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The environmental impact of concrete, its manufacture, and its applications, are complex, driven in part by direct impacts of construction and infrastructure, as well as by CO 2 emissions; between 4-8% of total global CO 2 emissions come from concrete. [1] Many depend on circumstances.
H 2 SO 4 + Ca(OH) 2 → CaSO 4 · 2H 2 O. When concrete also contains limestone aggregates or a filler addition, H 2 SO 4 reacts with calcite (CaCO 3) and water to also form gypsum while releasing CO 2: H 2 SO 4 + CaCO 3 + H 2 O → CaSO 4 · 2H 2 O + CO 2. Gypsum is relatively soluble in water (~ 1 – 2 g/L), so there is plenty of calcium and ...
Concrete waste that is rich in alkaline calcium compounds can be used to remove and recover various elements from an aqueous solution. Waste concrete has been used as a sorbent to remove phosphorus from wastewater after the removal of excess sludge in sewage treatment plants. [27] Concrete waste may also be used as an inexpensive gas treatment ...
Workability can be measured by the concrete slump test, a simple measure of the plasticity of a fresh batch of concrete following the ASTM C 143 or EN 12350-2 test standards. Slump is normally measured by filling an "Abrams cone" with a sample from a fresh batch of concrete. The cone is placed with the wide end down onto a level, non-absorptive ...
Textile waste is a huge issue for the environment, with around 2.1 billion tonnes of unsold or faulty clothing being disposed per year. Much of this is taken to landfill, but the majority of materials used to make clothes are not biodegradable, resulting in them breaking down and contaminating soil and water. [299]
The flow table test or slump-flow test is a method to determine consistency of fresh concrete. Flow table test is also used to identify transportable moisture limit of solid bulk cargoes. [ 1 ] It is used primarily for assessing concrete that is too fluid (workable) to be measured using the slump test , because the concrete will not retain its ...
Air entrainment in concrete is the intentional creation of tiny air bubbles in a batch by adding an air entraining agent during mixing. A form of surfactant (a surface-active substance that in the instance reduces the surface tension between water and solids) it allows bubbles of a desired size to form.
Eq. (1) can be used but in that form the variations of humidity and temperature with time cannot be introduced and the need to store the entire stress history for each finite element is cumbersome. It is better to convert Eq. (1) to a set of differential equations based on the Kelvin chain rheologic model.