Understanding the Basics of Concrete Strength
Concrete is among the most commonly used construction supplies and concrete strength is the main criteria used to choose concrete for different construction requirements. Concrete strength is indicated by its compressive strength. The compressive strength is rated in the form of psi, or pounds per square inch, ratings. Concrete manufacturers are required to display the psi ratings for every type of concrete they supply. Another unit used to denote the compressive strength is MPa or Megapascals, i.e. according to the SI system of measurements.
Different kinds of concrete, their recommended usage and respective concrete strengths have been explained below:
Concrete Type I—Regular Concrete
Regular concrete is available as pre-mixed concrete or as packaged concrete with mixing instructions listed by the manufacturer. The premixed form of regular concrete contains various aggregates that define its water-absorption and setting features. It is can be readily used by adding water according to the packaged instructions. Regular concrete contains various components like traces of Portland cement, brick sand and powdered stone. Regular concrete is commonly used in residential applications like strengthening the sidewalks or driveways and lining the curbs. It can also be used for basic installation purposes such as laying tiles.
This form of concrete offers a basic level of compressive strength, usually in the range of 1450 psi, 10 MPa, to 5800 psi, 40 MPa. Some manufacturers might further categorize regular concrete according to minor differences in psi ratings but usually this concrete is not recommended for heavy, load-bearing structures.
Concrete Type II—Stamped Concrete
Stamped concrete is commonly referred to as architectural concrete since it is not used for the conventional, constructional purposes, i.e. it is recommended for superficial applications. It is mainly used for giving a concrete surface, a better finish. Stamped concrete is very easy-to-handle and is recommended for home projects where the concrete surface of the walkways or parking places need to revamped. Stamped concrete is quick-setting and easy-to-clean. Its outer surface can be sealed for moisture protection and it insulates the inner concrete surface against abrasion.
Other applications of stamped concrete include reinforcing the rebar laid in a concrete surface that needs repairing. Stamped concrete is widely advised for landscaping the concrete borders of gardens since it has no cracks or edges and doesn’t allow the vegetation to grow through it.
Stamped concrete offers a mid-range in terms of compressive strength. Usually, concrete with ratings between 3000 and 4000 psi is recommended for stamped concrete applications.
Concrete Type III—High-strength Concrete/High-performance Concrete
High-strength concrete differs from normal-strength or regular concrete in terms of its improved compressive strength. This essentially means that high-strength concrete offers a greater degree of resistance to the applied pressure. It is recommended for any building any surface that needs to be durable against daily wear and tear apart from supporting an extensive load on a recurrent basis.
High-strength concrete is more expensive than regular concrete since it uses a higher concentration of superior ingredients like Portland cement and other, advanced admixtures. The admixtures or super-plasticizers are added to make the high-strength concrete more workable by rendering it a greater elasticity.
Usually, any concrete that offers a compressive strength rating than 6000 psi or 40 MPa is referred to as high-strength concrete. The greater compressive strength of high-strength concrete is achieved by lowering the water-cement, or W/C, ratio. Please note that lower W/C ratio ensures that the concrete sets faster and is more durable. High-strength concrete usually has a W/C ratio of about 0.35 or less, though this is seldom labeled as a part of the displayed ratings.