Concrete Retaining Wall

A retaining wall is construction of a structure that grasps the soil or rock from a building, area or structure. A concrete retaining wall is a structure that is made from concrete which is a material made from cement. A concrete retaining wall helps in aversion of down – slope movement or erosion and adds as a support to vertical or near vertical grade changes. 

To build a concrete retaining wall, many types of concrete are available. All these concretes carry the same ingredients but in different proportions. The design mix depends on the structure that is being built. The main ingredients that are needed to build a concrete retaining wall are:

• Cement: The most common type of cement that is used to build a concrete retaining wall is Portland cement which is a mixture of concrete, plaster and mortar. The concrete contains oxides of silicon, aluminium and calcium. This cement is made by heating limestone with clay. This heated substance is called clinker. Clinker is further grinded with a source of sulphate with the most commonly used substance as gypsum. Sometimes reinforced concrete is added to the mixture by adding metal reinforcing bars, plastic fibres or glass fibres.

• Water: Water when combined with cement forms a paste and the process is known as hydration. The paste easily glues the aggregate together and fills in void spaces. Less water would result in a stronger and durable concrete retaining wall. Contaminated or impure water mixed with concrete can also cause issues when setting the concrete retaining wall.

• Aggregates: Fine and coarse aggregates like natural gravel, crushed stone and sand make up most of the concrete mixture. Recycled aggregates that have already are availed from demolition or constructions are also used as partial replacements of natural aggregates. Decorative stone like quartzite, crushed glass and small river stones are also added to the concrete that is used for the concrete retaining wall for a decorative look.

• Chemical admixtures: A variety of chemical admixtures in the form of liquids or powders are added to the concrete mixture of the concrete retaining wall to give it certain qualities that are not availed from normal concrete mixes. The most common of these admixtures are:

• Accelerators like NaC1 CaCl2 increase the pace of hydration of the concrete.

• Retarders like table sugar or sucrose slow the hydration process and are used in large pours.

• Air entrainments distribute tiny air bubble in the concrete mixture of the concrete retaining wall which reduces damage that is caused during freeze thaw cycles. This also increases the concrete durability.

• Plasticizers or water reducing admixtures are used to increase the workability of plastic or fresh concrete. Alternatively they are also used to lessen the water content of the concrete mixture of the concrete retaining wall. This admixture also improves strength and durability.

• Pigments are used to change the colour of the concrete retaining wall surface.

• Corrosion inhibitors are used to reduce the deterioration of steel and steel bars in the concrete mixture of the concrete retaining wall.

• Bonding admixtures are added to the concrete mixture to bond old and new concrete.

• Pumping aids improve pumpability and thicken the paste to reduce dewatering, that is, the tendency for water to separate from the paste.

• Fly ash is a by – product of coal fired electric generating plants that are used to replace Portland cement to upto 60%.

• Ground granulated blast furnace is a by – product of steel production that is used to replace Portland cement by upto 80%.

• Silica fume is a by – product of silicon production and is used to increase strength and durability of the concrete.