Engineering in 2021 has been made so much easier with the use of computer aided design soft wares and other programs that enable the engineer to create designs more efficiently and effectively. However like existential questions such as “who am I?”, “Is there a God?” and “What should I eat for lunch today?” we are in awe of the engineering of the past. Wonders such as the Pyramids, Hanging Gardens of Babylon and the Parthenon are structures that will never cease to amaze future generations as those who designed and build these projects did not rely on computers nor soft wares (relax you engineers out there, I’m not invalidating your profession). In this blog, we hop into our metaphorical time machine, go back to 447BC and take a dive into the civil and structural engineering of the ancient world.
When we think of Ancient Greece, our minds usually go to the Olympics, Zeus or the 300 Spartans. But there is a lot more to Greece than these parts of history and a lot more of our technology used today can be accredited to the Ancient Greeks. A few notable and less talked about mentions include the spiral staircase, the crane and the Truss roof.
The Spiral Staircase
Spiral stair cases were first developed and used in Ancient Greece. There are reconstructed blueprints of Temple A in Selinunte, Sicily. Now before you start giving me a geography lesson, I do know very well that Sicily is in Italy. But, during the period that this staircase was built (470-480BC), Selinunte was a colony of Ancient Greece.
In 515BC the Ancient Greeks first developed the Crane. This device, although primitive when comparing it to modern technology, saved groups of labourers time, allowing them to complete the job quicker, and their backs. Although the Ancient Mesopotamians (now modern day Iraq) were first to develop the crane (known as a Shardouf and primarily used for water irrigation) the Ancient Greeks developed it into a tool that could be used when constructing buildings and other structures. The Greeks used men and animals such as donkeys to power and move these cranes.
The Truss Roof
A Truss Roof is a structural framework of timbers that are designed to support a roof and bridge the space between this roof and above a room. In 550BC these roofs were developed by Ancient Greek architects and engineers with the largest clear span being featured at the Temple of Olympian Zeus in Agrigento Sicily (noticing a theme here?). There are two distinction of truss roofs. The first being a closed truss in which the truss features a tie beam or roof framing with a ceiling so the framing is not visible. The second distinction is called an open truss which is where the truss contains an interrupted tie beam or scissor truss which allow a vaulted ceiling area and or roof framing open to view which is not hidden by a ceiling.
Published by the Greek Ministry of Culture, an ingredient list reads 2 parts lime, one part sand, one park clay, 10 eggs and water as needed. This concoction was not only used in ancient times but is still used today as heritage laws in Greece specify that any changes a property owner makes to their home that is deemed a heritage building must be reversible. This mortar makes provides for an strong yet removable extension or renovation to one’s property.
Similar to their ancient counterpart, The Ancient Egyptians were also the fore parents for many engineering and constructions tools used today. Notable mentions include; Hydraulic Engineering and The Great Pyramid of Giza.
Mainly used to replace missing rainfall in periods of drought, the Ancient Egyptians were originally reliant on the Nile River to provide sufficient watering for domesticated animals, crops and people. Like many other times throughout history, an over reliance on our natural world may be a recipe for disaster and in the case of the Ancient Egyptians, the Nile River was prone to flooding, destroying crops, homes and taking lives. As such the Ancient Egyptians used Lake Fayum as a natural reservoir to store surplus water to use throughout the country’s dry season. To combat the devastating floods caused by the Nile’s swelling, the Egyptians utilised hydraulic engineering and created drainage canals, managing water in a systematic way.
The Great Pyramid of Giza
From being built by aliens to being used as a praying place by hippies who believe this structure possesses power and energy, the construction of The Great Pyramid of Giza has been the topic of much debate. Interestingly, The Egyptian Pyramids were built with such precision that our current technology cannot replicate it. Each pyramid is perfectly aligned with true north and is estimated to be built with 2.3 million stone blocks which was estimated to be set out every two and half minutes. The chemical compound of the pyramid’s mortar is known but cannot be reproduced or replicated.
Every dynasty throughout China has brought many technological and engineering developments. Notable mentions include The Great Wall of China, The Crossbow and an improved version of Greek Fire.
The Great Wall of China
The Great Wall of China is seen to be symbolic of the pinnacle of Chinese technology, architecture and civil engineering. The Great Wall of China was built under the first Chinese Emperor Qin Shi Huang between 220 and 200 BC. The wall was mainly built from rammed earth, stones and wood. However, bricks were heavily used in many areas of the wall, as were materials such as tiles, lime, and stone. The size and weight of the bricks made them easier to work with than earth and stone, so construction quickened. Additionally, bricks could bear more weight and endure better than rammed earth. Stone can hold under its own weight better than brick, but is more difficult to use. Consequently, stones cut into rectangular shapes were used for the foundation, inner and outer brims, and gateways of the wall.
Popularised by Medieval Europe, China is responsible for engineering and developing the crossbow. In early developments, the Chinese Crossbow bows were made from composite material and used winches for large crossbows mounted on fortifications or wagons. Crossbows have been found in several tombs having been featured and found with the Terracotta Army in the tomb of Qin Shihuang
China’s response to Byzantium’s Greek Fire
Byzantium had developed a weapon that took form as a ship-mounted flame-throwing weapon. Greek Fire was used by the Byzantines to set fire to enemy naval ships. The Chinese adaption of this weapon saw Greek Fire (or as the Chinese used to call it Fierce-Fire Oil Cabinet) being used in contexts such as city walls and ramparts where the weapon was fitted with a horizontal pump and a nozzle of small diameter.
The Aztecs arrived in the Valley of Mexico and built one of largest and most powerful empires in Pre-Columbian Americas. Apart from their military might, the Aztecs were highly skilled engineers who build the marvelous city Tenochtitlan on one of the most difficult terrains. Their engineering achievements include the construction of a double aqueduct, a massive dike, causeways and artificial islands.
Prior to the popularisation of artificial islands by the UAE’s Dubai, the Aztecs created chinampas (floating or artificial islands) which enabled them to farm new land and reside on. In order to build a chinampa, the Aztecs staked out the shallow lake bed and weaved the stakes together to form fences. This fenced off, enclosed area was layered with mud, lake sediment and decaying vegetation which brought it above the level of the lake. These enclosed chinampa’s ranged anywhere from 90m by 5m to 90m by 10m. The lake provided the chinampas with moisture laden with decomposing organic wastes that irrigated and fertilized the artificial island’s soil, supporting an intensive and highly productive form of cultivation. The chinampas could produce up to 7 crops a year allowing enough food for the rising population of the Aztec cities.
As the Aztec population in Tenochtitlan grew so did the demand for fresh water. In the 1420s, they initiated the construction of the Chapultepec aqueduct to bring clean water to their city from the springs at Chapultepec on the mainland. This aqueduct ran for 3 miles and poured water into public fountains and reservoirs. This engineering feat has been hailed remarkable as very few ancient civilizations could master engineering and specifically, the construction of an aqueduct this sophisticated.
Lake Texcoco was the largest of five interconnected lakes and thus Tenochtitlan was constantly under threat from the large quantity of water surrounding it. A catastrophic flood in the mid 1400s almost destroyed the whole city. To address the issue, the Aztecs designed a huge dike or dam with a height of around 12ft and running for around 10 miles from the southern edge of the lake to the north. Made of sticks, weeds and stone, it was the largest earthwork in the Americas at the time. It was fitted with doors which could be raised or lowered to control the level of water behind it. Apart from protecting Tenochtitlan from floods, the dike also kept the brackish waters beyond the dike, to the east.
Although civil and structural engineering in 2022 Sydney is far more progressive and sophisticated than that of the Ancient and Medieval world, the inventions and engineering attempts of our fore parents has paved the way to the engineering we see all around us today. Speaking of revolutionary engineering solutions, Bellmont Façade Engineering uses premium and reliable grade technology to ensure your building is of the highest quality. Give us a call today on 02 9718 0775 or send us an email at email@example.com.
Concrete cancer is a problem many buildings can face. This phenomenon occurs when the internal framework, made from steel bars or mesh, is exposed to water or air. This exposure creates a build-up of carbonic acid which in turn creates rust, corroding the steel reinforcement. If no action is taken by the owners or tenants, this rust and decay will spread across the floor and into the walls, causing severe structural issues for the building. There have been numerous occasions where entire buildings have had to be pulled down and rebuilt as a result of concrete cancer. In other cases, such as the Champlain Tower in Miami, untreated concrete cancer caused the building to collapse which led to the death of three people. In this blog, we discuss the causes of concrete cancer, first signs of concrete cancer and the remedies.
Concrete Spalling Vs Concrete Cancer
Before dissecting concrete cancer, its causes and its potential remedies, it is important that we distinguish between concrete spalling and concrete cancer. These words are often used interchangeably. Concrete spalling describes the physical degradation and break-down of the concrete or cement rendering. Concrete cancer on the other hand refers to the spread and, if left untreated, worsening of concrete spalling. Although in most situations, concrete spalling is usually a sign of concrete cancer, these terms are not completely synonymous. Concrete spalling may also occur as a result of:
This is when water seeps into concrete structures through capillary absorption. This water is then frozen, creating micro cracks in the concrete surface. When the ice melts and temperatures rise, this damage is revealed. This cycle then repeats, increasing the number of and enlarging the microcracks. These cycles are typically seen where buildings endure below 0 degree temperatures such as Russia or Canada.
Poor Finishing Techniques
Many people believe that poor concrete finishing techniques only impact a floor or walls aesthetic value. Although this correct to a certain degree, the incorrect use of proper construction techniques can lead to Concrete Discoloration, Concrete Scaling, Concrete Curling, Concrete Crazing, or Concrete Cracking. To assist in minimising and reducing the discoloration of concrete it is imperative to ensure that the contractor has prepared the proper subgrade and subgrade uniform. It is also important to make sure that the worker does not finish the concrete prior to it bleeding. Concrete scaling is what happens when the concrete contains inadequate strength. Scaling sees the concrete slab flake off and or peel away. This may occur during freeze and thaw cycles. Concrete scaling can also occur when concretes are non-air-entrained or too little entrained air. Concrete Curling sees the bending of a concrete slab. This bending occurs as a result of different moisture and temperature levels between the top and bottom surfaces. A method of preventing this is making sure that the subgrade is damp during warm weather. It is also important to be careful when initially pouring the concrete mixture as segregation may occur, meaning, more moisture is found at the top of the concrete slap and less at the bottom. Workers should use proper control joints and should be vigilant when placing the steel reinforcements. Concrete Crazing is the inter connection and network of fine cracks and fissures. Although this does not impact the concrete’s strength or have any adverse effects on the concrete’s durability, it does look extremely unappealing when wet. This is caused by attempting to finish the concrete too early. Furthermore, it is important to make sure that no water is added to the concrete during the finishing process. Finally, concrete cracking can be caused by the improper compaction of the subgrade. It is important to make sure that all topsoil, organics and soft spots are removed from the surface as this will allow for proper compaction and help reduce the chances of settling.
The process of curing concrete can be defined and describing as providing adequate time to allow the concrete to achieve the desired properties for its intended use. It also is inclusive of providing adequate moisture and temperature for the concrete when pouring. Good concrete curing should see the enabling of prolonged hydration and the formation of a well-developed microstructure. When concrete is cured incorrectly or inadequately, reduced compressive strength development and increased drying shrinkage may occur. As such its abrasive resistance, durability and strength are all impacted, leading to concrete spalling.
A bad concrete mix
A bad concrete mix is usually a result of using incorrect quantities of cement or water, not creating a concrete mix that has been batched correctly for its application and may also be the result of recycled materials.
Causes of Concrete Cancer
Although concrete cancer can happen to any building in any location, there are several certain environmental factors that may prove to be predispositions for a building with concrete cancer. As concrete cancer can be caused by water, areas that are near the ocean may be locations of concern. Furthermore, locations and destinations around the world that contain extreme climates and weather conditions such as Mawsynram in India, which has been crowned the wettest inhabited place in the world, are also perfect conditions for concrete cancer to occur. Structurally speaking, properties with flat roofs are far more prone to concrete cancer as water is able to sit on this roof with very little to no run off. Other common triggers of concrete cancer may include design flaws and the incorrect implementation of materials throughout the construction phase such as the inadequate preparation of the reinforcing steel, incompatible support metals, poorly poured or insufficient concrete cover and finally, stress fractures from excessive weight and the close-to-surface positioning of the steel reinforcement. Poor waterproofing is a large catalyst for concrete cancer. The triggering of concrete cancer may occur when there a gaps or spaces around the membrane.
Signs of Concrete Cancer
Although there are many ways concrete cancer can rear its ugly head some common signs include crumbling, flaking or cracking of concrete as well as the appearance of rust stains or bubbling on the concrete or cement render. As the steel reinforcements and concrete weaken, more and more leaks will appear within the roof and walls.
How to Remedy Concrete Cancer
As stated, concrete cancer can be a very expensive, if not, fatal issue if left untreated or misdiagnosed. It is important to understand and know the variety of remedies that may occur as to best suit your budget. As such, the first step in remedying your concrete cancer is giving a civil or structural engineer a call. These engineers will come to your property and diagnose the issue at hand as well provide suggestions as to which methods you may choose to tackle this issue. Some methods of removing concrete cancer may include the site specific electro-chemical treatment (usually chose for properties near the ocean) or the simple removal of damaged concrete and the impacted steel. Of course this steel and concrete will be replaced with new material. Your chosen civil and structural engineer may apply an anti-carbonation coating in order to preserve the concrete.
It is important to keep an eye on your floors and walls as concrete cancer and subsequently, concrete spalling can spring up on residents of any property quite quickly. Individuals don’t notice concrete cancer in its early stages (it’s almost impossible to) so it is important to be extra vigilant when looking at your concrete when it appears on surface level, visible to the human eye. If you have noticed any strange marks on your concrete such as rust spots or bubbling and/or flaking or crumbing of your concrete send us an email at firstname.lastname@example.org or give us a call on 02 9518 0775 to speak to one of our expert engineers today.