In today’s technological age, building materials play an important role. Although construction is their most common application, no field of engineering would be complete without these materials. Furthermore, the construction materials industry is a significant contributor to our national economy because its output influences both the rate and quality of construction work.
Because of the vast range of applications for buildings and installations, as well as the diverse manufacturing processes, building materials must meet a wide range of requirements, including strength at low and high temperatures, resistance to ordinary and sea water, acids and alkalis, and so on.
The properties of building materials are used to divide them into distinct groups. The properties of building materials are dictated by their primary applications. Only a thorough understanding of material properties allows for rational material selection for specific service conditions.
There are generally two properties of building materials :
- Physical Properties
- Chemical Properties
Let’s have a look at the properties of these building materials in more detail.
Physical Properties of Building Materials
There are about 20 physical properties of building materials on which the selection on the construction materials can be done.
- Density
- Bulk Density
- Density Index
- Specific Weight
- Specific Gravity
- Absolute Specific Gravity
- Apparent Specific Gravity
- Porosity
- Void Ratio
- Hygroscopicity
- Water Absorption
- Weathering Resistance
- Water Permeability
- Frost Resistance
- Heat Conductivity
- Thermal Capacity
- Fire Resistance
- Refractoriness
- Chemical Resistance
- Durability
Density (ρ)
The mass of a unit volume of homogenous material is called as density. It is denoted by
Where,
M = mass (g)
V = volume (cm³)
Below image shows the density of some of most common building materials used in the construction industry.
Bulk Density (ρь)
The mass of a unit volume of material in its natural state is called as bulk density. It is calculated using the following formula:
Where,
M = specimen mass (kg)
V = specimen volume in natural state (m³)
Bulk density is less than density for most materials, but these parameters are nearly identical for liquids and materials like glass and dense stone materials. Bulk density has a big impact on properties like strength and heat conductivity.
The below image shows the bulk densities of some of the building materials:
Density Index (ρо)
The density index is the ratio of bulk density to density. It expresses the extent to which a material’s volume is filled with solid matter. Because there are no absolutely dense bodies in nature, density index is always less than 1.0 for almost all building materials.
Specific Weight (γ)
The specific gravity, also known as the unit weight, is the weight of a material per unit volume.
Where,
γ = specific weight (kN/m³)
ρ = density of material (kg/m)
g = gravity (m/s²)
In civil engineering, specific weight can be used to determine the weight of a structure built to carry specific loads while staying whole and within deformation restrictions. It is also used as a fluid property in fluid dynamics.
Specific Gravity (Gs)
The specific gravity of a material’s solid particles is the ratio of weight of given volume of solids to the weight of an equal volume of water at temperature of 4°C.
Absolute Specific Gravity (Ga)
True or absolute specific gravity is determined by excluding both permeable and impermeable spaces (voids) when determining the true volume of solids. The absolute specific gravity has little practical application.
Apparent Specific Gravity (Gm)
The apparent specific gravity or mass specific gravity is calculated by taking into account both permeable and impermeable void when calculating the true volume of solids. It is ratio of fine-grained material mass density to water mass density.
Porosity (n)
The degree to which pores are scattered across the volume of a substance is known as porosity. It’s calculated by dividing the volume of pores by the volume of the specimen.
Porosity is a good indicator of a material’s bulk density, heat conductivity, and durability, among other things.
Void Ratio (e)
The void ratio is the volume of voids divided by the volume of solids. When an aggregate is poured into a container of any kind, not all of the space within the container will be filled.
The term voids refers to the empty spaces between aggregate particles. The percentage of voids, like the specific weight, is influenced by the aggregate’s compactness and the quantity of moisture it contains. In most cases, void judgments are conducted on material that has been measured loose.
Hygroscopicity
The ability of a material to collect water vapour from the air is known as hygroscopicity. It is influenced by air temperature and relative humidity, as well as the type, number, and size of pores, as well as the composition of the substance.
Water Absorption
Water absorption refers to a material’s ability to absorb and hold water. It is represented as a percentage of the dry material’s weight or volume.
Where,
M1 = mass of saturated material (g)
M = dry material mass (g)
V = volume of material (mm³)
Weathering Resistance
Weathering resistance refers to a material’s capacity to withstand alternating wet and dry conditions for an extended length of time without significant deformation or loss of mechanical strength.
Also Read : Ceramics : Properties & Classification of Ceramic
Also Read : Timber – Classification, Types, Defects in Timber
Permeability of Water
Water permeability refers to a material’s ability to enable water to pass through it under pressure. Glass, steel, and bitumen are impermeable to water.
Frost Resistance
Frost resistance refers to a material’s capacity to withstand repeated freezing and thawing while losing significant mechanical strength. Under these conditions, the water held within the pores expands in volume by up to 9% when frozen. As a result pore walls are subjected to significant pressures and may possibly fail.
Heat Conductivity
The ability of a material to transfer heat is known as heat conductivity. The type of the material, its structure, porosity, pore character, and the mean temperature at which heat exchange occurs all have an impact. Because the air inside the pores facilitates heat transfer, materials with big pores have high heat conductivity. Heat conductivity is higher in moist materials than in drier ones. Since materials used in the walls of heated structures have this property, it is a major source of worry. It will have an impact on residential properties.
Thermal Capacity
Thermal capacity is a material’s ability to absorb heat as measured by its specific heat. Thermal capacity is important when calculating the thermal stability of heated building walls and the heating of a material, such as when pouring concrete in the winter.
Fire Resistance
The ability of a material to withstand the action of high temperatures without significant deformation or loss of strength is referred to as fire resistance. When exposed to fire or high temperatures for an extended period of time, fire resistance materials scorch, smoulder, and ignite with difficulty, but only burn or smoulder in the presence of flame.
Refractoriness
The ability of a material to tolerate continuous high temperature action without melting or losing shape is referred to as refractoriness. Refractory materials can withstand temperatures of 1580°C or higher for extended periods of time. Low-melting materials can survive temperatures below 1350°C, but high-melting materials can withstand temperatures ranging from 1350°C –1580°C.
Chemical Resistance
As the name suggests, chemical resistance describes a material’s ability to withstand acids, alkalis, sea water and gases. Natural stone materials, such as limestone, marble, and dolomite, are degraded by even weak acids, wood is acid and alkali resistant, and bitumen disintegrates when exposed to alkali liquors.
Durability
It refers to a material’s ability to withstand atmospheric and other factors.
Mechanical Properties of Building Materials
Strength, compressive, tensile, bending, impact, hardness, plasticity, elasticity, and abrasion resistance are all significant mechanical properties for building materials.
Strength
Strength refers to a material’s ability to withstand stresses induced by loads, the most typical of which are compression, tension, bending, and impact. The relevance of researching multiple strengths is underlined by the fact that materials like stones and concrete have strong compressive strength but poor tensile, bending, and impact strength.
Hardness
The ability of a substance to resist penetration by a harder body is referred to as hardness. The Mohs scale is used to determine material hardness. It’s a list of ten minerals sorted in ascending hardness order. Indentation of a steel ball is used to determine the hardness of metals and polymers.
| Mohs Hardness | Mineral | Chemical Formula | Absolute Hardness |
| 1 | Talc | Mg3Si4O10(OH)2 | 1 |
| 2 | Gypsum | CaSO4·2H2O | 2 |
| 3 | Calcite | CaCO3 | 14 |
| 4 | Fluorite | CaF2 | 21 |
| 5 | Apatite | Ca5(PO4)3(OH−,Cl−,F−) | 48 |
| 6 | Orthoclase feldspar | KAlSi3O8 | 72 |
| 7 | Quartz | SiO2 | 100 |
| 8 | Topaz | Al2SiO4(OH−,F−)2 | 200 |
| 9 | Corundum | Al2O3 | 400 |
| 10 | Diamond | C | 1500 |
Elasticity
Elasticity refers to a material’s capacity to regain its original shape and dimensions when a load has been removed. The deformation of solid bodies is proportional to the stress within their elasticity limits. The modulus of elasticity is the ratio of unit stress to unit deformation. Its high value denotes a material with extremely little distortion.
Plasticity
When a material is loaded, it can change shape without cracking, and it can retain that shape after the load has been removed, this behaviour of substance is referred as plasticity. Steel, copper, and hot bitumen are some of the examples of plastic materials.