We have studied the rheological behavior of concentrated cement suspensions in the absence and presence of comb polymers comprised of a polyacrylic acid (PAA) backbone and charge-neutral, poly(ethylene oxide) (PEO) teeth. These species possessed a uniform backbone molecular weight and graft density, with varying teeth molecular weight. Both PAA, a linear polyelectrolyte, and PAA/PEO comb polymers imparted initial stability to concentrated cement suspensions above a critical weight fraction, w* of 4 mg/(g of cement). Cement-PAA suspensions, however, set prematurely. Their rapid, irreversible stiffening stemmed from deleterious interactions between PAA and multivalent counterions in solution. Interestingly, the presence of PEO teeth comprised of only a few monomer units in length mitigated such interactions. The rheological property evolution of concentrated cement-PAA/PEO suspensions exhibited complex behavior ranging from the reversible gel-like response observed at short teeth lengths to a remarkable gel-to-fluid transition observed during the deceleratory period for systems comprised of longer PEO teeth. At longer hydration times, all cement-PAA/PEO suspensions exhibited initial elastic modulus values, G(i)' similar to exp(t/tau(c)) before the onset of the acceleratory period, followed by initial set. Their characteristic hydration time, tau(c), and set time depended strongly on the concentration of "free" carboxylic acid groups [COO-] arising from non-adsorbed polyelectrolyte species in solution.