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Cement hydration and strength development mainly depend on two silicate phases: tricalcium silicate (C 3 S) , and dicalcium silicate (C 2 S) . [1] Upon hydration, the main reaction products are calcium silicate hydrates (C-S-H) and calcium hydroxide Ca(OH) 2, written as CH in the cement chemist notation. C-S-H is the phase playing the role of ...
At low pore humidities (<75%), shrinkage is caused by a decrease of the disjoining pressure across nano-pores less than about 3 nm thick, filled by adsorbed water. The chemical processes of Portland cement hydration lead to another type of shrinkage, called the autogeneous shrinkage, which is observed in sealed specimens, i.e., at no moisture loss.
It also causes water bleeding at the surface of concrete slabs or rafts (with a dusty surface left after water evaporation). For all the afore mentioned reasons, it is strictly forbidden to add extra water to a ready-mix concrete truck when the delivery time is exceeded, and the concrete becomes difficult to pour because it starts to set. Such ...
Concrete cracks due to tensile stress induced by shrinkage or stresses occurring during setting or use. Various means are used to overcome this. Fiber reinforced concrete uses fine fibers distributed throughout the mix or larger metal or other reinforcement elements to limit the size and extent of cracks. In many large structures, joints or ...
Flow table with a grip and a hinge, 70 centimetres (28 in) square. In the American version of this test, the table is 10 inches (25 cm) diameter per ASTM C 230.; Abrams cone, open at the top and at the bottom - 30 centimetres (12 in) high, 17 centimetres (6.7 in) top diameter, 25 centimetres (9.8 in) base diameter.
The characteristic strength is defined as the strength of the concrete below which not more than 5% of the test results are expected to fall. [ 16 ] For design purposes, this compressive strength value is restricted by dividing with a factor of safety, whose value depends on the design philosophy used.
The consistency is a simple constant of proportionality, while the flow index measures the degree to which the fluid is shear-thinning or shear-thickening. Ordinary paint is one example of a shear-thinning fluid, while oobleck provides one realization of a shear-thickening fluid. Finally, the yield stress quantifies the amount of stress that ...
It is sometimes considered synonymous for pseudo-plastic behaviour, [1] [2] and is usually defined as excluding time-dependent effects, such as thixotropy. [ 3 ] Shear thinning is the most common type of non-Newtonian behavior of fluids and is seen in many industrial and everyday applications. [ 4 ]