Degree of hydration of OPC and OPC/FA pastes dried in different relative humidity

In this research; the degree of hydration of the pastes and the compressive strength of the 50
mm cubes prepared with the 100% cement and fly ash blended cement was determined. 24
hours after casting mortar cubes and the paste samples were cured for 28 days in the fog
room. After 28 days curing; a set of 3 cubes and a paste sample was dried in the 100%,
75%, 65%, 40% and 12% ambient relative humidity at the constant temperature of 27oC.
Drying conditions showed significant effects on the compressive strength and the degree of
hydration. Highest compressive strength of 70 MPa was measured for mortar cubes dried in
100% RH; similarly 97% degree of hydration was determined for 100% cement samples
dried in the 100% RH. For mortar cubes dried in 12% RH, the compressive strength was
measured between 47 and 53 MPa. The similar paste samples showed the maximum degree
of hydration as 81%. In conclusion, drying conditions have significant effects on the degree
of hydration of cement pastes, therefore other properties are also affected such as
compressive strength.