This study proposes approximate boundary conditions for a panel reinforced concrete (RC) slab to simulate the fatigue behaviors of a real bridge RC slab. To validate the approach, fatigue analysis of the panel RC slab is conducted using a finite element method (FEM) based numerical model with the bridging stress degradation concept. Both the proposed approximate boundary conditions, and those that have been typically employed in past studies, are used. The numerical results demonstrate that the panel RC slab with approximate boundary conditions experiences the same bending moment distribution and deformations around the loading locations as the load moves along the slab axis, similar to those of a real bridge RC slab. Moreover, the approximate boundary conditions reproduce the extensive grid crack pattern in the panel RC slab, which is similar to that generally observed in a real bridge RC slab. The results of this study establish that panel RC slab with approximate boundary conditions behaves in a similar manner to a real bridge RC slab, which results in a more realistic fatigue life estimation.
In this paper, the effects of retarding admixture, polycarboxylate (PCE) superplasticizer and supplementary cementitious material (SCM) on the rheology of high strength calcium sulfoaluminate (CSA) cement paste are investigated. At the water to binder ratio of 0.3, one PCE, two retarding admixtures, and three SCMs were used in the test. The test results show that much more PCE is needed for paste with citric acid than that with sodium borate to achieve a similar initial flowability. The reference paste and pastes mixed with sodium borate or fly ash exhibit shear thickening; pastes mixed with citric acid or silica fume exhibit shear thinning. The addition of citric acid increases the maximum shear stress of pastes, while the maximum shear stress can be significantly reduced by silica fume. Both the retarding admixtures and SCMs will strongly reduce the early-age compressive strength of the cement paste. At 28 days of age, CSA cement paste incorporating retarding admixtures has comparable strength to the reference paste. Silica fume has less negative effect on the compressive strength of the CSA cement paste due to the significant filling effect.