# Shrinkage-Induced Response of Composite Steel-Concrete Slabs: A State-of-the-Art Review
## 3 Time-Dependent Responses of Composite Slabs
### Continuous Composite slabs  
A number of continuous composite slabs have been tested to date to evaluate their long-term response as depicted in Table 3.  
Two-span continuous composite concrete slabs having 6300 mm of total length were cast on ComFlor 80 [57] steel deck with similar cross-section of 150 by 1200 mm [56]. In reference [56], sixteen composite slabs were monitored over time and they exhibited 4  
Figure 5: Mid-span deflections measured for simply-supported samples (LVDT-M = mid-span deflection) [53]. to 7 times higher long-term deflections after 90 days of drying than their instantaneous deflections under only self-weight. In this experimental work, different bonding between concrete and steel deck were created by the presence of embossments and grease, and different reinforcement ratios were adopted using mesh reinforcements, reinforcement bars and steel fibers. All samples were moist cured for 7 days from the day of casting. Long-term deflections of the three continuous composite slabs with 6900 mm total length over two spans were monitored for 376 days [55, 59]. All three slabs had the same cross-section with 150-mm thickness and 1200-mm width. These were cast on KF70[23] steel sheeting that was supported on the floor during casting. The slabs were moist cured for 28 days from the day of casting and they were then subjected to different levels of sustained loading. Three continuous composite slabs with 6300-mm total length over two-span and consisting of same cross-section of 510-mm-wide and 120-mm-deep were cast on DW-65 steel sheeting without propping. One of the slabs was prepared with natural aggregate, while the other two samples were made of recycled aggregate concrete. All slabs were wet cured for 6 days from the day of casting and subsequently monitored for their long-term responses for a period of 500 days [19]. Cracking over the interior support of two-span continuous composite slabs occurred in the specimens reported in [55, 59] over time due to shrinkage. After 376 days from casting, maximum crack widths recorded in the continuous slabs were about 0.2, 0.3, and 0.6 mm for the samples subjected to 0, 3.72, and 6.72 kN/m, respectively. Reference [19] confirmed the role played by non-uniform shrinkage effects when considering cracking. The occurrence of shrinkage influences the bending moment distribution and affects the magnitude of the negative moment over interior supports in the continuous static configurations [55, 59]. This behavior was also observed experimentally in [19]. The composite slabs made with recycled aggregate concrete experienced higher deflection than those prepared natural concrete because of the higher shrinkage exhibited by the recycled aggregate concrete [19]. Negligible end slips between steel sheeting and concrete were observed under service load [55, 59]. The time-dependent response of composite slabs cast with either steel mesh or polypropylene/poly-ethylene blend fibers were compared in [58]. As part of this experimental program, four 914-mm-wide and 4600-mm-long continuous slabs were cast on corrugated steel sheet with two different thicknesses (i.e., thicknesses of 125 and 150 mm) and wet cured for 7 days. After curing, slabs were placed in continuous support condition and subjected to their self-weight until 28 days from the day of casting. Thereafter, two 150-mm and two 125-mm thick slabs were uniformly loaded with 11.8 and 9.5 kN/m, respectively, and monitored for their long-term behavior. The ratio between the instantaneous deflections and long-term deflections of the slabs varied between 1.35 to 1.51. The ratio between the short-term crack widths and the long-term crack widths of these samples varied between 2.00 to 2.85. Recent experimental measurements carried out on three identical continuous slabs that varied only in their exposure conditions for drying was reported in [53]. Three 6200-mm-long continuous slabs were cast on Condeck HP(r)[21] Profiled sheeting under propped conditions.