ACI 308R-16 Guide to External Curing of Concrete

ACI 308R-16 Guide to External Curing of Concrete. The term “curing” has also been used in a more general sense to describe the process by which hydraulic cementi- tious concrete matures and develops hardened proper- ties over time as a result of the continued hydration of the cementitious materials in the presence of suffcient water and heat. While all concrete hydrates to varying levels of matu- rity with time, the rate and extent to which this development takes place depends on the natural environment surrounding the concrete and on the measures taken to modify this envi- ronment by limiting the loss of water, heat, or both, from the concrete; externally providing moisture and heat; or incor- porating special materials in the mixture design. 1.3—Curing and hydration of portland cement 1.3.1 Hydration of portland cement—Portland-cement concrete is a composite material in which aggregates are bound in a porous matrix of hardened cement paste. At the microscale, the hardened paste is held together by bonds that develop between the products of the reaction of cement with water and mechanically interlocks the aggregate. Similar products are formed from the reactions between cement, other cementitious materials, and water. Both the hydrate water and physically adsorbed gel water are distinct in the microstructure of the hardened cement paste, yet both are required concurrently as portland cement hydrates. Continued hydration of the cement is possible only when suffcient water is available both for the chemical reactions and for the flling of the gel pores being formed (Neville 1996). The amount of water consumed in the hydra- tion of portland cement is the sum of the water incorporated physically onto the gel surfaces plus the water incorporated chemically into the hydrate products themselves (Neville 1996; Powers and Brownyard 1947; Mindess and Young 1981; Taylor 1997). Because hydration can proceed only in saturated space, the total water requirement for cement hydration is approximately 0.44 g of water per gram of cement plus the curing water that needs to be added to keep the capillary pores of the paste saturated (Powers 1948).ACI 308R pdf download.