RESILIENT INFRASTRUCTURE June 1–4, 2016 STR-894-1 BOND STRENGTH OF RIBBED-SURFACE HIGH-MODULUS GLASS FRP BARS EMBEDDED INTO UNCONFINED UHPFRC Mahmoud Sayed-Ahmed Ryerson University, ON Khaled Sennah Ryerson University, ON ABSTRACT High-modulus (HM) ribbed-surface glass fiber reinforced polymer (GFRP) bars have recently been used in concrete bridge decks to avoid corrosion of steel reinforcement resulting from the use of de-icing salts in winter times in North America. Recently, prefabricated full-depth deck panels (FDDPs), made of normal strength concrete or high performance concrete and reinforced with GFRP bars, are used in Canada to acceleration bridge construction. The FDDPs are connected through panel-to-panel and panel-to-girder connections. These connections are filled with joint-filled cementitious materials as ultra-high performance fiber-reinforced concrete (UHPFRC). This paper presents the experimental program to investigate the bond strength of the GFRP bars embedded into unconfined UHPFRC using pull-out testing, leading to the proper GFRP bar development length required to determine the width of the closure strip between connected slabs. The longitudinal GFRP/UHPFRC interface is influenced by (i) the development length-to-nominal diameter of the bar ratio, (ii) the concrete cover-to-bar diameter ratio and (iii) the development length-to-embedment depth ratio due to lugs or headed-end and (iv) concrete compressive strength. GFRP bars embedded into UHPFRC would rely less on the friction and adhesion of the interface, and more on the bearing of the lugs against the concrete. These bearing forces act at an angle to the axis of the bar, causing radial outward forces. Pullout failure of the GFRP/UHPFRC interface leads to shearing of the lugs and bar slippage from the headed-end. Adequate bond strength between the GFRP/UHPFRC interfaces is necessary for design of jointed PDDFs. Therefore, accurate predictions of development length and bond strength of straight or headed-end bars without passing through the high localized stresses due to flexural are essential for safe design. Keywords: Ultra-High Performance Fibre Reinforced Concrete (UHPFRC), Glass FRP (GFRP), Pullout, development length, Design Codes, Experimental Testing, Accelerated Bridge Construction. 1. INTRODUCTION To accelerate bridge construction while maintaining high level of long-term durability and reduction in the maintenance cost, design engineers recently considered utilizing UHPFRC, which possesses high compressive and tensile strength compared to normal strength concrete. Also, they recently considered the use of GFRP bars for the same rationale. GFRP-UHPFRC structural section works together through (i) bonding between GFRP bars and surrounding UHPFRC that prevents slip of the bar relative to UHPFRC, (ii) concrete mix design that provides the structural member with high concrete capacity design loads, and (iii) similar rates of thermal expansion for the UHPFRC to the GFRP bars under environmental conditions. UHPFRC is made by mixing ordinary Portland cement, supplementary cementitious materials as the Silica Fume, fine aggregate as ground quartz, steel fiber reinforcement, admixtures as the high range water reducer (HRWR), and water (Graybeal, 2006 and 2007). UHPFRC is a self-consolidated concrete with high fluidity and deformation capability that levels itself without vibration. Its strength increases with age and curing, with early compressive strength of 100 MPa at 96 hours (4 days), 140 MPa at 28 days, and 150 MPa by the 56 days. The curing regime for the untreated concrete is meant to keep the concrete into the capped-plastic moulds in the lab-room condition.