foundation system of burj al arab

Selection of Drilling Slurry for Pile Foundation

Drilling slurry selection is very important in a drilling project which is principally depends on ground condition. Different types of slurries may be required for a project to drill pile through diverse ground formation. Thus it is clear that different types of slurries may be required to drill pile on one contract because of variation in ground condition within a borehole or borehole to borehole.Some factors that dominate on making decision on selection of types of drilling slurry or slurries are listed below:

• Economy 


• Groundwater and ground contamination with disposal


• Air temperature


• Ground temperature

Why should Superplasticizers be Compatible with Cement?

Superplasticizers offer us high workability for normal strength concrete and optimum workability for low water content in concrete to produce high strength concrete. In any purpose, when they are used at very low dosages, fewer problems are arrived. When high dosages of superplasticizers are required in concrete mix, the situation becomes completely different.

At first we have to decide when high dosages are required. To produce a normal strength concrete with high workability, a very low dosage is considered enough; the objective is to produce flowing property to concrete or to place a thick section of concrete having reinforcement congestion.

Admixture-cement compatibility becomes important, for high dosage of superplasticizers; it is not enough to consider cement and super plasticizers separately to comply with respective standards. Large dosage of superplasticizers can be achieved by applying re-dosage; which is considered has less influence on superplasticizers-cement compatibility. But often re-dosing is not possible.

So superplasticizers-cement compatibility has to be established in these cases; a perfect match of both materials will ensure retention of expected high workability for expected long period. The duration is often (60-90) minutes, but a retention period of even more up to 120 min can be achieved.

Now we have to be established required dosage of superplasticizers, at first, before assessing compatibility. The approach followed usually is to

• Determine water reduction as percentage relative to same workability of concrete without superplasticizers or other water reducing admixtures.

• According to BS 1881 : Part 105 or ASTM C230, we can use following table method.

• Mini-slump test introduced by Kantro can be applied alternatively.

Marsh cone was recommended by Aïtcin et al to determined time required to flow a specified amount (measured by volume) of grout having known amount of superplasticizers and cement through an specified orifice. The time required is called Marsh Flow-time,

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