摘要: |
Cracking of concrete bridge decks is often reported as a problem by state DOTs for both new and
existing bridges. There are many reasons for bridge cracking that can occur before or after concrete
hardening. Cracks can occur before hardening due to construction movement (movement of form or
sub-grade movement), chemical shrinkage (autogenous), high surface evaporation (plastic), and frost
damage (premature freezing and scaling). After hardening cracks can occur due to volumetric
movement (drying shrinkage, thermal contraction, and creep), structural design (design load and
fatigue), and chemical reactions (alkali-aggregate reaction, freeze-thaw damage, and corrosion). While
most of bridge deck cracks have little to no effect on immediate structural capacity, these cracks have
significant effects on bridge deck durability as they often lead to deterioration of the bridge deck. As
such, bridge deck cracking remediation is highly recommended especially in Northern states where
cracks allow deicers to penetrate through the deck and corrode reinforcing steel. There are several
options for bridge deck crack remediation with the most common options including crack injection,
crack sealers (flood bridge deck sealers), thin polymer overlays, and thick overlays. Selection of the
optimal technique relies on the properties of cracking conditions (crack widths, shape, and density) as
well as exposure and bridge-specific conditions. Currently, while some industry guidance in terms of
crack remediation strategies and their effectiveness to extend service life of cracked bridge decks
exists, the information is scattered and a comprehensive guide to the available repair options, their
suitability for different crack types, their service life benefits, and their costs does not. This study aims
to develop a decision matrix and guidelines to aid in selection of optimal bridge deck cracking
remediation options for Iowa DOT bridges based on specific user inputs. The outcomes of the study
will include a final report that summarizes the findings and proposed changes to the Bridge Deck
Manual and Construction Manual. In addition, WJE will develop training materials and deliver a
webinar-based training to familiarize the primary users with the developed decision matrix and
guidelines. |