A Quick History of Aggregates And Concrete
Written By: Team Sepro | Date: 23.07.19
Aggregate is the building block of civilization. Without the sand, stone, and gravel used in our infrastructure, modern society would simply not exist. While today we use heavy-duty aggregate equipment and portable plants to produce and recycle aggregate material, ancient civilizations did much of this work by hand. The fact that some structures have lasted over 5,000 years is a testament to the astonishing engineering knowledge and work of ancient people.
Let’s take a look at some of these structures and how aggregates played a vital role in ancient societies.
Early Signs Of Aggregate Use
Some of the earliest signs of aggregates in use are from Mesopotamia around 3000 BCE. Ancient Mesopotamians discovered the advantages of using hydraulic lime as cement. When mixed with water, the crushed lime aggregate would harden, acting as a binder between stones and bricks. Kilns were built to create the first fired bricks ever. These bricks were much stronger than the clay and straw bricks popular at the time.
With this technology, ancient Mesopotamians built houses made of strong stone with simple concrete floors, and even underground, waterproof systems. This was one of the reasons they were able to thrive in the hot desert climate. Some of these structures have survived to this day!
Aggregates In Ancient Egypt
Ancient Egyptians had access to an abundance of stone above ground. This ancient society used limestone, sandstone and granite to erect some of the most iconic buildings on the planet.
Historians originally believed that the limestone blocks that make up the Pyramids of Giza were cut right out of stone to fit perfectly beside each other. However, recent evidence suggests that the limestone blocks were instead cast in situ. Ancient workers hauled a mixture of limestone concrete to be cast in molds right in place on the pyramids.
Another popular building material at the time was granite. This tough stone was perfect for building columns due to its compressive strength. Extraction was laborious, as workers only had simple tools to work with, but they also had a lot of ingenuity.
Workers would cut a series of holes in the granite with a hammer and chisel. These holes were filled with wooden wedges and soaked with water. The water caused the wood to expand, forcing the rock to split. The workers would then break apart the granite into smaller pieces with chisels and hammers. The aggregate tools of 2500 BCE were made of iron, bronze, and wood (quite different from the jaw crushers and screening equipment we use today).
How Concrete Built The Roman Empire
Concrete is a mixture of aggregate and cement. The aggregate can be fine sand, or coarse stone, depending on its usage. The earliest large-scale use of concrete can be traced back to the Roman Empire.
The Romans discovered that adding volcanic ash, called pozzolan, to their concrete mixture allowed it to set underwater. Some rather unusual ingredients were also added to their concrete. Horsehair made the concrete less liable to crack while it hardened, and blood made it frost resistant. The blood would eventually dissolve, leaving air bubbles in the concrete and allowing it to expand and contract without breaking during drastic weather changes.
Roman concrete was used to build the Colosseum, Pantheon, and aqueducts among many other incredible architectural wonders.
The Pantheon was the largest dome in the world for more than a millennium and is still the largest unreinforced concrete dome to this day.
The Introduction Of Portland Cement
After the fall of the Roman Empire, their recipe for concrete was lost. It wasn’t until 1800 years later that an English chemist named John Smeaton discovered the formula for hydraulic lime. He used this material as mortar between blocks to successfully build the Smeaton’s Tower in the late 1750s. The problem with ocean buildings at this time was that cement mixtures were unable to harden underwater. His discovery (or rather re-discovery) changed this.
Mortar is the plaster that holds stones together. In order to create a material that binds properly, scientists experimented with grinding limestone and clay together in different ways.
In 1824, Joseph Aspdin cooked a mixture of limestone and clay into lumps and then crushed them into a fine powder. When he mixed this powder with water and fine aggregate, he found that it made a strong mortar that would harden underwater. He obtained a patent for this product and called it Portland cement.
Portland cement is still used today to build concrete structures.
Aggregate Equipment Today
Technology has made the extraction, production, and transportation of aggregate much easier. We no longer rely on people hammering with chisels to create useful aggregate material. The Grizzly King Jaw Crusher can process over 900tph of stone into crushed aggregate. Further, portable plants increase the flexibility of recycling and screening processes. To learn more about aggregate equipment and portable plants, contact the experts at Carminex.