Sunlight Photocatalytic Performance of ZnO Nanoparticles Synthesized by Green Chemistry Using Different Botanical Extracts and Zinc Acetate as a Precursor

In this work, the assessment of Azadirachta indica, Tagetes erecta, Chrysanthemum morifolium, and Lentinula edodes extracts as catalysts for the green synthesis of zinc oxide nanoparticles (ZnO NPs) was performed. The photocatalytic properties of ZnO NPs were investigated by the photodegradation of methylene blue (MB) dye under sunlight irradiation. UV-visible (UV-Vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Thermogravimetric (TGA), and Brunauer-Emmett-Teller analysis (BET) were used for the characterization of samples. The XRD results indicate that all synthesized nanoparticles have a hexagonal wurtzite crystalline structure, which was confirmed by TEM. Further, TEM analysis proved the formation of spherical and hemispherical nanoparticles of ZnO with a size in the range of 14–32 nm, which were found in aggregate shape; such a size was well below the size of the particles synthesized with no extract (~43 nm). ZnO NPs produced with Tagetes erecta and Lentinula edodes showed the best photocatalytic activity, matching with the maximum adsorbed MB molecules (45.41 and 58.73%, respectively). MB was completely degraded in 45 min using Tagetes erecta and 120 min using Lentinula edodes when subjected to solar irradiation.

Shape Characterizing of Aggregates Produced through Different Crushing Techniques

The aggregate shape properties produced from the different crushing techniques influence the performance properties of the asphalt mixtures. The objective of this study was to classify the aggregates into spherical, flat, elongated and flat, and elongated shapes, collected from impact crusher and jaw crusher of two sources, and to calculate the shape parameters, such as aspect ratio, shape factor, form factor, sphericity, roundness, and angularity index. In addition, this study also investigated the effects of this classification on the Marshall stability and volumetric properties of asphalt mixtures prepared from the respective shape of aggregates. The results showed that the aggregate of different fractions (passing 37.5 mm and retained on 4.75 mm) produced from the jaw crusher of Margalla quarry showed better shape parameters. The spherical aggregates collected from all crushers showed 20–30% higher Marshall stability of the blends by improving the mechanical and volumetric properties of the asphalt mixtures.

Analytical Solution for Chloride Diffusivity of Concrete with Aggregate Shape Effect

In view of the key role of chloride diffusivity in evaluating concrete durability, it is very important to determine this parameter accurately by an effective approach. This paper establishes an analytical solution for chloride diffusivity of concrete that can consider the aggregate shape. In this approach, the aggregate shape is simulated as an ellipse and the equivalent model is applied to calculate the chloride diffusivity of equivalent aggregate composed of interface transition zone (ITZ) and aggregate. With resort to this model, at the meso scale, the concrete can be reduced from the original three-phase composition to the two-phase one (i.e., equivalent aggregates and cement paste). Based on the mesostructure of concrete that consisted of randomly dispersed equivalent elliptical aggregates and cement paste, the generalized Maxwell’s approach is formed to determine the chloride diffusivity of concrete. The corresponding chloride diffusion test is conducted and the thickness of ITZ is reasonably determined as 0.04 mm by SEM test. By comparing with the experimental data, the accuracy of the analytical solution is confirmed. Finally, the impact of aggregate shape on chloride diffusivity is discussed. The analytical results show that the chloride diffusivity has a reduction with the increase of aggregate content or decrease of aspect ratio.

Laboratory Evaluation of Aggregate Friction and Texture Properties

Aggregate shape, texture, and angularity are important physical properties for the development of high-quality adhesive systems with asphalt binder, and a good quality aggregate skeleton in asphalt and concrete mixtures. These properties are commonly measured using systems that employ images of aggregate samples taken with a digital camera. In practice, macro-texture measurements are commonly conducted nondestructively at highway speed using high-frequency lasers. There is a need to investigate the application of these optical sensors for measuring aggregate texture in the laboratory. Researchers used a laser-based scanning system to test aggregates from five sources before and after Micro-Deval abrasion. The aggregate specimens were embedded in a ring-shaped polyester material and tested with the aggregate ring texturing system (ARTS) along with the dynamic friction tester (DFT) to characterize micro-texture and frictional properties. Researchers analyzed the laboratory test data to evaluate the relationship between DFT friction at 60 km/h (DFT60) and the micro mean profile depth obtained with the ARTS. This analysis showed that the igneous and gravel aggregates had better micro-texture and frictional characteristics compared with the dolomite and limestone aggregates. The results from this implementation project showed the potential for using the ARTS to improve the Texas Department of Transportation’s existing surface aggregate classification system. Further testing is needed to characterize aggregates from other sources and compile a more comprehensive and representative database with which to establish meaningful aggregate classification criteria that include surrogate statistics for expected field performance.

Effects of Coarse Aggregate Shape and Texture on Engineering Properties of Roller Compacted Concrete Prepared for High Traffic Routes

Use of roller-compacted concrete in pavement construction is increasing. Roller compacted concrete is a zero-slump, highly compacted concrete that is placed by equipment similar to that used in asphalt pavement construction. This investigation was conducted to collect the state-of-the-art information on effects of coarse aggregate size and texture on the strength and workability of roller-compacted concrete (RCC) for pavement construction and maintenance. Concrete specimens containing cubical and rough coarse aggregate, irregular and rough coarse aggregate, angular and rough coarse aggregate, rounded/spherical and smooth coarse aggregate, and flaky/elongated and rough coarse aggregate were prepared at 1:3:3 concrete mix ratio and 0.4 water cement ratio. Laboratory testing of specimens derived from the concrete specimens showed excellent results for cubical and rough coarse aggregate, irregular and rough coarse aggregate, and angular and rough coarse aggregate. Specimens from the rounded/spherical and smooth coarse aggregate, and flaky/elongated and rough coarse aggregate performed poorly in laboratory. The study therefore recommends the use of cubical and rough coarse aggregate, and irregular and rough coarse aggregate in the production of roller-compacted concrete for pavement construction and maintenance.

Reduction of cement content using graded aggregates in concrete production

The aim of this project was to reduce cement content in concrete mixtures by changing the aggregate grading. For this purpose, concrete mixtures were made with aggregates having different shapes, textures, and grading. However, the workability of concrete mix depends on its paste volume, paste composition, and the type of aggregate used. Concrete testing was performed, and concrete properties including slump, compressive strength, and tensile splitting test were tested. The effect of aggregate shape on workability was evaluated by comparing one aggregate combination to another. It was found that the aggregate combination with S/A= 0.4 GR-B-CA+NA-A-FA had optimum workability properties and generally, GR-B-CA+NA-A-FA consistently had the highest workability, as well as the highest paste volume demand. This can be attributed to its poor grading as a result of the gaps in GR-B-CA content. Compared with NA-A-CA + NA-A-FA, it resulted in concrete mixtures with lower paste volume demand.