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A w/c ratio higher than 0.60 is not acceptable as fresh concrete becomes "soup" [2] and leads to a higher porosity and to very poor quality hardened concrete as publicly stated by Prof. Gustave Magnel (1889-1955, Ghent University, Belgium) during an official address to American building contractors at the occasion of one of his visits in the ...
When atmospheric carbon dioxide (CO 2), or carbonate ions (HCO − 3, CO 2− 3 dissolved in water) diffuse into concrete from its external surface, they react with calcium hydroxide (portlandite, Ca(OH) 2) and the pH of the concrete pore water progressively decreases from 13.5 – 12.5 to 8.5 (pH of water in equilibrium with calcite).
Aqion is a hydrochemistry software tool. It bridges the gap between scientific software (such like PhreeqC [1]) and the calculation/handling of "simple" water-related tasks in daily routine practice.
Phenolphthalein's pH sensitivity is exploited in other applications: concrete has naturally high pH due to the calcium hydroxide formed when Portland cement reacts with water. As the concrete reacts with carbon dioxide in the atmosphere, pH decreases to 8.5–9. When a 1% phenolphthalein solution is applied to normal concrete, it turns bright pink.
Calculation of the true sorptivity required numerical iterative procedures dependent on soil water content and diffusivity. John R. Philip (1969) showed that sorptivity can be determined from horizontal infiltration where water flow is mostly controlled by capillary absorption: I = S t {\displaystyle I=S{\sqrt {t}}} where S is sorptivity and I ...
This process is often irreversible. Sufficient amount of free calcium ion and a high pH of 12 and above is needed to initiate and maintain the pozzolanic reaction. [2] This is because at a pH of around 12, the solubility of silicon and aluminium ions is high enough to support the pozzolanic reaction.
Contact with wet concrete can cause skin chemical burns due to the caustic nature of the mixture of cement and water (including rainwater). Indeed, the pH of fresh cement water is highly alkaline due to the presence of free potassium and sodium hydroxides in solution (pH ~ 13.5). Eyes, hands and feet must be correctly protected to avoid any ...
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]