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Building foundations and bases


How is the concrete foundation constructed?

Concrete foundation construction is divided into a number of work activities with specific objectives and a completion time is defined for each activity, for example marking foundation layout, excavation, base preparation including leveling and lean concrete placement, pouring of concrete and then placing of steel, pouring of concrete and curing, These activities are almost the same in almost all types of foundations but the sequence and technique of execution may differ slightly.

Also, each activity for building concrete foundations must be planned as it requires specific equipment at each stage. The construction plan for the institution is affected by the ability of the contractor to complete the project and the resulting costs of the project, so that each activity for building the foundation requires different skill sets of workers and different equipment. All construction activities must be arranged The foundation must be properly estimated and the resources required at different times of the activity.

For large construction projects, there can be a large number of foundations being poured in a single day. Therefore, each activity needs to be planned for this construction. The project plan for foundation construction should specify the amount of work involved in each activity and estimate the amount of materials required.

The number of tools, equipment, manpower and other resources that will be used for this construction must be planned in advance, for example placing concrete can involve the total number of cubic meters of concrete involved in the activity. Form construction is usually measured in square meters of concrete surface area.


Steps to build a concrete foundation:

1- Clearing the ground to start building the concrete foundation:

To start the actual construction, clearing the land from where the project site will be built is the first thing to consider. In this activity, the task of the construction personnel is to free the construction site for any obstacles and debris that may hinder and delay construction. Temporary facilities such as the engineers office, labor quarter, and material storage room must also be constructed. Temporary water, electrical supply and other related facilities before starting work, site perimeter fencing should also be constructed during this period.
2- Site planning and cadastral signature:

This activity includes the identification of reference points in the form of construction grid lines and marking at the level of the gate, this is done to ensure that the grids are set up on site according to the approved plans, the reference point must be properly marked and not to be disturbed throughout the construction period, the lines Network according to the approved drawing pre-construction planning, depending on the complexity and scale of the project, the construction networks can be planned through the use of theodolites or related surveying tools.

A more traditional method of laying out a building grid and more commonly used on smaller projects is through staking using batten board and stringers. Batching boards are temporary wooden frames used to suspend stringers. Strings are representations of grid lines in X and Y directions. According to approved plans, it will work. These serve as a guide throughout construction, so it is important to fix a reference line in both directions to use once the grids are in place as needed in construction. 

3- Commencement of excavation work:

Once the building point layouts and grid lines are completed, the excavation starts so that the depth of excavation depends on the recommendation in the soil investigation report but it is safe to say that the minimum level of excavation for comfort should stick to one meter below the level of the gate. Excavation is also a massive activity, You should therefore exercise caution during this phase, should the required excavations be exceeded with the existing neighbor structure exceeding 1.20m from the proposed level a shoring is recommended.
4- Compact the soil as required:

The excavated surface shall be compacted once the required excavation level is reached, then a layer of crushed gravel shall be added during compaction, in the standard compaction procedure the final compacted layer shall be checked to reach the required degree of compaction to not less than 95% of the maximum dry density, At this point an anti-termite treatment should also be considered on the ground. An application of hygiene cement or regular cement should follow afterwards in preparation for rebar work. Cleaning cement usually consists of 10mm thick lean concrete in order to evenly place the reinforcing bars.
5- Carrying out blacksmithing work:

Once the clean cement placement is prepared, the rebar works for the foundation and any foundation beams are the next activity, at this stage the foundation rebar is prepared according to the structural schedule along with the formwork, therefore proper and standard concrete cover must be observed during this procedure, the starting bars for the columns must also be installed according So before pouring concrete.

6- Casting the foundations and fixing the iron pillars:

The construction of the foundations should come after the reinforcing steel works, the concrete to be poured must be properly shaken so that the concrete especially the aggregate is fully dispersed in the base, the column reinforcement must be still fixed to the previously installed column starter bars, the proper concrete cover must be observed before the works in the scheme are closed, for For substructure columns an additional concrete covering of at least 50 mm up to the base level shall be considered to protect the rebar from possible corrosion due to sulphate attack.
7- Concrete pouring and bitumen coating applications:

Once the column tops are poured, time is given for the concrete to dry completely and then at least two layers of bitumen coating are applied to each of the column tops and base sides. The bitumen coating helps absorb moisture from the soil to prevent seepage into the underlying concrete.
8- Building bricks around the insulation:

The installation of solid concrete bricks is done along the perimeter or edge of the proposed project. This is to mark a boundary between the internal and external edges of the project. It is also useful that the difference between the internal floor finish level to the external pavement or ground level is large. Two coats of bitumen paint should also be used. Subsequently, in some cases a solid concrete perimeter brick is optional especially for areas where the soil properties are very hard.
9- Backfilling and Damping:

Once the basic structures such as substructures including the installation of solid concrete bricks have been completed, backfilling and compaction shall take place but partial backfilling and compaction shall be done to ensure that the required degree of compaction is met up to the bottom of the plank bond level of the girder bricks.