Bloomberg: Leaking concrete accelerants caused chemical burns

Via Bloomberg, this news: 

The muck pooling in the tunnel at the north end of the Las Vegas Strip had the consistency of a milkshake and, in some places, sat at least two feet deep. The tunnel-to-be, which would eventually stretch about half a mile, was part of a system intended to connect two hotels, the Encore Las Vegas and the Westgate, with the enormous Las Vegas Convention Center. Workers doing the digging later said they had to wade through the mud every day. It splashed up over their boots, hit their arms and faces and soaked through their clothes. At first, it merely felt damp. But in addition to the water, sand and silt—the natural byproducts of any dig—the workers understood that it was full of chemicals known as accelerants.

The accelerants cure the grout that seals the tunnel’s concrete supports, helping the grout set properly and protecting the work against cracks and other deterioration. They also seriously burn exposed human skin. At the Encore dig site, such burns became almost routine, workers there told Nevada’s Occupational Safety and Health Administration. An investigation by the state OSHA, which Bloomberg Businessweek has obtained via a freedom of information request, describes workers being scarred permanently on their arms and legs. According to the investigation, at least one employee took a direct hit to the face. In an interview with Businessweek, one of the tunnel workers recalls the feeling of exposure to the chemicals: “You’d be like, ‘Why am I on fire?’”

I'd love to know why calcium nitrate (or other potential curing accelerants) might cause burns, but I'm not particularly surprised exposure would cause some unpleasant symptoms.