Sultan Qaboos University

About: Sultan Qaboos University is a education organization based out in Muscat, Oman. It is known for research contribution in the topics: Population & Medicine. The organization has 7767 authors who have published 14605 publications receiving 241390 citations. The organization is also known as: SQU.

Cement Stabilization of Reclaimed Asphalt Pavement Aggregate for Road Bases and Subbases

Abstract: Pavement rehabilitation and reconstruction generates large quantities of reclaimed asphalt pavement (RAP) aggregate, and recycling into new asphalt paving mixtures is the predominant application. RAP acceptance in road bases and subbases has been limited because of the lack of laboratory and field performance data. In the Sultanate of Oman, recycling of pavement materials is not practiced. A previous study conducted at Sultan Qaboos Univ. indicated that RAP-virgin aggregate mixtures could be utilized in the subbase layer rather than in the base course. This paper presents the results of a laboratory evaluation of cement-stabilized RAP and RAP-virgin aggregate blends as base materials. Compaction and unconfined compressive strength tests were conducted on the following RAP/virgin aggregate mixtures: 100/0, 90/10, 80/20, 70/30, and 0/100%. Samples were prepared using 0, 3, 5, and 7% Type I portland cement and were cured for 3, 7, and 28 days in plastic bags at room temperature. A pavement design analysis of using various cement stabilized RAP-virgin aggregate mixtures as base materials was also undertaken. Results indicate that the optimum moisture content, maximum dry density, and strength of RAP will generally increase with the addition of virgin aggregate and cement. Longer curing periods will yield higher strength results. The ability of RAP aggregate to function as a structural component of the pavement is more pronounced when it is stabilized with cement rather than when blending with only virgin aggregate. A 100% RAP aggregate should not be recommended for use as a base material unless stabilized with cement. Cement stabilized RAP-virgin aggregate mixtures seem to be a viable alternative to dense-graded aggregate used in road base construction.

Effect of water on the thermo-physical properties of Reline: An experimental and molecular simulation based approach.

Abstract: Increasing applications of ionic liquids and their analogues, namely Deep Eutectic Solvents (DESs), requires further investigation into the effect of moisture content on the physico-chemical characteristics of these fluids. Although it is common practice to synthesize these fluids in a moisture-controlled environment, as moisture is generally considered to have an impact on their properties, there are no systematic studies on this. We herein examine the effects of water on Reline, a Type-III DES composed of urea and choline chloride. Experiments were performed to obtain the physical properties of aqueous Reline solution. We observed moderate changes in density, speed of sound, refractive index, and pH with increasing water fraction; however, the change in viscosity and conductivity was strong and exponential. In addition, molecular dynamics simulations were performed to analyze the intermolecular interactions of Reline and aqueous Reline solutions. The simulations primarily present the significance of urea–anion interaction to explain the low melting point of the DES. In the presence of water, the anion is preferentially hydrated as compared to urea or the cation. More interestingly, simulations help to classify the effects of water into different regimes. At low water fractions (<5%) the urea–urea interactions are enhanced, as is revealed through the hydrogen bond analysis. Beyond 25% water fractions, the components of Reline are individually hydrated and have high diffusivity, which is further reflected in the change in transport properties. The results presented herein provide valuable information on aqueous Reline solutions both in terms of experimental data and molecular insights, which in turn, we believe, might assist in developing further applications of Reline and other related DESs.

Mini-review: Inhibition of biofouling by marine microorganisms.

Abstract: Any natural or artificial substratum exposed to seawater is quickly fouled by marine microorganisms and later by macrofouling species. Microfouling organisms on the surface of a substratum form heterogenic biofilms, which are composed of multiple species of heterotrophic bacteria, cyanobacteria, diatoms, protozoa and fungi. Biofilms on artificial structures create serious problems for industries worldwide, with effects including an increase in drag force and metal corrosion as well as a reduction in heat transfer efficiency. Additionally, microorganisms produce chemical compounds that may induce or inhibit settlement and growth of other fouling organisms. Since the last review by the first author on inhibition of biofouling by marine microbes in 2006, significant progress has been made in the field. Several antimicrobial, antialgal and antilarval compounds have been isolated from heterotrophic marine bacteria, cyanobacteria and fungi. Some of these compounds have multiple bioactivities. Microorganisms are...