Understanding Thermal and Fire-Resistant Properties of Building Materials CPCPCM2055

Question 1

a)Thermal properties of building materials

Some of the common materials which are used for construction are timber, steel, cladding materials, plasterboards, concrete and insulation materials. The choice of these materials is largely influenced by the key thermal properties like their density, heat of combustion, emissivity, specific heat and conductivity. These are used for assessing the fire performance of materials which are used commonly for construction purposes.

Steel

It is one of the important materials used in construction mainly for giving mechanical strength to the structures (Han et al. 2020).

Density- It has a density of 7850 kg per cubic meter. it is almost constant at higher temperatures, therefore, has high resilience to fire and heat.

Emissivity- Emissivity of steel ranges from 0.2 to 0.9 at ambient environment. There are factors like oxidation, polishing, paint, galvanic coating and surface roughness which affect the steel emissivity (Jiang et al., 2018).

Thermal conductivity- it is a good conductor of heat, and its thermal conductivity is 45 watt per meter per kelvin. It is lower than pure iron and other metals.

Specific heat- its value remains constant at room temperature, and it ranges between 700 to 800 C.

There are advantages in using steel as it gives mechanical strength to the structure. It also reduces the weight of the construction, and this exerts less pressure on the ground. However, being good conductor of heat, it raises risk of fire. It is also susceptible to rust and corrosion.

Concrete

It is the primary material used in different forms for giving strength to the structures.

Density- the density of concrete is 2400 kg per cubic meter while wet concrete has a density of 2600 kg per cubic meter.

Emissivity- the effectiveness of the material in emitting energy like thermal radiation is termed as emissivity and for concrete its value is 0.54.

Thermal conductivity- it is 0.5 watt per meter per kelvin.

Specific heat it is 1050J/gK in the case of concrete.

One of the main advantages of concrete is its durability. It is also customisable and offers a lower cost. But it makes the structure very heavy and sensitive to weather conditions.

Timber

Hardwood is used for construction purposes as it has higher strength and has construction suitability (Abed et al., 2022).

Density- it is dependent on the type of wood and extent of moisture content. On an average, it is ranging from 300 to 900 kg per cubic meter.

Emissivity- it is ranging from 0.89 to 0.92 for hardwood.

Thermal conductivity- ranging from 0.12 to 0.17 W/mK for hardwood used in construction of buildings.

Specific heat- for oven-dried wood its value is 4500 kilocalories.

The heat of combustion- for hardwood it is ranging from 150-340C (Maraveas et al., 2015).

It has the advantage of being lightweight than other construction materials. It adds aesthetic value to the building. However, it is susceptible to fire, and this is one of its main disadvantages apart from natural degradation.

Cladding materials

These are the layers of materials used for thermal insulation, aesthetic purposes, and weather resistance. Density is dependent on the type of material used brick has a density of 1800-2200, stone has 2400-2800, timber has 500 to 900, metals like steel and aluminum have 2700 to 7850 while composite panels have a range of 1500 to 2000 kg/m3. Emissivity varies from material to material as aluminum has a range of 0.039 to 0.77 while red rough brick has 0.93 and fire clay has a value of 0.75. Thermal conductivity, specific heat, and heat of combustion are ranging from material to material.

Insulation materials

Different types of materials are used for insulation purpose. These materials help in slowing of the heat loss. Some of the commonly used insulation materials are rock wool, vermiculite, cellulose, urethane foam, cellulose, polystyrene, and fiberglass. Therefore, their values of density, emissivity, thermal conductivity, the heat of combustion, and specific heat are varying.

Plasterboards

These are the drywall or gypsum boards which are used for different purposes in building construction. Based on the requirement there are different materials which are used for making plasterboards like gypsum, paper liners, additives like foams and plastics, glass fibres. Hence, these have varying values for density, emissivity, heat of combustion, thermal conductivity etc.

b) Effect of thermal properties on fire resistance level

Thermal properties like thermal conductivity influence fire resistance level. As material will low values of thermal conductivity are good at fire resistance. The materials with higher values of specific heat absorb more heat and resist fire spread. materials like concrete and steel do not have combustion values and therefore, these resist in fire spread.

c) Combustible and non-combustible building materials

Combustible Materials -examples are paper, plastics, fabrics, insulation materials like foam and mineral wool polyethylene-filled aluminium panels, fibre insulation products, and wood.

Non-Combustible Materials examples are steel, glass, gypsum board, calcium silicate, and cement board, concrete, and masonries like stones and bricks.

Question 2

a) Non-combustibility of building materials

In order to ensure non-combustibility of building materials, it is necessary to select materials which are known for their non-combustibility like concrete and steel. It is also determined by conducting standardised tests like ASTM E136 and EN ISO 1182 (non-combustibility test).
The non-combustibility EN ISO 1182 test is used for exposing a material to high temperatures and then observing its behavior (Fangrat, 2016). If the material does not ignite and contribute to fire, then it is non-combustible. ASTM E136 is the standard test method for ascertaining combustibility using a vertical tube furnace where the material is exposed to 750C temperature (Hasburg et al., 2022). These tests are useful in ascertaining the fire performance of the materials. It is necessary to avoid materials that do not pass these testsas these raise the risk of fire spread and increased damage to the building.

b) AS1530.1 & AS1530.3 standards

Both of these standards are used for evaluating the fire performance of the materials used in building construction however, these use different techniques and are focussed on different features of materials.

AS1530.1 determines non-combustibility of the materials. In this test a material is placed in a high temperature furnace of 750C for half an hour. A substance is termed as combustible if it flames for more than five seconds and suffers from significant weight loss.

AS1530.3 is used for determining fire hazard properties like heat release, smoke release, ignitability, and flame propagation. In this test an assessment is done to determine to know ignitability, spreading of flames, amount of heat and smoke released. In this method, a material is exposed to a radiant source, and it is assessed in terms of flame propagation, ignitability, smoke, and heat release.

c) Small-scale, intermediate, and full-scale tests used for cladding testing

it is necessary to test the cladding materials for their fire resistance. It involves various scales of tests namely small-scale, intermediate, and full-scale tests for evaluating the performance and safety of a cladding material (Lannon et al., 2018).

Small-scale tests are used for assessing mechanical integrity and fire safety. Cone calorimeter test is used for measuring the rate of heat and smoke release and combustion features of small samples of materials. Single burning item test is used for evaluating the reaction of building products to fire in terms of heat release and spread of flame (MacLeod et al., 2024).

Intermediate-scale tests are used for rendering data on a realistic fire scenario which is manageable in a lab setting. Room corner test is one such test where fire performance of the cladding material is assessed at room environment and is focussed on heat release and flame spread.

Full-scale test is performed to get data on fire performance of materials in a real-life fire scenario. SP fire 105 test was done in Sweden and some Nordic countries to find out the fire behaviors of faade cladding materials in a multistorey building. Similarly, BS8414 test is used in UK to assess the fire performance of cladding systems external to a building (Cho & Park, 2018).

Question 3

a) Surry Hills, Sydney, Australia

This incident took place on May 25, 2023, when two teenage boys lit a heritage building on fire. This building was abandoned and therefore nobody cared for its maintenance. The interiors of the building were made of wood and the sprinkler system was not working. Cladding materials were also wood while bricks were used for the external construction. This wood was well dried and seasoned serving as a perfect fuel. fire retardant was also not used on wood (Hossain, 2023). Hence, the fire spread so quickly and damaged it completely.

b) Grenfell Building, North Kensington, England

Fire in this building took place due to an electrical fault at the fourth floor. The cladding material was polyethylene-filled aluminium panels and for insulation purpose foam was used. The fire spread due to the external cladding system, and it burned for 60 hours.

c) Torre Dei Morro, Milano, Italy

In this incident, the fire spread quickly due to the cladding material used which was polystyrene and aluminium. These contributed to the rapid spread of fire both upwards and downwards and caused damage to the entire building (McLaggan et al., 2021).

In all these case studies, the main learning made is that the choice of material used as cladding is very important. A project manager must ascertain the fire performance of the material used. It will help avoid the risk of fire and major casualties due to its rapid spread. Furthermore, a fire extinguishing system must be maintained to contain the fire before it spread rapidly. This is the best method of preventing fire from spreading. Therefore, right choice of cladding material is essential in protecting from the fire hazard and controlling the fire in case of an accident. Hence, these steps can be taken to check fire hazard and prevent damage to the building.

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