Reinforced concrete

February 16, 2021 | By: Arch. Benjamin K. Panganiban, Jr. (As published in the Philippine Star last February 16, 2020)

EVERYWHERE you go, you see high-rise condominiums or low-rise commercial and residential buildings coupled with beautiful and manicured landscapes and poolscapes making such structures stand out in full appreciation of the general public.

These structures that add beauty and stability are made of construction materials that have stood the test of time most notably, skyscrapers and landmarks. They have used a lot of reinforced concrete as this is the dominant indigenous material commonly found across the globe.

While concrete has been used since the Roman times as a construction material and even way earlier, it was only in the 1850s that iron was introduced as a reinforcing material to concrete by French industrialist Francois Coignet. In the 1880s, German Civil Engineer G.A. Wayss used steel as a reinforcement to concrete.

Now Reinforced Concrete is one of the most widely used construction materials in modern history. Concrete and steel acomplement each other. While plain unreinforced concrete is relatively brittle and extremely poor to withstand stress, steel or reinforced steel on the other hand, form a bonding strength that resist tensile forces and form a strong bond together with concrete that is able to resist applied forces and eventually acting as a singular structural element.

On the other hand, reinforcing steel increases the overall strength of concrete when combined either in the form of steel rods, cables, wire mesh, and bars embedded in concrete before it sets.

In the construction industry, the disadvantage of concrete over structural steel system is the construction time as concrete has to be given a certain period of time to cure, while structural steel can be readily fabricated and immediately installed. Therefore, new technology and methods today have improved the usage of reinforced concrete to trim down the construction period.

Cast-In-Place Concrete or poured-in-place concrete is the most common concreting technique undertaken in the construction site and is a preferred choice for foundations, columns, beams, slabs and walls. To shorten the curing period or even regulate its hardening process, today’s technology has the admixtures and retarders added to the concrete mix before pouring to the forms with the rebars in place.

Pre-Cast Concrete is another form of concrete that is prepared, cast and cured in a factory or off-site area using moulds or forms that are re-usable. Then, they are delivered to site and joined together to form a complete structure. Like a Lego toy, they are connected, welded and is economical and sometimes practical. The advantage of pre-cast concrete is it is fast, reduce site delays, have fewer environmental impacts such as noise pollution and dust, and makes sure program timeframe is attained.

Today, buildings have a combination of cast in place concrete, pre-cast concrete and structural steel works. The beauty of pre-cast concrete is that steel reinforcements are already incorporated and that loading stresses are also introduced in the structural member during fabrication. Much more, the performances and strengths are greatly improved.

Tilt-Up Construction is another form of construction technique to shorten the construction time. Here the concrete ground base is first constructed, then the structural supports are formed and fabricated on the ground then tilted up to a vertical position. A crane is used here especially tilting -up panels or walls.

Warehouses were most famous in using these construction method before. Today, hotels, houses, schools and offices are now using this tilt-up method either as a single story or multi-story.

Most architects specify and use reinforced concrete, notably the branded ones or the most commonly used brands while most builders agree and conform to this because reinforced concrete today is much more durable and stable, has good thermal stress, fire-resistant and low-maintenance. The beauty of reinforced concrete today is that it will last a lifetime, maybe centuries even from now where the architecture of the past will be much more appreciated by future generations.