Concrete is the backbone of all construction today. Every structure you see around you is built on a firm foundation of concrete. What happens when that very foundation weakens? When this happens, we see buildings crumbling or developing cracks within a few years of construction. This leads to dangerous living conditions where there is fear of the structure collapsing. Is the concrete itself to be blamed? No. Often concrete is not handled and used properly, leading to accelerated erosion. Let’s explore some more reasons that lead to the development of cracks in concrete.
Reasons Why Concrete Cracks
- Excess water in the mix – A common malpractice when treating concrete is adding excess water to the concrete mix. Concrete needs a certain capacity of water to strengthen its core, but anything above the standard limit causes more harm than good. When this excess water evaporates from the concrete, it leads to further shrinkage. It’s best that your construction team is aware of the exact proportions of water and concrete to be mixed.
- Rapid drying of the concrete – While excess water causes harm to concrete, so does rapid drying. This drying then leads to excess evaporation of water from the surface, leading to map cracking. While this usually affects the aesthetics of the structure, if not controlled, it can affect the deeper layers leading to cracks within the building. A process called curing usually prevents rapid drying. Here moisture levels in concrete are regulated by adding proportionate amounts of water.
- Improper strength concrete poured on the job – Every structure needs a certain weight-bearing capacity. From skyscrapers to small houses – every building has a different requirement for concrete. This concrete often comes in a range of different ‘strength capacities’. A common error is to use a lower or higher grade strength concrete without matching it with the structural requirements of the building. This then leads to cracks and eventual damage.
- Lack of control joints – Control joints are used in concrete to strategize the cracks. These joints are placed in areas where temperature, shrinkage, and other factors will lead to cracks. This gives the builders control over deciding where the concrete will crack while minimizing damage. When these control joints are missing, the concrete will crack in fragments that will cause heavy damage.
Types of Cracks in Concrete
Concert develops cracks because of varied reasons and each such crack can be identified because of its unique characteristics. In this section, we will explore more about the types of cracks in concrete and what each type indicates. Identifying the causes of cracks can help you think of preventative steps.
- Cracks caused by deformation – There are many forces that act upon concrete. The most common are tensile, compressive, and shear forces. It is because of these forces that deformation occurs, which leads to cracking. To identify such cracks, you must see the geometry of the crack. For instance, parallel cracks are caused due to compression, whereas perpendicular cracks are caused due to applied forces or tensile forces.
- Cracks caused by hydraulic shrinkage – The process of hardening often causes exposed concrete to shrink. This shrinkage is a natural phenomenon. Yet when the forces of this shrinkage become greater than the concrete’s inherent strength, it causes deformation. These cracks are usually seen in concrete joints or in areas where reinforcements were done.
- Cracks caused by thermal shrinkage – Cracks due to thermal shrinkage are often seen in large structures. Here, as the name thermal suggests, the variation in temperature leads to deformations. As we know, concrete undergoes a drying process where the heat usually dissipates. Sometimes when there is an unequal distribution of heat in the structure, it causes cracks to occur.
- Cracks caused by swelling – Concrete can swell due to multiple reasons. The most common ones are presence of sulfates presence in the earth. Apart from that, freezing of water in the concrete leads to an expansion of the entire concrete. Oxidation is another reason for the swelling of concrete. These all lead to one occurrence – an increase in internal tensile force which reduces the strength of concrete.
Cracks caused by corrosion of the steel reinforcement – TMT bars are often used to strengthen concrete. When these TMT rebars corrode over time, it leads to development of cracks in the concrete structure.
How to Limit the Cracking Phenomena?
You can prevent the different types of cracking in concrete by following a few simple but effective methods. Let’s explore these reasons in depth in this section.
- Start with a sound subgrade – When overlaying concrete with other elements, it’s essential to ensure the 2 elements layer and bond properly. This is what’s known as a sound subgrade. If these aren’t layered well, then the material will detach from the concrete, leaving it exposed to wear and tear.
- Modify the concrete mix – Understand the proportions of water you need before adding it to the concrete mix. Consult the manufacturer, who will accurately inform you about the right proportions to be added. If the mix is smooth, it means you have added enough water. In case you feel the mix is crumbly, then add more water. Keeping this simple trick in mind can help prevent damage.
- Install Steel Joints – Add steel joints in potential crack areas. This will help control the cracks and also minimize the damage caused due to them. With this method in place, the cracks will be restricted to vulnerable areas instead of the whole slab.
Properly cure the concrete – Constant hydration of the slab will help curb the rapid drying due to evaporation. Besides adding water, curing also involves covering the concrete with cotton mats soaked in water. This process, if carried out properly, will cause fewer deformations and cracks.
Concrete forms the spine of any structure and needs to be well protected. As covered in the article, this can be done right at the initial stage by strengthening the concrete with strong raw materials and processes. Sree Metaliks Limited offers just these materials that will strengthen your concrete structures and safeguard them for years to come. The brand is a renowned name in the construction industry and offers quality products at an affordable range. So, if you want your structures to remain strong, then invest in right materials.