Effect of freeze and thaw cycle on the mechanical properties of engineered cementitious composites with un-oiled fibers containing liquid and solid polymers

Nowadays, the application of the engineered cementitious composites(ECC) is expected to highly develop. Due to the lack of access to oiled- polyvinyl alcohol (PVA) fibers in many parts of the world, the implementation of the ECC has contained many difficulties. In this study, to increase the mechanical properties of ECC with the use of un-oiled PVA fibers, the polymers of styrene butadiene rubber (SBR), and ethylene vinyl acetate (EVA) were taken into account to resolve the abovementioned issue. Herein, also in order to enhance the tensile and flexural properties of ECC, the cement was replaced by polymers. Accordingly, a total of 7 mix designs were planned to conduct the proposed tests. The compressive strength, uniaxial tensile strength, and three-point bending tests were performed on the ECC at their 28-day age with consideration of the freeze and thaw cycle. The results of this research illustrated that the use of polymers can enhance the tensile and flexural properties of the ECC with un-oiled PVA fibers. The tensile strain in this study increased by more than 3% after the application of the polymers. Furthermore, the compressive strength increased by more than 47 MPa, and the deflection at the mid-span reached more than 9 mm in the bending test. However, the results showed that the use of polymers was effective on the freeze and thaw cycle and almost preserved the mechanical properties of the ECC. SBR latex has higher compatibility with the ECC in comparison with EVA powder.

Effect of compatibilisers on the cure characteristics and mechanical properties of ternary rubber blend composites

Purpose This paper aims to study the effects of various compatibilisers (maleic anhydride (MAH), methyl methacrylate/butyl acrylate emulsion lattice, and adhesion system (HRH)) on properties of carbon black (CB) filled with natural rubber (NR)/styrene-butadiene rubber (SBR)/ nitrile butadiene rubber (NBR) blends). A series of NR/SBR/NBR blends at a 30/30/40 blend ratio reinforced with 45 phr of CB was prepared using the master-batch method. Design/methodology/approach The tensile properties such as the tensile strength, stress at 100, 200 and 300% elongations, and elongation at break (EB)% were studied. Additionally, the morphological properties of compatibilised and uncompatibilised composites were compared to determine the optimal compatibiliser content. Findings The influence of compatibilisers appeared on all the properties studied. The properties of the blends compatibilised with prepared emulsion are very distinct from those of blends compatibilised with MAH and adhesion systems. Research limitations/implications Interactions among the different components of blends at the interfaces have a high impact on the interfacial properties of the rubber blend. Practical implications Compatibilisers significantly improve the physicomechanical properties of the resulting composites with the loading of investigated compatibilisers because of the uniform dispersion of CB in the rubber matrix. Social implications Using blends in the rubber industry leads to high-efficiency production of low-cost products. Originality/value The rubber blending has a significant positive effect on a wide range of applications such as structural applications, aerospace, military, packaging, tires and biomedical. Hence, improving the compatibility of blends will make new materials suitable for new applications.

Evaluation of Polymer Modified Mortar and Bonding Agent for Structural Repair

Polymer modified mortar is found to be suitable for structural repair and strengthening of damage structural elements. Conventional mortar is not preferred in repair of concrete since it has inferior mechanical property and durability performance. Polymer based mortar is an alternative to conventional mortar with enhanced mechanical properties. However, there are limited specifications and guidelines available for specifying PMM mixes for structural repair work. The research work aims to evaluate the mechanical performance of polymer based mortar with varying concentration of styrene butadiene rubber latex at laboratory scale. Another aspect in repair of corrosion damage structures is the bond between the substrate concrete and repair mortar. In order to study the effectiveness of bonding agents, the performance evaluation of bonding agents has been evaluated using slant shear test and pull-off test as per ASTM C 882 and EN 1542 respectively. Findings of study indicates that at 8-10 percent concentration of dry polymer solid by cement mass in polymer based mortar is the optimum dosage. Styrene-butadiene rubber based polymer mortar showed improvement in flow in comparison to normal mortar however, mixes with crushed sand shows decrease in flow which is due to presence of more fines. Slant shear and pull-off test method shows epoxy bonding agent give better bond strength as compared to SBR latex.

Setting Relationships between Structure and Devulcanization of Ground Tire Rubber and Their Effect on Self-Healing Elastomers

The use of devulcanized tire powder as an effective reinforcement in self-healing styrene-butadiene rubber (SBR) compounds has been investigated for the first time in this work. For this purpose, the evolution of the microstructure of the rubber from end-of-life tires (ELTs) was studied during granulation, grinding and devulcanization through an exhaustive characterization work in order to relate the final microstructure with the mechanical response of the repaired systems. Different morphologies (particle size distribution and specific surface area) obtained by cryogenic and water jet grinding processes, as well as different devulcanization techniques (thermo-mechanical, microwave, and thermo-chemical), were analyzed. The results demonstrated the key influence of the morphology of the ground tire rubber (GTR) on the obtained devulcanized products (dGTR). The predictions of the Horikx curves regarding the selectivity of the applied devulcanization processes were validated, thereby; a model of the microstructure of these materials was defined. This model made it possible to relate the morphology of GTR and dGTR with their activity as reinforcement in self-healing formulations. In this sense, higher specific surface area and percentage of free surface polymeric chains resulted in better mechanical performance and more effective healing. Such a strategy enabled an overall healing efficiency of more than 80% in terms of a real mechanical recovery (tensile strength and elongation at break), when adding 30 phr of dGTR. These results open a great opportunity to find the desired balance between the mechanical properties before and after self-repair, thus providing a high technological valorization to waste tires.