Causes of Concrete Cracking in Bridges Effective Practices for Control of Concrete Cracking Two approaches for crack control are possible: oThe first approach is to prevent the cracks if Possible oThe second approach is to ensure that adequate reinforcement is present to control crack widths if cracking occurs.

the Bridge Construction Records and Procedures Manual. 14 . 6-2 Curing Bridge Decks . Proper curing of concrete deck surfaces is one of the key elements in controlling cracks. The Specifications. 15. require bridge decks to be cured by both the curing compound method and the water method.

Thermal cracking occurs during the hardening state. When cement reacts with water, heat of hydration is released from the cement, as a result thermal expansion occurs in the concrete member. Thermal crack possibly will be a full depth crack. Control of thermal crack width also relies on temperature drop of concrete from the Peak to normal

Fatigue I for compression in concrete and tension in the reinforcement. – Tension in prestressed concrete components. – Crack control in decks. – Service II limit state for yielding of steel and for bolt slip. – Foundations settlement. 4

Thermal Cracking • Thermal cracking develops when the tensile stress exceeds the tensile strength of concrete: – Random map cracks in large foundation – A series of vertical cracks in walls (widest near the base) – Uniformly spaced cracks in beams (perpendicular to the longest dimension) • Mostly, a durability issue: easy pathways for

Bridge Decks • Concrete Deck Maintenance & Repair • Crack Sealing • Determine the type of crack and its cause before attempting to seal the cracks, since this may affect the type of repair. • Small Cracks - Liquid Sealers - Small cracks can be filled by some of the liquid sealers on the market to waterproof decks.

Transportation Research Synthesis - Bridge Deck Cracking 3 basalt, can also decrease the amount of cracking. Concrete mixes with good quality, clean, low shrinkage aggregate with high aggregate to past ratio have been observed to perform better. (1, 5 - 12) d. Admixtures, fly ash, etc.

Many concrete bridge decks develop transverse cracking and most of these cracks develop at early ages, some right after construction and some after the bridge has been opened to traffic for a period of time. Transverse cracks usually occur when concrete is set and widen with time. These cracks have been observed in most geographical locations and on many superstructure types.

Control Joints are not intended to stop cracking but rather control cracking. It is best to cut joints as early as possible either while finishing with a concrete groover or within 6-18 hours after finishing with a concrete saw. Plan out your control joint spacing 24-36 times the depth of your concrete slab.

Reinforcement is basically dormant until the concrete cracks. After cracking, it becomes active and controls crack widths by restricting crack growth. 10 tips for crack width control

Section 502 - Concrete Bridges Section 505 - Steel Reinforcement • Other Specifications as referenced in Chapter 3 18.2.2 Material Properties The properties of materials used for concrete slab structures are as follows: f' c = specified compressive strength of concrete at 28 days, based on cylinder tests 4 ksi, for concrete slab superstructure