Empirical Investigation of Post-Tensioned Concrete Bridge Deck Condition in Nigeria’s Federal Highway Network

Post-tensioned concrete bridge decks in Nigeria's federal highway network are approaching and exceeding their designed service lives, yet systematic empirical condition assessment of this specific structure type has not been published in the literature. This study provides an empirical condition investigation of 20 post-tensioned concrete bridge decks on federal highways across the North West and South West zones. A comprehensive structural investigation methodology was adopted for each bridge, including visual inspection, rebar cover measurements by covermeter, concrete core drilling (two cores per span), carbonation depth testing, chloride content profiling, and tendon duct void inspection by ground-penetrating radar. Condition states were assigned using a modified PONTIS condition rating system adapted for the Nigerian context. Results indicate that 45 percent of assessed bridge decks are in Condition State 3 (significant deterioration), with 15 percent in Condition State 4 (severe deterioration requiring urgent intervention). Ground-penetrating radar identifies tendon duct voids in 38 percent of assessed spans, indicating incomplete grouting. Delamination detected by chain drag testing covers an average of 12 percent of deck area per bridge. The correlation between deck age and condition deterioration is significant but moderated by traffic loading intensity. The study contributes the first systematic empirical condition database for post-tensioned bridge decks in Nigeria and recommends a federal bridge management system incorporating post-tensioned deck-specific inspection protocols.

Keywords: post-tensioned concrete, bridge deck condition, federal highways, structural deterioration, empirical investigation