There has been no established chemical bonding between custom tray resin and the elastomeric impression materials without the use of manufacturer's recommended specific tray adhesive. The present study was aimed to compare the bond strength of the manufacturer recommended tray adhesives with the universal tray adhesives using the medium body consistency vinyl polysiloxane (VPS) material and custom tray made of autopolymerising resin and visible light cure (VLC) resin. A total 90 cubicle specimens of autopolymerising resin and 90 specimens of VLC resin were tested for its tensile bond strength. Effectiveness of universal tray adhesive was compared with manufactured tray adhesive. Each of these specimens was then subjected to tensile load in hounsefield universal testing machine at a cross head speed of 5 mm/min and the results were compared and evaluated using one way analysis of variance and post hoc Tuckey's test. Analysis of bond strength revealed that the universal tray adhesive showed better strength and was statiscally significant when compared to the manufacture supplied tray adhesive. Comparison between both the groups, VLC resin showed better bond strength as compared to autopolymerizing resin. Universal tray adhesive had better tensile bond strength than the manufacturers recommended tray adhesive with the medium body viscosity VPS impression material for both autopolymerising and VLC tray resin.
Concrete is the most widely used composite construction material. Fine aggregate plays a very important role for imparting better properties to concrete in its fresh and hardened state. Generally, river sand was used as fine aggregate for construction. Due to the continuous mining of sand from riverbed led to the depletion of river sand and it became a scarce material. Also, sand mining from river bed caused a lot of environmental issues. As a substitute to river sand, Robo sand has been used. In this present experimental study a comparative study has been carried out to check the usability of Robo sand in place of natural sand. This study involves determination of some major properties of concrete like compressive strength, split tensile strength, flexural tensile strength and durability in acidic medium made of both the sands. Based on proposed studies, quality of Robo sand is equivalent to natural sand in many respects, such as cleanliness, grading, strength, angularity, specific gravity. Conclusion have been arrived that Robo sand produced from VSI (vertical shaft impact or) is a suitable and viable substitute to river sand and could be effectively used in making concrete which provides adequate strength and durability for the concrete. In the design of concrete structures, concrete is taken into account by taking its compressive strength value. The compressive strength of the concrete made of Robo sand is observed to be very nearer to the strength of the concrete made of natural sand in the present investigation, there by 100% replacement is reasonable.
Fly Ash (FA) and Ground Blast Furnace Slag (GBS) are by-products obtained from the burning of coal in the thermal power plants and blast-furnace used to produce iron respectively. With a view to preserve natural materials like river sand and high energy consuming cement efforts are made to explore the possibility of replacing them with alternate materials including the industrial solid waste materials in the production mortar and concrete. It is in this context the setting time of FA and the workability of mortar are examined with these replacements. In the present investigation, 25% and 50% of Cement (C) is replaced by FA; and 25%, 50%, 75% and 100% of Sand (S) by GBS. Normal consistency and setting time increased with increasing replacement of cement with fly ash. However, the addition of 2% Calcium Chloride reduced the setting time of all pastes. Also, the results indicated that cement with upto 50% of FA can be considered without seriously jeopardizing the setting time. The workability test on 1:3 mortar on all combinations were performed to get a flow value of 110 + 5 as per IS 2250-1981. To enhance the workability and consequently increase their strength 2% of super plasticizer has been incorporated. The water cement ratio increased with increase in replacement of sand by GBS. The replacement by FA upto 50% did not reduce the water cement ratio of normal cement mortar. Also, workability tests on mortar samples have shown that, GBS can be used up to 50% of sand.
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