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When the tensile strength of concrete is exceeded, cracks appear. Adding an air entrainment agent during the mixing of fresh concrete induces the formation of tiny air bubbles in the fresh concrete slurry. This creates numerous small air-filled micro-cavities in the hardened concrete serving as empty volume reserve to accommodate the volumetric ...
This reaction is accompanied by hydration and swelling of the alkali gel leading to the expansion of the affected aggregates. The pH of the fresh alkali gel is very high and it has often a characteristic amber color. The high pH of young alkali gel exudations often precludes the growth of mosses at the surface of concrete crack infilling. 2.
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] Reinforced concrete is the most common form of concrete.
If concrete is fully dried, it does not creep, but it is next to impossible to dry concrete fully without severe cracking. Fig. 1. Changes of pore water content due to drying or wetting processes cause significant volume changes of concrete in load-free specimens.
The early strength of the concrete can be increased if it is kept damp during the curing process. Minimizing stress prior to curing minimizes cracking. High-early-strength concrete is designed to hydrate faster, often by increased use of cement that increases shrinkage and cracking. The strength of concrete changes (increases) for up to three ...
Adding these extra chemicals can cause issues with the concrete because it isn’t part of the natural freezing and melting process that the concrete was made to go through. Think of the driveway ...
Air entrainment is beneficial for the properties of both fresh and hardened concrete. [7] In fresh concrete, air entrainment improves workability and makes it easier to handle and pump. It also helps prevent bleeding and segregation, unwanted processes that can occur during mixing. In hardened concrete, air entrainment strengthens the material ...
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