Concrete Foundations – Construction Guide

Foundations are the base on which a structure, building or component of a  larger building is constructed. Foundations have their own unique designs and concreting these foundations requires a number of highly regulated steps. Including: site inspection and obtaining approvals from various authorities. Inspection activities take place just to ensure the safety of the ground environment. Foundations are generally made of concrete, a material that is long lasting and relatively inexpensive with high strength and waterproof properties.

Good concrete foundations should have a perfectly proportionate concrete mix that should be approved by the concerned authorities. The construction process for concrete foundations will need a suitable formwork and proper execution of activities such as shuttering, mixing of various ingredients to form the required concrete and barrowing and pouring of the concrete.

Some common types of concrete foundations include:

  • Concrete block foundation
  • Concrete pier foundation
  • Concrete slab foundation

Tools Required for Construction

The key tools required for building concrete foundations are listed below:

  • Barrow
  • Protective gear
  • Batten
  • Shovel

Materials Required

The typical materials required for building concrete foundations are listed below:

  • Cement
  • Sand
  • Aggregate
  • Brick

Undertaking the Work

Construction of concrete foundations does require a preparation process for the concrete mix but what is equally important is how to test the soil, select the concrete, get the concrete delivered and how to handle the concrete once it is delivered.

Given below is an in depth explanation of processes that play a major role in the construction of concrete foundations:

  1. Soil compaction
  2. Preparation of the concrete mix
  3. Formation of shallow strip foundations
  4. Selection and delivery of the concrete

Soil Compaction

For any kind of concrete foundation the most important thing to be taken care of initially is soil compaction. Soil compaction removes excess moisture and reduces air voids in the soild below and around where the foundations are to be built.

The following process will enable you to judge whether the soil on which you intend to construct a concrete foundation has sufficient amount of water for compaction.

  • Take some soil and squeeze it to form the shape of a tennis ball.
  • Drop this soil ball down from a height of 1 ft.
  • The soil ball holds together when the moisture content is favorable and then breaks into uniform pieces when dropped.
  • If the soil is very dry you will find it difficult to make the ball and when too much of moisture is present in the soil, it will leave behind traces of soil on your fingers.
  • To avoid these issues make sure the soil is dried before compaction.

Preparation of the Concrete Mix

To prepare the concrete mix, you should keep the proportion of cement, sand and aggregate in the ratio 1:3:6. You can also use ready mixes with the same ratio of components.

Formation of Shallow Strip Foundations

  • For a shallow strip foundation you will need a concrete strip that is 600 mm wide.
  • Place the concrete strip at about a meter depth into the ground and the depth of the strip should be a minimum of 150 mm.
  • Build two skins of brick from the ground level.
  • Fill the gaps between the two brick skins with a light concrete mix to prevent lateral pressure.
  • Use a wider trench while constructing the brickwork below the ground level.
  • The trench that you select should be sturdy and the sides of the excavation should be straight and vertical.
  • Construction of the formwork will be required when soil falls out from the sides of the trench as it is excavated. In such situations, it is the formwork, which is basically a firm wooden structure that will keep the shape of the concrete work intact.

Selection and Delivery of the Concrete

As mixing the concrete by hand is highly impossible you will have to get the concrete delivered by a ready mix lorry. For this, you need to specify the particular mix you need with the correct ratio and fix a delivery date.

As the ordering of the concrete takes place, you will also have to focus on allocating a proper place for the concrete lorry to be parked near the site thus preventing too much of barrowing. You will also have to be ready to receive the concrete in advance and for this ensure that you consult with the neighbors and then fix another place on the street for the lorry to be parked. Also make sure to provide a clear access route between the lorry and the foundation trenches so as to obtain a steady to and fro movement of barrow loads.

After receiving the concrete see to it that the barrow is held steadily as the concrete is loaded in the trench. While dealing with the concrete you will have to wear protective gear and avoid eye and skin contact as the concrete can cause alkali burns on the skin. See to it that the concrete is leveled properly in the trench without any empty spaces. After the trench is filled to a specific level, use a batten to level the surface. Finally, use a shovel to remove the concrete left behind while barrowing.

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