SGC Tests for Influence of Material Composition on Compaction Characteristic of Asphalt Mixtures
Compaction characteristic of the surface layer asphalt mixture (13-type gradation mixture) was studied using Superpave gyratory compactor (SGC) simulative compaction tests. Based on analysis of densification curve of gyratory compaction, influence rules of the contents of mineral aggregates of all sizes and asphalt on compaction characteristic of asphalt mixtures were obtained. SGC Tests show that, for the mixture with a bigger content of asphalt, its density increases faster, that there is an optimal amount of fine aggregates for optimal compaction and that an appropriate amount of mineral powder will improve workability of mixtures, but overmuch mineral powder will make mixtures dry and hard. Conclusions based on SGC tests can provide basis for how to adjust material composition for improving compaction performance of asphalt mixtures, and for the designed asphalt mixture, its compaction performance can be predicted through these conclusions, which also contributes to the choice of compaction schemes.
Meso-scale study on compaction characteristics of asphalt mixtures in Superpave gyratory compaction using SmartRock sensors
Abstract Compaction degree is an essential parameter to characterize the construction quality and performance of asphalt pavement. Under the same compaction conditions, asphalt mixtures with different aggregate sizes and gradation may exhibit different compaction characteristics. Accordingly, this paper aims to study the compaction characteristics of asphalt mixture at the meso-scale through particle response of the mixture by using SmartRock sensor. Firstly, a laboratory test scheme of the asphalt mixture is designed and the SmartRock sensors are used to obtain the internal stress of the mixture during compaction. By comparing the particle stress with the height of the specimen, it is inferred that the stress state of the particles can reflect the compactness of the compacted material, and the change rate of compaction degree in logarithmic coordinates is proposed to characterize the compaction performance of the asphalt mixture. Furthermore, the quantitative analysis is comprehensively conducted related to the different nominal maximum aggregate size (NMAS), locations and gradation types. The results reveal that the asphalt mixture with larger NMAS has a better compactibility in terms of forming a stable skeleton structure, and the mixture in the middle of specimen can be compacted more easily than that in the top and bottom area of specimen. It can be aslo found that the gradation type affects the compaction performance through the probability of coarse aggregates interlocking with each other. The open-graded mixture (i.e, PAC-16) is relatively faster to achieve the target compaction degree than gap-graded and dense-graded mixtures (i.e, SMA-16 and AC-16, respectively). Although the asphalt mixture with larger NMAS and coarser gradation can reach a certain compaction degree with a rapid speed, it doesn't mean the mixture can achieve higher compaction degree finally under the action of subsequent compaction work. The test result shows that the asphalt mixture with coarser aggreages is relatively difficult to compact with lower final compactness. The experimental research sheds substantial light on the internal relationships between the response of the particles and compaction charateristics of asphalt mixture at meso-scale.
Improved Skin Penetration Using In Situ Nanoparticulate Diclofenac Diethylamine in Hydrogel Systems: In Vitro and In Vivo Studies
Delivering diclofenac diethylamine transdermally by means of a hydrogel is an approach to reduce or avoid systemic toxicity of the drug while providing local action for a prolonged period. In the present investigation, a process was developed to produce nanosize particles (about 10 nm) of diclofenac diethylamine in situ during the development of hydrogel, using simple mixing technique. Hydrogel was developed with polyvinyl alcohol (PVA) (5.8% w/w) and carbopol 71G (1.5% w/w). The formulations were evaluated on the basis of field emission scanning electron microscopy, texture analysis, and the assessment of various physiochemical properties. Viscosity (163–165 cps for hydrogel containing microsize drug particles and 171–173 cps for hydrogel containing nanosize drug particles, respectively) and swelling index (varied between 0.62 and 0.68) data favor the hydrogels for satisfactory topical applications. The measured hardness of the different hydrogels was uniform indicating a uniform spreadability. Data of in vitro skin (cadaver) permeation for 10 h showed that the enhancement ratios of the flux of the formulation containing nanosize drug (without the permeation enhancer) were 9.72 and 1.30 compared to the formulation containing microsized drug and the marketed formulations, respectively. In vivo plasma level of the drug increased predominantly for the hydrogel containing nanosize drug-clusters. The study depicts a simple technique for preparing hydrogel containing nanosize diclofenac diethylamine particles in situ, which can be commercially viable. The study also shows the advantage of the experimental transdermal hydrogel with nanosize drug particles over the hydrogel with microsize drug particles.