Indirect Tensile Modulus Research Articles

Mechanical performance of asphalt mixture containing eco-friendly additive by recycling PET

The reason for conducting this research was to examine asphalt mixtures and the influence of additives obtained from recycled Polyethylene Terephthalate (PET) on their mechanical properties. Due to this, after the chemical recycling of PET, the substance resulting from the chemical reaction was added to the asphalt binder in different contents. In order to evaluate the mechanical performance of mixtures containing additives, a variety of different mechanical tests were carried out. In order to accomplish this goal, tests including dynamic creep, indirect tensile strength (ITS), and indirect tensile modulus (IDTM) were carried out to determine rutting, moisture susceptibility, and resilient modulus, respectively. The SCB test is used to determine how well a material resists cracking when subjected to low temperatures. The results showed that the addition of an additive derived from recycled PET could increase the rutting resistance, significantly improve resistance against moisture damage and increase cracking resistance at low temperatures. In accordance with the findings of the indirect tensile strength tests, indirect tensile modulus and SCB was the best performance related to the asphalt mixture containing 2% recycled PET. However, this result was different in the dynamic creep test, and the asphalt mixture containing 1% additive showed the best performance. The results of data analysis with one-way analysis of variance showed that all the data obtained in this study are statistically significant considering the confidence factor of 95%, so it can be said that the addition of recycled PET additive has a significant effect on the mechanical properties of the asphalt mixture.

Strength and resilient modulus characteristics of emulsion-stabilised demolition wastes in pavement structures

The use of bitumen emulsion has commonly been limited to pavement surface treatments or stabilising virgin aggregates. There is a lack of experimental evidence about the resilient modulus responses of bitumen emulsion-stabilised recycled demolition wastes in pavement applications. The aim of this study is to evaluate the effect of bitumen emulsion on the tensile strength and resilient modulus responses of recycled crushed concrete aggregate and crushed brick for pavement base/subbase course applications. A type of slow-set anionic bitumen emulsion was used at different contents of 0, 1, 2, and 3 % by dry weight of aggregates to prepare compacted specimens. The specimens were dried back to 70 and 90 % of the compaction moisture content to simulate the field conditions. Specimens were next investigated through a comprehensive testing program, including indirect tensile strength, indirect tensile modulus, and repeated triaxial loading tests. Results showed that the tensile strength of the mixtures generally increased as the emulsion content increased. The inclusion of 2 % and 3 % bitumen emulsion to RCC and CB provided the highest indirect tensile resilient modulus (ITMr) at 359 and 310 MPa, respectively, for those samples cured for 3 h. The highest ITMr results were obtained from samples cured for 3 days at 40 °C in a dry state with the inclusion of 2 % emulsion. For CB and RCC specimens, the results were 2808 and 3361 MPa, respectively. However, specimens of CB and RCC with 3 % emulsion that were cured for 3 days at 40 °C and then soaked in water at 25 °C exhibited the highest ITMr at 1981 and 2900 MPa, respectively. The resilient modulus in the majority of the specimens peaked at 2 % emulsion content, which was recommended as the optimum emulsion content. Results also indicated an enhanced resistance to moisture damage in demolition wastes through emulsion stabilisation. This study proposes, validates and promotes the sustainable approach of emulsion stabilisation of recycled aggregates used in the construction of pavement structures.

Strength and Stiffness Evaluation of a Fiber-Reinforced Cement-Stabilized Fly Ash Stone Dust Aggregate Mixture

The utilization of waste fly ash in road construction is primarily confined to its use in embankment filling or as a stabilizer when combined with lime and cement. Its application in structural pavement layers, such as the base and subbase, faces a challenge due to the high volume of fine particles, which renders it brittle when stabilized. In this study, fly ash was blended with stone dust and aggregated to enhance its gradation. Subsequently, it was stabilized with cement to bolster its strength, rendering it suitable for pavement use. Additionally, polypropylene (PP) fibers were introduced to mitigate the brittleness of the mixture. An extensive experimental investigation was conducted to assess the strength and stiffness properties, including compressive strength, indirect tensile strength, flexural strength, cyclic indirect tensile modulus, and flexural modulus of fiber-reinforced cement-stabilized mixtures of fly ash, stone dust, and aggregate. The experimental results reveal that the addition of PP fibers up to 0.25 wt.% enhances compressive strength, but any further increase in fiber content leads to a reduction in strength. However, indirect tensile strength and flexural strength show improvement, with an increase in fiber percentage up to 0.5 wt.%. It was observed that cement content plays a dominant role in stabilizing these materials. Appropriate relationships have been established between strength and modulus parameters for stabilized mixtures. Based on the strength and stiffness study, a combination of 70% fly ash and 30% stone dust aggregate with 6% cement can be considered for the base layer. Regarding the behavior of indirect tensile strength and flexural strength, an optimum fiber percentage of 0.35% is recommended.

Performance Evaluation of Steel Slag on Hot Mix Asphalt Mixture

Researchers have been actively exploring alternative substances to modify asphalt mixtures and improve their qualities. While asphalt has been the traditional binder used in road construction due to its excellent adhesive and waterproofing properties. In this investigation, an assessment is conducted in a laboratory environment to evaluate the effectiveness of incorporating recycled steel slag as an addition in hot mix asphalt. The utilization of the Superpave mix design methodology was employed in this study to modify fine steel slag with a particle size of 300 m. Various percentages of steel slag modifier, namely 5%, 10%, 15%, and 20% of the total weight of the fine aggregate, were incorporated. The outcomes of this investigation revealed that the mixtures containing steel slag exhibited superior performance compared to those without any slag addition, serving as the control sample (0% (slag. The inclusion of steel slag in the asphalt mixes has demonstrated a significant enhancement in stability while concurrently reducing the levels of permanent deformation. The outcomes derived from the study indicate that asphalt mixtures containing steel slag additives at varying proportions (5%, 10%, 15%, and 20% by weight of the fine aggregates) exhibited superior performance in terms of the indirect tensile modulus test, static creep test, and dynamic creep test when compared to the control sample. Notably, the results highlight that the incorporation of 15% steel slag yielded the most favorable overall performance values among the tested asphalt mixes.

Evaluation of Moisture Damage Potential in Hot Mix Asphalt Using Polymeric Aggregate Treatment.

To enhance the moisture damage performance of hot mix asphalt (HMA), treating the aggregate surface with a suitable additive was a more convenient approach. In this research, two types of aggregate modifiers were used to study the effect of moisture damage on HMA. Three different aggregate sources were selected based on their abundance of use in HMA. To study the impact of these aggregate modifiers on moisture susceptibility of HMA, the indirect tensile strength test and indirect tensile modulus test were used as the performance tests. Moisture conditioning of specimens was carried out to simulate the effect of moisture on HMA. The prepared samples’ tensile strength ratio (TSR) and stiffness modulus (Sm) results indicated a decrease in the strength of the HMA after moisture conditioning. After treating the aggregate surface with additives, an improvement was seen in dry and wet strength and stiffness. Moreover, an increasing trend was observed for both additives. The correlation between TSR and strength loss reveals a strong correlation (R2 = 0.7219). Also, the two additives indicate increased wettability of asphalt binder over aggregate, thus improving the adhesion between aggregate and asphalt binder.

Propriedades mecânicas de concretos asfálticos dosados com rejeitos do beneficiamento magnético a seco do minério de ferro

Este estudo avalia o comportamento mecânico de três misturas asfálticas, uma de referência e duas com substituição dos agregados naturais por rejeitos finos de minério de ferro. Os rejeitos são provenientes de uma inovadora tecnologia de obtenção, a separação magnética a seco. A metodologia consistiu de um programa experimental dividido em quatro etapas: (i) determinação das características físicas, mineralógicas e ambientais dos agregados; (ii) obtenção as propriedades reológicas e empíricas do cimento asfáltico de petróleo; (iii) dosagem dos materiais de revestimento asfáltico pela metodologia Superpave; (iv) realização de ensaios de dano por umidade induzida, resistência à tração por compressão diametral, fadiga à tensão controlada, módulo de resiliência e uniaxial de cargas repetidas nas misturas asfálticas. Os concretos asfálticos que continham agregados alternativos apresentaram propriedades de rigidez e fadiga similares à mistura de referência. Entretanto, com a utilização de rejeitos de minério de ferro houve maior susceptibilidade ao acúmulo de deformações permanentes.

The water resistance of a recycled base with foamed bitumen in the aspect of road binder composition

The paper describes research results of recycled base which was performedin a cold deep recycling technology with foamed bitumen and different type of hydraulicmixed binder in the aspect of water resistance. An individual design of a composition of abinder enables to achieve a precise adjustment of a binder’s impact to local conditions andrequired parameters of a recycled base. The design a recycled base with foamed bitumensimulated a cold deep recycling process with materials from existing crushed bituminouspavement layers ("technology in-situ"). To produce the foamed bitumen a road bitumen ofpenetration grade 50/70 was used. Moreover, the following mineral components werecategorised as a waste material: reclaimed asphalt pavement, 0/31,5 mm aggregate andaggregates for soil gradation improvement 0/4. A composition of the recycled base consisted of the binders prepared in the laboratory as a result of a mix of three basic components.The percentage of individual road binders was determined in line with the plan of thesimlex-centroid experiment. For the purpose of determining an influence of such a hydraulicroad binder on the water resistance in recycled base, the following tests were carried out:void contents Vm, tensile strength ratio TSR (water resistance). Additionally, an evaluationof increase of indirect tensile modulus (IT-CY) was conducted. On the basis of the testresults, a varied impacts of tested hydraulic road binders on mechanical properties andwater resistence of recycled base with foamed bitumen were observed. On the basis of theplan of the experiment, it was possible to determine the recommended road binder composition that enabled to obtain the water resistance in the recycled base with foamed bitumen

THE EFFECTS OF (RAP) ON THE LABORATORY PERFORMANCES OF HOT MIX ASPHALTS

The use of reclaimed asphalt pavement (RAP) in flexible pavement surface layer has been a major sensitive issue in the construction industry. Due to limited space available in landfills, the amount of high quality virgin aggregate declines, and the high price of oil, the use of RAP in new asphalt concrete mixtures has become very attractive. This research has been conducted to study the laboratory performances of HMA mixture containing RAP, in which Marshall properties and resilient modulus characteristic were evaluated [4,6,7]. A Marshall mix design mixture containing 0% RAP with binder (60/70) was used as the control mixture for evaluating properties of mixtures containing 25% and 40% RAP. Marshall tests and Indirect Tensile Modulus (Resilient Modulus) were performed on samples of the three mixes. Comparing the results of the conducted tests indicated that the use of RAP in Hot Mix Asphalt (HMA) was advantageous in all properties measured. The mix containing RAP showed reduction in Marshall Stability, indirect tensile value, and Resilient Modulus, and the higher the temperature the lower of resilient modulus values, but the results are acceptable by Egyptian code specifications. Therefore, it is preferred to use mixes containing RAP in highways with studied proportions.

Laboratory Investigation on the Effects of Flaky Aggregates on Dynamic Creep and Resilient Modulus of Asphalt Mixtures

This paper presents an investigation on the effects of flaky aggregates in asphalt mixture. In general, aggregate characteristics are critical to the performance of asphalt mixture. Therefore, flaky aggregate is normally avoided simply because it has significant contribution towards the gradation and reduces the interlocking characteristics of aggregates within asphalt mixture. In practice, it is recommended that the amount of flakiness aggregate should be limited to 25% or less. This study evaluates the mechanical properties of asphalt mixture specimens prepared with various percentages of flaky aggregates particularly 10%, 20% and 30% by the total weight of the mixture. Several laboratory tests were conducted including Marshall properties test, Indirect Tensile Modulus test and Dynamic Creep test. The results show that higher bitumen content is required with the increased in the amount of flaky aggregates added to mixture. Furthermore, greater amount of flaky aggregates tends to reduce the mixture’s resilient modulus and its resistance against permanent deformation.

Evaluation and Validation of Characterization Methods for Fatigue Performance of Asphalt Mixes for Western Australia

The determination of appropriate pavement thickness using laboratory determined parameters is one of the key issues facing the road manager. Five different types of asphalt mixes were produced in laboratory to modify pavement performance mixture. The main objective of this study is to evaluate the characterization methods for fatigue performance of asphalt mixes to Western Australia road. In this study, laboratory test for indirect tensile modulus, dynamic creep, wheel tracking and aggregate gradation tests were taken to analyze each asphalt mixtures for a design traffic road. The results and analysis showed that AC20-75 asphalt mix blow is the most effective and efficient in pavement performance than the other asphalt mixes. AC14-75 was the second in rank to strengthen and durability of asphalt pavement. All asphalt mixes in this study can be used to strength and stable the overall stiffness of pavement, and modification rank can be described as AC20-75 Blow > AC14-75 Blow > AC14-50 Blow > AC7-50 Blow > SMA7-50 Blow in this research.