Flight Crew Air Transport Pilot (ATP)
Ground Event / Encounter FOD
General None Reported / Taken
Environment - Non Weather Related
After consulting with the First Officer (FO) we elected to use Max auto braking for landing on [GFK] Runway 35L. The braking action was 45/45/35 mu report. I wanted to land and stop in the first 2/3 of the 7200 foot runway. Upon touchdown; full reverse was applied to both engines. Auto brakes worked as advertised. As we slowed 80 knot and 60 knot calls were made from the FO. Reversers were stowed as per standard operating procedure. As we came to a slow crawl; dust entered the air conditioning system and dust mist filled the cockpit. Main cargo fire warnings illuminated.I instructed the FO that the fire warnings were from the dust from the runway. Subsequently the Main Cargo fire warnings ceased on the taxi into the gate. Taxi in and shutdown were uneventful.The runway was very contaminated with sand from deicing the runway unbeknownst to the crew.I think that if I had known the runway was not only contaminated with snow and ice and that it had great quantities of sand debris on the runway; I still would have used max auto brakes; however I would have used less engine reversers and would have come out of reverse sooner.
Air Cargo Captain reported that after landing on a runway contaminated with sand the aircraft filled with dust that had been ingested by the packs following use of reverse thrust.