Part of the KMP project design calls for new alumina and coke storage silos. These silos were both designed as seamless structures, which required them to be constructed using slipforming and poured as a single continuous concrete pour.
Slipforming is a challenging process for concrete supply, as the rate of hardening of the concrete must be carefully controlled to be fast enough to support the weight of new concrete poured on top, but slow enough to mix with the next layer without creating seams or separation between loads or layers. Kentron developed a new mix design with special admixture dosing to provide the slump and workability retention and hardening speed that ideally suited for the silo pours.
The coke silo required 900m3 of concrete, and was poured over a 6-day period in late July. The pour rate was quite slow- averaging around 7m3 per hour- but production had to continue around the clock without any interruptions from start until finished. Adding to the challenge of this pour was the ambient temperatures, as the midday temperature would climb above 30 deg. C and then drop to near 10 deg C overnight.
The alumina silo used 1,300m3 of concrete, and also required 6 days of continuous operation to complete.