Design errors that can lead to subsequent deteriora­tion of concrete structures can be placed into two categories: inadequate structural design and lack of attention to details.57 Inadequate structural design occurs when the structure is exposed to a load greater than it is capable of carrying or if it sustains greater strain than its strain capacity. Inadequate considera­tions of temperature change or concrete creep and accidental impact can also result in damage. Typical symptoms of inadequate design include spalling and cracking of concrete. Poor detailing of a structure may result in localized concentration of stresses that result in cracking, which in turn can permit water or chemicals to access the concrete or ponding of water to produce saturated concrete. Poor detailing does not generally lead directly to concrete failure but can contribute to the action of one of the other specific causes of concrete failure.57 Examples of inadequate structural design include insufficient concrete cover over steel reinforcement, improper sizing and place­ment of steel reinforcement, inadequate section geometry, inadequate provision for drainage, abrupt changes in section, material incompatibility, and inadequate provision for deflection.

Poor construction practices and negligence can result from not following specified procedures or from carelessness. Poor construction practices do not lead directly to failure or deterioration of concrete but can cause defects that lead to concrete cracking. Examples of concrete cracks that can result from poor construction practices include plastic shrinkage, plastic settlement, early thermal contraction, crazing, and long-term drying shrinkage. The resulting con­crete cracking then can enhance the adverse impacts of mechanisms (such as described in the next section) and lead to concrete degradation. Poor construction prac­tices and negligence are best addressed through ade­quate quality assurance/quality control in conjunction with an aggressive inspection program. Examples of poor construction practice include adding additional water to concrete to facilitate placement or finishing, improper mixing and curing, improper consolidation, and improper location of steel reinforcement.

Lack of knowledge about the importance of care­ful selection and specification of materials and use of admixtures can also result in durability issues. This can include improper cement contents, use of poor quality or contaminated aggregates, incorporation of additives that can produce corrosion such as calcium chloride accelerators, and incorrect water-cement ratios.

Improper or inadequate maintenance also can con­tribute to the deterioration of concrete structures. Examples ofinadequate maintenance include moisture exposure and penetration caused by unrepaired cracks, improper application of coatings, damaged waterstops, and failure to clean drains and drain pathways.