Browsing by Subject "Tensile strength"

Now showing 1 - 5 of 5

An evaluation of the tensile strength of asphalt binder and mortar with recycled asphalt additives at low temperatures
(2017-08) Rodriguez, Rogelio Gabriel; Bhasin, Amit
A standard grading system is used to evaluate the properties and expected performance of an asphalt binder. The most common grading system used in the US today is the performance grading (PG) system. This system prescribes an operational temperature range within which the binder is expected to perform satisfactorily without resulting in rutting, fatigue cracking or thermal cracking as a distress. On the low-temperature and thermal cracking end, this system uses both a metric related to stiffness and rate of relaxation (m-value) to establish a low temperature grade for a given asphalt binder. Although these parameters provide some information on the rate of relaxation and overall rigidity of the asphalt binder they don’t include an evaluation of the tensile strength of the asphalt binder. The tensile strength of the binder can furnish critical information about its resistance to cracking including thermal cracking. The asphalt industry has become particularly interested in the impact of recycled asphalt pavement (RAP) and additives such as rejuvenators on the behavior and performance of the material. The goal of this study was to evaluate the tensile strength characteristics of asphalt binders and composites in addition to their stiffness characteristics. The study was conducted in three parts: (1) the evaluation of tensile strength of asphalt binders with similar performance grades, (2) the evaluation of tensile strength of asphalt binders as a function of the amount of recycled asphalt binder added to the virgin binder, and (3) the influence of recycled asphalt and rejuvenators on the stiffness and tensile strength of asphalt mortars. In addition to these three objectives, this study also developed simplified methods to prepare and evaluate the tensile strength of asphalt binders and mortars as a material characterization tool to screen or evaluate the efficacy of RAP, rejuvenators, and other additives. Results show that similarly graded binders have a significant variability both in terms of their stiffness and strength and that rejuvenators can be used with RAP to achieve a balance of stiffness and strength.
Evaluation of Class F fly ash-based alkali-activated materials for Civil and Petroleum Engineering applications
(2021-05-11) Horan, Cameron Rae; Oort, Eric van; Juenger, Maria C. G.
Advancements in technology have allowed oil, gas and geothermal well construction in into progressively more challenging subsurface environments, with deeper depths, higher temperatures and pressures, etc. With this progress arises the need for well cementing solutions that can perform better than ordinary portland cement (OPC), with an ability to better handle high pressure / high temperature (HPHT) conditions while possessing a more tolerant chemical composition to drilling mud contamination. Faulty cement jobs due to poor performance of OPC have allowed for the occurrence of micro annuli, putting many wells at risk of a well integrity failure. Such a failure compromises zonal isolation, which can in turn lead to high costs for repair that have not typically been factored into operating budgets. Likewise, civil infrastructure durability has become a key concern for much of the United States due to aging structures and the deterioration of OPC concrete with time. While performance concerns pose a significant risk, the CO₂ emissions associated with OPC production are also at the forefront of concerns about climate change. The topic of this report is alkali-activated materials (AAM) or geopolymers, produced from fly ash, which are currently investigated for use as OPC alternatives. They are of interest because suitable strengths and rheological behaviors have been observed when these materials are subjected to elevated temperatures or mud contamination. To understand the effects of various activators and fly ash compositions on geopolymer formulations, a variety of tests have been conducted at different temperature and pressure conditions. These tests include measurements of rheological behavior, set time, unconfined compressive strength (UCS), tensile strength, and bond strength. As a result of this testing, it has been shown that geopolymers exhibit desirable rheological profiles and set times for a variety of different applications. Their compressive strength was also shown to be equivalent to - or greater than - OPC for most formulations. Furthermore, their tensile strengths and bond strength profiles were often found to be better than OPC. Ultimately, with this research, geopolymers are shown to be viable and appropriate alternatives to OPC for both the oil, gas and geothermal well construction as well as the civil infrastructure industry. An added benefit of geopolymers is that the base material is a waste material, with no further release of CO₂ in manufacturing. Thus, there is the opportunity to utilize a new material for cementation purposes that outperforms OPC while decreasing environmental impacts.
Fatigue Analysis of Short Carbon Fiber Reinforced Composite Components Manufactured Using Fiber-Reinforced Additive Manufacturing
(2022) Rajeshirke, Mithila; Fidan, Ismail; Gupta, Ankit; Mäntyjärvi, Kari
Fiber-reinforced additive manufacturing (FRAM) has become quite popular in several industries. The technology offers an opportunity to improve the existing mechanical performance of the part. This research study has presented a successful methodology to fabricate the FRAM- based composite parts with improved fatigue properties. Most engineering applications are subjected to cycling loading which makes the fatigue study an important analysis. The scope of this paper is to present the fatigue properties of short carbon fiber-reinforced Polyethylene Terephthalate Glycol (SCFs/PETG) of 13.78% by weight. The fatigue behavior was analyzed by varying the 3D printing process parameters i.e., infill orientation (0°, 45°, and 90°), and infill layer heights (0.2 and 0.3 mm). The tests are carried out on 1600 N as a maximum load of fatigue cycle with a 0.1 stress ratio, for the specimens with 90° and 45° orientations with 0.2 and 0.3 mm layer heights. For 0° orientation, both 0.2 and 0.3 mm layer height specimens are applied to 2600 N as maximum load, keeping the stress ratio the same as 0.1. Analysis of Variance (ANOVA) is used to statistically analyze the testing data to understand the influence of input variables on fatigue properties.
Tensile strength of asphalt binder and influence of chemical composition on binder rheology and strength
(2014-08) Sultana, Sharmin; Bhasin, Amit; Liechti, Kenneth M.; Prozzi, Jorge A.; Zhang, Zhanmin; Fowler , David W.
Asphalt mixtures or asphalt concrete are used to pave about 93% of about 2.6 million miles paved roads and highways in the US. Asphalt concrete is a composite of aggregates and asphalt binder; asphalt binder works as a glue to bind the aggregate particles. The mechanical response of the asphalt binder is dependent on the time/rate of loading, temperature and age. An asphalt concrete mixture inherits most of these characteristics from the asphalt binder. Also the asphalt binder plays a critical role in providing the asphalt concrete the ability to resist tensile stresses and relaxing thermally induced stresses that can lead to fatigue and low temperature cracking, respectively. Hence, it is very important (but not sufficient) to ensure that asphalt binders used in the production of asphalt concrete are inherently resistant to cracking, rutting and other distresses that a pavement may undergo. Current binder specification (AASHTO M-320) to evaluate its fatigue cracking is based on the stiffness of the binder and not on its tensile strength. Also, measurements following current specifications are made on test specimens subjected to a uniaxial mode of loading that does not produce the same stress state in the binder as in the case of asphalt concrete. Another challenge in being able to produce binders with inherently superior performing characteristics is the fact that the asphalt binders produced in a refinery do not have a consistent chemical composition. The chemical composition of asphalt binder depends on the source and refining process of crude oil. There is a need to better quantify the tensile strength of asphalt binder and understand the relationship between the chemical composition of asphalt binders and its mechanical properties. The knowledge from this study can be used to engineer asphalt binders that have superior performance characteristics. The objective of this research was to quantify the tensile strength of asphalt binder, develop a metric for the tensile strength and identify the relationship between chemical composition and mechanical properties of asphalt binder. Laboratory tests were performed on binders of different grades using a poker chip geometry to simulate confined state by varying the film thickness, rate of loading and modes of loading. The chemical properties of asphalt binder were studied based on SARA fractionation. The findings from this research showed that the modified correspondence principles can unify and explain the rate and mode dependency of asphalt binder. This study also quantified the relationship between chemical composition, and rheological and mechanical properties of asphalt binder. Finally, a composite model was developed based on the individual properties of chemical fractions which could predict the dynamic modulus of the asphaltenes doped and resins doped binder.
Use of ionic liquid for producing regenerated cellulose fibers
(2011-05) Jiang, Wei, Ph. D.; Chen, Jonathan Yan; Xu, Bugao
The objectives of the research are to establish the process of obtaining regenerated fibers and films from wood pulp and bagasse pulp with the ionic liquid 1-Butyl-3-methylimidazolium Chloride (BMIMCl) as a solvent; to study the impacts on tensile strength of different spinning parameters; to find the optimal spinning condition, and to obtain regenerated cellulose products with flame retardant properties. Solutions were obtained by dissolving cellulose (wood/bagasse) pulp into the BMIMCl. The solutions were extruded in a dry-jet and wet-spinning method using water as a coagulation bath. The obtained fibers were tested to evaluate the properties such as tensile strength, thermal property, thermal mechanical property, crystal order, and ionic liquid residue in obtained fiber. The orthogonal experiments were designed to find out the strongest affective variable and the optimal condition of the spinning process. The regenerated cellulose films with melamine resin or zinc oxide were obtained. Their flame retardant properties were tested. Cellulose fiber with melamine resin was also obtained. Thermo-gravimetric analyzer (TGA) was used to measure the thermal properties of obtained products, and to calculate their activation energies. Dynamic mechanical analysis (DMA) was used to determine the thermal mechanical properties of obtained fibers. Wide angle X-ray diffraction (WAXD) was used to measure the degree of crystallinity and degree of crystal orientation. The tensile strength was tested by a tensile machine. To evaluate the quantity of ionic liquid residue in the regenerated fibers, the instrumental methods of FT-IR and Mass Spectrometry were applied. Research results indicated increases in the degree of crystallinity and storage modulus under a higher fiber drawing speed. Both regenerated bagasse fibers and regenerated wood fibers had similar thermal properties. However, the regenerated bagasse fibers showed a higher degree of crystallinity and a higher tenacity than the regenerated wood fibers obtained under the same condition. The study also revealed water treatment would be helpful for eliminating the ionic residue in regenerated fibers. It was also found the concentration of cellulose in the BMIMCl solution affected the tensile strength of regenerated fiber mostly. Certain amount of melamine or zinc oxide nanoparticles contained in the cellulose matrix could improve the flame retardant property effectively.