Soil: The Four Characteristics Of Soils And Building Materials

CHAPTER TWO

2.1 Soil.

Soil is referred to as the topmost part of the earth’s surface which forms a loose layer of varying thicknesses, it consist of unconsolidated products of rock erosion and organic decay, along with bacteria and fungi. Soil development results from climate and living matter acting upon parent material as conditioned by the topography over time (brady and weil, 2012). In other terms as stated by different authors, soil is usually a combination of actions, such as wearing or breaking down of rocks by weathering, the interaction of dissolved silicates present in the parent rock with various soluble salts to form clay minerals and the decomposition of vegetables and plant matter (Scott 1977, Rigassi and CRETerre-

The four types of materials that soils are composed of are namely, Gravels, Sands, Silts and Clays, of particular note amongst these materials, gravels and sands has the ability to withstand alternate humidity and dryness without any of its properties being altered, thus a fundamental importance of building

These are also products of decomposed rocks, developed under the influence of weathering; they are often composed of particles of silica or quartz, sand ranges in size from 0.06mm to 2mm (lazslo et al. 1993)

According to Rigassi and CRETerre- EAG (1985), they are stable constituents of soil, they lack cohesion when dry and this is because of the weak effect of films of water near there surface, but has a very high degree of internal friction, that is great mechanical resistance to movement between particles which make them up. They further stated that sands do not shrink or swell because of the low adsorption on their surfaces.

2.1.1.3 Silts.

Silts are rock grounded up so fine that the individual grains cannot be seen with the naked eyes; they tend to hold together when wet and compressed. (wolfskill et al, 1981). Engineering science categorized Silts as particles made up of grain sizes ranging from 0.002 (2µ) to 0.06mm. (Minke, 2006). From the physical and chemical point of view the silt component of soil is virtually identical to the sand component, the only difference being on of size. Silt gives soil stability by increasing internal friction. The film of water between the particles grants a certain degree of cohesion to silty soil. Because of their high degree of permeability silty soils are very sensitive to frost. They are also subject to small scale swelling and