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Crumb rubber modified crack sealants to improve performance

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Crack sealing is considered one of the least expensive and cost effective maintenance activity used on pavements. In some cases, crack sealing suffers from premature failure due to various material, environmental, and construction issues. A survey that was conducted as

Crack sealing is considered one of the least expensive and cost effective maintenance activity used on pavements. In some cases, crack sealing suffers from premature failure due to various material, environmental, and construction issues. A survey that was conducted as part of this study showed that the highest sealant failure year occurring on the second year. Therefore, any attempt to increase the sealants’ service life by addressing and improving the sealant properties and their resistance to failure will benefit the effectiveness of this treatment.

The goal behind this study was to evaluate the potential improvement in performance of hot applied sealant material commonly used in the Phoenix area, and evaluate the performance of using a neat binder modified with crumb rubber (at 5 and 10% by weight of binder) as a low-grade sealing material. The sealants was also modified with crumb rubber at 2.5, and 5% by weight fo the sealant. Six ASTM tests were conducted for the comparison. These tests are the Standard Penetration Test (SPT) and Cone Penetration Test (CPT), Resilience Test, Softening Point Test, Brookfield Viscometer Test, and Dynamic Shear Rheometer (DSR).

The results showed that adding only crumb rubber to a neat binder for its potential use as a crack sealant is inadequate to meet the specifications expected for sealants. However, the modification of the sealant with crumb rubber showed some benefits, such as increased elasticity and decreased temperature susceptibility. A crumb rubber content of 2.5% by weight of the sealant was recommended.

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Date Created
2016

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Properties of activated crumb rubber

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ABSTRACT Pre-treated crumb rubber technologies are emerging as a new method to produce asphalt rubber mixtures in the field. A new crumb rubber modifier industrially known as "RuBind" is one such technology. RuBindTM is a "Reacted and Activated Rubber" (RAR)

ABSTRACT Pre-treated crumb rubber technologies are emerging as a new method to produce asphalt rubber mixtures in the field. A new crumb rubber modifier industrially known as "RuBind" is one such technology. RuBindTM is a "Reacted and Activated Rubber" (RAR) that acts like an elastomeric asphalt extender to improve the engineering properties of the binder and mixtures. It is intended to be used in a dry mixing process with the purpose of simplifying mixing at the asphalt plant. The objectives of this research study were to evaluate the rheological and aging properties of binders modified with RuBindTM and its compatibility with warm mix technology. Two binders were used for this study: Performance Grade (PG) 70-10 and PG 64-22, both modified with 25% by weight of asphalt binder. Laboratory test included: penetration, softening point, viscosity, Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR). Tests were conducted under original, short and long -term aging conditions. Observations from the test results indicated that there is a better improvement when RuBindTM is added to a softer binder, in this case a PG 64-22. For short-term aging, the modified binder showed a similar aging index compared to the control. However, long term aging was favorable for the modified binders. The DSR results showed that the PG 64-22 binder high temperature would increase to 82 °C, and PG 70-10 would be increased to 76 °C, both favorable results. The intermediate temperatures also showed an improvement in fatigue resistance (as measured by the Superpave PG grading parameter |G*|sinä). Test results at low temperatures did not show a substantial improvement, but the results were favorable showing reduced stiffness with the addition of RuBindTM. The evaluation of warm mix additive using EvothermTM confirmed the manufacturer information that the product should have no negative effects on the binder properties; that is the modified binder can be used in a warm mix process. These results were encouraging and the recommendation was to continue with a follow up study with mixture tests using the RuBindTM modified binders.

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Date Created
2014

A study of heating and degradation of acrylonitrile-butadiene-styrene/polycarbonate polymer due to ultraviolet lasers illumination during localized pre-deposition heating for fused filament fabrication 3D printing

Description

With the growing popularity of 3d printing in recreational, research, and commercial enterprises new techniques and processes are being developed to improve the quality of parts created. Even so, the anisotropic properties is still a major hindrance of parts manufactured

With the growing popularity of 3d printing in recreational, research, and commercial enterprises new techniques and processes are being developed to improve the quality of parts created. Even so, the anisotropic properties is still a major hindrance of parts manufactured in this method. The goal is to produce parts that mimic the strength characteristics of a comparable part of the same design and materials created using injection molding. In achieving this goal the production cost can be reduced by eliminating the initial investment needed for the creation of expensive tooling. This initial investment reduction will allow for a wider variant of products in smaller batch runs to be made available. This thesis implements the use of ultraviolet (UV) illumination for an in-process laser local pre-deposition heating (LLPH). By comparing samples with and without the LLPH process it is determined that applied energy that is absorbed by the polymer is converted to an increase in the interlayer temperature, and resulting in an observed increase in tensile strength over the baseline test samples. The increase in interlayer bonding thus can be considered the dominating factor over polymer degradation.

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Date Created
2017

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Utilization of thermoplastic mounting studs for simple performance testing on hot mix asphalt

Description

The objective of the research is to test the use of 3D printed thermoplastic to produce fixtures which affix instrumentation to asphalt concrete samples used for Simple Performance Testing (SPT). The testing is done as part of materials characterization to

The objective of the research is to test the use of 3D printed thermoplastic to produce fixtures which affix instrumentation to asphalt concrete samples used for Simple Performance Testing (SPT). The testing is done as part of materials characterization to obtain properties that will help in future pavement designs. Currently, these fixtures (mounting studs) are made of expensive brass and cumbersome to clean with or without chemicals.

Three types of thermoplastics were utilized to assess the effect of temperature and applied stress on the performance of the 3D printed studs. Asphalt concrete samples fitted with thermoplastic studs were tested according to AASHTO & ASTM standards. The thermoplastics tested are: Polylactic acid (PLA), the most common 3D printing material; Acrylonitrile Butadiene Styrene (ABS), a typical 3D printing material which is less rigid than PLA and has a higher melting temperature; Polycarbonate (PC), a strong, high temperature 3D printing material.

A high traffic volume Marshal mix design from the City of Phoenix was obtained and adapted to a Superpave mix design methodology. The mix design is dense-graded with nominal maximum aggregate size of ¾” inch and a PG 70-10 binder. Samples were fabricated and the following tests were performed: Dynamic Modulus |E*| conducted at five temperatures and six frequencies; Flow Number conducted at a high temperature of 50°C, and axial cyclic fatigue test at a moderate temperature of 18°C.

The results from SPT for each 3D printed material were compared to results using brass mounting studs. Validation or rejection of the concept was determined from statistical analysis on the mean and variance of collected SPT test data.

The concept of using 3D printed thermoplastic for mounting stud fabrication is a promising option; however, the concept should be verified with more extensive research using a variety of asphalt mixes and operators to ensure no bias in the repeatability and reproducibility of test results. The Polycarbonate (PC) had a stronger layer bonding than ABS and PLA while printing. It was recommended for follow up studies.

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Date Created
2018

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Superpave Mix Design and Laboratory Testing of Reacted and Activated Rubber Modified Asphalt Mixtures

Description

Crumb rubber use in asphalt mixtures using wet process technology has been in practice for years in the United States with good performance history; however, it has some drawbacks that include the need for special blending equipment, high rubber-binder temperatures,

Crumb rubber use in asphalt mixtures using wet process technology has been in practice for years in the United States with good performance history; however, it has some drawbacks that include the need for special blending equipment, high rubber-binder temperatures, and longer waiting time at mixing plants. Pre-treated crumb rubber technologies are emerging as a new method to produce asphalt rubber mixtures in the field. A new crumb rubber modifier known as Reacted and Activated Rubber (RAR) is one such technology. RAR (industrially known as “RARX”) acts like an Enhanced Elastomeric Asphalt Extender to improve the engineering properties of the binder and mixtures. It is intended to be used in a dry mixing process with the purpose of simplifying mixing at the asphalt plant. The objective of this research study was first to perform a Superpave mix design for determination of optimum asphalt content with 35% RAR by weight of binder; and secondly, analyse the performance of RAR modified mixtures prepared using the dry process against Crumb Rubber Modified (CRM) mixtures prepared using the wet process by conducting various laboratory tests. Performance Grade (PG) 64-22 binder was used to fabricate RAR and CRM mixtures and Performance Grade (PG) 70-10 was used to fabricate Control mixtures for this study. Laboratory tests included: Dynamic Modulus Test, Flow Number Test, Tensile Strength Ratio, Axial Cyclic Fatigue Test and C* Fracture Test. Observations from test results indicated that RAR mixes prepared through the dry process had excellent fatigue life, moisture resistance and cracking resistance compared to the other mixtures.

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Date Created
2018

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Effect of using Organosilane with Crumb Rubber Modified Hot Mix Asphalt Mixtures

Description

Crumb rubber use in asphalt mixtures by means of wet process technology has been in place for several years in the United States with good performance record; however, it has some shortcomings such as maintaining high mixing and compaction temperatures

Crumb rubber use in asphalt mixtures by means of wet process technology has been in place for several years in the United States with good performance record; however, it has some shortcomings such as maintaining high mixing and compaction temperatures in the field production. Organosilane (OS), a nanotechnology chemical substantially improves the bonding between aggregate and asphalt by modifying the aggregate structure from hydrophilic to hydrophobic contributing to increased moisture resistance of conventional asphalt mixtures. Use of Organosilane also reduces the mixing and compaction temperatures and facilitates similar compaction effort at lower temperatures. The objective of this research study was first to perform a Superpave mix design for Crumb Rubber Modified Binder (CRMB) gap-graded mixture with and without Organosilane; and secondly, analyse the performance of CRMB mixtures with and without Organosilane by conducting various laboratory tests. Performance Grade (PG) 64-22 binder was used to create the gap-graded Hot Mix Asphalt (HMA) mixtures for this study. Laboratory tests included rotational viscometer binder test and mixtures tests: dynamic modulus, flow number, tensile strength ratio, and C* fracture test. Results from the tests indicated that the addition of Organosilane facilitated easier compaction efforts despite reduced mixing and compaction temperatures. Organosilane also modestly increased the moisture susceptibility and resistance to crack propagation yet retaining equal rutting resistance of the CRMB mixtures.

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Date Created
2018

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Surface Activation of Rubber to Enhance the Durability and Chemo-Mechanics of Asphalt

Description

It is common to use crumb rubber as modifier in bitumen. Good performance of crumb rubber in bitumen has been reported in terms of improving characteristics like higher skid resistance, reducing noise, higher rutting resistance and longevity. However, due to

It is common to use crumb rubber as modifier in bitumen. Good performance of crumb rubber in bitumen has been reported in terms of improving characteristics like higher skid resistance, reducing noise, higher rutting resistance and longevity. However, due to the vulcanization, the polymeric crosslinked structure of crumb rubber suffers from inadequate dispersion and incompatibility in bitumen where storage stability becomes an issue. To solve this problem, partial surface devulcanization of the rubber via chemical and microbial surface activation was examined in this study showing both method can be effective to enhance rubber-bitumen interactions and subsequently storage stability of the rubberized bitumen. To ensure proper surface activation, it is important to thoroughly understand chemo-mechanics of bitumen containing rubber particles as well as underlying interaction mechanism at the molecular level. Therefore, this study integrates a multi-scale approach using density functional theory based computational modeling and laboratory experiments to provide an in-depth understanding of the mechanisms of interaction between surface activated rubber and bitumen. To do so, efficacy of various bio-modifiers was examined and compared it terms of both surface activation capability and durability of resulting rubberized bitumen. It was found that biomodifiers with various compositions can have either synergistic or antagonistic effect onchemo-mechanics of rubberized bitumen. The study was further extended to study the interplay of Polyphosphoric Acid (PPA) and these biomodified rubberized bitumens showing not all modifiers have high synergy with PPA in bitumens. Finally, durability of rubberized bitumen was studied in terms of its resistance to Ultraviolet (UV) aging. It was shown that there is a strong relation between composition of biomodified rubberized bitumen and its resistance to UV-aging.

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Date Created
2020