Technical Questions

Requirements for durable concrete

Q. Assuming that concrete is made from the correct ingredients and in the correct proportions, what other requirements must be met to ensure a durable structure, that is, a structure with long life?

 A. The important overall requirements are related to measuring, mixing, transporting, placing, curing, and inspection (ACI 304R):

1. All materials should comply with specifications.
2. The methods of storing, handling, and measuring all ingredients should be such that the selected mixture can be accurately obtained at all times.
3. The concrete should be adequately mixed, and it should be transported and placed by methods that will avoid segregation and loss of ingredients. The consolidated mass should be uniform without rock pockets or honeycombed areas (ACI 309).
4. The arrangement of joints and methods for bonding successive lifts of concrete are important details that can vitally affect the performance of the structure even though the concrete itself is durable. Provisions should be made in the structural plans for drainage to avoid areas of constant saturation that would be more susceptible to damage by freezing than other portions of the structure.
5. Curing of the concrete should not be neglected. This includes protection against extremes of temperature as well as provision for ensuring availability of moisture during the critical early period. No detail of concrete construction offers such possibilities for increased strength and durability at so low a cost as is offered by the possibilities of better curing (ACI 308, 305, 306).
6. Careful inspection should be enforced in all of the above operations (ACI Manual of Concrete Inspection, SP-2).

References: SP-1(02); SP-2(07); ACI 201.2R-16; ACI 309.2R-15; ACI 308R-16; ACI 305.1-14; ACI 306.1-90; ACI 304R-00

Topics in Concrete: 318 Building Code; Concrete Fundamentals; Durability; Specifications