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Degraded concrete and rusted, exposed reinforcement bar (rebar) on Welland River bridge of the Queen Elizabeth Way in Niagara Falls, Ontario. 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 ...
Surface of a concrete pillar of the building of the National Gallery of Canada at Ottawa presenting the typical crack pattern of the alkali-silica reaction (ASR). Note the typical fatty aspect of the yellow silicagel exudations imbibing the concrete surface along the two sides of the cracks.
A fairly well-defined reaction front can often be observed in thin sections; ahead of the front the concrete is normal, or near normal. Behind the reaction front, the composition and the microstructure of concrete are modified. These changes may vary in type or severity but commonly include: Extensive cracking; Expansion
Concrete fracture analysis is part of fracture mechanics that studies crack propagation and related failure modes in concrete. [17] As it is widely used in construction, fracture analysis and modes of reinforcement are an important part of the study of concrete, and different concretes are characterized in part by their fracture properties. [ 18 ]
Filler materials are particles added to binders (resin, thermoplastics, cement) to make a composite material. Filler materials improve specific properties or make the product cheaper. [1] Coarse filler materials such as construction aggregate and rebar are used in the building industry to make plaster, mortar and concrete.
The initiation time is related to the rate at which carbonation propagates in the concrete cover thickness.Once that carbonation reaches the steel surface, altering the local pH value of the environment, the protective thin film of oxides on the steel surface becomes instable, and corrosion initiates involving an extended portion of the steel surface.
From January 2011 to May 2011, if you bought shares in companies when Jon F. Hanson joined the board, and sold them when he left, you would have a 4.6 percent return on your investment, compared to a 7.0 percent return from the S&P 500.
Calcium aluminates can form complex salts in combination with different types of anions.Two series of calcium aluminates are known in cement chemistry: AFm and AFt phases, being respectively mono- or tri-substituted with a given divalent anion X (e.g. SO 2− 4, CO 2− 3, or hosting a divalent impurity such as SeO 2− 4 [3]...), or with two units of a monovalent anion, e.g. OH −, Cl − ...