Citi-Con has successfully completed complex structural repairs on bins 21 and 22 for a leading steward of raw materials in the food production industry. These interventions represent the most critical component of the extensive specialist concrete repair and corrosion protection solutions that the company has already undertaken for this client across various silo complexes.
Given the high-risk nature of the work, the project was supervised by Dion Rudolph, Citi-Con’s experienced Project Manager, who also provided valuable input into the engineer’s repair design to improve constructability, drawing on his extensive expertise in concrete repair and corrosion protection.
“With our proven track record in extending the design life of these structures, we bring the practical, on-site expertise needed to deliver a successful outcome. Working safely in an area of the Free State where temperatures often exceed 30°C and winds can intensify with little warning was part of our daily reality. By incorporating improved design features upfront, we were able to plan effectively around these conditions and maintain project momentum,” Rudolph says.
A case in point was his suggestion to increase the hole plate tolerances to a 50 mm outer diameter clearance, which significantly accelerated the work without compromising safety.
Leveraging his extensive rigging experience, he devised an innovative method to hoist the 38.5 kg plates to the various working faces – addressing the fact that they were too heavy for rope-access technicians to carry. Cutting the plates was not an option, as this would have compromised their structural integrity.
The scope involved reinforcing the primary support beams – 10 on the rigid side of bin 22 and two on the flexible side of bin 21 – which tie into the steel beams which interconnect the structure linking the machine tower to the concrete silo. Over time, differential movement between the machine tower and the concrete silo structures caused shear-related distress on the metal beams and concrete spalling at the concrete anchoring points (beam-wall) connections. If left unaddressed, this deterioration posed a significant risk of structural failure.
Work began on bin 22, replacing the five front and five rear H-plate assemblies in sequence. Rudolph and his team started at the lowest level, completing one H-plate assembly per day.
“There was zero margin for error; even the slightest mistake could have triggered a collapse,” he says. “When reinforcing the final beams, we were working at heights of approximately 37 m and within extremely tight tolerances of two to three millimetres when positioning the plates.”
The engineered solution required cutting back each existing beam by 50 mm and installing a new H-plate reinforcement system.
Rudolph’s team began by cutting back each existing beam, removing it, and then using it as a template for precise measurement and drilling.
Six 200 mm-deep holes were then drilled through the concrete using one of Citi-Con’s powerful industrial Hilti drill machines. Thereafter, threaded bars were inserted and secured with chemical anchoring mortar that achieved full strength in just 30 minutes.
A 600 × 600 × 12 mm internal plate was then hoisted and aligned with a 100 × 100 × 6 mm washer plate and nut to secure the internal anchor point.
This was followed by reattaching the new A4 stainless-steel plate using high-tensile bolts, spring washers, and lock nuts.
“Once again, rigorous quality control was maintained throughout,” he says. “All plates were CO₂ welded at 45° and 90° angles. Offering deep penetration and high deposition rates, CO₂ welding is particularly suited to thick steel. A sealant was also applied between the concrete silo walls and the new H-plates to prevent water ingress and possible rusting in the future, followed by anti-corrosion and final protective coatings.”
By the time the project was completed, Citi-Con had safely handled and installed more than 924 kg of structural steel as part of this innovative turnkey structural engineering solution.
“This project reinforces our position as the trusted partner for advanced silo repair and strengthening. By combining practical engineering insight with precision execution, we continue to extend the lifespan of these vital structures,” Rudolph concludes.
