Analytical Investigation for Determining Ressilient Modulus for Interface Layer of Aggregates
Quality road aggregates have become rare and costly in many places in India due to massive construction activities required for the development of new infrastructure facilities. The pavement industry seeks ways of improving lower quality materials that are readily available for use in roadway construction. Cement treatment has become an accepted method for increasing the strength and durability of soils and marginal aggregates. However, cement-stabilized bases can also be the source of shrinkage cracks in the stabilized base layer, which can reflect through the asphalt surface. Introducing “Interface Layer of Aggregates (ILA)” between stabilized base and bituminous concrete (BC) layer appears to be very favorable. The present paper presents the determination of resilient modulus of ILA using FPAVE software. Figures have been developed to determine resilient modulus, varying the CBR value, the thickness of cement treated base and the thickness of interface layer of aggregates which is useful to determine the pavement thickness for cement treated base.
Development and Performance of Interlayer Stress-Absorbing Composite in Asphalt Concrete Overlays
An interlayer stress-absorbing composite (ISAC) was developed and evaluated for the purpose of effectively alleviating or mitigating the problem of reflection cracking in an asphalt concrete (AC) overlay. ISAC materials and performance properties were carefully selected through comprehensive theoretical studies and laboratory evaluation programs. The ISAC system consists of a low-stiffness geotextile as the bottom layer, a viscoelastic membrane layer as the core, and a very high stiffness geotextile for the upper layer. In order to evaluate the effectiveness of the ISAC layer to control reflective cracking, a laboratory pavement section with an AC overlay placed on a jointed portland cement concrete slab was constructed and tested in an environmental chamber. A mechanical device was used to simulate thermal strain in the slab, and the joint was opened and closed at an extremely slow rate. The testing was conducted at −1.1°C, and strain in the overlay was monitored using a sensitive linear variable differential transducer device. The force required to pull and push the slab was monitored using a load cell placed between the slab and a hydraulic ram. Performance of ISAC was evaluated by comparing the cycles to failure of an ISAC-treated overlay with the performance of a control section without ISAC and of test sections containing two commercially available products. The base isolation properties of the ISAC system were demonstrated in the laboratory evaluation studies, which indicated that the ISAC system vastly outperformed the control section and the sections with the two commercial products tested. Several years of field performance testing have show that the ISAC system is highly effective for mitigating reflective cracking in AC overlays used on both airport and highway pavement systems.
Scaffolds Containing Spirulina sp. LEB 18 Biomass: Development, Characterization and Evaluation of In Vitro Biodegradation.
Polymer nanofibers are nanomaterials that can be used as scaffolds in tissue engineering. The objective of this study was to develop, characterize and evaluate the in vitro degradation of a biomaterial consisting of nanofibers produced from biodegradable and biocompatible polymers with potential applications as a scaffold for tissue regeneration and containing Spirulina sp. LEB 18 biomass as the bioactive compound. The polymers used were poly(hydroxybutyrate-co-hydroxyvalerate) and polycaprolactone. The polymeric solutions exhibited sufficiently high viscosity to produce uniform nanofibers with diameters between 335 and 617 nm. The applied conditions were as follows: a voltage of 25 kV, a distance from the capillary to the collector of 120 mm, a capillary diameter of 0.80 mm, and 12% polycaprolactone and a blend of 5% polycaprolactone and 10% poly(hydroxybutyrate-co-hydroxyvalerate). The biomass was incorporated into the nanofibers at a concentration of 3%, and the incorporation was confirmed using confocal microscopy. The nanofibers were characterized using differential scanning calorimetry and thermogravimetric analysis, which showed that the addition of biomass did not alter the thermal properties of the biomaterial. The addition of biomass improved the tensile strength and elongation of the scaffolds compared with those produced with polymers alone. A biodegradation assay showed enzymatic action toward the biomaterial, simulating the behavior of natural tissue. Based on the analysis, it was concluded that the scaffolds that were produced have the potential to be applied in the field of tissue regeneration as biomaterials with pharmacological properties.