Partially Replacing Fly Ash with Limestone Powder in the Paste - Influence and Characterization
Paste filling is an important research direction of coalmine "green mining" which can dispose coalmines solid waste and achieve environmental protection. The mechanical properties such as compressive strength, workability, ulti- mate tension value, shear strength and splitting strength of paste, in which the fly ash was partially replaced by limestone powder, was studied. Adiabatic temperature rise, setting time, shear strength, permeability, frost resistance and dry shrinkage of different substitution rate were investigated and the results were compared with traditional paste. The test re- sults showed that the influence of limestone powder on workability, permeability and frost resistance performance of paste was slight, the setting time of paste were shortened, adiabatic temperature rise and mechanics performance of paste were decreased, dry shrinkage value was increased with limestone powder content increasing.
Use of Man-made Sand with High Content Stone Powder in Concrete
Laboratory tests were carried out on the large size concrete specimen (three-graded coarse aggregate) to investigate the mechanical property and dry shrinkage characteristics of the concrete containing high content stone powder man-made sand. The results demonstrate that the high content stone powder man-made sand added in the concrete is helpful to improve the workability, mechanical and anti-cracking property. It is found that the optimum content of the stone powder is 16%, beyond which the dry shrinkage increases with the content of the stone powder. It is noticed that the characteristics of dry shrinkage is also influenced by the size of the specimens, the size and grading of the aggregate etc. The study suggested that the early curing is important for the concrete which uses the high content stone powder man-made sand as its fine aggregate.
Unidirectional hexagonal rare-earth disilicide nanowires on vicinal Si(100)-2×1
Rare-earth disilicide nanowires grown on vicinal Si(100) with a miscut of 2–2.5° toward the [110] azimuth at 600 °C were studied by scanning tunneling microscopy and compared with those grown on flat Si(001). In contrast to rare-earth disilicide nanowires grown on flat Si(100) surfaces, the nanowires grow unidirectionally along the [01̄1] direction of the vicinal Si(100) surface. Rare-earth disilicide nanowires form bundles composed of single nanowire units on both flat and vicinal surfaces. Yet, on the vicinal surface, the bundle width is comparable to the width of the terrace. The average nanowire length on the vicinal substrate is longer than that on the flat substrate. Scanning tunneling spectroscopy shows that the rare-earth disilicide nanowires have metallic properties.