damage and permanent deformation. These properties have been evaluated using indirect tensile strength and uniaxial repeated loading tests. The results show that the NHL has improved the permanent deformation characteristics and resistance to moisture susceptibility.

Towards a high-performance asphalt concrete for extreme climatic conditions using asphaltenes and polyethylene terephthalate fibres

Asphalt pavement experiences various deteriorations in different weather conditions due to the viscoelastic nature of asphalt binder. This study aims to develop a high-performance asphalt concrete (HPAC) for extreme temperature conditions by incorporating waste polyethylene terephthalate (PET) fibres and asphaltenes, a by-product from Alberta oil sands. First, performance of asphalt binder modified with asphaltenes is evaluated according to the Superpave performance grading (PG) system. Next, to improve low-temperature properties, HPAC mixtures modified with PET fibre at percentages of 0.05–0.30% are tested for compactibility to reflect field construction considerations. Then, performance tests including dynamic modulus; indirect tensile strength test at low temperatures; and Hamburg wheel-track at high temperature are conducted for an effective evaluation of the unmodified and modified mixtures that are prepared using a combination of the dry and wet mix methods. Results of binder PG tests reveal that with 12% asphaltenes, the modified binder is suitable for HPAC applications. The mixes with and without PET fibres exhibit similar compactibility and meet air void requirements of a maximum 6%, and incorporating PET fibres increases stiffness by up to 3.3%. Compared with the unmodified mixes, an optimum dosage of 0.15% PET fibre increases fracture energy by up to 27% at −10 °C and enhances tensile strength by up to 18% at 0 °C. The mixture with the optimum dosage also exhibits excellent rut resistance at 60 °C showing no signs of moisture damage sensitivity. As a result, it boasts a remarkable rutting resistance index that is five times higher than that of the control unmodified mix.

Preparation and Mechanism Analysis of Stainless Steel AOD Slag Mixture Base Materials.

To promote resourceful utilization of argon oxygen decarburization (AOD) slag, this research developed a new three-ash stabilized recycled aggregate with AOD slag, cement, fly ash (FA), and recycled aggregate (RA) as raw materials. The AOD slag was adopted as an equal mass replacement for fly ash. The application of this aggregate in a road base layer was investigated in terms of its mechanical properties and mechanistic analysis. First, based on a cement: FA ratio of 1:4, 20 sets of mixed proportion schemes were designed for four kinds of cement dosage and AOD slag replacement rates (R/%). Through compaction tests and the 7-day unconfined compressive strength test, it was found that a 3% cement dosage met the engineering requirements. Then, the unconfined compressive strength test, indirect tensile strength test, compressive rebound modulus test, and expansion rate test were carried out at different age thresholds. The results showed that the mixture's strength, modulus, and expansion rate increased initially and then stabilized with age, while the strength and modulus initially increased and then decreased with increasing R. Secondly, based on X-ray diffraction (XRD) and scanning electron microscopy (SEM) used to analyze the mechanism, it was found that the strength, modulus, and expansion rate of the new material can be promoted by blending AOD slag, due to its ability to fully stimulate the hydration reaction and pozzolanic reaction of the binder. Finally, based on the strength and modulus results, R = 3% was identified as the optimal ratio, which provides a reference point for the effective application of AOD slag and RA in road base materials.

Development of a Predictive Model for the Indirect Tensile Strength Load–Displacement Curve for Asphalt Mixtures

The indirect tensile (IDT) strength test is one of the common laboratory tests conducted to characterize asphalt mixtures. The IDT load–displacement curve is used to calculate various indicators to evaluate the cracking performance of asphalt mixtures. This study evaluated the effect of the mix composition on the IDT load–displacement curve. Asphalt mixtures with different characteristics, including binder content, binder grade, and mix gradation, were prepared and tested. The study developed statistical regression models to predict the entire IDT load–displacement curve using parameters that describe the mix composition and properties, including the binder complex shear modulus and phase angle, aggregate gradation, and binder content. The results demonstrated that the predicted model parameters were found to correlate well with those calculated from the experimental IDT load–displacement curves. All predicted cracking performance indicators calculated from the predicted IDT load–displacement curve had a strong correlation with those calculated from the measured IDT load–displacement curve. The proposed model can be used as a tool to check the preliminary cracking performance of the asphalt mixtures during the mix design stage. In addition, the mix composition can be adjusted to improve the cracking performance of the designed mix (e.g., adjust binder grade, binder content, gradation, etc.).

Coupled effects of Crumb Rubber and zeolite on the performance of dense-graded asphalt mixture: a study using a balanced mix design approach

ABSTRACT This research aims to investigate the effect of different levels of Zeolite and Crumb Rubber (CR) on the durability and mechanical performance of dense-graded asphalt mixture to specify a suitable dosage of these additives. 2%, 4%, and 6% of Zeolite as a water-based warm mix additive and 8% and 16% CR were used. Indirect Tensile Strength (ITS), Semi-Circular Bending (SCB), and Hamburg Wheel Tracking (HWT) tests were respectively used to investigate the moisture damage, fracture and rutting resistance. Moreover, performance interaction diagrams are used to determine the appropriate percentage of the additives. The results showed that modified asphalt with Zeolite and CR have better resistance to rutting and cracking, and with the increase in the amount of these additives, this improvement has been more significant. However, CR diminished the resistance against moisture damage; Zeolite had a positive effect on moisture damage and it compensates for the weakness of modified dense-graded asphalt mixtures with CR. The performance interaction diagram of dense-graded asphalt mixtures has recommended the use of 4%, and 6% of zeolite with and without 8% of CR as the most ideal percentages of employing these additives, taking into account their correct performance against cracking, moisture damage, and rutting damage.

Evaluation of the Mechanical Behavior of Soil Stabilized with Asphalt Emulsion Using Multi-Stage Loading

The objective of this research was to assess the mechanical response (resilient and plastic) of soil stabilized with petroleum asphalt concrete using asphalt emulsion under multi-stage loading. To enhance the adhesion of the asphalt film to the soil grains, the stabilized soil underwent air-drying curing for seven days. Dosage was conducted through the indirect tensile strength test using diametral compression. With the optimum content determined in the dosage (2% emulsion), additions and removals of 0.5% asphalt emulsion from this content were performed. Consequently, three specimens were molded with concentrations of 1.5%, 2%, and 2.5% of slow-setting cationic asphalt emulsion. These specimens were then subjected to drained triaxial tests under multi-stage loading, using 5 different stress pairs, totaling 50,000 cycles. Analyzing the regions defined by the total and permanent deformation curves allowed studying the plastic and elastic response, the proportionality between these regions, and the increase in elastic and plastic regions of the soil and stabilized soil in a single test, providing a more accurate interpretation. Regarding the measured deformations, as the deviator stress was increased with each loading cycle, the stabilized samples exhibited an increase in plastic deformations compared to the natural soil (control). It was also observed a proportional increase in the resilient region, indicating that the addition of asphalt made the soil less rigid but provided cohesion that was absent before stabilization. Doi: 10.28991/CEJ-2024-010-01-02 Full Text: PDF