Cody Burr

The first human cement was mud, as long as it contained a sufficient clay content. This was used to bind things together or simply as the building material itself. Theoretically, early people learned that mud by itself was mud, but not all types of mud were good, good mud needed the right amount of clay in it to be useful. When mixed with sticks and grass the mud became stronger, something new, a polymer. This was an early form of cement. A realization like this would likely lead the innovator to experiment further with new material, to play with different types of mud and additives. With no small effort, the first homes and vessels were formed. Simply by itself, the mud would not last in weather, so a roof was added. Necessity drove innovation, an industry of cementists was born. Undoubtedly ancient forms of cement were discovered all over the world in every society where people began building permanent structures. Various civilizations discovered their own version of cement independently, though undoubtedly recipes were also shared through the commingling of cultures, or stolen, especially when various peoples were absorbed into the bottom of a dominant culture.

One such story of cement involves the Nabataens. Originally a nomadic people of the Arabian Desert, the Nabataens later became a distinct and influential empire; partly from their ability to thrive in a difficult landscape, they were essentially oasis builders, facilitated in part by a new type of cement. Though it’s impossible to know exactly how ancient peoples like the Nabataens discovered the predecessor to modern cement, quicklime, there are probable theories. One involves a connection to the ceramics industry from its use of kilns. If the kiln or cooking pit was lined with limestone it’s possible the limestone rock could release CO₂ transforming it into quicklime. This would be possible if the temperature was high enough. Cultures around the world discovered and manufactured quicklime, a white cementitious materiel commonly used to whitewash stone. This is technique is so ancient it isn’t clear who discovered it first or if it was discovered independently by various cultures. Many of the largest pyramids on both sides of the Atlantic were at one point covered with a limestone whitewash.

The Nabataeans even incorporated fine silica powder found in concentrated deposits as a methods to create waterproof cement. This type of additive is known as a pozzolan. In combination with specialized tools and tamping methods this new cement produced a water impervious concrete. This allowed them to capture and preserve the scant waters through a network of aqueducts and cisterns scattered throughout the Arabian desert. Hidden bellow the earths surface or in caves, liquid life was stored safely away from the heat. This new cement allowed them to live and thrive within an arid desert landscape, their own designed oases. Innovations like these have allowed desert dwelling peoples to thrive in harsh landscapes, long before air conditioners and portable spray fans.

Their wealth and prosperity didn’t go unnoticed though, and at some point in the continuum of history the Nabateans were annexed into the Roman empire. Romans are also known for their cement, and are famous for their use of pozzolans. The roman pozzolans were obtained from volcanic ash deposits scattered throughout the empire. One of these deposits was in the city of Pozzuoli, the materials namesake, near Mt. Vesuvius. These reactive materials were used only for the most important or architecturally complex structures. Aside from pozzolans some recipes listed animal fat, milk and blood as admixtures to improve the properties of concrete, there is some truth to this. Through centuries of experimentation the Romans were able to construct what is still the world’s largest non-reinforced concrete dome (Pantheon). Though not as tough as modern polymer concrete, many Roman concretes are more durable and longer lasting than the modern material. This is partly due to the lack of metal reinforcements which invariable rust and cause failure of the structure. Attributed to this durability is in part the pozzolan, but that didn’t explain the mysterious self healing ability of some Roman concretes. The long lost secret, quicklime, and a particular component of it called, a lime-clast. This material within quicklime dissolves overtime with rainwater water and relocates into cracks and voids like a mineral glue, thus preventing the crack from spreading. Some Roman concretes used in seawall construction points to the salt water in creating mineral growths that improve long term durability. Still, much remains unknown of Roman concretes and their techniques, there were innumerable types used for different purposes. Some Roman piers are still sitting around in the brine to this day. Modern cement would have crumbled long ago.

Quicklime cement was common in ancient times used by people such as the Nabateans, though until it could be proven its benefits are largely forgotten, or ignored. The benefits of pozzolans are not as recently discovered as the self healing ability of lime-clasts in but still they remain a ‘new material’, largely underutilized in the construction industry throughout the world. This is important because the use of pozzolans can reduce the use of cement, as cement is more energetically costly to produce. Cement production world wide contributes at most 8 percent to global CO₂ emissions. At this moment, the most commonly used cement in the world is portland lime cement.