Concrete retarding admixtures are used to decrease the process of setting. By delaying the initial setting time, the concrete mixture can remain in its fresh mixed condition for a longer period of time before hardening. The use of retarders is advantageous for complicated concrete laying or grouting. A unique architectural surface treatment can be achieved by using retarding admixtures in conjunction with other types of additives.
The two main categories of retarding agents are organic and inorganic. Organic retarders include vine oil, terpenes, lignins, and resins. These materials are effective at low concentrations (less than 2% by weight) and exhibit minimal toxicity. Inorganic retarders include aluminum sulfate, calcium carbonate, and sodium metasilicate. These materials are more effective at higher concentrations (10-20% by weight) and can cause corrosion if not used properly. Retarder selection depends on the required setting time and any restrictions from local building codes.
Retarded concrete must still be placed in strong plastic bags or containers to prevent contamination from the environment. The bags should be removed no later than 24 hours after placement to allow sufficient time for the concrete to cure. If the retarder is an additive, it will need to be re-introduced into the mix during the placement process.
For more information on retarding admixtures, consult an architect or engineer who can help you choose the best type of concrete for your project along with appropriate additives.
A body with uniform retardation is diminishing since retard implies to decline or decrease at a steady pace with regard to time. Retardation is represented by a negative slope and a negative acceleration value. Overall, it's the inverse of acceleration. This line is also slanted towards the time axis. In other words, it has a negative slope.
In physics, uni-directional rotation produces a body with uniform angular velocity. That is, its speed doesn't change when viewed from a fixed point on its surface. For example, a bicycle wheel spins uniformly even though it contains many radii which are not equivalent distances around its circumference. A body in uniform motion will appear to be at rest against a stationary observer unless there are other forces at work. For example, if a ball is rolling down an inclined plane, it will appear to be at rest despite continuing to roll forward.
In astronomy, a body such as planet that appears to be dimming over time due to distance effects is said to have uniform retrogression. The phrase "uniform retrogression" was first used by William Henry Smyth in 1882 while discussing the possibility that the planets might be drifting further away from the Sun relative to Earth. The idea was soon after rejected by astronomers because it was believed that any mass that large would be disrupted by solar wind pressure and collapse under its own weight.
The phenomenon of resistance to motion through a fluid is defined as retarding force. The term also applies to forces that resist the movement of objects through Earth's atmosphere, as in wind or gravity. In physics and engineering, a retarding force is any force that tends to slow down or reverse the motion of an object.
In physics and chemistry, the word "force" is used to describe two different physical phenomena: mechanical force and electromagnetic force. Mechanical force is the push or pull on an object caused by another object. It can be repulsive (for example, when two magnets are pulled together) or attractive (as between the earth and a rocket). Electromagnetic force is the interaction between moving charges that creates a force. This type of force is responsible for the attraction between electrons and nuclei, and between molecules via polar bonds. It can also cause currents to flow in conductors such as wires, which can be used to generate power or act as brakes in motors.
Mechanical force acts over large distances and can act on objects that are far away from each other. For example, when you throw a ball, the ball generates mechanical force on the bat because of its mass. The bat then generates mechanical force on the ball because it is heavier than air.