Are small cracks in the cement lining normal?
• Yes. These cracks (sometimes resembling a spider web) are caused by the fact that iron and cement have different thermal expansion coefficients. As the temperature changes prior to installation these cracks can occur. These cracks are normal and are of little concern due to a process called autogenous healing. Simply stated, autogenous healing is the ability of cement to heal itself. In the presence of moisture, cement extrudes calcium hydroxide which, upon exposure to the atmosphere, is converted to calcium carbonate which seals the crack. These calcium carbonate crystals are formed when the carbon dioxide in the air and water carbonates the free calcium oxide in the cement and the calcium hydroxide liberated by the hydration of the tricalcium silicate of the cement.
