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The addition of an accelerator speeds the setting time and thus cure time starts earlier. [1] This allows concrete to be placed in winter with reduced risk of frost damage. [2] Concrete is damaged if it does not reach a strength of 500 pounds per square inch (3.4 MPa) before freezing. [3]: 19
Visible frost damage develops after an accumulation of micro-cracks as a result of several freeze-thaw cycles. [ 1 ] [ 2 ] Frost damage can be prevented by the use of frost-proof materials, i.e. , a material which has sufficient closed pores, by which the volume increase caused by the freezing of water in capillary pores can be absorbed by the ...
Accelerated curing is any method by which high early age strength is achieved in concrete. These techniques are especially useful in the prefabrication industry, wherein high early age strength enables the removal of the formwork within 24 hours, thereby reducing the cycle time, resulting in cost-saving benefits. [ 1 ]
Self-consolidating concrete or self-compacting concrete (SCC) [1] is a concrete mix which has a low yield stress, high deformability, good segregation resistance (prevents separation of particles in the mix), and moderate viscosity (necessary to ensure uniform suspension of solid particles during transportation, placement (without external compaction), and thereafter until the concrete sets).
Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures to a solid over time. Concrete is the second-most-used substance in the world after water, [1] and is the most widely used building material. [2] Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined. [3]
After sufficient setting and hardening of concrete (after 28 days), the progressive loss of capillary water is also responsible for the "drying shrinkage". It is a continuous and long-term process occurring later during the concrete life when under dry conditions the larger pores of concrete are no longer completely saturated by water.
The tremie concrete placement method uses a vertical or nearly vertical pipe, through which concrete is placed by gravity feed below water level. [4]The lower end of the pipe is kept immersed in fresh concrete so that concrete rising from the bottom displaces the water above it, thus limiting washing out of the cement content of the fresh concrete at the exposed upper surface.
Concrete has a relatively high thermal mass, meaning that it takes a long time to respond to changes in ambient temperature. [9] This is a disadvantage when rooms are heated intermittently and require a quick response, as it takes longer to warm the entire building, including the slab.