  The feasibility of detecting a heavy charged Higgs boson,
m(H^{+-})>m(t)+m(b), decaying in the H^{+-}->tb channel is studied with the
fast simulation of the ATLAS detector. We study the gg->H^{+-}tb production
process at the LHC which together with the aforementioned decay channel leads
to four b-quarks in the final state. The whole production and decay chain reads
gg->H^{+-}tb->t\bar{t}b\bar{b}->b\bar{b}b\bar{b}l\nu\bar{q}q'. Combinatorial
background is a major difficulty in this multi-jet environment but can be
overcome by employing multivariate techniques in the event reconstruction.
Requiring four b-tagged jets in the event helps to effectively suppress the
Standard Model backgrounds but leads to no significant improvement in the
discovery potential compared to analyses requiring only three b-tagged jets.
This study indicates that charged Higgs bosons can be discovered at the LHC up
to high masses (m(H^{+-})>400 GeV) in the case of large tan(beta).
