Specific weight of chalk, its properties and weight calculation table

In construction work, chalk is used quite often. It is a carbonate rock whose composition consists largely of calcite, and to a lesser extent of dolomite impurities, organogenic substances and sandy clay-type particles. In pure chalk, the latter account for less than 5 percent.

Table of the specific weight of chalk

Chalk is a porous carbonate rock, so practical calculations usually use reference values rather than estimating density from appearance alone. The actual value depends on strength, porosity, moisture content and particle size. The average specific weight of chalk ranges from 1.4 to 2.7 g/cm³. Low-strength chalk is about 1.4-1.55 g/cm³, weak chalk is about 1.8 g/cm³, medium-strength chalk is about 2.4 g/cm³, and dense strong chalk ranges from 2.69 to 2.72 g/cm³.

To make calculations of the specific weight and bulk density of chalk easier, a clear table with these values is presented below.

Properties of chalk

By origin, this material is classified as limestone, which in turn is divided into chemogenic, organogenic and clastic types. In terms of physical and mechanical characteristics and properties, they all differ greatly from one another. Chalk, like shell rock, belongs to the group of organogenic limestones.

Chalk is a white weakly cemented rock, the largest share of whose composition is calcite (approximately from 91 to 98.5 percent). Some types of chalk may contain powdery calcite with particles smaller than 0.01 mm, with fragments of very small shells making up about 60 percent of the composition.

Chalk is characterized as a transitional type of limestone between organogenic and chemogenic limestones. The specific weight of chalk averages from 1.4 to 2.72 g/cm³, and the volumetric weight is approximately about 1.51 g/cm³. Natural chalk can have high moisture content and porosity: some reference data give values around 32 percent moisture and 44 percent porosity. On the mineralogical scale, chalk is a soft rock because it mainly consists of calcite.

Natural chalk does not have frost resistance, because after several freezing and thawing cycles it breaks down into many pieces measuring from 1 to 3 mm. Sometimes this is considered a positive property of chalk, because during such processes its action aimed at neutralizing soil is preserved for a long time.

Types of chalk

Initially, it was believed that a material such as chalk was a rock mass that was identical in physical properties and chemical composition in all places of occurrence. However, during increased exploitation of this material, it was established that these characteristics vary depending on the type of chalk. Therefore, before extraction, geological and technological mapping is carried out at deposits so that only high-quality chalk is mined later.

Chalk is usually divided into types according to strength. The following types of chalk are distinguished:

• chalk of low strength
• weak chalk
• medium-strength chalk
• strong dense chalk