CONCRETE FOUNDATION

A concrete foundation is a base for a structure. It refers to the lower base portion of a building which is used to support all the loads acting on the building. These may include gravity

A concrete foundation is a base for a structure. It refers to the lower base portion of a building which is
used to support all the loads acting on the building. These may include gravity load, lateral loads, and
the self weight of the building. A foundation is that part of the structure that transmits loads to the soil
safely. The type and size of the foundation required varies based on the structure that is going to be
placed upon it.
Since most foundations are buried, concrete or brick masonry are most commonly used. Concrete has
been used since olden times for this purpose because it is inexpensive, hard-wearing and resistant to
fire. It is a popular choice of material in the building industry because it is extremely strong and also
efficient at spreading the weight of large structures. Concrete may used either with or without
reinforcing bars.
The foundation of any structure is vital to its safety and longevity. The stability of the concrete
foundation affects the structure and integrity of the whole building. Any weaknesses in the foundation
can have a huge impact and will detriment the building. Thus, correct planning and construction is
absolutely vital in order to prevent undesired consequences.
The foundation of buildings varies based on the existing soil conditions and also on a case-to-case basis.
Different concrete grades are used according to each situation. Grades of concrete are defined by the
strength and composition of the concrete, and the minimum strength the concrete should have
following 28 days of initial construction. The required grade is recommended by the structure engineer
depending on the bearing capacity of soil and the recommendations made by the soil investigation
team. The selection of grade depends mainly on two criteria: structural criteria such as the bearing
capacity of soil, size and load of foundation, seismic aspects, etc. and also on durability criteria. For the
foundations of low-height buildings, the recommended grades of concrete are M20, M25, M30, etc.
Steps in constructing a concrete foundation:
 Decide on the type of foundation. The two basic types of foundation are shallow and deep
foundations. Shallow foundations are built on hard surfaces or on level ground, and are usually
not more than 3 feet deep. Deep foundations, on the other hand, are used for more complex
projects. They are generally used when soil conditions are poor or when building a structure on
irregular terrain. Thus, the type of foundation to be selected depends on the area where it is
located and the type of structure that will be placed on it.
So the first thing to do is to investigate the soil conditions.
 Then, determine and locate the actual corners of the foundation. Calculate how deep you need
to dig the hole for the concrete slab. Dig and excavate the area of the foundation slab. Dig down
twice the thickness of the slab. Clean up the hole and lay a barrier to protect the concrete
flooring.
 Next you need to install the footings. Set footings 2 feet across to properly space the form work
and align the 2 inch wide by 10 inch long boards to build the forms for your footings. Then,

square and level the form. Care should be taken to ensure that the formwork is strong and
firmly in place as adjustments cannot be made to the form after the concrete is poured.
 Prepare your concrete. Add water to the cement in the required and correct proportions and
stir constantly. Then, prepare your concrete foundation by pouring the ready concrete into the
form. Use a trowel to level it off and smooth it over.
 Finish the work by allowing the concrete to dry. Remove the forms after the concrete dries
thoroughly. This will usually take at least 24 hours.
 Make sure to soak the concrete and keep it wet for the next few days in order to avoid cracking.
Sometimes, cracks are noticed after pouring in concrete foundations. This mainly occurs due to the
shrinkage effect of concrete. Cracks appear on the surface due to the loss of capillary water and increase
in tensile strength. It may also be due to bad concrete pouring methods and vibration, incorrect
component proportions or insufficient plasticity of concrete. Weather conditions play a major role in
how well concrete cures. This is why in areas where high temperatures are an issue, the pouring of
concrete is mainly done at night. This helps to avoid cracks formed due to shrinkage to a large extent.
Care must also be taken to soak the concrete at intervals for a few days after pouring.
Advantages:
Concrete foundations are one of the most popular choices for residential and commercial buildings as
they provide builders and owners with several advantages. They offer better performance at a
competitive price.
 Design flexibility: Concrete foundations can take on any shape or design required, which
provides several advantages.
 Strength: Foundations made out of poured concrete have a much better compressive and
flexural strength. They are extremely strong and durable and they don’t shift it there’s
movement of the soil underneath the building.
 Water and fire resistance: The increased strength, density, and joint-free construction of poured
foundations dramatically reduce basement water problems. It also offers much better
protection against fire.
 Maintenance: Foundations made out of concrete are practically maintenance-free. They have an
excellent resistance to rot and decay, and thus have a very long lifespan.
Drawbacks:
However, there are also a few drawbacks to using concrete as a structural foundation. One of them is
that it poses a few problems to the environment. Its installation process is also quite toilsome and time-
consuming. It can be used only at a shallow depth in the absence of hefty, heavy and special
equipments. Such usage may also lead to corrosion and soil compaction in the surrounding area, which
negatively affects neighboring plants and buildings. Moreover, if concrete is not prepared properly,
cracks can occur. Consequently, despite the fact that concrete is initially cheaper, the cost to repair it is
quite the opposite as sometimes, the entire concrete may have to be dug up to repair leaks or cracks.

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