Bacteria-modified lime grout for sustainable retrofitting of historic masonry: Multi-scale characterization and GPR-based in-wall validation
Construction and Building Materials, vol.542, 2026 (SCI-Expanded, Scopus)
- Publication Type: Article / Article
- Volume: 542
- Publication Date: 2026
- Doi Number: 10.1016/j.conbuildmat.2026.148051
- Journal Name: Construction and Building Materials
- Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, INSPEC
- Keywords: Bacteria-modified lime grout, Bio-based repair materials, Ground-penetrating radar (GPR), Historic masonry retrofitting, Viridibacillus arenosi
- Yıldız Technical University Affiliated: Yes
Abstract
Historic masonry conservation requires compatible, injectable grouts capable of filling internal voids. This study developed a lime grout modified with cave-derived Viridibacillus arenosi (A6). Bacterial suspension replaced 0–100% of the mixing water, and G50 was selected through a normalized multi-criteria evaluation of fresh-state injectability and stability, achieving the highest overall score of 0.650. G50 and the bacteria-free REF grout were compared using mechanical, capillary, SEM–EDS and MIP analyses, while G50 was injected into two laboratory model walls monitored by GPR before injection and after 3 and 90 days. Increasing bacterial-suspension content reduced yield stress, plastic viscosity and sand-column penetration time, while water-retention capacity generally decreased and bleeding remained within a narrow range of 4.7–5.0%. At 90 days, G50 showed 46% higher mean compressive strength and lower capillary absorption than REF. Its total intruded mercury volume was 62.9% lower, and its MIP-derived intrusion porosity was 13.76% versus 40.73% for REF. SEM–EDS revealed qualitative morphological and elemental differences between REF and G50. GPR-derived estimated void ratios decreased from 6 to 7% before injection to 2.5–3% after 3 days and 1.5–1.75% after 90 days, consistent with grout penetration and temporal changes in wall response. Overall, G50 exhibited improved injectability and hardened-state performance relative to REF under the investigated conditions, while GPR monitoring documented effective grout penetration and progressive in-wall response. These findings indicate the promising potential of bacteria-modified lime grout as an injectable consolidation material for historic masonry.