Search results
Results From The WOW.Com Content Network
Figure 2 - Failure probability and target service life in performance-based service life models for reinforced concrete structures. Performance-based approaches provide for a real design of durability, based on models describing the evolution in time of degradation processes, and the definition of times at which defined limit states will be ...
4 ions to precipitate CaSO 4 ·2H 2 O . A fraction of SO 2− 4 ions can also be trapped, or sorbed, into the layered structure of C-S-H. [3] These successive reactions lead to the precipitation of expansive mineral phases inside the concrete porosity responsible for the concrete degradation, cracks and ultimately the failure of the structure.
Concrete has a very low coefficient of thermal expansion, and as it matures concrete shrinks. All concrete structures will crack to some extent, due to shrinkage and tension. Concrete which is subjected to long-duration forces is prone to creep. The density of concrete varies, but is around 2,400 kilograms per cubic metre (150 lb/cu ft). [1]
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 ...
2)) present in the hardened cement paste to give gypsum: H 2 SO 4 + Ca(OH) 2 → CaSO 4 · 2H 2 O. When concrete is carbonated by atmospheric carbon dioxide (CO 2), or if limestone aggregates are used in concrete, H 2 SO 4 reacts with calcite (CaCO 3) and water to also form gypsum while releasing CO 2 back to the atmosphere: H 2 SO 4 + CaCO 3 ...
(2) The thermal expansion coefficients of concrete and steel are so close (1.0 × 10 −5 to 1.5 × 10 −5 for concrete and 1.2 × 10 −5 for steel) that the thermal stress-induced damage to the bond between the two components can be prevented. (3) Concrete can protect the embedded steel from corrosion and high-temperature induced softening.
Fibers are added for long term durability of concrete. Glass [14] and polyester [15] decompose in alkaline condition of concrete and various additives and surface treatment of concrete. The High Speed 1 tunnel linings incorporated concrete containing 1 kg/m 3 or more of polypropylene fibers, of diameter 18 & 32 μm, giving the benefits noted ...
The paste has a porosity of about 0.4 to 0.55 and an enormous specific surface area, roughly 500 m 2 /cm 3. Its main component is the tri-calcium silicate hydrate gel (3 CaO · 2 SiO 3 · 3 H 2 O, in short C 3 S 2 H 3). The gel forms particles of colloidal dimensions, weakly bound by van der Waals forces.