Foundation, Concrete and Earthquake Engineering

Becoming Durability of Concrete a Central Feature

This topic actually covers significance of durability of concrete. In designing concrete structure once only mechanical properties of concrete in relation to initial coat was considered. We know what are the mechanical properties of concrete? But in recent years we have to concentrate on durability ; here we will learn about these facts.

At first we will start with socio-economic implications. The structures which were constructed having less concern of durability, before reaching its service life, suffer severe or considerable deterioration.
Repairing a deteriorated concrete floor slab
This fact was observed and treated seriously when cost of replacement and repair of  concrete structures to rehabilitate them found to be significant portion of total budget of construction.

Let us consider an industrially developed country, where maintenance and repair cost of existing structures is reached 40 % of total cost of overall development and maintenance work. That is only 60% budget is remaining for new construction.

Thus engineers are bound to be conscious about durability due to increase in cost of replacement and increasing emphasis on cost to produce longevity of structures rather than initial cost.

Again durability of structures or materials is closely related to ecology. 
Conservation of energy and material is common feature that are considered very frequently in application and development of different technology. We know concrete constructed of fine aggregate, coarse aggregate, binding materials (most commonly cement) and some admixtures or additives in the presence of water.

In case of fine aggregate artificial sand and crushed glass particles are using to conserve natural sand. The coarse aggregates are also replaced by some extent or fully by glass particles, industrial by-products and recycled products.

Aggregate from crushed concrete
Aggregate from crushed concrete is included in ASTM and ACI code providing some provisions. The replacement of aggregate by glass, by-products or crushed concrete always associated with some unexpected reactions while hydration which are mitigated by necessary modification by adding flyash, ASR controlling admixtures and pozzolanic modification of aggregate (say fineness).

The most costly element of concrete is cement which is also partially replaced by different pozzolanic materials and industrial by-product (say BFS). So we have some idea about conservation of concrete materials. We can conserve materials also by providing longer service life of concrete structure, which is achieved by durability considerations; thus furnishes an ecological step.
Prestressed concrete LPG tank
Now concrete is using in many challenging environment having industrial exposure, hostile marine environment and as container of corrosive chemicals or pressurized gas vessels. Concrete pipes are using in many purposes of industrial and municipal activity. This exposure extremity also forced designer to be conscious about durability.

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