Concrete Bridge Deck Quality Mapping with Seismic Methods

The state of practice for acceptance of newly constructed concrete bridge decks is typically based on the compressive or flexural strength of specimens prepared and cured under ideal conditions. These tests do not address how the quality of construction is affected by placement, compaction, curing, and environmental conditions during construction. Cores obtained from the finished product can also be used for quality assessment, but coring is expensive and specimens may suffer from internal damage. Several nondestructive testing (NDT) technologies are readily available that can be used to evaluate the quality of concrete slabs under field conditions. These technologies are typically based on seismic–sonic or electromagnetic principles. Seismic–sonic methods rely on measuring the velocity of propagation of elastic waves within the concrete. Velocities can be converted to modulus of elasticity and related with confidence to strength. A case study is presented in which seismic–sonic methods were used to detect construction problems along a bridge deck. On the basis of the NDT results, several candidate cores were extracted. Cores were tested for abrasion durability and chloride ion penetration. Overall lower modulus concrete exhibited unacceptably high abrasion and chloride ion permeability, confirming that seismic methods may be a reliable means of determining concrete quality for in-place structures.