Film model for coated cement concrete

The performance of a polymer concrete coated cement concrete under sulfuric acid environment was studied for 3 years. Both dry and wet concrete specimens were used in this study. The mass transfer coefficient ratio of cement concrete to polymer concrete was over 12. Coated cement concrete cylinders with pinholes were used to study the chemical resistance of the coated concrete under sulfuric acid environments to represent the worst sewer condition. Effects of pinhole sizes on the performance of coated concrete were studied, and changes in weight of the coated concrete specimens were measured regularly. The weight change in coated cement concrete was modeled using a film model and the effect of the pinhole sizes on the performance of the coated concrete was quantified.     

Removal of Lead from Contaminated Water and Clay Soil Using a Biosurfactant

Lead removal from water and contaminated soils was investigated using biosurfactant, anionic, and nonionic surfactants in continuously stirred batch reactors. Lead-contaminated water up to 100?mg/L and clay soil up to 3,000?mg/kg were used in this investigation. The surfactant concentration up to 10 critical micelle concentration was used. The speciation of lead into the micelles was quantified and the lead removal efficiency depended on the level of contamination, surfactant type, and concentration. Of the surfactants used, biosurfactant (produced from used vegetable oil) had the best removal efficiency (75%) at a lead contamination of 100?mg/L in water at pH of over 12. The Fourier-transformed infrared spectroscopy study showed that the carboxyl group in the biosurfactant was effective in removing the lead from the solution. Langmuir and Freundlich relationships were used to represent the micelle partitioning of lead in the surfactant solutions. Desorption of lead from contaminated kaolinite clay was represented using linear isotherms. The biosurfactant solution had a higher micelle partitioning for the lead from contaminated water and desorbing the lead from the contaminated soil compared to the other chemical surfactants.     

Fabrication and Electromechanical Characterization of Silver-Clad BSCCO Tapes

The powder-in-tube technique consisting of industrial processes such as wire drawing and rolling has been widely used to fabricate superconducting tapes. In the present investigation a novel technique was adopted to fabricate BSCCO 2223 tapes. Instead of wire drawing, the silver billet was reduced in size by groove rolling. Stress conditions during groove rolling were analyzed and appropriate changes were incorporated to optimize the deformation process. Subsequent thermomechanical treatment resulted in tapes with average critical current densities of 18,000 A/cm². Phase development and microstructural evolution during the thermomechanical treatment were studied using XRD, SEM, and TEM. The electromechanical properties of monofilament and composite BSCCO tapes were evaluated by subjecting them to in situ tensile tests. The strain tolerance of the composite was found to be better than that of the monofilament BSCCO tape.     

Relationship between Texas Cone Penetrometer Tests and Axial Resistances of Drilled Shafts Socketed in Clay Shale and Limestone

Modern methods for designing drilled shafts in soft rock require knowledge of the compressive strength and modulus of the rock. However, rock jointing at many sites prohibits the recovery of samples of sufficient length and integrity to test rock cores in either unconfined or triaxial compression tests. Since rational design procedures usually require values of compressive strength, surrogate methods must be employed to estimate the compressive strength of the rock. The surrogate methods considered in this study was Texas cone penetrometer tests, and performed at several sites in North Central Texas. In order to develop the relationships between Texas cone penetrations and side and base resistances of rock socketed drilled shafts, three field load tests were conducted. Based on the field study and literature reviews, a relationship between Texas cone penetration tests and axial resistances of rock socketed drilled shafts was proposed.     

Mechanical and physical properties of sintered YBCO-metal bulk composites with silver powder and fibres

Silver powder and continuous fibres were used in developing sintered YBa₂Cu₃O_7–x (YBCO)-metal composites because applications require further improvement in mechanical and physical properties of the bulk superconducting elements without affecting the critical current capacity. The weight ratios of silver powder to YBCO and silver fibre to YBCO were varied up to 50% and 5%, respectively, in the beam elements. The effect of silver addition on the density of the composite has been quantified. Stress-strain-critical current properties of bulk YBCO-metal composite elements were investigated in bending at 77 K. The addition of silver powder reduced the sintering temperature, increased the dimensional changes after sintering and also improved the strength, toughness and critical current capacity compared to the monolithic. Silver fibres, (aspect ratios varying between 70 and 110), aligned along the length of the element restricted the changes in dimensions of the composite after sintering and also influenced the stress-strain-current capacity relationship, strength and toughness of the composite to varying degrees. The mixture theory was used to predict the composite flexural strength based on the composition of the composite, constituent properties and porosity.     

Curing and constitutive relationships for polyester mortar

The compressive and tensile properties of polyester mortar were studied under various curing conditions, temperature, and strain rate. The curing temperature was varied from room temperature to 80°C. The behavior of polyester mortar was studied using a uniform sand with strain rate and temperature varied between 0.01 to 6 percent strain per minute and 22°C and 120°C, respectively. The strength, failure strain, modulus and stress-strain relationships of polyester mortar are influenced by the curing method, testing temperature, and strain rate to varying degrees. The influence of test variables on the mechanical properties of polyester mortar are quantified. Pretreating the aggregates with a silane coupling agent further enhances the compressive and tensile strength of the mortar. The compressive modulus and splitting tensile strength of polyester mortar are related to the compressive strength. A constitutive model is used to predict the compressive stress-strain behavior of polyester mortar.     

Modeling Water and Sulfuric Acid Transport through Coated Cement Concrete

The behavior of coated cement concrete in water and sulfuric acid was investigated over a three-year period. Two epoxy-based coatings were selected and cylindrical concrete specimens were coated and used in this investigation. The concrete-to-coating mass transfer coefficient ratio varied from 8 to 10. The penetration of liquids through bulk coating materials and coated concrete with and without holidays (pinholes) was studied. The mass change of the specimens was measured at regular intervals and a total of 64 coated specimens were tested. Coated concrete specimens with and without holidays had different performance with long-term immersion in deionized (DI) water and 3% sulfuric acid. Mass transfer models were developed using film and bulk concepts and were used to predict the increase in mass in coated concrete in nonreactive DI water and reactive 3% sulfuric acid solutions. The mass transfer model parameters for various solution-coating combinations were obtained from experiment data. The parameters of the effect of holiday size on the liquid transport process were also identified based on the experiment results.     

Effect of strain rate and temperature on the performance of epoxy mortar

The behavior of epoxy mortar was studied under various curing conditions, temperature and strain rate. The effect of aggregate size and distribution on the mechanical properties of epoxy mortar was also studied. Epoxy mortar with a uniform fine sand was cured at various temperatures to determine the optimum curing condition. The strain rate was varied between 0.01 to 6 percent strain per minute and the testing temperature between 22°C and 80°C. The strength, modulus, and compressive strain-strain relationship of polymer mortar are influenced by the curing method, testing temperature, and strain rate to varying degrees. The influence of test variables on the mechanical properties of epoxy mortar are quantified. Compared to the uniformly graded fine aggregate fillers the gap-graded aggregates produced polymer mortar with better mechanical properties. The compressive modulus and splitting tensile strength of epoxy mortar are related to their compressive strength. A new nonlinear constitutive model is proposed to predict the complete compressive stress-strain behavior of epoxy mortar. The constitutive relationship parameters are also related to the testing temperature and logarithmic strain rate.     

Effects of temperature and strain rate on the tensile behavior of polypropylene composites insulator coatings used in offshore deepwater pipelines

Polypropylene (PP) composites are being increasingly used as thermal insulation coatings in both onshore and offshore pipelines. In this study, the direct tensile behavior of pure PP, PP with glass microsphere filler, and PP with 65% glass filler were investigated at 22, 60, and 90 °C temperatures at various strain rates from 0.003/min to 0.300/min. Fourier transform infrared spectroscopy and scanning electron microscope studies were used to characterize the materials. Stress–strain relationships of the materials were nonlinear in the elastic and inelastic domains. Addition of glass fiber to the PP increased the elastic modulus, but the yield strength and yield strain were reduced along with the ductility. Based on the experimental results, constitutive models coupling the strain rate and temperature have been developed to predict the yield strength, the initial elastic modulus and secant modulus at yield for the PP composites. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45209.