Effects of Sodium Sulfate Attack on Concrete Incorporated with Drying-Wetting Cycles

It has been widely observed that sulfate attack can damage the durability of concrete. This research investigated the mass loss and damage degree of concrete under sodium sulfate attack incorporated with drying-wetting cycles. The impact factors, including water-binder ratio, solution concentration of sodium sulfate, fly ash content, curing time, and drying-wetting cycle system, were observed to influence the sodium sulfate attack by the mass loss rate and damage degree at regular time intervals. Also, the hydrates of sulfate-attacked samples were analyzed using X-ray diffraction. Results indicated that a high water-binder and high-concentration sodium sulfate solution could accelerate the transportation of sulfate ion inside the concrete and the deterioration degree of concrete. Appropriate fly ash and longer curing time can effectively improve the internal pore structure of concrete to reduce the sulfate corrosion damage. The sulfate ion erosion and deterioration degree of the concrete are synchronously intensified along with the increase of the baking-immersing time ratio. The trend of the predicted life for concrete is basically consistent with the damage evolution result, indicating the feasibility of the Weibull distribution model to predict the service life of concrete under sodium sulfate attack incorporated with drying-wetting cycles

Application of Epoxy-Asphalt Composite in Asphalt Paving Industry: A Review with Emphasis on Physicochemical Properties and Pavement Performances

One of the failure mechanisms associated with asphalt paving layers, especially on steel deck bridges, is large permanent deformation, which adversely affects its long-term performance in service. Thus, epoxy resin was introduced in asphalt paving industry to tackle permanent deformation of asphalt mixtures due to its thermosetting nature. In this review, epoxy resin as a dominant component of the epoxy-asphalt composite system was first considered, followed by a discussion on its curing methods and curing mechanism. Furthermore, the physicochemical property and mechanical performance of epoxy asphalt and epoxy asphalt mixture were thoroughly examined. Crosslink density of epoxy asphalt dictates its viscosity and thus the allowable construction time. Phase separation and dispersion of asphalt particles in the epoxy matrix was observed for epoxy-asphalt composite, and it showed superior elastic behavior and deformation resistance capability when compared with conventional asphalt materials. Furthermore, epoxy asphalt mixture exhibited significantly higher compressive strength, much better rutting resistance, and superior durability and water resistance properties. However, its low-temperature cracking resistance was slightly compromised

Anti-Skid Characteristics of Asphalt Pavement Based on Partial Tire Aquaplane Conditions

This study presented a finite element model of radial tire-asphalt pavement interaction using ABAQUS 6.14 software to investigate the skid resistance properties of asphalt pavement under partial tire aquaplane conditions. Firstly, the pavement profile datum acquired by laser scanning were imported to Finite Element Analysis (FEA) software to conduct the pavement modeling. Secondly, a steady state rolling analysis of a tire on three types of asphalt pavements under drying conditions was carried out. Variation laws of the friction coefficient of the radial tire on different pavements with different pavement textures, tire pressures, and loads on the tire were examined. Subsequently, calculation results of the steady state rolling analysis were transmitted to dynamic explicit analysis, and an aquaplane model of a radial tire on asphalt pavements was built by inputting the flow Euler grids. The tire-pavement adhesive characteristics under partial aquaplane conditions are discussed regarding the aquaplane model. Influences of the thickness of water film, the texture of asphalt pavement, and the rolling speed of the tire on the vertical pavement-tire contact force are analyzed. It is found that the vertical contact force between open graded friction course (OGFC) pavement and tire is the highest, followed by stone mastic asphalt (SMA) pavement and dense graded asphalt concrete (AC) pavement surface. The vertical contact force between tire and pavement will be greatly reduced, even with increasing speed or water film thickness. As tire speed increases from 70 km/h to 130 km/h, the tire-pavement contact force is reduced by about 25%. Moreover, when the thickness of water film increases from 0 (dry condition) to 4 mm and then to 12 mm, the vertical contact force reduced 50% and 15%, respectively, compared with under the dry contact condition. This study provided a key theoretical reference for safe driving on wet pavements

Rheological models for non-newtonian viscosity of modified asphalt binders and mastics

This paper is aimed at providing a comprehensive experimental work on the viscosity behavior of different modified asphalt binders and mastics, as well as exploring mathematical representations of the results in attempts to predict the viscosity and flow behaviors according to Vinogradov-Malkin and Phillips-Deutsch models. The modified asphalt binders were prepared in the unaged and aged states using styrene-butadienestyrene (SBS), ethylene-vinyl acetate (EVA), and crumb rubber (CR); while the hydrated lime (HL) and fly ash (FA) were selected to produce the binder-filler mastics. To widen the study findings, the additives (polymers, rubber, and fillers) were applied at different possible levels of modification. To prepare the aged bituminous materials, the rolling thin-film oven (RTFO) was utilized for the short-term aging, while the pressure aging vessel (PAV) was further used to induce the possible long-term aging of same materials. Binders and binder-filler mastics were tested using a bob and cup geometry. The viscosity behavior was investigated under various effects of testing conditions including ranges of shear rates and temperatures. It was found that the effect of shear rate dominates and therefore the non-Newtonian shear thinning prevails at low temperatures particularly for binders containing high concentrations of additives. Even the base asphalt binder exhibits shear thinning behavior after a certain limit of shear rate. Based on the studied 38 curves, in general, Vinogradov-Malkin and Phillips-Deutsch models were found in a good agreement with the corresponding measurements especially the latter

Nozzle design in a fiber spinning process for a maximal pressure gradient

The thickness of a spinneret is always a geometrical constraint in nozzle design. The geometrical form of a nozzle has a significant effect on the subsequent spinning characteristics. This paper gives an optimal condition for maximal pressure gradient through the nozzle

Pressure distribution on spinning spinnerets

A two-dimensional model is used to study the pressure distribution in a chamber of a spinneret system. Darcy’s law is adopted for determining the inlet and outlet velocities of the flow. The pressure distribution on the spinneret plate is obtained, and the dead zone, where no nozzle exists, can be optimally determined

Optimal spinneret size for improvement of fiber's mechanical property

The effect of spinneret size and place on diameter and tensile property of cellulose acetate fibers is studied, and a criterion for the maximal breaking energy is obtained, and the spinneret distribution can be optimized for each spinning condition

Adhesion evaluation of asphalt-aggregate interface using surface free energy method

The influence of organic additives (Sasobit and RH) and water on the adhesion of the asphalt-aggregate interface was studied according to the surface free energy theory. Two asphalt binders (SK-70 and SK-90), and two aggregate types (limestone and basalt) were used in this study. The sessile drop method was employed to test surface free energy components of asphalt, organic additives and aggregates. The adhesion models of the asphalt-aggregate interface in dry and wet conditions were established, and the adhesion work was calculated subsequently. The energy ratios were built to evaluate the effect of organic additives and water on the adhesiveness of the asphalt-aggregate interface. The results indicate that the addition of organic additives can enhance the adhesion of the asphalt-aggregate interface in dry conditions, because organic additives reduced the surface free energy of asphalt. However, the organic additives have hydrophobic characteristics and are sensitive to water. As a result, the adhesiveness of the asphalt-aggregate interface of the asphalt containing organic additives in wet conditions sharply decreased due to water damage to asphalt and organic additives. Furthermore, the compatibility of asphalt, aggregate with organic additive was noted and discussed

Dendrotoxin-κ suppresses tumor growth induced by human lung adenocarcinoma A549 cells in nude mice

Voltage-gated K+ (Kv) channels have been considered to be a regulator of membrane potential and neuronal excitability. Recently, accumulated evidence has indicated that several Kv channel subtypes contribute to the control of cell proliferation in various types of cells and are worth noting as potential emerging molecular targets of cancer therapy. In the present study, we investigated the effects of the Kv1.1-specific blocker, dendrotoxin-κ (DTX-κ), on tumor formation induced by the human lung adenocarcinoma cell line A549 in a xenograft model. Kv1.1 mRNA and protein was expressed in A549 cells and the blockade of Kv1.1 by DTX-κ, reduced tumor formation in nude mice. Furthermore, treatment with DTX-κ significantly increased protein expression of p21Waf1/Cip1, p27Kip1, and p15INK4B and significantly decreased protein expression of cyclin D3 in tumor tissues compared to the control. These results suggest that DTX-κ has anti-tumor effects in A549 cells through the pathway governing G1-S transition