Partial versus full high-performance cementitious grout replacement for seismic strengthening of RC shear walls

To clarify the seismic response of RC shear walls retrofitted via high-performance cementitious grout (HPCG) replacement, five specimens were tested under quasi-static loading, focusing on the effects of replacement extent (partial versus full) and replacement location (boundary element, single side, double side) on the failure mode, load-displacement response, stiffness degradation, and energy dissipation capacity. The results showed that the fully replaced specimen achieved a 10.5% increase in peak horizontal load, accompanied by significant gains in stiffness, ductility, and energy dissipation capacity, with an acceptable 4.5% reduction in ultimate displacement. The three partially replaced specimens exhibited increased load-carrying capacity and stiffness, reduced ultimate displacement, and comparable ductility; among them, the boundary element replacement specimen offered the best balance between strength enhancement and deformation capacity. A preliminary comparative measure was proposed to enable quantitative comparison among the investigated schemes, yielding the following ranking in descending order: full replacement, boundary element replacement, double-side replacement, and single-side replacement. A refined finite element model, validated against the test results, was further employed for parametric analysis. The analysis revealed that the peak horizontal load increased with the compressive strength of both concrete and HPCG; for concrete, the increase rate gradually slowed, whereas for HPCG, it remained approximately linear. The peak horizontal load also increased with the replacement rate, though with a progressively diminishing return. Within the investigated range, a replacement height of 1.0 times the shear wall length provided favorable load-carrying capacity. Additionally, a calculation method for the load‑carrying capacity of RC shear walls strengthened with HPCG was established and subsequently validated against the test results.