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Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined.
A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (aggregate) together. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete. Concrete is the most widely used material in existence and is behind only water as the planet's most-consumed resource.
Reinforced concrete, also called ferroconcrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel bars (rebar) and is usually embedded passively in the concrete before the concrete sets. However, post-tensioning is also employed as a technique to reinforce the concrete. In terms of volume used annually, it is one of the most common engineering materials. In corrosion engineering terms, when designed correctly, the alkalinity of the concrete protects the steel rebar from corrosion.
The term chloride refers to a compound or molecule that contains either a chlorine ion, which is a negatively charged chlorine atom, or a non-charged chlorine atom covalently bonded to the rest of the molecule by a single bond. Many inorganic chlorides are salts. Many organic compounds are chlorides. The pronunciation of the word "chloride" is.
Rebar, known when massed as reinforcing steel or steel reinforcement, is a steel bar used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and aid the concrete under tension. Concrete is strong under compression, but has low tensile strength. Rebar significantly increases the tensile strength of the structure. Rebar's surface features a continuous series of ribs, lugs or indentations to promote a better bond with the concrete and reduce the risk of slippage.
Calcium chloride is an inorganic compound, a salt with the chemical formula CaCl2. It is a white crystalline solid at room temperature, and it is highly soluble in water. It can be created by neutralising hydrochloric acid with calcium hydroxide.
Calcium hydroxide (traditionally called slaked lime) is an inorganic compound with the chemical formula Ca(OH)2. It is a colorless crystal or white powder and is produced when quicklime (calcium oxide) is mixed with water. It has many names including hydrated lime, caustic lime, builders' lime, slaked lime, cal, and pickling lime. Calcium hydroxide is used in many applications, including food preparation, where it has been identified as E number E526. Limewater, also called milk of lime, is the common name for a saturated solution of calcium hydroxide.
In chemistry, efflorescence is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water, or occasionally in another solvent. The water, with the salt now held in solution, migrates to the surface, then evaporates, leaving a coating of the salt.
Ferrocement or ferro-cement is a system of construction using reinforced mortar or plaster applied over an "armature" of metal mesh, woven, expanded metal, or metal-fibers, and closely spaced thin steel rods such as rebar. The metal commonly used is iron or some type of steel, and the mesh is made with wire with a diameter between 0.5 mm and 1 mm. The cement is typically a very rich mix of sand and cement in a 3:1 ratio; when used for making boards, no gravel is used, so that the material is not concrete.
Accelerants, or accelerators, are substances that increase the rate of a natural or artificial chemical process. They play a major role in chemistry, as most chemical reactions can be hastened with an accelerant. They are commonly used in contexts such as fire investigation where they can indicate arson, in construction to speed the curing of building materials, and in sulfur vulcanization to produce rubber products such as tyres. In fire investigation, accelerants are often detected through laboratory analysis of fire debris. Various types of accelerants exist, including liquids, solids, and gases, each with specific properties and applications. Understanding accelerants is crucial in forensic science, engineering, and other fields where controlled chemical reactions are essential.
Calcium nitrate are inorganic compounds with the formula Ca(NO3)2(H2O)x. The anhydrous compound, which is rarely encountered, absorbs moisture from the air to give the tetrahydrate. Both anhydrous and hydrated forms are colourless salts. Hydrated calcium nitrate, also called Norgessalpeter (Norwegian salpeter), is mainly used as a component in fertilizers, but it has other applications. Nitrocalcite is the name for a mineral which is a hydrated calcium nitrate that forms as an efflorescence where manure contacts concrete or limestone in a dry environment as in stables or caverns. A variety of related salts are known including calcium ammonium nitrate decahydrate and calcium potassium nitrate decahydrate.
The water–cement ratio is the ratio of the mass of water to the mass of cement used in a concrete mix:
Concrete cover, in reinforced concrete, is the least distance between the surface of embedded reinforcement and the outer surface of the concrete. The concrete cover depth can be measured with a cover meter. The purpose of concrete cover is to protect the reinforcement from corrosion, fire, and other potential damage.
Ground granulated blast-furnace slag is obtained by quenching molten iron slag from a blast furnace in water or steam, to produce a glassy, granular product that is then dried and ground into a fine powder. Ground granulated blast furnace slag is a latent hydraulic binder forming calcium silicate hydrates (C-S-H) after contact with water. It is a strength-enhancing compound improving the durability of concrete. It is a component of metallurgic cement. Its main advantage is its slow release of hydration heat, allowing limitation of the temperature increase in massive concrete components and structures during cement setting and concrete curing, or to cast concrete during hot summer.
An AFm phase is an "alumina, ferric oxide, monosubstituted" phase, or aluminate ferrite monosubstituted, or Al2O3, Fe2O3 mono, in cement chemist notation (CCN). AFm phases are important hydration products in the hydration of Portland cements and hydraulic cements.
Friedel's salt is an anion exchanger mineral belonging to the family of the layered double hydroxides (LDHs). It has affinity for anions as chloride and iodide and is capable of retaining them to a certain extent in its crystallographical structure.
Concrete degradation may have many different causes. Concrete is mostly damaged by the corrosion of reinforcement bars due to the carbonatation of hardened cement paste or chloride attack under wet conditions. Chemical damages are caused by the formation of expansive products produced by various chemical reactions, by aggressive chemical species present in groundwater and seawater, or by microorganisms. Other damaging processes can also involve calcium leaching by water infiltration and different physical phenomena initiating cracks formation and propagation. All these detrimental processes and damaging agents adversely affects the concrete mechanical strength and its durability.
Sulfur concrete, sometimes named thioconcrete or sulfurcrete, is a composite construction material, composed mainly of sulfur and aggregate. Cement and water, important compounds in normal concrete, are not part of sulfur concrete. The concrete is heated above the melting point of elemental sulfur at ca. 140 °C (284 °F) in a ratio of between 12% and 25% sulfur, the rest being aggregate.
Calcium nitrite is an inorganic compound with the chemical formula Ca(NO
2)
2. In this compound, as in all nitrites, nitrogen is in a +3 oxidation state. It has many applications such as antifreeze, rust inhibitor of steel and wash heavy oil.
The durability design of reinforced concrete structures has been recently introduced in national and international regulations. It is required that structures are designed to preserve their characteristics during the service life, avoiding premature failure and the need of extraordinary maintenance and restoration works. Considerable efforts have therefore made in the last decades in order to define useful models describing the degradation processes affecting reinforced concrete structures, to be used during the design stage in order to assess the material characteristics and the structural layout of the structure.
References
- ↑ Justnes, H. (2000): Accelerator Blends for Portland Cement. Proceedings of Cement and Concrete Technology in the 2000s, September 6–10, 2000, Istanbul, Turkey, Vol. 1, pp. 433-442
- ↑ ACI 306R-88: Cold Weather Concreting. "Archived copy" (PDF). Archived from the original (PDF) on 2011-07-25. Retrieved 2011-03-05.
{{cite web}}: CS1 maint: archived copy as title (link) - 1 2 Korhonen, Charles J.; Cortez, Edel R.; Durning, Timothy A. (1997), "Antifreeze Admixtures for Concrete", Special Report 97-26, Cold Regions Research and Engineering Laboratory, ISBN 9781428913158
- ↑ "ASCC Position Statement #31" (PDF). Concrete International. Vol. 32, no. 2. American Concrete Institute. February 1, 2010. p. 55. Archived from the original (PDF) on January 23, 2016. Retrieved June 23, 2016.
- ↑ Cement Admixtures Association: Admixture Sheet – ATS 4: Accelerating admixtures, "Archived copy" (PDF). Archived from the original (PDF) on 2011-09-03. Retrieved 2011-03-05.
{{cite web}}: CS1 maint: archived copy as title (link) - ↑ Nmai, Charles; Corbo, Jack (November 1, 1989). "Sodium thiocyanate and corrosion of steel in concrete and mortar". Concrete International. Vol. 11, no. 11. pp. 59–67.
- ↑ Volset, D. (2010). The use of antifreeze agents. http://www.mapei.com/public/NO/linedocument/the_use_of_anti-freeze_agents.pdf
- ↑ "The Use of Calcium Sulfoaluminate Rapid Setting Cement for Underground Construction". 26 November 2013.
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