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A violet color indicates still alkaline areas and thus non-carbonated concrete. Carbonated zones favorable for steel corrosion and concrete degradation are colorless. [3] [4] The presence of water in carbonated concrete is necessary to lower the pH of concrete pore water around rebar and to depassivate the carbon steel surface at low pH.
The humidity content of concrete is one of the main influencing factors of CO 2 diffusion in concrete. If concrete pores are completely and permanently saturated (for instance in submerged structures) CO 2 diffusion is prevented. On the other hand, for completely dry concrete, the chemical reaction of carbonation cannot occur.
Sulfate attacks, an hat appellation covering different concrete degradation mechanisms: Delayed ettringite formation (DEF), also known as internal sulfate attack (ISA) when the temperature of fresh concrete exceeds 65 °C during its setting and hardening; External sulfate attack (ESA), and; Thaumasite form of sulfate attack (TSA).
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
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ASTM C1293: "Test Method for Concrete Aggregates by Determination of Length Change of Concrete Due to Alkali-Silica Reaction". It is a long-term confirmation test (1 or 2 years) at 38 °C in a water-saturated moist atmosphere (inside a thermostated oven) with concrete prisms containing the aggregates to be characterised mixed with a high-alkali ...
Using a slotted spoon, transfer cranberries and rosemary to a wire rack set in a baking sheet to drain. Let dry until sticky but no longer wet, about 30 minutes. Place remaining 1/4 c. sugar in a ...
Download QR code; Print/export ... Concrete degradation (3 P) F. Fibre-reinforced cementitious materials ... Pages in category "Concrete"