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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 cement specially selected to induce ASR. The concrete prisms are not directly immersed in an alkaline solution, but wrapped ...
Alkali–aggregate reaction is a term mainly referring to a reaction which occurs over time in concrete between the highly alkaline cement paste and non-crystalline silicon dioxide, which is found in many common aggregates. This reaction can cause the expansion of the altered aggregate, leading to spalling and loss of strength of concrete.
Concrete made from ordinary Portland cement without additives has a relatively impaired resistance to saltwater. [35] In contrast, EMCs exhibit high resistances to chloride and sulphate ion attack, together with low alkali-silica reactivities (ASR). [26] For example, durability tests have been performed according to the "Bache method" (see ...
It can also be of advantage for cement quality reasons, since it reduces the alkali content of the clinker. The alkali content is a critical property of cement. Indeed, cement with a too high alkali content can cause a harmful alkali–silica reaction (ASR) in concrete made with aggregates containing reactive amorphous silica.
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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A senior FEMA official instructed subordinates to freeze funding for grant programs, hours after a judge ordered the Trump administration to stop such pauses.
Concrete sealers are applied to concrete to protect it from surface damage, corrosion, and staining. They either block the pores in the concrete to reduce absorption of water and salts or form an impermeable layer which prevents such materials from passing.