Mixing, placing and curing

In the production of foundry sand concrete, conventional mixing, placing, and curing are easily referable. 

Concrete Microsiructure. Documents the investigation of variables which control cement hydration and microstructural development during the mixing, placing and curing of concrete. 179 pages. SHRP-C-340, 15... 

The optimization approach to any activity in technology, economics or other fields is aimed at finding methods of determining the best solutions in an objective way. In particular, optimization of composite materials deals with problems of the selection of the values of several variables, which determine their composition and internal structure. Other variables that describe the conditions of mixing, vibration, placing and curing may also be included. 

Blocks made from the cement mixed with seawater cracked and disintegrated. Blocks made from cement mixed with fresh water performed very well, however, even when placed and cured in seawater [9]. While natural cement mortars mixed with seawater have not displayed this same tendency to disintegrate rapidly, these results did guide later concrete work. 

As HPC is relatively new to most ready-mixed concrete plants and finishers that have not worked with the concrete before it is important that all parties involved in a construction project be informed about the production, placing, finishing and curing of HPC. The following critical aspects of HPC use in the field are presented as a reference to the practitioner. They cover three main topics ... 

There are two other mixing systems that should be considered as having progressed beyond the development stage and will likely be instituted as production systems for the manufacture of composite propellant. The first is a proprietary system developed by Rocketdyne and referred to as the Quickmix system (10). Here the solid ingredients, such as oxidizer and fuel additives, are placed in a dilute slurry with low viscosity, volatile, and immiscible carrier. These slurries, a minimum of two, and the fluid polymer and curing agent streams are metered to a continuous fluid mixer. The effluent from the mixer then flows to a separator and... 

Casting is the simplest processing technique the mould is filled with a liquid, which, at ambient temperature, has such a low viscosity that it is able to fill the mould under its own weight. After filling, a chemical reaction should take place to form the material. With thermosets this is a reaction between the components which, prior to filling, have been mixed together, and which react into a three-dimensional network. Sometimes a catalyst is added to initiate or accelerate this reaction. Dependent on the combination chosen, curing takes place at room temperature or at an elevated temperature. 

Small (much less than stoichiometric) amounts of diamines sometimes are added to the hydroxyl portion of the adhesive to provide a rapid but limited molecular weight increase as soon as the components are mixed.61,62 In this way a two-package adhesive can be made that will flow easily before mixing but will not readily flow after mixing. Such adhesives can be applied to vertical surfaces or overhead, and will remain in place until the bonds are closed and cured. 

This is done by loading cylinders 6" in diameter and 12" high in compression perpendicular to the axis of the cylinder. Cylinder molds must be filled with the same mix and at the same time that the concrete is placed, and should be placed at once in the same vertical position, in a place where they will be undisturbed until the concrete is hard and the cure sufficiently advanced to accept traffic. If it becomes necessary to move them, do so very gently and carefully, but on no account disturb them for the first 24 hours. 

Mat-like paving materials for pedestrian areas are produced by mixing the compositions with the formulations as given in Table 1, placing them in molds, pressing them with hot rollers and curing at ambient temperature. 

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