Concrete carbonation materials

Bicarbonate ion is usually the chief anion in freshwaters. In and on silicate rocks, the HCOj concentration is usually 50 to 200 mg/L, whereas in groundwaters that contact a few percent carbonate materials up to pure limestone and dolomite, bicarbonate levels are usually in the range of 200 to 400 ppm. Seawater contains 140 mg/L HCOj. Carbonate alkalinity (CO3 ) rarely exceeds 10 mg/L. Why The presence of caustic alkalinity (free OH ) at pH s above 10 usually indicates artificial contamination of a water by, for example, Ca(OH)2 (portlandite) from the setting of concrete at newly completed wells. Cg concentrations can reach 1000 ppm as HCO3 in sodium carbonate-bicarbonate brines found in evaporative, closed basin lakes. 

Further, the availability and proximity of a large source of carbonate material, namely the bioclasts and carbonate intraclasts within the Namorado Sandstone, probably provided supersaturation conditions and sites of nucleation for intense calcite cementation. Sombra et al. (1995) attributed the tabular geometry of calcite-cemented zones to the lateral coalescence of concretions in carbonate clast-rich units in the Namorado Sandstone. 

Greenfield TK, Carbon-fiber laminates for repair of concrete structures, Materials Performance, 34(3), 36-38, 1995. 

It is known from the past that hydrates leach from concrete. Taylor [21] has proposed various measures against leaching by using Pozzolanic materials, alumina cement, dense concrete, carbonated concrete, autoclave curing, and so on. Even ancient concrete used 5000 years ago in China [22] did not use steel the cement close to today s low-heat Portland cement had carbonated, and had helped to maintain the long-term soundness of the material. Based on such information, the leaching resistance of carbonated concrete and Pozzolan material was evaluated. The dissolution equilibrium relationships... 

Pitly, D., 2009. Carbon fibre growing as reinforcing material in precast concrete. Carbon Fibre Gear website (http //www. carbonfibregear.com/author/davidpitiyuk/). 

The third important acid is produced by all life forms CO2. It is excreted as the end product of metabolism and reacts with water to carbonic acid, which may dissolve to carbonates. In case of concrete, carbonic acid may dissolve the binding material, lime, and cause serious corrosion problems. 

Not long ago, the terms high performance composites and advanced composites were applied only to such composite materials as carbon fibre reinforced plastics and metal matrix composites, used in the construction of aircraft, rockets and satellites. These terms are now used for concrete-like materials and have similar meaning they are materials of improved selected properties, designed and produced for special applications. The concept of high performance is expressed by the following technical terms ... 

In few cases, parameters identification at a reference state (generally at room temperature) will be sufficient. This implies that in most situations constitutive law parameters must evolve to be representative of the real situation (e.g., the carbon materials have to operate at a temperature near 1000 °C while the concrete maybe influenced by the relative humidity of the atmosphere). 

Heat capacities of a new porous carbon material called "Woodceramics" were investigated by means of DSC. Fibreboards made from pine wood Firms ra-diata) were impregnated with phenol resin, dried, harden-treated at 135°C and then burnt at 800 or 2800°C. These new ceramics exhibited special characteristics like high heat and corrosion resistance, heat and electrical conductivity, impermeability to gas and hardness. The observed heat capacities between ambient and 250°C with 0.5 to 0.94 J/(g K) for the 2800°C sample and even 1.0 to 5.5 J/(g K) for the 800 C sample are relatively large compared with those of metals and alloys and rather close to those of rubber, porcelain or concrete [64]. 

A typical large three-phase ferroalloy furnace using prebaked carbon electrodes is shown in Eigure 4. The hearth and lower walls where molten materials come in contact with refractories are usually composed of carbon blocks backed by safety courses of brick. In the upper section, where the refractories are not exposed to the higher temperatures, superduty or regular firebrick may be used. The walls of the shell also may be water-cooled for extended life. Usually, the furnace shell is elevated and supported on beams or on concrete piers to allow ventilation of the bottom. When normal ventilation is insufficient, blowers are added to remove the heat more rapidly. The shell also may rest on a turntable so that it can be oscillated slightly more than 120° at a speed equivalent to 0.25—1 revolution per day in order to equalize refractory erosion or bottom buildup. 

Sa.tura.tion Index. Materials of constmction used in pools are subject to the corrosive effects of water, eg, iron and copper equipment can corrode whereas concrete and plaster can undergo dissolution, ie, etching. The corrosion rate of metallic surfaces has been shown to be a function of the concentrations of Cl ,, dissolved O2, alkalinity, and Ca hardness as well as buffer intensity, time, and the calcium carbonate saturation index (35). 

Applicability Most hazardous waste slurried in water can be mixed directly with cement, and the suspended solids will be incorporated into the rigid matrices of the hardened concrete. This process is especially effective for waste with high levels of toxic metals since at the pH of the cement mixture, most multivalent cations are converted into insoluble hydroxides or carbonates. Metal ions also may be incorporated into the crystalline structure of the cement minerals that form. Materials in the waste (such as sulfides, asbestos, latex and solid plastic wastes) may actually increase the strength and stability of the waste concrete. It is also effective for high-volume, low-toxic, radioactive wastes. 

Three other compounds of s-block elements—calcium oxide (CaO, known as lime ), sodium hydroxide (NaOH), and sodium carbonate (Na2 CO3)—are among the top 15 industrial chemicals in annual production. Lime is perennially in the top 10 because it is the key ingredient in construction materials such as concrete, cement, mortar, and plaster. Two other compounds, calcium chloride (CaCl2 ) and sodium sulfate (Na2 SO4 ), rank just below the top 50 in industrial importance. 

Brick Construction Brick-lined construction can be used for many severely corrosive conditions under which high alloys would fail. Brick linings can be installed over metal, concrete, and fiberglass structures. Acid-resistant bricks are made from carbon, red shale, or acid-resistant refractory materials. Red-shale brick is not used above 175°C (350°F) because of spalling. Acid-resistant refractories can be used up to 870°C (1600°F). See Table 25-10. 

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