# Shrinkage-Induced Response of Composite Steel-Concrete Slabs: A State-of-the-Art Review
## 3 Time-Dependent Responses of Composite Slabs
### Simply-Supported Composite Slabs
Time-dependent experimental results of one-way simply-supported composite slabs made of recycled aggregate concrete with different thicknesses and loading conditions have been reported in [18; 20]. Four simply-supported composite slabs having 3300-mm length and 510-mm width were cast on DW-65-510-170 steel deck. Slabs possessed two different thicknesses of 120 and 180 mm, and were subjected to different sustained loading conditions that ranged between 0 and 9.0 kN/m. The long-term tests were monitored for 268 days from the day of casting. Reference [14] presented the long-term response of three simply-supported post-tensioned slabs, i.e., two samples were cast on profiled steel sheeting Condeck HP [21] and PrimeForm [22] and one specimen was prepared with a solid concrete slab. All samples were 7200-mm-long and had identical cross-section with 900-mm width and 180-mm depth. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Ref. ** & **Sample ID** & \(f_{c}\)1  & \(w_{sus}\)1  & \(t_{0}\)1  & \(t_{k}\)1  & \(L\)\(U_{0}\)1  & \(b\)1  & \(D\)1  & **Steel Sheeting** \\ \hline  & & **[MPa]** & **[kN/m]** & **[Days]** & **[Days]** & **[mm]** & **[mm]** & **[mm]** & \\ \hline  & CCS-NAC-L & 57.5 & 4.5 & & & & & & \\  & CCS-RAC-L & 47.4 & 4.5 & 28 & 500 & 6300 & 510 & 120 & DW-65 \\  & CCS-RAC-SH & 47.4 & 0 & & & & & & \\ \hline  & CS1 & & & & & & & & \\  & CS2 & 32 & 0 & 14 & 267 & 6200 & 634 & 120 & Condeck HP\({}^{\circled{\circled{\circled{\circled{\circled{\circled{\circled{\circled{\circled{\circled{\circled{\circled{\circled{\circled{\circled{\  
The prestressing forces were applied in two stages at day 2 and day 7 from the day of casting, and subsequently, all slabs were unpropped to place them in simply-supported conditions. The long-term behavior was induced by shrinkage effects and by creep induced by the slab self-weight. The tests were monitored for a period of 239 days. The post-tensioned slab prepared with the solid slab (exposed to dry from both sides) experienced less than one-fifth of the deflection of the post-tensioned composite slabs (sealed at the bottom of the slab by the presence of the profiled steel sheeting). These comparisons highlighted the importance of accounting for the influence of shrinkage gradients when predicting deflections in composite slabs. Six post-tensioned simply-supported composite samples cast with different dimensions, number of prestressing strands, continuity of the steel sheeting and curing conditions were presented in [54]. Four of the slabs were 7200-mm-long, and the other two were 8650-mm-long. The slab thicknesses varied between 180 and 225 mm. All slabs were wet cured for 7 days from the day of casting and prestressing were completed by two stages at day 2 and day 6 from the day of casting. All samples were then placed in a simply-supported static configuration. The specimens exhibited similar long-term deflections except the one covered with curing compound after casting. The latter sample (i.e., cast with curing compound) exhibited half of the time-dependent deflections measured for the other post-tensioned composite specimens. In a recent study, the influence of specifying different drying conditions on the time-dependent deflections of simply-supported composite slabs was presented in [53]. All slabs had a length of 3200 mm and were 634-mm-wide and 120-mm-deep. Those drying conditions of composite slabs were considered to replicate different scenarios that take place during building construction. For this purpose, three drying conditions were considered: (i) The top surface of one composite slab was sealed after casting; (ii) a second sample was sealed on its top surface after 37 days from casting to reflect the scenario in which a slab is sealed by floor finishes or by other treatments during construction; and (iii) the top surface of the third sample was left exposed for drying. The long-term measurements recorded for these specimens are illustrated in Figure 5.