  Under an increasing applied shear stress ($\sigma$), viscosity of many dense
particulate suspensions increases drastically beyond a stress onset
($\sigma_0$), a phenomenon known as discontinuous shear-thickening (DST).
Recent studies point out that some suspensions can transform into a stress
induced solid-like shear jammed (SJ) state at high particle volume fraction
($\phi$). SJ state develops a finite yield stress and hence is distinct from a
shear-thickened state. Here, we study the steady state shear-thickening
behaviour of dense suspensions formed by dispersing colloidal polystyrene
particles (PS) in polyethylene glycol (PEG). We find that for small $\sigma$
values the viscosity of the suspensions as a function of $\phi$ can be well
described by Krieger-Dougherty (KD) relation. However, for higher values of
$\sigma$ ($>> \sigma_0$), KD relation systematically overestimates the measured
viscosity, particularly for higher $\phi$ values. This systematic deviation can
be rationalized by the weakening of the sample due to flow induced failures of
the solid-like SJ state. Using Wyart-Cates model, we propose a method to
predict the SJ onset from the steady state rheology measurements. Our results
are further supported by in-situ optical imaging of the sample boundary under
shear.
