This month’s extensive renewal of the State Route 30 bridge, a two-lane structure that traverses Mackeys Creek in the northeast corner of Mississippi, was completed on time and on budget. A layer of PENETRON ADMIX-treated concrete on the bridge now provides the necessary waterproofing and corrosion resistance by preventing the intrusion of water, de-icing salts, and chemicals.
The Mississippi Department of Transportation (MS DOT) approved a $1.76 million project budget for the complete renovation of the State Route 30 bridge between CR 121 and SR 793 in Tishomingo, MS. Completion of the project will help minimize future maintenance and avoid any further damages that would make a costly bridge replacement necessary in the future.
“Over the years, the concrete surface of the bridge had been severely damaged by freeze-thaw cycles and corrosion caused by the intrusion of water and de-icing salts,” explains Christopher Chen, Director of The Penetron Group.
The Mississippi DOT approved the application of PENETRON ADMIX-treated concrete for the bridge deck overlay. Initially, the damaged concrete surface of the bridge (two-lanes wide) was hydro-blasted to expose the top layers of reinforcing steel. The exposed concrete structure was then covered with the PENETRON ADMIX-treated concrete, ensuring a high degree of impermeability and optimal protection against any future intrusion of water and de-icing salts.
Mitigating Freeze-Thaw Cycles in Concrete
B&B Concrete, the project’s ready-mix supplier, followed Mississippi DOT specifications and submitted a concrete mix design proposal based on PENETRON ADMIX crystalline technology, designed to mitigate freeze-thaw damage. Integrating a permeability reducing, crystalline waterproofing solution would optimize concrete durability by reducing the ingress of water and harmful substances into the concrete matrix.
In climates with cold weather, freeze-thaw cycles are a major reason for the deterioration of exposed concrete bridges and roads. Water that penetrates the concrete expands in freezing weather, causing internal pressure. This leads to cracking in the concrete and the following thaw allows the water to penetrate even deeper into the newly formed cracks. This cycle repeats itself until the damage from spalling of the concrete surface requires costly repairs or replacement of the concrete structure.
Ensuring a Long Life for Bridges
“When used in pavements and bridges, concrete is expected to have a long service life – and ideally require minimal maintenance,” adds Christopher Chen. “However, when exposed to freeze-thaw cycles, especially in the presence of de-icing salts and chemicals, a bridge’s concrete matrix can suffer extreme deterioration, requiring frequent maintenance and premature replacement. Fortunately, PENETRON ADMIX-treated concrete testing shows this type of deterioration can be reduced and slowed down with crystalline technology.”