(a) Locations of cores extracted from bridge structure I-395 over Main Street in Bangor, Maine, USA. (b) Results of the DRI from extracted cores. MS1: abutment wall under the bridge deck, sheltered (no cracking); MS2: exposed portion of the abutment wall (map cracked); MS3: exposed portion of the wing wall (map cracked). The shaded cells give the proportions of each petrographic feature to the DRI value. CrCA: cracking in the coarse aggregate particles; OCrCa: opened cracking in the coarse aggregate particles; Cr + RPCA: cracking in the coarse aggregate particles + reaction product; CrCP: cracking in the cement paste; Cr + RPCP: cracking in the cement paste + reaction product; CAD: coarse aggregate debonded; RR: reaction rim; RPAV: reaction products in air void of the cement paste