Dmr Mitchell

Effect of Antistrip Additives on Surface Free Energy Characteristics of Asphalt Binders for Moisture-Induced Damage Potential

In this study, the effect of antistrip additives on asphalt binders was evaluated by both laboratory tests and a proposed chemical model of asphalt binder based on the surface free energy characteristics. Two performance graded asphalt binders, namely, PG 64-22 and PG 70-28 and two amine-based liquid antistrip additives, namely, AD-Here HP Plus and Redicote E-6 were evaluated at different percentages (0.25 %, 0.75 %, and 1.5 %). It was found that 1.5 %AD-Here HP Plus and 1.5 % Redicote E-6 increased the total SFE of PG 64-22 by 67 % and 208 %, respectively. Also, the acid components of PG 64-22 and PG 70-28 are 2.9 dyne/cm and 2.5 dyne/cm, respectively, whereas, the corresponding base components are 0.4 dyne/cm for both. With the addition of 1.5 %. Redicote E-6 in PG 64-22, the acid component of the binder reduced by 92 % and the base component of the binder increased by 1141 %.

A Study on Properties of Foamed-Asphalt-Treated Mixes

From both economical and ecological points of view, cold recycling is much more beneficial than hot recycling. However, due to not only the intrinsic properties of binding mechanisms but also the difficulties of process control, cold recycling did not gain common acceptance in Taiwanese paving industries. For the further development of environment-friendly paving materials and construction processes, this particular study investigated the engineering properties of foamed-asphalt-treated bases in Taiwan. Using a laboratory foaming plant, work was performed on local materials to produce foamed-asphalt-treated cold mixtures. The engineering properties of foamed-asphalt-treated mixes were tested and compared with those of hot recycled mixes. Test results show the benefits of utilizing high percentages (80%) of milled asphalt in foamed asphalt mixes. The optimum asphalt content of foamed asphalt mixes can be reduced from 3.5 to 2.0%, which is less than the mixes consisting of all new aggregate, and the moisture resistance of the mixture is enhanced. Resilience modulus and fatigue data show that foamed-asphalt-treated mixes perform as well as hot recycled mixes.

An Internal Conical Mandrel Technique for Fracture Toughness Measurements on Nuclear Fuel Cladding

An understanding of the limiting stress level for crack initiation and propagation in a fuel cladding material is a fundamental requirement for the development of water reactor clad materials. Conventional tests, in use to evaluate fracture properties, are of limited help, because they are adapted from ASTM standards designed for thick materials, which differ significantly from fuel cladding geometry (small diameter thin-walled tubing). The Internal Conical Mandrel (1CM) test described here is designed to simulate the effect of fuel pellet diametrical increase on a cladding with an existing axial throughwall crack. It consists in forcing a cone, having a tapered increase in diameter, inside the Zircaloy cladding with an initial axial crack. The aim of this work is to quantify the crack initiation and propagation criteria for fuel cladding material. The crack propagation is monitored by a video system for obtaining crack extension δa. A finite-element (FE) simulation of the ICM test is performed in order to derive J integrals. A node release technique is applied during the FE simulation for crack propagation and the J-resistance curves (J-δa) are generated. This paper presents the test methodology, the J computation validation, and results for cold-worked stress relieved Zircaloy-4 cladding at 20° and 300°C and also for Al 7050-T7651 aluminum alloy tubing at 20°C.

Anisotropy of Field-Compacted Asphalt Concrete Material

This note presents a study to quantify the degree of anisotropy induced in situ by the compaction equipment. Large asphalt concrete samples were cut from the field and sawed in the laboratory to give prismatic specimens 200 × 80 × 80 mm3. The specimens were tested in all directions, at 40°C, using low sinusoidal load. The dynamic modulus obtained at different frequencies was used as the indicator of anisotropy in the three principal directions. Analyses of variance were conducted. They indicated that the material is not isotropic, but rather cross-anisotropic.

Utilization of Steel Slag Aggregate for Road Bases

Industrial wastes and byproducts have to be disposed off properly so that their environmental impacts are minimized. Alternatively, some of these materials can be utilized in recycling processes, manufacturing of new products, or as construction materials. This paper presents an effective way of utilizing the steel slag aggregate (SSA), which is a byproduct of the steel manufacturing process, in road construction. A comprehensive study was conducted to characterize SSA and determine the potential for its use in road bases. Testing results indicated that SSA is an environmentally safe product and has physical and chemical properties that make it an excellent candidate for road base construction. Laboratory and field data have shown the superior performance of SSA over the locally available calcareous sediments. The resulting California Bearing Ratio values are doubled and the water sensitivity is much less when using SSA instead of the local calcareous material.

Dynamic Testing of Materials with the Rotating Disk Indirect Bar-Bar Tensile Impact Apparatus

An experimental method is proposed to investigate the tensile behavior of materials at high strain rates by using a developed split Hopkinson tension bar, rotating disk indirect bar-bar tensile impact apparatus. The mechanically-filtered input tensile pulse is generated by incorporating a prefixed metal bar connected between the impact block and the input bar. The pulse amplitude is controlled by the diameter of the prefixed metal bar. The pulse duration is determined by the length of the prefixed metal bar and the velocity of the impact hammer. Dynamic properties of metallic and nonmetallic materials are presented as examples by using this developed rotating disk indirect bar-bar tensile impact apparatus.

A Laboratory Study of the Effectiveness of Various Additives on Moisture Susceptibility of Asphalt Mixtures

Antistripping additives are used routinely to improve water resistance of asphalt mixtures. Different additives have different improvement effectiveness in water resistance. In this study, the effects of various additives on the moisture susceptibility of asphalt mixture are studied with the retained Marshall stability test, Lottman test, and immersion wheel tracking test. Asphalt mixtures were modified with Portland cement, hydrated lime, lime slurry, and liquid antistripping agents. The results show that the lime-slurry-treated asphalt mixtures have better resistance to moisture susceptibility than mixtures treated with other materials, and have better long-term moisture stability than the liquid antistripping agents. The liquid-antistripping-agent-treated asphalt mixtures have better resistance to moisture stability before long-term aging. Portland-cement-treated asphalt mixtures show slightly improved water resistance. Asphalt mixtures become more resistant to moisture damage through short-term aging. It was confirmed that the Lottman and the immersion tracking methods are better methods to evaluate moisture susceptibility than the retained Marshall stability methods.

Determination of Thermal Properties of Soils in a Geotechnical Centrifuge

Studies conducted in the past reveal that heat transfer through a soil mass depends basically on its thermal properties and hence estimation of soil thermal properties is essential. Efforts have been made by researchers to estimate thermal properties of soils with the help of analytical or numerical models and by conducting laboratory or field experiments. Though laboratory tests are inexpensive, quick, and easy to perform, they lack simulation of real-world conditions in terms of in situ stresses. To overcome this, field tests, which are relatively costly and time consuming, are found to be quite useful. However, these tests offer either little or no direct control over the boundary conditions. To overcome these difficulties, researchers have turned to geotechnical centrifuge modeling for simulating migration of heat through the soil mass. In order to achieve this, it is necessary to determine the influence of an accelerated environment on thermal properties of soils. With this in view, an attempt was made to establish a working methodology for estimating thermal properties of soils, compacted at different dry densities, in a geotechnical centrifuge; details are presented in this technical note.

Evaluation of the ASTM J Initiation Procedure Using the EURO Fracture Toughness Data Set

The multiple specimen procedure for the evaluation of a JIc value as presently measured using ASTM E 1820 is examined using the large fracture toughness dataset from the EURO round robin. Although a standard test procedure for JIc determination has been in use for more than 20 years, the multiple specimen option has not been regularly reassessed during that time. The EURO dataset was generated to evaluate the transition fracture toughness methods for steels. However, many of the test results produced ductile fracture information in terms of a final J versus ductile crack extension. This is the same information that is measured in a multiple specimen J initiation fracture toughness test. The dataset has more than 300 individual points of J versus crack extension and may be the largest dataset of that type produced for one material. Therefore, it is a useful dataset for evaluating the multiple specimen JIc procedure in ASTM E 1820. This evaluation showed that a value of JIc cannot be determined for a dataset containing more than 300 points, even though these points gave a consistent J-R curve. The criteria that are used for qualification of the data eliminate all of the points as being not qualified. This raises some serious concerns about the usefulness of the method as it is presently written, especially the restrictive nature of the qualification rules. Individual qualification criteria are examined and recommendations made for developing a more reasonable test method, one that can be used in the future to evaluate a multiple specimen fracture toughness for materials typically used in structural applications.

Vapor Permeances, Air Permeances, and Water absorption Coefficients of Building Membranes

Building membranes are integral parts of North American buildings. Some are installed beneath commonly used exterior claddings, brick, and stucco to reduce the risk of water infiltration into the wall systems. Others are used for controlling vapor diffusion though the envelope or as the airtight element of the air barrier system of the envelope. To determine the suitability of a membrane for its intended application, it is necessary to have reliable information on its inherent physical properties. This paper reports the water vapor permeance, the air permeance, and the water absorption coefficient for 18 building membranes that are found in North American markets today. These membranes include paper-based as well as polymer-based materials. The properties reported here show that at the design stage most of the membranes can be considered as the airtight element of air barrier systems and as part of the second line of defense against rainwater penetration. The membranes provide a range of values for water vapor permeance and therefore open up opportunities for a designer to integrate innovative vapor diffusion control strategies for exterior walls and to prolong their service lives.