Guide to Durable Concrete

Description

Concrete is one of the most widely used constructionmaterials in the world. This fact attests to concrete’sperformance as a versatile building material. Durabilityrepresents one of the key characteristics of concrete that hasled to its widespread use. Durability of hydraulic-cementconcrete is determined by its ability to resist weathering action,chemical attack, abrasion, or any other process of deterioration.Durable concrete will retain its original form, quality, and serviceability when exposed to its environment.

Properly designed, proportioned, placed, finished, tested, inspected,and cured concrete is capable of providing decades of servicewith little or no maintenance. Certain conditions or envi-ronments exist that will lead to concrete deterioration.Attacking mechanisms can be chemical, physical, ormechanical in nature, and originate from external or internalsources. Chemical and physical attacking mechanisms oftenwork synergistically. Depending on the nature of attack,distress may be concentrated in the paste, aggregate, orreinforcing components of the concrete (or a combinationthereof).The various factors influencing durability and the particularmechanism of deterioration should be considered in thecontext of the environmental conditions to which theconcrete would be subjected.

In addition, considerationshould be given to the microclimate to which the specificstructural element is exposed. Deterioration, or the severityof deterioration, of a given structure may be affected by itsorientation to wind, precipitation, or temperature. Forinstance, exterior girders in a bridge structure may beexposed to a different and more aggressive environment thaninterior girders.The concept of service life is increasingly used for thedesign of new structures. To provide durable concrete, thespecific demands on the concrete in its intended use shouldbe given careful consideration. Required service life, designrequirements, and expected exposure environments (macroand micro) should be determined before defining theappropriate materials and mixture proportions necessary toproduce concrete suitable for a particular application. Theuse of good materials and proper mixture proportioning willnot necessarily ensure durable concrete.

Appropriate measures of quality control, testing, inspection, placement practices, and workmanship are essential to the production of durable concrete. Properly designed testing and inspection programs that use trained and certified personnel are also important to ensure that durable concrete is produced. ACI has a number of certification programs that are applicable. This guide discusses the more important causes of concrete deterioration and gives recommendations on how to prevent such damage. Chapters on fresh concrete, freezing and thawing, alkali-aggregate reaction (AAR), aggressive chemical exposure, corrosion of metals, and abrasion are included .Fire resistance of concrete and cracking are not addressed indetail, because they are covered in ACI 216.1, 224R, and224.1R, respectively.