Meso-scale simulation of non-uniform steel corrosion induced damage in recycled aggregate ductile concrete

Abstract

Engineered cementitious composite (ECC) is a ductile construction material with higher damage tolerance compared to conventional concrete. This paper investigates the damage pattern and propagation of reinforced recycled aggregate concrete (RAC) using finite element simulation. Simulations were conducted on RAC members containing brittle matrix and ductile matrix (ECC) subject to uniform and non-uniform corrosion product expansion loads. A two-dimensional five-phase meso-scale level analysis approach was adopted by implementing individual material properties of aggregates, adhered mortar to the aggregates, old interfacial transition zone (ITZ), new ITZ, and cement matrix. Prescribed deformations were applied to the steel concrete interface as corrosion product expansion loads. The physical geometry of each aggregate was mapped from experimental images. The obtained results indicated that the damage first appeared around the ITZs and then propagated into matrix and mortar. It was also found that damage propagated much slower in RAC with ductile matrix compared to that of RAC with brittle matrix. Furthermore, RAC with ductile matrix showed distributed damage pattern while RAC with brittle matrix showed localized damage pattern. Simulation results also showed that non-uniform corrosion product expansion induced faster damage propagation than uniform rust expansion. The new ITZ had higher cracking susceptibility in the RAC composite structure due to its lower tensile strength. With the meso-level modeling technique, aggregate shape and orientation effects on cracking propagation in RAC due to corrosion product expansion were obtained. The uneven damage propagation patterns were observed with the increasing loading level due to the confinement to cement matrix from the aggregate. The less confined area showed more extensive damage areas but lower damage levels. The ITZs experienced less cracking along locations where the aggregates facing the corrosion product expansion load. In contrast, the locations where the faces of aggregates parallel to the load direction had severe damage. It was mainly because of the higher tensile and shear stresses in the parallel direction, even though the distance to the expansion load was greater. The aggregate shape and orientation had significantly less impact on damage pattern and propagation in ductile matrix RAC members than brittle matrix ones. The reason was that ECC material has distributed cracking behavior instead of major cracking in the damage propagation stage even though the studied members have the same tensile strength. The meso-scale numerical simulations of RAC under expansion load around rebar provide insights into the influences of non-uniform corrosion on damage propagation in brittle and ductile RAC members.