Essay Sample on Underwater Concrete

Introduction

Some of the construction works require the special skills of underwater concrete which involve placing the concrete under water. In this case, the best material to use must be free from dilution by the water, must be self-compacting and should also spread out easily. In most cases, a pebble aggregate s used in underwater concrete along with some mineral additives such as silica fumes and fly ashes which amount to a certain percentage of the cement used. In the recent past, many improvements have occurred in underwater concreting making concrete the material o the future. This essay is a description of the process and some of the factors that should be considered when carrying it out.

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Several admixtures are added to the concrete to make it more adhesive and more compact even after it spreads out. The ad, mixtures act to prevent the washing away f the cement or sand from the concrete that has been recently placed underwater by binding the agents that have been used in the process together even before they are dry. They also provide higher integrity of the material which in turn reduces the pollution of the environment by concrete. The admixtures are best used intertidal zones, splash zones, and even deep underwater placement. There er several types of admixtures depending on what material they are made of. They include admixtures that are based on hybrid polymers which contain about 20% sodium nitrate and is not harmful to marine life. Their presence enables them to ct as bonding factors in the cementitious system and increase the cohesivity of the materials that are used in underwater concreting. The second common type of admixtures are the admixtures that are based on poly-carboxylates and are used primarily in areas that require high flow ability and is acceptable for the environment since it has no harm. The third classification is the admixtures that are based on poly-carboxylates and phosphonates. They produce a mixture that is not very viscous and still lasts as long as the other types of admixtures. Anti-washout admixtures prevent erosion of the concrete material as it is being placed. It is also harmless to fish as the materials that are used to make it are not toxic to the environment. Finally, there is fly ash which is made by burning pulverized coal in electric generation plants and exists in several classes such as class C and class F fly ash (Rodriguez). The material is environmentally friendly and is easier to use in cold weather. It also prevents the shrinking of cement after it has been spread out.

In a recent study to evaluate the effect of underwater concrete on the environment, the results showed that the organisms had grown over the concrete irrespective of their previous environments (Mariak). This is a proof that it is not all the underwater concretes that are harmful to the aquatic life as earlier thought by scientists. The concrete, however, alters the pH of the water around them which has some influence on the marine life around the applied areas. The experiment also proved that some of the additives that are based on the poly-carboxylates and phosphonates have minimal growth of organisms o them which shows that they are not that friendly to the life forms that exist in the natural environment.

Underwater concrete needs to be applied with care, and the applied surfaces should not be disturbed before the concrete has properly dried out. In cases where the weather is cold, the concrete may require to be protected for a period of up to seven days. The material must also e placed at a temperature of about 5degrees to avoid the effect of shrinking of the cement. It is therefore essential to have the necessary skills before application of the concrete mixture.

Works Cited

Mariak, Aleksandra, et al. "Influence of selected additives and admixtures on underwater concrete and the environment." MATEC Web of Conferences. Vol. 219. EDP Sciences, 2018.

Rodriguez, Juan. "Uses, Benefits, And Drawbacks Of Fly Ash In Construction". The Balance Small Business, 2018, https://www.thebalancesmb.com/fly-ash-applications-844761. Accessed 27 Nov 2018.