Tag Archives: Constructions

Why Americans use drywall instead of concrete and bricks to build houses in areas prone to natural disasters?

The only natural disaster that concrete and brick houses are better at dealing with are fires.

With tornadoes most damage is done by winds so strong that they dismantle concrete, brick, or stone either directly or by throwing debris into them only slightly more slowly than they do wood. You can make a tornado bunker that is above ground with 4 foot thick walls and steel reinforcement. Homes do not do that, even in places that they make concrete homes.

Hurricanes tend to do most of their damage with flooding. Concrete and Bricks flood and mold just as easily as wood. When they are washed away the ground itself is washed away so they break just as easily too. For the extremely powerful hurricanes we have the same wind issues as tornadoes.

For earthquakes the concrete and brick homes are far worse than wood. They are too rigid unless very expensive tech and building practices are used and so they just crumble when an earthquake happens as they cannot flex.

And finally they are 3-10 times more expensive than wooden homes. Chances of you actually losing your home in your lifetime are low, and you get insurance to protect against it. So it is far better for most to spend what money they have to build a larger nicer home.

Also, drywall is not a structural weight bearing material. It is the interior finishing of the wall. Wood is the structural component and wood/fiberglass is the outdoor wall slat.

What is the difference between concrete and cement?

Cement and concrete are two terms people often get confused with and use out of places. People often say ‘cement sidewalk’ or ‘cement mixer’ but the proper terms are ‘concrete sidewalk’ and ‘concrete mixer’. While it may seem harmless using these words interchangeably, it is still technically incorrect. Even though both cement and concrete are construction materials, they are two distinct products.
The cement is actually one of the ingredients of the mixture we call concrete. It is primarily made up of lime and silica. Those two materials constitute for about 85% of cement. Other ingredients include calcium, iron, aluminum and a few others. These materials are mixed and heated in large kilns to very high temperature, ranging from 2,700°F to 3000°F, to form a product known as clinkers. Clinkers are small pellets which resemble marbles. These are later ground into a finely powdered form and gypsum is often added. The final product is what we call cement. When water is added to cement, a chemical process takes place, allowing it to harden. The cement acts as a binding product that helps to hold the ingredients of concrete together.
Cement is basically divided into two types; hydraulic and non-hydraulic. Hydraulic cement uses water to start a chemical reaction and hardens irrespective of the water content and becomes water resistant. This is suitable for wet conditions and underwater structures. Non-hydraulic cement, on the other hand, doesn’t harden when mixed with water which makes it unsuitable for most conditions.
The most prevalent type of cement is the Portland cement or Ordinary Portland Cement (OPC). Portland cement is a generic name for the hydraulic cement used in construction. It was developed by Britishman Joseph Aspdin in 18th century. Portland cement itself is classified into 8 types, according to specifications.
Concrete is actually a mixture of cement, water and other aggregates. The aggregates include crushed mostly chemically inert materials like stones, gravel and sand. The amount and type of aggregates vary according to application of concrete. They usually make up 60% to 80% of the mixture. Cement constitute for up to 15% of the total mass of concrete and the latter cannot be made without the former. The ratio of water to cement is very important, as it determines the strength of concrete. Too much water will weaken the mix.
Concrete is one of the most used construction materials, due to its strength, durability and resistance to fire and water. It gets stronger over time because of the continued hardening.

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Which is the largest religious monument in the world?

Angkor Wat, the temple complex located in Siem Reap province, Cambodia is the largest religious monument in the world. Its name translates to City of Temples in Khmer language. The word ‘Angkor’, meaning city, was derived from the Bengali word Nokor Wat means temple grounds. An amazing example of the Khmer architecture, the temple complex was built by the Khmer King Suryavarman II in the early 12th century. It was built as a Hindu and later went on to be converted into a Buddhist temple. Suryavarman conceived it as his state temple and the eventual mausoleum.

Angkor Wat

Angkor Wat is dedicated to god Vishnu, a fact that marks a departure from the tradition of Khmer kings, who used to follow the Shaiva traditions. The edifice is a national symbol of Cambodia, and is featured in the national flag of the country.
Legend has it that Angkor Wat was constructed by Hindu god Indra as a palace for his son Precha Ket Mealea. The construction began during the reign of king Suryavarman II who ruled till his death in 1150. Most of the works had finished by the time of his death. Later, the enemies of the Khmers attacked and sacked the city. Later a new king named Jayavarman VII restored the empire. He built a new capital and state temple a few distance away from the temple. They are called Angkor Thom and Bayon temple.
In the following years, Angkor Wat gradually converted to a Buddhist temple. From 14th century, it was occupied by Buddhist monks. After the 16th century, the temple was more or less abandoned and was overgrown with vegetation. In 19th century, Henri Mouhot, a French naturalist and explorer, was the one who re-discovered the temple and popularized it in the western world. The temple underwent considerable restoration works in the 20th century, often interrupted by the revolts in Cambodia.
The temple compound extends to over more than 500 acres. It is surrounded by a moat with a perimeter of 5.5 kilometers. The temple itself is an example of magnificent architecture and amazing sculpture. The central tower of the temple is 65 meters high and is surrounded by four smaller towers. The architecture is modeled after the mythological peak Mount Meru.
It is covered with countless sculptural decorations. They feature many scenes from Hindu epics Ramayana and Mahabharata and a large number of deities. The temple is now a UNESCO World Heritage Site and a famous tourism destination. More than a million people visit the great architectural wonder every year.

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How many workers were employed for construction of the Great Pyramid of Khufu?

The first conjecture about the number of workers engaged in building this pyramid (which is also called the Pyramid of Giza and the Pyramid of Cheops) has been given by the Greek scholar Herodotus. He said that about 1,00,000 workmen had toiled to build Khufu’s pyramid around 2500 BC. Herodotus was a historian and not an engineer but his estimate was not questioned – not without reason. If Taj Mahal, which is considerably small in size when compared to the pyramid, required 22,000 workmen to build it in 22 years, the pyramid could have easily needed 1,00,000 men. However, this estimate appears to have been greatly exaggerated. The latest estimate mentions 12,000 only, while the findings of the Denver Museum of Natural History claim that in the beginning 12,800 would have been required and towards the completion of construction 621 could have been more than sufficient!

How can we believe that such a huge structure was built by only so many workmen? There is no definite information regarding this in contemporary records, so we have to work it out for ourselves. For this, it is necessary for us to assume certain things. The first important assumption is regarding time factor.

How many years did it take to build the pyramid? King Khufu had started work on the pyramid immediately after ascending the throne. He ruled for 23 years before his death. It is highly likely that Khufu’s courtiers were continuously monitoring the work and speeded it up on observing Khufu’s failing health during the later years. So we many assume that at the time of the king’s death, the pyramid was almost ready. The construction therefore must have taken 8,400 days. We may also assume that the workmen worked on all the days of the week.

After having estimated the time taken for construction, we now have to count how much energy was spent in building the great pyramid. The pyramid is 146.7 meters (481 feet) high and its base is a square with each side 230.4 meters (756 feet) long. We can calculate the volume of pyramid with the formula: 1/3 x Bh (where B is the area of base and h is height).

The volume would thus work out to 1/3 x 230.4 x 230.4 x 146.7 = approx. 2.6 million cubic meters.

However, from the point of view of the workmen and also to have an idea of the amount of effort put in, it may be more relevant to consider weight rather than volume. Mainly limestone has been used in Khufu’s Pyramid – almost 2.3 million slabs. The weight of limestone is, on an average, 2,700 kg per cubic meter.

So the total mass of material used works out to 2700 x 2.6 million = 7 billion kilograms.

It would require 25,20,000 million Joules of energy to construct this pyramid from the base to the peak (Joule is a unit to measure energy or work, like calorie). A healthy workman can give output equivalent to 2,40,000 Joules per day. So, about 1,250 workmen should be able to construct Khufu’s Pyramid in 8,400 days.

The quarries supplying limestone were at some distance. Slabs of an average of 2.5 tons would be cut from the quarries to be transported to the construction site by a different group of workmen. How did they transport the slabs? A cart with wheels would not been able to bear the weight. A safe and easy way of doing this was to convert slabs into component of wheel. Such a wheel would be much broader than the wheel of a cart and the weight would be evenly distributed, so there would be less chances of breakdown. However, this discovery was made nearly 2,400 years after the age of the pyramids. The stones for Khufu’s pyramid were probably shifted on round, long and thick wood logs. (Ancient Egyptian wall carvings also show that this was the practice).

In the limestone quarries, boulders had to be hewed into smaller pieces, finished into slabs and dragged along the place of construction. The founder and main mathematician of Denver Museum of Natural History, Stuart K. Wyre calculated that 14 laborers per cubic meter of slabs would be needed for dragging them to the construction site. Since Khufu’s pyramid was built in 8,400 days we assume that 310 cubic meters of slabs were fixed daily. The quarry and transporting laborers would then have been 14 x 310 = 4340. Add 1,250 laborers needed for construction to this figure and the final tally comes to 5,590 laborers.

Surprised? Herodotus estimated the number as 1,00,000 and this number was generally accepted. On the other hand, the new estimate of 5,590 is barely 6% of that! Consider this as an average figure. The great pyramid of Egypt took 8,400 days to build and it is not likely that the number of workmen remained the same throughout. The base of the pyramid covered much more area than the rest of the structure. So a large number of laborers must have worked on the ”ground floor”. After that, the structure gets narrower and the ”upper floors” might have required lesser number of workmen.

Final estimate is that in the beginning, there were 12,800 workmen and at the top of the pyramid the number reduces to 621. This is because the narrow peak would not require too many slabs. Moreover, there was not enough space for many people to work there. Another thing we learn from the chart is that during the construction of the base, 50% laborers were needed for quarrying and transportation and 50% for laying the slabs. When construction reached the peak, the ratio undergoes a drastic change. Fewer slabs were needed but still around 72% laborers were engaged in the challenging job of transporting the stones to the top. The laborers laying the slabs were not more than 28% of the total labor force. The point to be noted is that the number of laborers varied at different stages of construction but the average figure was less than 10,000!

More reading:
Great Pyramid of Giza (Wikipedia)
Wonders of the World (Wikipedia)
Egyptian pyramid construction techniques (Wikipedia)

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What is the secret behind strength and durability of the Great Pyramid of Khufu?

The Great Pyramid of Khufu is ranked no.1 in Antipater’s list of Seven Wonders. It is the oldest of the wonders, having being built 4 to 4.5 millenniums ago and the only ancient wonder still existing today. That sure rises the question as to what makes it stand still till now.

The base of the pyramid is a wide square and the apex is pointed so it is natural that the structure would remain intact. But more important is the uniformity maintained in the slopes on all four sides. Four corners at the base have to be at equal angles. If this is not ensured, then not only all the four edges would not meet at the top but the weight of the pyramid would also not be distributed evenly all over the base. With about 5 million tons of weight being borne by the slabs at the base, some would break because of more pressure on one side and less on the other. In the course of time, there would be further cracks in the broken slabs of the stone. If the weight of the pyramid causes the slab to slip even a little, those above would also get dislodged. The pyramid will eventually fall apart.

The craftsmen who built approximately 80 pyramids in Egypt must have been well versed in trigonometry. They have not compromised at all in maintaining the slope of each of the sides. The angle of the highest pyramid – the Great Pyramid of Khufu – is 51°50’40”. All four sides of Khufu slope up in exactly the equal manner and finally meet at the top at the central point of the structure. Note that the angles are not integers but fractions. A degree of angle can be divided into 60 fractions called minutes and each minute can be further subdivided into 60 seconds for surgical precision. While building a structure of this height, it must have been really difficult to maintain accuracy of high order but this has been achieved in the Great Pyramid of Khufu. The Khafre pyramid next to Khufu has slopes of 53°10’ and a third pyramid named Menkaure had slopes 51°20’25”.

When the construction work of pyramids was undertaken in the Nile River valley modern engineering instruments were not invented. This really makes historians wonder why and how Egyptians took on such a gigantic engineering project of building pyramids. Without machines to assist in the construction work, it would have taken a large number of workmen to do the job.

More reading:
Great Pyramid of Giza (Wikipedia)
Wonders of the World (Wikipedia)

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Which is the world’s largest construction in terms of ground area?

While 828 meters high Burj Khalifa (known as Burj Dubai prior to its inauguration) is the tallest building in the world today (as of February 2011), the world record holder of a construction covering the largest ground area since last fifteen years is Japan.

The construction is Osaka’s Kansai International Airport (photo, above). Japan constructed the airport within a period of five years and opened it for civil aviation in 1994. The runway, terminals and parking area as well as the approach road to Kansai airport have been constructed above the Osaka Bay on thousands of steel piles and more than 1 million concrete columns driven in the sea bed. This mega-project was taken up in order to restrict the traveling time between Osaka city and the airport to less than 30 minutes and only seaward direction was available for it. The meticulousness of planning is revealed by the fact that although there is only one runway the provision has been made for parking 41 airplanes.

Although the height of this construction is negligible, its length is 4.27 kilometers and width is 1.25 kilometers making its overall area 5.33 square kilometers. It was the most ambitious project since the construction of the pyramids besides being the most expansive – costing 15 billion dollars. In order to ensure flawless construction of the project technologically advanced Japanese did not hesitate to engage the services of the Italian architect named Renzo Piano and the British engineer Peter Rice.

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Is the Great Pyramid of Giza only Wonder of the World in its original form today?

Yes. The only one! Begun as a royal tomb in about 2600 BC, the Great Pyramid of Giza (also called the Pyramid of Khufu and the Pyramid of Cheops) is the largest of Egypt’s 80-odd pyramids and the only Wonder which has survived to this day. It stood in splendor 2,000 years before any of the other six Wonders were built.

Located outside Cairo, near Giza, the burial tomb of King Cheops is made up of 23,00,000 limestone blocks averaging 2.5 tons each. The total mass of these blocks is nearly 58,40,000 tons and the volume is 25,68,000 cubic meters. Most blocks weigh 2.25 tons, while some would tip the enormous scale at 13.5 tons. The pyramid’s width at the base is 230 meters, thus covering an area of slightly more than 13 acres. This is large enough to enclose 88 Taj Mahals. The original height of the pyramid was 146.5 meters, but with the loss of its apex stones, it is now reduced to 137 meters.

More reading:
Great Pyramid of Giza (Wikipedia)
Wonders of the World (Wikipedia)

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