Specialty concrete mix designs, such as latex-modified concrete, micro-silica, and high-strength concrete are no match for the power of Rampart’s ultra-high pressure (UHP) hydrodemolition equipment operating at 35,000-psi and 32 to 48 gpm. Compared to typical concrete, which has an average strength of 4,000 – 4,500 psi, high-strength concrete will have an average compressive strength of 8,000 – 10,000 psi. High-strength concrete removal can be accomplished via hydrodemolition!
An “industry” rule of thumb suggests that a minimum of 3.5 to 1 is required to hydrodemolish concrete. Essentially, you need 3.5 psi water pressure for each 1 psi of concrete strength. In order to effectively remove 10,800 psi concrete, the hydrodemolition equipment must be capable of operating in the range of 37,000 psi. Rampart is one of the few hydrodemolition companies utilizing UHP waterjets operating at 35,000 psi. Our UHP waterjets provided more than enough power to perform high-strength concrete removal (10,800 psi) on a historical bridge in Stone Harbor, NJ
Much of the hydrodemolition equipment in use today, averages 17,000 psi. Based on the rule of thumb, this equipment is only capable of removing concrete with a compressive strength of less than 5,000 psi. This would have been insufficient pressure to perform the concrete removal in Stone Harbor. Nor would it be sufficient to remove a 7,400 psi bridge deck in Georgia.
High strength concrete, however, will affect concrete removal production. The removal rate is inversely proportional to the concrete compressive strength. For example, if concrete removal were proceeding at 200 sf per operating hour in 4,000 psi concrete at a specific depth and the strength increases to 8,000 psi (cross a control joint to high strength concrete) the production would decline to 100 sf per operating hour while maintaining the same depth of removal. As a result, it is important for the specifier to state the concrete strength in the bid documents. A typical proposal to perform hydrodemolition will include the compressive strength on which the proposal was prepared.