جستجو در تالارهای گفتگو

EVALUATION OF COAL WASTE ASH AND RICE HUSK ASH ON PROPERTIES OF PERVIOUS CONCRETE PAVEMENT G. Shafabakhsh and S. Ahmadi Abstract The use of pervious concrete has been significantly considered in recent years. This consideration is due to the properties of pervious concrete in relating to the environmental sustainability that is utilized in the effective management of the runoff from rainfall. Coal extraction and rice husk obtained from milling, produces wastes that have no application and followed by environmental pollution. The purpose of the current research, is to evaluate of the effects of coal waste ash (CWA) and rice husk ash (RHA) and to compare between the mechanical properties of pervious concrete pavement. Therefore, both of these wastes were burned and after that XRF testing it was observed that they both achieve Pozzolanic properties. In order to strengthen pozzolanic cement paste has been used CWA and RHA as a cement replacement in concrete mixtures. The results indicated that the addition of RHA and CWA improved the mechanical properties of pervious concrete, however the optimum percentage is dramatically varying. Among these, the effectiveness of CWA is more significant compared to RHA. By increasing the amount of CWA and RHA to the optimum level, the permeability of the pervious concrete will decrease simultaneously. Meanwhile, after the optimum level, it will be reversed. Keywords Pervious Concrete Pavement, Mechanical Properties, Rice Husk Ash, Coal Waste Ash چکیده استفاده از بتن متخلخل به طور قابل توجهي در چند سال اخير مورد توجه قرار گرفته است. اين توجه به دليل ويژگي هاي بتن متخلخل در رابطه با محيط زيست پايدار در مورد مديريت موثر رواناب ناشي از بارندگي مورد توجه مي باشد. استخراج زغال سنگ و پوسته برنج بدست آمده از شالیکوبی، پسماندهایی را تولید می کند که هیچ کاربردی نداشته و آلودگی محیط زیست را در پی دارد. هدف از این پژوهش بررسی اثر ضایعات زغال سنگ سوخته و خاکستر پوسته برنج و مقایسه بین این دو بر خصوصیات مکانیکی روسازی بتنی متخلخل می باشد. بنابراین در این مطالعه هر دوی این مواد پسماند سوزانده شده و بعد از انجام آزمایشاتXRF مشخص گردیدکه هر دو این مواد خاصیت پوزولانی پیدا می کنند. در مطالعه حاضر به منظور تقویت خمیر سیمان از پودر ضایعاتی زغال سنگ سوخته و خاکستر پوسته برنج به عنوان جایگزین بخشی از سیمان در ترکیبات بتن استفاده شده است. نتایج نشان می­دهد اضافه شدن پودر ضایعاتی زغال سنگ سوخته و خاکستر پوسته برنج سبب بهبود خصوصیات مکانیکی بتن متخلخل می شوند این در حالی است که محدوده درصد بهینه آنها متغیر می­باشد. در این بین اثر پودر ضایعاتی زغال سنگ سوخته بسیار چشمگیرتر از خاکستر پوسته برنج بوده است و از طرف دیگر با افزایش مقدار پودر ضایعاتی زغال سنگ سوخته وخاکستر پوسته برنج تا مقدار بهینه نفوذپذیری بتن متخلخل کاهش و در ادامه افزایش می یابد. منبع دانلود 29-2-8.pdf

The Influence of Pet Fibers on the Properties of Fresh and Hardened Concrete N Shamskia There is a worldwide interest in using fibers of different types in concrete mixtures. In this regard, as the use of PET fibers has gradually increased during the last decade, this study aims to investigate the effects of PET fibers on the mechanical properties of hardened concrete and the workability of fresh concrete. To this end, different contents of PET fibers (PC= %0, %0.5, %1 and %1.5) are added to a concrete mixture and the workability of fresh concrete samples are measured by the slump tests. Furthermore, the load-displacement behavior of the concrete samples is investigated in flexural and compression samples. Results of this study reveal that PET fibers can noticeably change the energy absorption of concrete samples, especially in flexural specimens. منبع دانلود JSEG191348691400.pdf

Development of Fiber Reinforced SCM for Sustainable Construction Iman Mehdipour 1 ; Nicolas Ali Libre2 ; Mohammad Shekarchia1 The sustainability of the built environment is increasingly coming to the forefront of infrastructure design and maintenance decisions. To address this, development of a new class of more sustainable cement-based materials is needed. Fiber reinforced self-consolidating mortar (FRSCM) was developed by optimizing the micromechanical parameters, which control composite properties in the hardened state, and the processing parameters, which control the rheological properties in the fresh state. The addition of fibers may take advantage of its high performance in the fresh state to achieve a more uniform dispersion of fibers, which can help to mitigate the shrinkage of the self-consolidating composite. In other words, fibers can have rheological and mechanical synergistic effects and that optimized fiber combinations can better increase mechanical performance while maintaining adequate flow properties for fiber reinforced self-consolidating mortar. In this study, effects of aspect ratio (l/d) and volume fraction (Vf) of polypropylene (PP) fiber on the free shrinkage and mechanical properties of FRSCM were investigated. Besides, the rheological properties of fiber reinforced SCMs are investigated by mini-slump and mini V-funnel tests. Nine mortar mixtures are prepared containing 0 to 0.7 percent of 6 and 12 mm length polypropylene fibers. The shrinkages of hardened mortar were measured since removing the molds and the measurements were continued up to six months. The results show that, the optimum volume fraction of polypropylene fiber content in SCMs to achieve appropriate rheological and mechanical properties is about 0.3% of the mixture volume. On the other hand, increasing the volume fraction and aspect ratio of PP fibers to about 0.7% causes the mechanical properties to drop considerably. This could be due to balling of fibers or fibers coagulation in the mixtures which decreases the mechanical properties. منبع دانلود JSEG41313868600.pdf