These polyanions have carboxylate groups whereby cations bind them, especially Ca2+ in this early phase, as it is the most readily available ion, crosslinking into calcium polyacrylate chains that begin to form a gel matrix, resulting in the initial hard set, within five minutes.
These polyanions have carboxylate groups that can be bound by cations, particularly Ca2+ in this early stage due to its availability. This binding leads to crosslinking of calcium polyacrylate chains, forming a gel matrix and causing an immediate hardening effect within five minutes.