Phase Transition Behaviors of Hydroxypropyl Methylcellulose Induced By Small Molecular Weak Acids

In this paper, phase change material hydroxypropyl methylcellulose (HPMC) was chosen to investigate the influence of small molecular weak acids on its phase transition temperature. The results showed that all of the chosen small molecular weak acids such as acrylic acid (AA), methacrylic acid (MAA), DL-lactic acid (LA), citric acid (CA) and acetic acid (AAc) can trigger the decrease of phase transition temperature of HPMC at different pH. With the increase of pH, AA, LA, CA and AAc can further lower the phase transition temperature, on the contrary, the phase transition temperature of HPMC increased with MAA. The change range of LCST was largest around pKa compared with other pH values because triggering effect changed gradually from hydrogen bonding effect to salt effect upon the increase of pH. Besides, phase transition temperature can also be reduced by the increase of acid concentration. This is attributed to smaller distance between molecules caused by higher concentration leading to stronger hydrogen bonding effect or salt effect. This paper provided a new perspective to modulate the LCST of phase change material by small molecular weak acids at different pH.

Use of polyethylene terephthalate as an Anti-stripping agent in GLASSPHALT

This study evaluates the use of polyethylene terephthalate (PET) in Glassphalt aimed at increased bonding effect of bitumen, reduced stripping and increased in stability and strength. Control mix were prepared with bitumen content of 5.0, 5.5, 6, 6.5 and 7% to determine the optimum bitumen content (OBC). Optimum glass content (OGC) was obtained from samples prepared with glass content of 5, 10, 15, 20, and 25% replacement by weight of fine aggregates. The OBC and OGC were used prepare samples with PET content of 2, 4, 6, 8, and 10% by weight of the OBC. The optimum PET content had a higher stability value of 5.8kN and higher air void of 3.8% when compared to the control mix. Stripping value tests showed that PET modified glassphalt had 0% stripping after a period of 48 hours. Waste PET of 6.6% in 16% glassphalt is recommended for use as an anti-stripping agent.

Influence of Geocomposite Properties on the Crack Propagation and Interlayer Bonding of Asphalt Pavements

The application of geocomposites as reinforcement in asphalt pavements is a promising solution for the maintenance/rehabilitation of existing pavements and for the construction of new pavements, whose effectiveness strongly depends on the physical and mechanical properties of the geocomposite. This study aims at assessing the influence of four different geocomposites, obtained by combining a reinforcing geosynthetic with a bituminous membrane, on the crack propagation and interlayer bonding of asphalt pavements. First, a laboratory investigation was carried out on double-layered asphalt specimens. The crack propagation resistance under static and dynamic loads was investigated through three-point bending tests (carried out on specimens with and without notch) and reflective cracking tests respectively, whereas the interlayer shear strength was evaluated through Leutner tests. Then, a trial section was constructed along an Italian motorway and a Falling Weight Deflectometer (FWD) testing campaign was carried out. The laboratory investigation highlighted that—as compared to the unreinforced system—the geocomposites increased the crack propagation energy in the layer above the reinforcement from five to ten times, indicating that they can significantly extend the service life of the pavement by delaying bottom-up and reflective cracking. However, they also worsened the interlayer bonding between the asphalt layers (de-bonding effect). The field investigation indicated that all geocomposites decreased the stiffness of the asphalt layers with respect to the unreinforced pavement as a consequence of the de-bonding effect, thus corroborating the laboratory results. Based on the results obtained, it is desirable that the geocomposite possess a high energy dissipation capability and an upper coating ensuring good adhesion between the asphalt layers. The monitoring of the existing trial section in the future will provide useful data on the long-term field performance of reinforced pavements subjected to actual motorway traffic.

Mutual Comparison Studies of Mono and Di Cations in Binary and Ternary Aqueous Electrolytes Solution at 298.15 K

Densities and viscosities of binary and ternary electrolytes solution have been determined experimentally at 298.15 K. The results obtained from density and viscosity measurement have been used to calculate apparent molar volume φv partial molar volume φov at infinite dilution, relative viscosities hrel, A and B coefficients, and free energies of activation of viscous flow of solvent Δ µ10# and solute Δ µ20. The results are discussed in terms of the dehydration effect of the weak ion-ion and strong ion-solvent interactions. The properties of these systems are discussed in terms of the charge, size, and hydrogen bonding effect.

Hydrothermal Aging and Bonding Properties of a New Room Temperature Cured Structural Adhesive in Building Components

his paper firstly explores the hydrothermal aging performance of a new room temperature cured structural adhesive at four different levels of relative humidity through dynamic mechanical analysis (DMA). The results show that the strengthening effect of post-curing was stronger than weakening effect of humidity. Then, the Arrhenius equation was introduced to calculate the ratio of the apparent activation energy of this adhesive at the glass transition temperature before and after hydrothermal aging. The little change of the ratio suggests that the adhesive boasts a strong resistance to hydrothermal aging. In addition, the adhesive was tested on concrete structures at room temperature to observe its repairing effect of concrete cracks. The observations reveal that the compressive strength of the cracked concrete block repaired by the adhesive was as high as 90.5% of that of the intact concrete block. Furthermore, the adhesive was used to bond rebars to concrete under three different constant tensile speeds. The results demonstrate that the bonding effect was better under slow constant loading.