Concrete is an artificial stone-like material used widely for different construction projects. It is becoming popular in almost every city and rural area. Those bridges, roads, highways, skyscrapers, and properties that we see everywhere are most likely made up of concrete. Although concrete is known to be cost-effective due to its long-lasting strength, there are also limitations associated with it.
Below is the list of disadvantages that comes with using concrete as a building material.
Low Tensile Strength
Although concrete are highly compressed in structure, it exhibits a low tensile strength. Compression and tensile strength are different. Tensile strength pertains to the capacity of a certain material to resist breaking down under extreme pressure, while compression is the ability to withstand heavy weights and forces. Normally, the tensile strength of concrete is 1/10th of its compressive strength.
Concretes have a low level of durability, which is the ability of a certain material to withstand impact energy or force. Compared to other materials like steel, concrete has significantly low toughness. Concrete’s toughness is only 1-2% of steel.
Low Specific Strength
Specific strength refers to the ratio of strength to density. It is controlled by decreasing the density and increasing the strength. It means that the denser or thicker the material, the less strength it carries. The specific strength of a typical concrete is just half of steel. Having a variation of concretes like lightweight concrete & high-strength concrete can lessen this limitation.
Formwork is Inevitable
Since fresh concrete is liquid or almost in a liquid form, the formwork is required to mold it in shape and support its weight. But the formwork is quite expensive to acquire and install. Its installation is also labor-intensive and time-consuming.
Partially Brittle Material
There are three major modes of failure of materials – quasi-brittle failure, ductile failure, and brittle. Glass and mild steel are the typical samples of materials that fall under the brittle and ductile failure categories. Brittle materials fail the onset of tension or force. Since concretes show a strain-softening characteristic, they are considered partially or quasi-brittle materials.
These kinds of materials like concrete will go through little deformations first before complete failure or breakdown. The deformation serves as a warning. The less deformation means lesser risk for failure. Additionally, plain concretes have low fracture toughness. This is one of the major disadvantages of plain concrete. That is why concretes are usually incorporated in steel to have some tension resistant properties, while it takes the compression loads effectively. Therefore, reinforced concrete is a second-generation concrete that has more stability and strength as wire mesh or steel bars are embedded in it.
Long Curing Time
Most of the time concrete achieves the target compressive strength in 28 days after the casting and curing process. The full-strength development needs the right ambient temperature that is controlled over a month. This is quite time consuming, but it can be remedied by undergoing a process of microwave curing or steam curing through admixtures.
Needs Strict Quality Control
Concrete demands strict quality control during the process of mixing, casting, and curing. Every step of the process needs a high level of precision and efficiency. The workers also need to be highly skilled and trained to follow the right processes. A little mistake on the number of materials added or on the mixing of materials could greatly affect the overall quality of the concrete. If quality control is not implemented among workers, concrete is susceptible to poor strength and performance issues.
Working with Cracks
Concrete easily cracks when the tensile stress exceeds the tensile strength of it. Plain concretes are very susceptible to cracking during high tension occurrence. Shrinkage is the primary cause of cracking in concretes. When the concrete solidifies and dries, it shrinks. This is caused by the evaporation of excess water poured out during the mixing process. This shrinkage causes forces in the concrete that can induce the slab to crack.
Although concrete is the most widely used construction material in the world, it still lacks ductility. Ductility is characterized by the capacity of the material to be hammered out thin or undergo certain changes of form without breaking down. In short, it is a state of malleability or flexibility. Concrete is highly dependent on detailed steel reinforcing bar or rebar cages to get some tensile strength and confinement features in order to act in a ductile manner.