# Working State of ECC Link Slabs Used in Continuous Bridge Decks
## 1 Introduction  
The beam bridge is known as the most common spanning structure applied in traffic engineering. For highways and bridge approach systems, the simply supported steel or prestressed concrete beam bridge with multiple spans is a suitable choice. Bridge expansion joints erected between adjacent simply supported bridge spans play an important role in accommodating the deformations of superstructure resulting from service loads, thermal effect, shrinkage, creep, and foundation settlement [1]. Besides, those expansion joints between the adjacent bridge decks are expected to protect the components below from being corroded by fluid chemical substances. The mechanical joint normally requires maintenance of high economic cost, otherwise it tends to deteriorate due to the exposure to severe environment as well as the continuous traffic wear and tear. Water leakage and flow of deicing salts through deteriorated joints are the constant sources of damage in bridge deck, girder, and substructure [2]. Therefore, the durability of mechanical expansion joints has become a major issue, bearing on the driving comfort, integrity, and service life of bridge structures. By constructing uninterrupted deck surface over multiple spans without mechanical expansion joints, the continuous bridge decks or integral abutment bridges are developed [3]. One frequently-used approach to achieve the continuous bridge decks is the replacement of expansion joints by link slabs, which reduces both the costs of installation and maintenance associated with expansion joints. The link slab connecting two adjacent simple-span girders has to accommodate the deformations caused by multiple factors, e.g., traffic loads and temperature variation. [PERSON] and [PERSON] investigated the working behavior of continuous deck and proposed a design method for the steel reinforced concrete link slab [4]. This method introduced by [PERSON] and [PERSON] has made significant contributions to the development of bridges with jointless decks. However, the brittleness and limited durability of concrete materials under certain conditions count against their application to the link slabs in a complicated stressing state. In the past decades, steel reinforced concrete link slabs have always experienced premature concrete cracking [5]. The crack width and extent of cracking are so difficult to control that the salt water is likely to permeate through the link slab, thereby leading to reinforcing steel corrosion, concrete spalling, and eventually structural failure. Targeting the shortcomings of traditional concrete, efforts have been made to develop the engineered cementitious composites (ECC) of adequate ductility complemented with acceptable levels of cost. The substantial benefits of using ECC have been demonstrated by its improved mechanical properties [6; 7] and durability properties [8; 9; 10]. With these merits versus other cement-based materials, ECC has recently become a particularly preferable class of material able to meet the functional requirement for structural applications [11; 12]. The outstanding energy absorption capacity enables ECC to be used in seismic and protective structures [13; 14]. The low crack width and desired durability of ECC facilitate its use in corrosion-resistant structures [15; 16]. Furthermore, it is reported by existing literature that the structural performance of ECC link slab for jointless bridge deck is governed by the tensile strength, ductility, crack width, and some other material attributes [17; 18; 19]. The design concept for ECC link slab was successfully implemented in a construction project in southeast Michigan [20]. A full-scale load test following the construction was conducted to explore the structural responses of ECC link slab, which confirmed that the simply supported nature of spans remained in spite of the incorporation of ECC link slab.