Ever wondered what the difference is between cement and concrete? Well, maybe not...but here at Studio50, concrete is an everyday thing. It’s not unusual to hear the two terms used interchangeably, but they are definitely two very different things.
Forms of concrete have been around for thousands of years, but the ancient Romans were prolific builders using concrete. Their concrete was made by mixing seawater, lime, volcanic rock and ash to form a mortar. They were able to build underwater structures, by packing this rocky paste into wooden forms. When immersed in seawater, a chemical reaction was triggered, the water hydrated the lime and reacted with the volcanic ash to “glue” everything together. This enabled the Romans to build their baths, piers, harbours, bridges and aqueducts, many of which still exist today.
The easiest analogy that illustrates the difference between cement and concrete is to think of cement as the flour, and concrete as the bread. You can’t make concrete without cement. Cement is a blend of a variety of raw materials - calcium (usually limestone), silicon, aluminum and iron. The most common type of “modern” cement is Portland cement, (named for the limestone mined on the Isle of Portland, Dorset.) Fun fact #1: Many famous London landmarks were built from Portland limestone after the Great Fire of 1666, such as St. Paul’s Cathedral, the London Bridge, and Buckingham Palace.
A cement mixture alone has admirable adhesive qualities that bind well to various surfaces, but it is typically prone to cracking, and not suitable for jobs larger than repairing broken or crumbling concrete. When cement is mixed with water, it creates a paste. Once aggregates (sand, stones, rocks, gravel, fibres) are added to the mix, and turns into concrete once it starts to hydrate. This hydration process is an exo-thermic reaction, and is called the heat of hydration. Heat actually emanates from concrete during this process, and is really evident in the shop when Kim has spent the day casting a table full of Rock Bottoms.
The generic ratio for concrete is 1 part cement, 2 parts sand, and 3 parts aggregate. Adding water to the mix holds it all together until it hardens. The strength properties of the concrete are directly related to the amount of water added. Simply put, adding a lot of water to the mix will make the compound easier (more malleable) to use, but a drier (less workable) mix will make the finished product stronger and more durable. “The fun part,” says Steve, “is finding a happy balance of water to control how it flows and how much effort to exert to get it into all corners of the forms. Way too much water will cause segregation, which is when all the heavy aggregates fall out of suspension from the cementitious paste and the water bleeds to the top.” The strength of the cement comes from the paste surrounding each aggregate particle, filling up all the spaces between the particles. Kim likes to use the blockade scene from Guardians of the Galaxy to explain this bond. When Nova Prime Irani Rael (Glenn Close) orders from her command post, “All Nova Pilots interlock, and form a blockade! The Dark Aster must not reach the ground!” she knows that when all the fighter planes closely align, they will form an impenetrable “net”. As the Irish proverb tells us, “There is no strength without unity.”
Over the past decade, Steve and Kim have experimented with countless different “recipes”, ratios and curing times to achieve our signature Gaia texture as well as other custom mix designs for Studio50's furniture and lifestyleware collections. Technical and scientific hours of R&D have been invested into hand-casting long lasting, lightweight, and strong concrete pieces for people and the spaces they live, gather, rest, love and call home.