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  2. Properties of concrete - Wikipedia

    en.wikipedia.org/wiki/Properties_of_concrete

    Twenty eight days is a long wait to determine if desired strengths are going to be obtained, so three-day and seven-day strengths can be useful to predict the ultimate 28-day compressive strength of the concrete. A 25% strength gain between 7 and 28 days is often observed with 100% OPC (ordinary Portland cement) mixtures, and between 25% and 40 ...

  3. Sulfate attack in concrete and mortar - Wikipedia

    en.wikipedia.org/wiki/Sulfate_attack_in_concrete...

    Cement hydration and strength development mainly depend on two silicate phases: tricalcium silicate (C 3 S) (), and dicalcium silicate (C 2 S) (). [1] Upon hydration, the main reaction products are calcium silicate hydrates (C-S-H) and calcium hydroxide Ca(OH) 2, written as CH in the cement chemist notation.

  4. Electrical resistivity measurement of concrete - Wikipedia

    en.wikipedia.org/wiki/Electrical_resistivity...

    Increasing concrete water content; Increasing concrete porosity; Increasing temperature; Increasing chloride content; Decreasing carbonatation depth; When the electrical resistivity of the concrete is low, the rate of corrosion increases. When the electrical resistivity is high, e.g. in case of dry and carbonated concrete, the rate of corrosion ...

  5. Carbonyl group - Wikipedia

    en.wikipedia.org/wiki/Carbonyl_group

    In organic chemistry, a carbonyl group is a functional group with the formula C=O, composed of a carbon atom double-bonded to an oxygen atom, and it is divalent at the C atom. It is common to several classes of organic compounds (such as aldehydes , ketones and carboxylic acid ), as part of many larger functional groups.

  6. Schmidt hammer - Wikipedia

    en.wikipedia.org/wiki/Schmidt_hammer

    The test hammer hits the concrete at a defined energy. Its rebound is dependent on the hardness of the concrete and is measured by the test equipment. By reference to a conversion chart, the rebound value can be used to determine the concrete's compressive strength. When conducting the test, the hammer should be held at right angles to the ...

  7. Carbon–oxygen bond - Wikipedia

    en.wikipedia.org/wiki/Carbon–oxygen_bond

    A carbon–oxygen bond is a polar covalent bond between atoms of carbon and oxygen. [1] [2] [3]: 16–22 Carbon–oxygen bonds are found in many inorganic compounds such as carbon oxides and oxohalides, carbonates and metal carbonyls, [4] and in organic compounds such as alcohols, ethers, and carbonyl compounds.

  8. Compressive strength - Wikipedia

    en.wikipedia.org/wiki/Compressive_strength

    As per Indian codes, compressive strength of concrete is defined as: Field cured concrete in cubic steel molds (Greece) The compressive strength of concrete is given in terms of the characteristic compressive strength of 150 mm size cubes tested after 28 days (fck). In field, compressive strength tests are also conducted at interim duration i.e ...

  9. Creep and shrinkage of concrete - Wikipedia

    en.wikipedia.org/.../Creep_and_shrinkage_of_concrete

    Changes of pore water content due to drying or wetting processes cause significant volume changes of concrete in load-free specimens. They are called the shrinkage (typically causing strains between 0.0002 and 0.0005, and in low strength concretes even 0.0012) or swelling (< 0.00005 in normal concretes, < 0.00020 in high strength concretes).