Materials Used in Bridge Construction

Stones, Timber, Concrete and Steel are the traditional materials that are used to carry out bridge construction. During the initial period, timber and stones were used in the construction, as they are directly obtained from nature and easily available. Brick was used as a subgroup construction material along with stone construction. Stones as construction materials were very popular because of its durable properties. Many historic bridges made from stones are still present as a symbol of past architectural culture. But some of the timber bridge have been washed away or are in the stage of degradation due to their exposure to the environmental conditions. As time passed, the bridge construction has undergone more development in terms of materials used for construction than based on the bridge technology. The concrete and steel are manmade refined materials. The bridge construction with these artificial materials can be called the second period of the bridge engineering. This hence was the start of modern bridge engineering technology. Modern bridges make use of concrete or steel or in combination. Different other innovative materials are being developed so that they can well suit with the bridge terminologies. Incorporation of fibers which comes in the category of high strength gaining materials is now incorporated for the construction of bridges. These materials are also used in order to strengthen the existing bridges.

Concrete for Bridge Construction

Most of the modern bridge construction make use of concrete as the primary material. The concrete is good in compression and weak in tensile strength. The reinforced concrete structures are the remedy put forward for this problem. The concrete tends to have a constant value of modulus of elasticity at lower stress levels. But this value decreases at a higher stress condition. This will welcome the formation of cracks and later their propagation. Other factors to which concrete is susceptible are the thermal expansion and shrinkage effects. Creep is formed in concrete due to long time stress on it. The mechanical properties of concrete are determined by the compressive strength of concrete. The reinforced or the prestressed concrete is used for the construction of bridges. The reinforcement in R.C.C provides the ductility property to the structure. Nowadays, ductility reinforcement is provided as an additional requirement mainly in the earthquake resistant construction. RCC is nowadays made from steel, polymer or other combination of composite materials. Much sustainable materials is available that can take the role of cement. This is a new innovation in sustainable bridge construction. When compared with RCC bridge construction, prestressed concrete is the most preferred and employed. A pre-compressive force is induced in the concrete with the help of high strength steel tendons before the actual service load. Hence this compressive stress will resist the tensile stress that is coming during the actual load conditions. The prestress is induced in concrete either by means of post tensioning or by means of pretensioning the steel reinforcement. Many disadvantages of normal reinforced concrete like strength limitations, heavy structures, building difficulty is solved using prestressed concrete

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