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The ultimate strength of concrete is influenced by the water-cementitious ratio (w/cm), the design constituents, and the mixing, placement and curing methods employed.All things being equal, concrete with a lower water-cement (cementitious) ratio makes a stronger concrete than that with a higher ratio. [2]
High-strength concrete has a compressive strength greater than 40 MPa (6000 psi). In the UK, BS EN 206-1 [3] defines High strength concrete as concrete with a compressive strength class higher than C50/60. High-strength concrete is made by lowering the water-cement (W/C) ratio to 0.35 or lower.
Cubic or cylindrical samples of concrete are tested under a compression testing machine to measure this value. Test requirements vary by country based on their differing design codes. Use of a Compressometer is common. As per Indian codes, compressive strength of concrete is defined as: Field cured concrete in cubic steel molds (Greece)
It also flows much better than ordinary concrete, having the consistency of a milkshake. The first known use of CLSM was in 1964. [ 2 ] CLSM is typically a ready mix concrete rather than soil cement which is a low strength cement made using local soil, and is similar to a slurry .
A higher ratio gives a too fluid concrete mix resulting in a too porous hardened concrete of poor quality. Often, the concept also refers to the ratio of water to cementitious materials, w/cm. Cementitious materials include cement and supplementary cementitious materials such as ground granulated blast-furnace slag (GGBFS), fly ash (FA), silica ...
The volumetric mixer varies in capacity size up to 12 m 3 and has a production rate of around 60m 3 an hour depending on the mix design. Many volumetric concrete mixer manufacturers have innovated the mixer in capacity and design, as well as added features including color, multiple admixes, fiber systems, and the ability to do gunite or shotcrete.
Their addition allows to decrease the water-to-cement ratio of concrete or mortar without negatively affecting the workability of the mixture. It enables the production of self-consolidating concrete and high-performance concrete. The water–cement ratio is the main factor determining the concrete strength and its durability. Superplasticizers ...
When water is mixed with portland cement, the product sets in a few hours and hardens over a period of weeks. These processes can vary widely, depending upon the mix used and the conditions of curing of the product, [18] but a typical concrete sets in about 6 hours and develops a compressive strength of 8 MPa in 24 hours. The strength rises to ...