A laboratory investigation into the structural performance and mechanical properties of plain and reinforced concrete elements affected by alkali silica reaction.
The object of this study was to help clarify some of the fundamental
problems occurring in plain and reinforced concrete structural elements
suffering from the degradation phenomenon of alkali silica reaction.
A laboratory based testing programme was used, so that extreme
conditions for generating alkali silica reaction could be used which are not
readily achieved in actual structures. Special concrete mixes were also
used in which the alkali silica reaction occurs within a period of months
rather than years so that observation of the properties of the reacted
concrete could be taken throughout the reacti ve process.
The laboratory tests undertaken are as follows: fresh and hardened
behaviour of alkali silica reactive (ASR) model mixes; mechanical
properties and expansion behaviour of ASR concrete; structural behaviour
of reinforced ASR concrete beams and columns; bond between
reinforcement and ASR concrete in prisms and beams; restraint effect of
ASR upon plain and reinforced concrete structural elements.
This work shows that, ASR causes an unacceptable level of
progressive damage to plain and reinforced concrete. The degradation and
expansion in plain ASR concrete is higher than that in reinforced
concrete. ASR in concrete reduces the strength and elastic modulus; the
stiffness of reinforced beams; the axial load and ultimate bending moment
capacity of columns; the ultimate bond between concrete and
As a result of expansion in non-symmetrically reinforced structural
elements, ASR causes either sagging or hogging displacement. The
restraint imposed by reinforcement in ASR concrete elements is however
beneficial in terms of inhibiting expansion and crack development, and
exerting a small degree of post tensioning which generally improves the
strength of members. Preloading of ASR concrete also results in an
improvement in the mechanical properties.