| Cement Gel | (Concrete Engineering) The colloidal gel (glue like) material that makes up the major portion of the porous mass of which hydrated cement paste is composed. |
| Cementitious | (Concrete Engineering) Having cement-like, cementing, or bonding type properties. Material or substance producing bonding properties or cement-like materials. |
| Chair(s) | (Concrete Engineering) In concrete formwork, the support for the reinforcing steel. |
| Change of State | (Concrete Engineering) The process whereby liquid is heated to the point of evaporation changing the liquid into a gas the condensation of a gas on a cooler surface returning it from gaseous to liquid form. |
| Cold Joint | (Concrete Engineering) A visible lineation which forms when the placement of concrete is delayed. The concrete in place hardens prior to the next placement of concrete against it. |
| Colloidal | (Concrete Engineering) A gel-like mass which does not allow the transfer of ions |
| Condensation | (Concrete Engineering) When a moisture laden gas comes in contact with a cooler surface a change of state from gaseous to liquid occurs. |
| Consistency | (Concrete Engineering) The degree of plasticity of fresh concrete or mortar The normal measure of consistency is slump for concrete and flow for mortar. |
| Consolidation - | (Concrete Engineering) Compaction usually accomplished by vibration of newly placed concrete to minimum practical volume, to mold it within form shapes and around embedded parts and reinforcement, and to eliminate voids other than entrained air. |
| Construction Joint | (Concrete Engineering) The contact between the placed concrete and concrete surfaces, against or upon which concrete is to be placed and to which new concrete is to adhere, that has become so rigid that the new concrete cannot be incorporated integrally by vibration with that previously placed. Unformed construction joints are horizontally placed or nearly so. |