Cracks in hardened concrete

Finally, cracking in hardened concrete may be caused by propagation of exiting cracks (reflective cracks) owing to lack of subgrade support or swelling/shrinkage of soil material. 

Expansive cements based on calcium oxide are rarely used because of difficulties in controlling the extent and the kinetics of expansion. It has been suggested that expansive additives based on free CaO should be used to prevent early age thermal cracking in hardening concrete (Ebensperger and Springenschmidt, 1992). 

---