  Locally-rotationally-symmetric Bianchi type-I viscous and non -viscous
cosmological models are explored in general relativity (GR) and in f(R,T)
gravity. Solutions are obtained by assuming that the expansion scalar is
proportional to the shear scalar which yields a constant value for the
deceleration parameter (q=2). Constraints are obtained by requiring the
physical viability of the solutions. A comparison is made between the viscous
and non-viscous models, and between the models in GR and in f(R,T) gravity. The
metric potentials remain the same in GR and in f(R,T) gravity. Consequently,
the geometrical behavior of the $f(R,T)$ gravity models remains the same as the
models in GR. It is found that f(R,T) gravity or bulk viscosity does not affect
the behavior of effective matter which acts as a stiff fluid in all models. The
individual fluids have very rich behavior. In one of the viscous models, the
matter either follows a semi-realistic EoS or exhibits a transition from stiff
matter to phantom, depending on the values of the parameter. In another model,
the matter describes radiation, dust, quintessence, phantom, and the
cosmological constant for different values of the parameter. In general, f(R,T)
gravity diminishes the effect of bulk viscosity.
