Gain in strength

The twist of yam plays an important role and low twist appears to be essential for maximum increase in strength. Grey yam with soft doubling twist gives stronger yam. 

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Ductility and malleability Lower Gain in strength more than offsets the loss in these properties... 

Extruded films are sometimes bi-axially stretched, in particular PE and PP films, which gain in strength and transparency by biaxial orientation. The stretching takes place at elevated temperatures, but below the melting point. The edges of the film are gripped by a series of clips, which diverge in the transverse direction and simultaneously accelerate in the machine direction. 

Stabilisation is a much slower process, which occurs progressively over several months, and involves the reaction of lime with the siliceous and aluminous components of the soil. The lime raises the pH to above 12, which results in the formation of calcium silicates and aluminates. These are believed to form initially as a gel, which coats the soil particles, and which subsequently crystallises as calcium silicate/aluminate hydrates. Those hydrates are cementitious products, similar in composition to those found in cement paste. The rate of crystallisation is temperature dependant and may take many months to reach completion. The resulting gain in strength (measured by the California Bearing Ratio Test [26.11]) is progressive, as illustrated in Fig. 26.2. 

The amount of water-reduction or gain in workability will be increased by overdosing. Overdosing can also, in certain instances, result in retardation and/or a degree of air entrainment. Where there is no air entrainment the gain in strength, and other properties will develop normally after the initial retardation period. 

A consolidation analysis is also related to a strength analysis (section 8.4.2), since the consolidation degree is directly related to the gain in strength. Each stability analysis should accurately model the geometry and characteristics of the fill at the corresponding point in time. 

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