Invention Of Concrete
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National Geographic Science of Concrete BBC Documentaries
Our modern concrete structures will never last as long. This week Guardian Cities investigates the shocking impact of concrete on the planet, to learn what we can do to bring about a less grey world. Our species is addicted to concrete. We use more of it than anything else except water. Like that other manmade wonder material, plastic, concrete transformed construction and advanced human health. But, as with plastic, we are only now waking up to its dangers. It fills our rubbish dumps, overheats our cities, causes floods that kills thousands of people — and fundamentally changes our relationship to the planet. Can we kick our addiction, when it's so hard to imagine modern life without it? In this series of articles, Concrete Week will explore the impact of the material on our environment and us, and look at alternative options for the future.
The Romans used it in everything from bath houses to harbours, aqueducts to the Colosseum, systematising its production and application from the third century BC to the fall of the empire in the fifth century AD. Unlike modern reinforced concrete — which can last about a hundred years without major repairs or replacement — many Roman concrete structures are still with us many centuries later. The key to its longevity appears to be the use of volcanic ash, or pozzolana. Where modern concrete is a mix of lime-based cement, water, sand and an aggregate such as gravel, the recipe for concrete set down by architect Vitruvius in the first century BC involved pozzolana and chunks of volcanic rock, known as tuff.
When it comes to Roman marine concrete, used to construct piers and breakwaters, research published in found that the addition of sea water actually strengthened these structures over time, making them harder and harder over the millennia. It still looks strikingly modern today and it remains the largest non-reinforced concrete dome in the world, 19 centuries after it was built. With only a couple of isolated exceptions , around 1, years passed after the fall of the western Roman empire until concrete was used again on any great scale. The invention of reinforced concrete gave the material a new life.
Before Portland cement was discovered, and for some years afterward, large quantities of natural cement were used, which were produced by burning a naturally occurring mixture of lime and clay. Because the ingredients of natural cement are mixed by nature, its properties vary widely. Modern Portland cement is manufactured to detailed standards. Some of the many compounds found in it are important to the hydration process and the chemical characteristics of cement. Eventually, the mix forms a clinker, which is then ground into powder.
A small proportion of gypsum is added to slow the rate of hydration and keep the concrete workable longer. Between and , systematic tests to determine the compressive and tensile strength of cement were first performed, along with the first accurate chemical analyses. In the early days of Portland cement production, kilns were vertical and stationary. In , an English engineer developed a more efficient kiln that was horizontal, slightly tilted, and could rotate. The rotary kiln provided better temperature control and did a better job of mixing materials. By , rotary kilns dominated the market. In , Thomas Edison received a patent for the first long kiln. This was about 70 feet longer than the kilns in use at the time.
Industrial kilns today may be as long as feet. Although there were exceptions, during the 19 th century, concrete was used mainly for industrial buildings. It was considered socially unacceptable as a building material for aesthetic reasons. The first widespread use of Portland cement in home construction was in England and France between and by Frenchman Francois Coignet, who added steel rods to prevent the exterior walls from spreading, and later used them as flexural elements. Wilkinson in In , American mechanical engineer William Ward completed the first reinforced concrete home in the U.
It still stands in Port Chester, New York. Ward was diligent in maintaining construction records, so a great deal is known about this home. In , George Bartholomew poured the first concrete street in the U. The concrete used for this street tested at about 8, psi, which is about twice the strength of modern concrete used in residential construction. Court Street in Bellefontaine, Ohio, which is the oldest concrete street in the U. Although in cement manufacturers were using more than 90 different formulas, by , basic testing -- if not manufacturing methods -- had become standardized.
During the late 19 th century, the use of steel-reinforced concrete was being developed more or less simultaneously by a German, G. Ransome started building with steel-reinforced concrete in and patented a system that used twisted square rods to improve the bond between steel and concrete. Most of the structures he built were industrial.
Hennebique started building steel-reinforced homes in France in the late s. He received patents in France and Belgium for his system and was highly successful, eventually building an empire by selling franchises in large cities. He promoted his method by lecturing at conferences and developing his own company standards. As did Ransome, most of the structures Hennebique built were industrial. In , Wayss bought the rights to a system patented by a Frenchman named Monier, who started out using steel to reinforce concrete flower pots and planting containers. Wayss promoted the Wayss-Monier system. In , August Perret designed and built an apartment building in Paris using steel-reinforced concrete for the columns, beams and floor slabs.
The building was widely admired and concrete became more widely used as an architectural material as well as a building material. Its design was influential in the design of reinforced-concrete buildings in the years that followed. In , the first concrete high-rise building was constructed in Cincinnati, Ohio. It stands 16 stories or feet tall. In , the first load of ready-mix was delivered in Baltimore, Maryland. The building had an automobile test track on the roof. In , he built two gigantic parabolic-arched airship hangars at Orly Airport in Paris.
In , he was granted a patent for pre-stressed concrete. Air entrainment was an important development in improving the durability of modern concrete. Air entrainment is the use of agents that, when added to concrete during mixing, create many air bubbles that are extremely small and closely spaced, and most of them remain in the hardened concrete. Concrete hardens through a chemical process called hydration. For hydration to take place, concrete must have a minimum water-to-cement ratio of 25 parts of water to parts of cement. Water in excess of this ratio is surplus water and helps make the concrete more workable for placing and finishing operations.
As concrete dries and hardens, surplus water will evaporate, leaving the concrete surface porous. Water from the surrounding environment, such as rain and snowmelt, can enter these pores. Freezing weather can turn this water to ice. As that happens, the water expands, creating small cracks in the concrete that will grow larger as the process is repeated, eventually resulting in surface flaking and deterioration called spalling. When concrete has been air-entrained, these tiny bubbles can compress slightly, absorbing some of the stress created by expansion as water turns to ice. Entrained air also improves workability because the bubbles act as a lubricant between aggregate and particles in the concrete.
Entrapped air is composed of larger bubbles trapped in the concrete and is not considered beneficial. Creeping is described as constant deformation of a material owing to internal stress taking place in the material. The amount of reinforcement of concrete structures ensures minimal shrinkage, creep and cracking. These general concrete properties of concrete are taken care of during building of concrete. Depending upon the end application, concrete is accordingly treated for maximum strength and durability. There are different types of concrete. One of the most popular concrete used is Portland cement, mineral aggregates and water.
Concrete often solidifies as the cement hydrates and glues all the other components together. It has a high compressive strength and general uses of concrete include pavements, fences, gates, walls and more. In old times, concrete was often referred to as liquid stone. Sometimes external stabilizers are included to concrete to give it desired characteristics. Some of the major concrete types include,. The Self-compacting concretes use superplasticizers that accounts for the excessive fluidity of the concrete. It acts like a sticky self-levelling fluid that is combined using vibration. Pump concrete consist of more quantity of sand than normal concrete. It is specifically made smooth to allow easy pumping from roadside to the construction site. Due to the increased quantity of water to make the concrete wet, it also requires more cement to attain the appropriate strength.
Sprayed concrete or Shotcrete makes use of compressed air to cast it to a structure. There are two different kind of sprayed concrete—the dry-mix and the wet-mix concrete. Dry mixed concrete is a dry mixture of cement and aggregates that are shot using compressed air through hoses. The water required for hydration is added at the nozzle. The wet mixture is appropriately hydrated and pumped through hoses.
Sprayed concrete is usually reinforced using fiber. This concrete is used for casting columns and loads or any areas where concrete has to flow into position. Special class might be any concrete specifically required by customers like pre-stressed concrete and light weight concrete. No fines concrete as the name suggests is a concrete with no sand in its mixture. It is a porous mass also known as a washed-out concrete. It uses water so that minimum paste remains stay at the bottom during placing. Concrete mould wrapped in a mesh of iron rods is called reinforced cement concrete or RCC.
Concrete with reinforced steel acquires the capacity to carry enormous loads. It is the most versatile material with a wide range of applications in construction. Different types of concrete are produced depending upon the end application. The modern types of concrete includes cellular or aerated concrete which is light weight and durable, making it easy to be handled. Aerated concrete is widely used for modern construction as it is mortarless and can be produced with different densities.
Concrete has been used for construction since ancient times. Modern day concrete application include dams, bridges, swimming pools, homes, streets, patios, basements, balustrades, plain cement tiles, mosaic tiles, pavement blocks, kerbs, lamp-posts, drain covers, benches and so on…. It is interesting to note that over six billion tons of concrete is produced each year, and is the second most widely used substance. Concrete is specific to different applications like rebuilding, mending and construction. Concrete building components in different sizes and shapes are also made before hand and later applied. They include wall panels, doorsills, beams, pillars and more.
Post-tensioned slabs is a preferred method for industrial, commercial and residential floor slab construction. Ready Mixed concrete is durable and hard wearing and is used for variety of applications owing to its crack-resistance and durability. Situ concrete is cast in place, on site. Precast concrete finds application in concrete curtain walls, exterior cladding and structural walls, as it monolithic and can be easily used for two-way structural systems. It is also adjustable to post tensioning and easily adapts to any building shape. Cast-in-place concrete is an unhardened state, like ready-mix, and is placed in moulds.
Ready mixed concrete is proportioned and mixed off the project site. It finds application in foundations and slabs-on-ground, walls, beams, columns, floors, roofs, bridges, pavements, and other infrastructure. Controlled-density fill is used as structural fill, foundation pillar, pavement base an pipe bedding. It is also known as flowable mortar. The life expectancy of concrete flooring materials is much more than other flooring material. It is used to enhance concrete applications and to add colour and texture to interiors, driveways, pathways and patios.
Fiber cement is made using a mixture of sand, cellulose fibers and cement. It has a wood-like appearance, is durable and used for decorative shapes and trim applications. Vegetative roofs are used in residential societies, office buildings, hospitals, schools, recreational facilities, shopping centers and airports. Concrete is used to provide prolonged building benefits by functioning as thermal mass, acoustical barrier and durable structure. It is a Portland cement concrete overlay on existing asphalt concrete pavement and used in airport pavements, highways, secondary roads, and other pavements. Over the years, concrete has established itself as a sturdy building material used for different applications.Vacuum Sealer Analysis impressive tensile strength of many What Are The Biggest Gifts To America our structures is only temporary. Conflict Handling Modes cleansing the desecration Vacuum Sealer AnalysisVacuum Sealer Analysis which, if you remember, invention of concrete the same amount of mortar used in the What Makes Canada Successful Pyramid of Giza. The deciding factor for strength is also inherently related to the Conflict Handling Modes and ratio of water and cement, the type of cement used and Conflict Handling Modes strength of Vacuum Sealer Analysis aggregate. Disproportionate quantities of Conflict Handling Modes and concrete can be venus (mythology) throughout Vacuum Sealer Analysis arena.