8 FACTORS AFFECTING SETTING & HARDENING OF CEMENT

Factors Affecting the Setting and Hardening of Portland cement

(1) The Impact of Cement’s Composition

The mineral composition of cement and their ratios are the main factors affecting the setting and hardening of cement. As mentioned above, various mineral components will reveal different characteristics when reacting with water. For example, the increase of C3A can speed up the setting and hardening rate of cement, and the heat of hydration is high at the same time.
Generally speaking, if mixed materials are added into the cement clinker, the anti-erosion will increase, and the heat of hydration and the early strength will decrease.

(2) The Mixing Amount of Gypsum

Gypsum is called the retarding agent of cement which is mainly used for regulating the setting time of cement and is an indispensable component. Without gypsum, cement clinker can condense immediately by mixing with water and release heat. The major reason is that C3A in the clinker can dissolve in water quickly to generate a kind of calcium aluminate hydrate, a clotting agent, which will destroy the normal use of cement. The retardation mechanism of gypsum is: when cement is hydrated, gypsum reacts with C3A quickly to generate calcium sulfoaluminate hydrate which deposits and forms a protection film on the cement particles to hinder the hydration of C3A and delay the setting time of cement.
If the content of gypsum is too little, the retardation affect will be unobvious. Too much gypsum will accelerate the setting of cement because gypsum can generate a clotting agent itself. The appropriate amount of gypsum depends on the content of C3A in the cement and that of SO3 in gypsum, and it also related to the fineness of cement and the content of SO3 in clinker. The amount of gypsum should account for 3%-5% of the cement’s mass. If the content of gypsum exceeds the limit, it will lower the strength of cement and it can even lead to poor dimensional stability, which will cause the expanded destruction of cement paste. Thus, the national standard requires that the content of SO3 should not be more than 3.5%.

(3) The Impact of Cement’s Fineness

The size of cement particles directly affects the hydration, setting and hardening, strength and heat of hydration.

The finer the cement particles are, the larger the total surface area is and the bigger the area contacting with water is. Thus, the hydration will be quick, the setting and hardening will be accelerated correspondingly, and the early strength will be high.

However, if the cement particles are too small, it is easy for them to react with the water and the calcium dioxide in the air to destroy the storage of cement. If the cement is too fine, its shrinkage is large in the hardening process. Thus, the finer the cement is ground, the more energy will lose and the higher the cost will be. Usually, the grain size of the cement particles is within 7-200pm (0.007-0.2mm).

(4) The Impact of Curing Conditions

The curing environment has sufficient temperature and moisture which is conducive to the hydration and setting and hardening process of cement and benefits the development of the early strength. If the moisture of the environment is very dry, the water in the cement will evaporate, leading to insufficient hydration and ceasing of the hardening. Serious cracks will happen sometimes.
Usually, the temperature rises at the time of curing, and the hydration of cement and the development of early strength become fast. If the hardening process occurs at a low temperature, the final strength won’t be affected though the development of the strength is slow. But if the temperature is under 0⁰C, the hydration of cement will stop and the strength will not only stop growing but also destroy the structure of cement paste due to the condensation of water.
In actual projects, the setting and hardening process of cement products is accelerated by steam curing and autoclave curing.

(5) The Impact of Curing Age

The hydration and hardening of cement is an ongoing process in a long period. With the increase of the hydrating degree of various clinker minerals in cement particles, gels will grow and capillary porosities will decrease, which enables the strength to rise with the increase of age. It is proved that cement develops rapidly within 28d and slowly after 28d.
Building materials in civil engineering

(6) The Impact of the Mixing Water Content

If the cement consumption is unchanged, the increase of the mixing water content will enhance the amount of capillary porosities, lower the strength of cement paste, and extend the setting time. Therefore, in practical projects, the amount of water and cement will be changed without modifying the water-cement ratio (the minimum amount of cement is regulated to ensure the durability of concrete) when the liquidity of cement concrete is adjusted.

(7) The Impact of Admixture

Hydration, setting, and hardening of Portland cement are constrained by C3S, C3A. And all the admixtures that affect the hydration of C3S, C3A can change the performance of the hydration, the setting and hardening of Portland cement. For example, the accelerator agents (such as CaC12, Na2S04) can accelerate the hydration and the hardening of cement and improve its strength. On the contrary, the retarding agents (such as calcium lignosulphonate) can delay hydration and hardening of cement and affect the development of the early strength.

(8) The Impact of Storage Conditions

The inappropriate storage will expose cement to moisture. The particle surfaces agglomerate because of hydration which seriously reduces the intensity. Slow hydration and carbonization will happen due to the impact of the water and C02 in the air, even though the storage is good.

The strength decreases by 10%-20% after 3 months, by 15%-30% after 6 months, by 25%-40% after 1 year, so the effective storage period of cement is 3 months and the cement should not be stored for a long time.

ORIENTATION TO THE ARCHITECTURE PROFESSION

 
 ROLE OF AN ARCHITECT IN THE BUILT ENVIRONMENT



Architects are professionals who have a key role to play in society: buildings and the users of buildings are responsible for the majority of carbon emission and it is said that the built environment influences behaviour. Good design is essential to improving the performance of buildings and our social living environment. Construction is an important industry, not only in new build, but in urban regeneration, adaptive reuse, and energy transformation of existing building stock.

Role of Architecture and Place

Architecture and place is led by Architect, Who focuses on place-making, sustainable economic growth and development delivery.
He have responsibility for the development and implementation of policies on design in the built environment.
Helping to turn policy intentions into actions, architecture and place strive to

• create successful, thriving and sustainable communities;
• deliver better public buildings which contribute to improved service delivery and represent good value for money;

• tackle the barriers to good quality development, through education, skills and advocacy.

Better place-making

Distinctive, high quality places as well as high quality buildings are vitally important to the social, environmental and economic success of our cities, towns and rural communities.
Good place-making can provide communities with an important cultural context; a sense of pride and belonging; and a sense of local and national identity. It can provide environments which function well; link well with surrounding settlements and provide attractive areas in which to socialise, to move around and to do business.

Good design

• safe, welcoming places can be created to which people would wish to return frequently, and which would have a greater chance of longevity.

Sustainable development

"Good design" in the built environment must, by definition, involve an approach which responds to issues of climate change and other sustainable development concerns.
Architect should  intended to embed a more sustainable way of thinking and create certainty to support investment in new technologies as we move towards a low-carbon economy. This can creates a long-term framework and place at the forefront of global efforts to tackle climate change.

7 wonders of architecture in India

India has been the centre of the world for too long in the ancient past. Few of world’s most important religions has originated from India. Buddhism was once the dominating religion in India and Buddhist monasteries and stupas were built all over India before it eventually spread to other countries. Around 8th century AD, with the advent of Shankaracharya, Hinduism revived and it saw many Hindu rulers including Pallavas and Cholas building architectural wonders. Rajputs built various magnificent hill forts in Rajasthan to protect their own areas.

After the invasion from Muslim rulers in the 11th century, India for the first time saw influences from the middle east, with Afghan and Persian architectural designs mixing with the exiting Indian styles.  Mughals ensured that India has some of the finest Islamic architecture in India. Portuguese, French, Dutch and Britishers later attacked India, leaving their footprints with various churches and influences from European style of monuments.

India has been a land of architectural marvels and here is our list of 7 wonders of architecture in India.

1. Taj Mahal, Agra, Uttar Pradesh

Part of the 7 wonders of the world, this list had to start with Taj Mahal. Taj Mahal is an mausoleum built in a span of 22 years in the 17th century by Mughal emperor Shah Jahan for his beloved wife Mumtaz. Taj Mahal displays a combination of Hindu and Indo-Islamic architecture. Huge white marble terrace on which rests the famous white marble dome, flanked by four tapering minarets. Within the dome lies the jewel-inlaid cenotaph of the deceased queen.

 

 

 

 

 

2  Nalanda Ruins, Nalanda, Bihar

Nālandā was an ancient center of higher learning in Bihar, India. The university of Nalanda is located in the Indian state of Bihar, and was a Buddhist center of learning. The great library of Nalanda University was so vast that it is reported to have burned for three months after the invaders set fire to it, ransacked and destroyed the monasteries, and drove the monks from the site.

 

 

 3. , Tawang, Arunachal Pradesh

Tawang Monastery in Arunachal Pradesh is the largest monastery in India. It was founded near the small town in accordance with the wishes of the 5th Dalai Lama. It is very close to the Tibetan border, in the valley of the Tawang-chu which flows down from Tibet. The monastery is also known in Tibetan as Galden Namgey Lhatse, which translates to ‘Celestial paradise in a clear night.’

 

 4. Ruins of Vijaynagar Empire, Hampi, Karnataka

Hampi ruins are a UNESCO world heritage site, listed as the Group of Monuments at Hampi. The Vithala temple complex at Hampi in state of Karnataka has 56 musical pillars, which are constructed such that when stuck, each one emits a unique musical tone. The Virupaksha temple, site of the ancient city of Vijaynagar, is the main centre of pilgrimage at Hampi. It has three towers, which rise to a height of 160 feet and are nine tiered. It dates back to the first half of the fifteenth century.

 

 

 

 

5. Sun Temple, Konark, Odisha

The Surya – mandir (sun-temple) of Konark, derived from the words Kona (Corner) and Arka (Sun), is known not only for its architectural grandeur but also for the intricacy and profusion of sculptural work. The entire temple has been conceived as a chariot of the sun god with 24 wheels, each about 10 feet in diameter, with a set of spokes and elaborate carvings. Seven horses drag the temple and two lions guard the entry, crushing the elephants.

 

 

 

 

 

 

 

 

 

 

 

 

6. The Iron Pillar, Delhi

Dating back to the 4th century A.D., the Iron pillar of Delhi bears Sanskrit inscription in Brahmi script which states that it was erected in the honor of the Hindu god, Vishnu and in the memory of the Gupta King Chandragupta II. It highlights ancient India’s achievements in metallurgy. The pillar is made of 98 percent wrought iron and has stood more than 1600 years without rusting or decomposing. The pillar is 7 meters high and 17 inches in diameter at the base and 12 inches in diameter at the top. It might not be the most beautiful architectural  monument in India, but it sure is one of the wonders of India.

 

7. Ajanta & Ellora Caves, Aurangabad, Maharashtra

Ajanta Caves, thirty in number were made in 2nd century BC. The themes are religious and centred around Buddha. Paintings are done on ground of mud-plaster. Ellora caves are rock-cut shrines representing three different faiths, Buddhism, Hinduism and Jainism, known for their striking proportion, elaborate workmanship, architectural content and sculptural ornamentation. Both Ajanta and Ellora Caves are part of UNESCO world heritage sites and are one the most exotic caves of India depicting India’s architectural brilliance in the past.

 



How did you like our list of these 7 beautiful architectural monuments in India?
If you think any particular heritage structure should have been included in this, leave your thoughts in the comments.