Dear reader we have discussed about many aspects of bentonite in our previous posts. It is very common drilling fluid used in bored pile construction. The importance of drilling fluid is beyond scope of this post, but we have discussed about this in our previous posts. We have discussed about some tests about quality of bentonite like methylene blue capacity. Here we will discuss about some requirements of bentonite in bored pile foundation work.
The pre-requirements of applying bentonite is to submit all properties, relevant in this regard, of bentonite before commencing boring operation to authority.
a. The maximum limit of sand content is 6%
b. Viscosity of bentonite must lie between (29-50) sec.
c. While using bentonite at (2-6)% by weight, the density should be in the range of (1.02-1.15) Ton/m3.
d. PH should be greater or equal to 9.5.
These requirements can be altered when design engineer considered them okay. In case of PH less than 9.5, in no circumstances bentonite slurry can be used.
When PH of bentonite slurry is greater than 9.5, it looks dirty, QC engineer have authority to reject slurry to be used further.
The level of bentonite slurry should be kept at least 2 m above water table and this level are always maintained not less than 2m form top of steel casing.