Dear reader perhaps you have read our post about methylene blue capacity for determining quality of bentonite; our procedure for determining clay minerals in concrete is almost same as that of this test as we are dealing with same clay minerals in this post. This is smectite.
Bentonite is also clay of same group derived usually from volcanic ash. We have discussed numerous posts about bentonite and drilling fluids, mostly related to drilling of pile.
The test method is named as methylene blue absorption test and described by Pettifer and Hills in 1985. At first we like to introduce methylene blue; it is a dyeing pigment that is soluble in water usually of organic origin. When it is dissolved in water it produces blue color.
When clay of swelling properties (smectite group) remains in aggregates the methylene blue don't produce blue color as it is absorbed by clay minerals. This phenomenon facilitates us to predict presence of clay minerals. The amount of methylene blue required, gives a measure of concentration of search clay minerals.
Dear reader we have provided the limit, according to ASTM C-33, of deleterious particles in aggregates for concrete and we have already learnt harmful impact of clay minerals and other deleterious particles in aggregate on fresh and hardened concrete.
The details test procedure, limitations and practicability of this test will be discussed in next part of this topic. Please stay with us