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The present work analyzes the effect of various factors on the hydration of pentasodium triphosphate. The experimental method
is based on application of the hydration test. Technical-quality products with different proportions of phase I and phase
II have been used. The variables studied are phase I/phase II ratio, initial temperature, particle size, stirring rate and
composition of the slurry (presence of hexahydrate crystals and water hardness). The results have been discussed according
to a kinetics model that includes a series of stages of a physical nature (dissolution of anhydrous salt and the crystallization
of the hexahydrate), as well as of a chemical nature (solvation of the ions in solution). Crystallization of the hexahydrate
may be the controlling stage in the process. 相似文献
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Polygonella myriophylla is a perennial shrub endemic to the Florida scrub. Striking bare zones surround maturePolygonella stands. Quantitative measurements of root distribution show that fewPolygonella roots extend into the bare zones, supporting the hypothesis that the bare zones result from chemical interference byPolygonella with the growth of other species. Bioassays of soils collected biweekly for one year from beneathPolygonella, the bare zone, and adjacent grassed areas confirm that the germination and growth of grasses is reduced inPolygonella soil and soil from the surrounding bare zone. Compared to adjacent grassed area soil, the average germination of bahiagrass (Paspalum notatum) was 71% inPolygonella soil and 81% in bare zone soil, and average shoot dry weight was 48% inPolygonella soil and 81% in bare zone soil. Seasonal variation in the inhibition of grass germination and growth was not pronounced. 相似文献
88.
A partex surface was modified by a UV‐curing system with epoxy acrylate (EB‐600). A set of formulations was prepared with oligomer and the trifunctional monomer trimethylol propane triacrylate in different combinations of percentages (1–5%) of sand to study the role of sand in various physical properties of UV‐cured thin films, as well as partex surfaces. Increased pendulum hardness (PH), gloss, adhesion, and abrasion values were obtained by the addition of sand into the partex surfaces. The best results were obtained with the formulation containing 3% sand. An enhanced PH and a decreased percentage of gel content of the UV‐cured film was observed with an increase of the sand concentration. A simulated weathering test was performed with partex surfaces cured by a formulation containing 3% sand in the base coat. The losses of the physical properties were found to be lower over the surface treated with the formulation containing sand. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2385–2392, 2002 相似文献
89.
为提高混凝土的质量,配比很重要,其中沙子精确计量是关键因素之一。提出并设计了超声波系统测量沙子料位;为保证测量精度,采取自动增益控制电路和温度补偿。经实验证明:该方法简单、可行,为沙子质量的检测提供了一种新的参考方法。 相似文献
90.
High-strength concrete with different fine aggregate 总被引:3,自引:0,他引:3
High-strength concrete (HSC) has undergone many developments based on the studies of influence of cement type, type and proportions of mineral admixtures, type of superplasticizer and the mineralogical composition of coarse aggregates. Most studies were carried out using natural sand with rounded and smooth grains. In practice, crushed sands from various sources are frequently used in concrete. In this paper, two aspects of the effect of crushed sands on HSCs are presented. First, the performance of crushed sands in relation to natural sand using a low water/cement (w/c) ratio and fixed coarse aggregate and cement content is analyzed. Results show that concrete with crushed sand requires an increase of superplasticizer to obtain the same slump. It also presents a higher strength than the corresponding natural sand concrete at all test ages, while its elastic modulus is lower at 28 days and is the same after that. Studies on the development of hydration and mortar phase of concrete show that the increase of strength can be attributed to the improvement of paste-fine aggregate transition zone. Second, the influence of the mineralogical source of the crushed sands was studied using three different types of crushed sands (granite, limestone and dolomite) with similar grading. Two mixtures containing 450 and 485 kg/m3 cement and low w/c ratio are analyzed. Results show the adverse effects of shape and texture on workability of concrete, but the compressive strength of concrete is improved. Granite crushed sand appears as the most advantageous sand for this purpose. 相似文献