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Abrams' law (also called Abrams' water-cement ratio law) [1] is a concept in civil engineering. The law states the strength of a concrete mix is inversely related to the mass ratio of water to cement. [1] [2] As the water content increases, the strength of concrete decreases. Abrams’ law is a special case of a general rule formulated ...
Abrams investigated the influence of the composition of concrete mixes on the strength of the end product. Some of the results of his research were: the definition of the concept of fineness modulus; the definition of the water–cement ratio; a concrete slump test for the
Headway is the distance or duration between vehicles in a transit system. The minimum headway is the shortest such distance or time achievable by a system without a reduction in the speed of vehicles. The precise definition varies depending on the application, but it is most commonly measured as the distance from the tip (front end) of one ...
Extra heavy concrete sleepers [10] 87.8 m (288 ft 11 ⁄ 16 in) North American rail network: 1,435 mm (4 ft 8 + 1 ⁄ 2 in) Absolute minimum radius; not on lines for general service 85 m (279 ft) Windberg Railway (de:Windbergbahn) 1,435 mm (4 ft 8 + 1 ⁄ 2 in) (between Freital-Birkigt and Dresden-Gittersee) - restrictions to wheelbase 80 m ...
A lower ratio leads to higher strength and durability, but may make the mix more difficult to work with and form. Workability can be resolved with the use of plasticizers or super-plasticizers. A higher ratio gives a too fluid concrete mix resulting in a too porous hardened concrete of poor quality.
In modern times, Punggol metro line in Singapore uses a moving block system to achieve a headway of 90 seconds, so the route capacity is 40 trains per hour. [20] The Moscow Metro achieves 40 trains an hour as well, additionally it has aimed to achieve 50 trains an hour in the future (a train every 72 seconds).
The opposite situation, i. e. when the void ratio is relatively small (dense soils), indicates that the volume of the soil is vulnerable to increase (swelling) under unloading – the smectite (montmorillonite, bentonite) partially dry clay particles present in an unsaturated soil can swell due to their hydration after contact with water (when ...
In 1957 John Philip introduced the term sorptivity and defined it as a measure of the capacity of the medium to absorb or desorb liquid by capillarity. [1]According to C Hall and W D Hoff, the sorptivity expresses the tendency of a material to absorb and transmit water and other liquids by capillarity.