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I agree with the title that reinforced concrete gains strength with time, but can also

deteriorate if not correctly designed or constructed. Correct procedures need to be

followed, such as testing and material selection, and also care must be taken. If not

the concrete will not have the desired effect and may lead to a disaster. In regards to

putting the cost over the service life of the concrete, I agree with the idea of investing

more into the design of concrete to lengthen the lifespan of the material. This has an

environmental benefit as we do not expose the environment to the harmful gasses

and toxins that are a by product of the concrete production process more than

necessary. In this essay I will discuss the construction methods and also the benefits

of using reinforced concrete and how it differs from normal concrete. I will also

discuss how, in my opinion, it can be more economically and environmentally

effective to invest more in the construction of the concrete at the time of construction

rather than having to replace the concrete later on when it has deteriorated due to

design flaws or poor quality raw materials. It is also important that we discuss how

green procurement of the materials to be used in concrete can help to improve the

construction industry in regards to environmental awareness. The environment is a

very important talking point and affects every industry, especially construction. I feel

that a greater emphasis on the construction of the concrete could reduce the need

for replacing the concrete in the future, and I plan on discussing this in this essay.

“Concrete is a ubiquitous material and its versatility and ready availability have

ensured that it has been and will continue to be of great and increasing importance

for all types of construction throughout the world.”1 According to “Concrete

Conundrum” it is the most widely used material in the world2. But many people

underestimate the work that goes into the selection of which concrete to use and

also its production. The concrete production process is a long process which starts

with the production of the cement. The raw materials go through many steps before

we get the finished product which we call cement. A very common type of cement

used today is Portland cement. “Well over 95% of the cement used in concrete

throughout the world is Portland cement in its various forms.”3 From the cement

water is added to produce the dense material that takes up so much of the land. Due

to engineering advancements through the years’ people have found ways to improve

the strength of concrete and one those improvements has been the invention of

reinforced concrete4. What distinguishes reinforced concrete from normal concrete is

the inclusion of steel. In reinforced concrete, a mixture of smooth and ribbed steel

bars as well as steel mesh is used to give the concrete extra strength. This extra

strength comes from the idea that the concrete will provide the resistance to a

compressive force while the steel can resist the tensile forces.

1 Construction Materials, Their Nature and Behaviours. 4th Edition, Peter Domone and John Illston

2 Concrete Conundrum, Chemistry World | March 2008

3 Construction Materials, Their Nature and Behaviours. 4th Edition, Peter Domone and John Illston

4 Reinforced Concrete: \"A Classic Invention\"\" The Science News-Letter 23, no. 633 (1933): 330-31.

Niall Lavery: 15320966

Construct Materials Assignment

Reinforced concrete, like all concrete, gains strength over time. This happens

through a process known as hydration. Hydration is a chemical reaction that occurs

as the different particles within the cement react with water. “According to New

Developments in Understanding the Chemistry of Cement Hydration,” Gypsum is

added to the material to help slow down the reaction5. Hydration is an exothermic

reaction. An exothermic reaction is one which produces heat during the reaction.

What many people think is that concrete gains its strength from all the water in the

substance drying out, but this is not the case. It is possible for concrete to be dry but

not fully hydrated, producing a material that is not fully suitable for construction.

Instead what happens is the cement particles bind with the water to create the

concrete. This is a very long process hence why cement continues to gain strength,

even years after it has been poured. However, the rate of hydration reduces over

time. As hydration takes a long time there are different admixtures available to speed

up the process, and also to slow down the process further if desired. Admixtures are

chemicals that can be added to the concrete to change its appearance or properties.

However, these extra admixtures can sometimes be bad for the environment and the

benefits must be weighed against the consequences before it is decided upon.

Concrete in general gains it’s strength from the individual grains present in the

cement producing spikes that interlock, to form a solid structure.

However, if the concrete is not designed correctly then the material will lose strength,

deteriorate over time and will need to be replaced, or worse: the entire structure may

need to be taken down. This is a serious problem as the structural integrity of the

project may rely on the continued strength of the concrete. In many cases the

concrete will be the deciding factor if a building stays standing or not and this is why

it is very important that the concrete preserves the strength it has, if not continue to

gain strength. This is why it is crucial that the people in the construction industry take

care and do not use poor quality materials that will jeopardize the strength of the

structure. Currently Ireland has a depleting reserves of the materials needed to

produce cement. These materials known as aggregates, are various types of rocks

that after a process known as clinkering are crushed to become cement. Due to the

depleting reserves of the aggregates it is becoming very common for recycled

aggregate to be used in the production of new cement. It is cost effective to use

recycled concrete as a portion of the admixtures but his can also be dangerous. This

is why it is very important that any concrete is checked before use. There are certain

substances, which if found in the make up of the cement, can cause serious damage

to the material in the future. One such substance is pyrite. Pyrite is an extremely

reactive material and if present in the concrete can have serious repercussions,

ranging from cracks in the surface to total collapses of the building. Pyrite is very

common in Ireland so it is crucial that it is checked for. It is important that a qualified

petrographer checks the quality of the rocks being used. The petrographer will check

the the geological breakdown of the cement to make sure it is ‘Clean and Clay Free.’

This is why good site practice can both save the contractors money and also reduce

their environmental impact.

5 New Developments in Understanding the Chemistry of Cement Hydration, D. D. Double, P. C. Hewlett, K. S. W. Sing and J. F. Raffle

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences

Vol. 310, No. 1511,

Niall Lavery: 15320966

Construct Materials Assignment

In the past when deciding on contactors or materials to be used in a project it was

often the cheapest method that would prevail. Today however money isn’t the only

concern that people have when choosing their concrete. In the last few years ‘green

procurement’ of goods is becoming increasingly important. Green Procurement is

defined by the Irish Department of Housing, Planning and Local Government as \"a

process whereby public authorities seek to procure goods, services and works with a

reduced environmental impact throughout their life cycle when compared to goods,

services and works with the same primary function that would otherwise be

procured.”6 Finding ways to protect the future’s environment is becoming a key issue

in building practice today. This is quite evident by the increasing use of ‘GGBS’

Cement. ‘GGBS’ Cement is Ground granulated blast-furnace slag. It is an extra step

in the cement process which involves using the iron build up found on the inside of

the rotary kiln, mixed with the Portland cement. It increases lifespan of the concrete

while also reducing price7. By increasing the lifespan of the concrete it will not be as

necessary to replace the concrete as soon as it might have need to be if poorly

constructed concrete was used.

In conclusion, reinforced concrete will continue to gain strength as long as it is

produced properly. That means that the correct procedures need to be taken, testing

happens and materials used. The idea of putting the lifespan of concrete over the

price, which may be more expensive at the time, can save money in the future but

more importantly can have a very positive impact on the environment. Without the

need to replace the concrete due to poor design or diminishing strength we save the

environment from the excess of gasses and toxins that are produced from the

construction of concrete. From the raw materials aspect, it is very important that

companies use green procurement of materials when producing their products. A

growing method is using GGBS in concrete. It increases lifespan of the concrete

while also reducing price. This makes the cheaper method argument of producing

concrete redundant. It is important that for the continued use of concrete and the

protection of the land that we take any necessary steps to ensure we do not harm

the environment further.

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