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Precast concrete is a construction product produced by casting concrete in a reusable mold or "form" which is then cured in a controlled environment, transported to the construction site and maneuvered into place; examples include precast beams, and wall panels, floors, roofs, and piles.
Concrete and asphalt have relatively weak tensile strength, and typically form random cracks as they age, shrink, and are exposed to environmental stresses (including stresses of thermal expansion and contraction). Control joints attempt to attenuate cracking by designating lines for stress relief. They are cut into pavement at regular intervals.
Concrete floor of a parking garage being placed Pouring and smoothing out concrete at Palisades Park in Washington, DC. Workability is the ability of a fresh (plastic) concrete mix to fill the form/mold properly with the desired work (pouring, pumping, spreading, tamping, vibration) and without reducing the concrete's quality.
A simple visualization of the forming process Vacuum forming machine to produce inner liner/food liner of refrigerator. Vacuum forming is a simplified version of thermoforming, where a sheet of plastic in various forms of High Impact Polystyrene Sheet (HIPS) for low impact products, or ABS for bathroom shower trays, and HDPE for exterior vehicle parts, plus various other types of vacuum ...
After the mold is rotated and all the surfaces are sufficiently coated with the melt-flow, the rotation stops and the melt-flow is allowed to pool at the bottom of the mold cavity. [20] Wall thickness is important for corner radii as well. Large outside radii are preferable to small radii. Large inside radii are also preferable to small inside ...
This allows the entire mold to be made from green sand and from removable patterns. The disadvantage of this is more mold-making operations are required, but it is usually advantageous when the quantities are low. However, if large quantities of casting are required, it is usually more cost effective to simply use a core. [6]
Compression molding is a method of molding in which the molding material, generally preheated, is first placed in an open, heated mold cavity. The mold is closed with a top force or plug member, pressure is applied to force the material into contact with all mold areas, while heat and pressure are maintained until the molding material has cured; this process is known as compression molding ...
Gypsum concrete is lightweight and fire-resistant. A 1.5-inch slab of gypsum concrete weighs 13 pounds per square foot versus 18 pounds per square foot for regular concrete. [10] Even though gypsum concrete weighs less, it still has the same compressive strength as regular concrete, based on its application as underlayment or top coat flooring ...