Concrete technology

Soundness in concrete

     It is essential that a comment paste once it has set doesn't undergo a large change volume such expansion maintain due to the delay or slow hydration of some components presence in the hardn cement.
This can be measured by lachaterlier's
Apparatus.

             

The widning of the split caused by the expansion of cement is greatly magnify and can be easily measured . The cylinder is placed on a glass plate filled with cement paste of standard consistency and covered with another glass plate the all assembly is that immersed in a water at 20°C for 24hours at the end of the period of the Distance between the indicators  is measured and the mould is immerse in water again and brought to the boil in 25 to 30 minutes after boiling for one hour the assembly is taken out an after cooling the distance between the indicators again measured  the increase in distance represent the expansion of cement .

NOTE 01 :-
For Portland cement it is limited to 10mm if it is exceed to this value the cement can be rejected.

NOTE 02 :-
How it should be checked reusing the rejected cement.
Rejected cement should be spread airated for 7days then again a sample should be tested by the apparatus if this expansion it is not exceed 5mm the cement can be utilized for the construction activities.