In the construction and design industry, concrete is claimed to have a life span of nearly a 100 years. The Pantheon and Colosseum built 2000 years ago are testament to the life of concrete. It is even considered the ideal material choice for tornado resistant structures and nuclear bunkers.
Looking at the subject from a practical point of view, things get a little more complicated. Concrete in itself is a durable material in its various forms. Material quality, craftsmanship, usage, maintenance and climate are deciding factors in its longevity.
To assess how long concrete in houses can last, we need to first understand where it is used in buildings and how it is affected.
Applications of Concrete in Houses
Concrete is used in mixes of various proportions, with and without rebars in different parts of a house:
Perhaps the substructure of a house (basement and foundation) employs the most use of concrete in a house. You may have heard of terms like raft, strip, pad and pile foundation. These are different types of reinforced concrete footings used in houses and other buildings.
Basements and cellars constructed in excessively damp conditions are also made of concrete. It helps in resisting the lateral pressure of earth as well as water proofing (to an extent).
Reinforced concrete beams are used in houses to help distribute and transfer vertical loads down to the foundation. They may be located at different levels like plinth, lintel and floor slab to serve different functions.
Concrete slabs are used at different parts of the house starting from the plinth floor all the way to the roof. Plain Cement Concrete (PCC) is used for ‘earth’ level subfloors. Reinforced Cement Concrete (RCC) is used to create all other suspended features like floor slabs, sunshades, roofs etc.
These walls are factory made embedded with rebar and infused with fibre. This mode of construction is used in modular housing as well as mass building projects. Precast walls are beneficial in bringing down cost as well as increasing build speed.
Concrete Block Wall
Concrete blocks are an economical alternative to conventional building blocks. They are composed of aggregate and sand. They are lightweight, durable and can withstand a considerable amount of load.
Cast-in situ Wall
There are a number of scenarios where cast in place concrete walls are used. The most widely known among these are nuclear bunkers and tornado proof facilities. This is because of the high level of safety provided by reinforced concrete shells against impacts.
Another important application of this method is the construction of retaining walls. Reinforced concrete retaining walls can be made at a third of the size of a masonry or rubble wall. Though costs can go up, this is the safer choice when constructing on hilly tracts.
Apart from these, concrete is used in the construction of various features like outdoor pathways, driveways, sheds and the like. Now that we have a general picture of where concrete is used in a house, let’s take a look at how its life is affected by time and it’s environment.
Factors that affect the life of concrete elements
The life of houses made of concrete drops when the health of its elements deteriorates. Most of these are issues are avoidable with adequate care and maintenance.
Quantifying these damages in terms of lifespan is impractical as they depend on the scale of the impact and usually other associated factors.
Quality of Concrete and Craftsmanship
Concrete is a proportionate mix of aggregate, cement and water based on usage. The life of a concrete structure depends on the quality of its ingredients. An anomaly in the blend can cause the structure to weaken, hence reducing its life span.
Construction defects can include but are not limited to improperly compacted mixes and inadequate curing. Special care must be taken by the contractor to ensure longevity for the concrete structure.
Overloading and Impacts
When a concrete slab or wall is loaded beyond its designed limit, it tends to deform and crack. In a house, this can happen when a room’s slab is filled with dead load (like furniture) more than intended. Yet, a moderately well designed slab will not fail without exhibiting considerable symptoms.
Scenarios like a vehicle collision or impacts of airborne debris during a tornado may affect the health of a concrete structure. In the event of such an incident, it is advisable to consult a professional to reinforce the damaged structure.
Formation of rust on the rebar embedded in the concrete is one of main culprits behind its deterioration. When the steel is damaged, it affects the concrete around it thus making it lose its compressive strength and cracking.
Corrosion can set into steel reinforcement in concrete in as soon as 15 years. Precautions should be taken to prevent seepage of water, carbonation and other chemical effects.
Expansion and Contraction
Like all materials, concrete expands and contracts when subjected to changes in temperature. This may happen at a different rate than other connected built mass like masonry. Such an event can cause structures to crack. This is more so a concern with the freeze-thaw cycles in experienced in US.
Techniques like the use of expansion joints are the solution to preventing such damages to concrete houses.
This could be in the form of any form of precipitation like rain and snow. Humidity and capillary action can also harbor water damage in concrete structures. Dampness seeps through the mass taking along a myriad of chemical agents which disintegrate the concrete, consecutively leading to corrosion.
Brutalist architecture from Europe in the 1950s and Socialist Modernism shortly thereafter from USSR have beautiful concrete structures that have stood the test of time.
Concrete is a versatile and tough material that can be used in the construction of houses effectively. Quality control during construction and periodic maintenance will ensure that they stand safely for a 100 years or more.
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