Case Study # 1
Underground Reinforced Concrete Vault Restoration

Problem: More than 40 underground reinforced concrete vaults housing steam distribution control equipment had suffered from the ingress of de-icing salt laden water to varying degrees. In some cases the 12-in thick walls had deteriorated the full thickness due to severe corrosion of the embedded reinforcing steel. In other vaults over 50% of the thickness of the 12-in thick roof slabs had been lost.

The challenge was how to provide long-lasting repairs and how to repair the concrete from within the vaults, as carrying out complete removal and re-construction work within the busy city streets was not desirable - as well as the fact that several utility services were buried in the backfill above the vaults.

Solution: PJ Materials Consultants devised a strategy which provided for permanent support of the roof slabs and low-pressure grouting techniques to repair the deterioration using a highly fluid but durable concrete mix -followed by protection of all the concrete using a penetrating sealer and techniques that reduced the effects of water infiltration. A specialist contractor was selected after a pre-qualification program and most of the disruptive work was carried out during evenings and night-times.