Material Properties

The average concrete compressive strength at the day of testing for the three bridge decks was 7000, 4500, and 5278 psi (48.2, 31, and 36.4 MPa), respectively. The concrete compressive strengths were determined using 4 x 8 in. (102 x 204 mm) concrete cylinders cast for each bridge deck and cured under the same conditions as the deck. Concrete was provided by a local ready-mix supplier.

Tension coupons of MMFX and Grade 60 steel were tested according to ASTM-A370 specific­ations. The measured stress-strain characteristics of the MMFX and grade 60 steel are shown in Figure 2. The MMFX reinforcing bars exhibit a linear stress-strain relationship up to 100 ksi (689 MPa) followed by a non-linear behavior with ultimate strength of 173 ksi (1193 MPa). According

to the ASTM-A370 offset method (0.2% offset) the yield strength of MMFX steel was found to be 120 ksi (827 MPa). The initial modulus of elasticity was determined to be 29,000 ksi (200 GPa), followed by a non-linear behavior and reduction in the modulus of elasticity at stress higher than 100 ksi (689 MPa). The yield strength of the Grade 60 steel was determined to be 68 ksi (469 MPa).