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The concrete samples with various erosion states were disintegrated inside the overpressure vessel using high-velocity water jet and depth of penetration was measured. Removing of the eroded parts of samples was also tested using low-pressure generated continuous or pulsing fan jets and rotating jets. The influence of the erosion states, water jet techniques, traverse rate and stand-off distance on the disintegration volume was studied and the surface topography was investigated. The high-pressure generated continuous water jet was applied in the overpressure vessel used for simulation of pressures equivalent to the submersion to several depths under the water level. The low-pressure generated continuous or pulsing jets were applied in air conditions. Some samples of special decorative concretes were also studied. [ABSTRACT FROM AUTHOR]

Abstract: The paper is dealing with the effects of flat high-speed water jet on concretes affected by high temperature. Research should help to correct use of water jet technology in repair works on concrete structures especially after wildfires in tunnels, underground garages, etc., which are exposed to enormous thermal stress. Four concrete mixtures were prepared for tests of interaction of water jet with concrete. The samples were exposed to 200°C and 600°C and for comparison one third of samples were left unaffected. It was found, that both lower traversing velocity (cutting speed) and higher water pressure led to removal of higher amount of concrete. Higher temperature loading caused decrease of concrete strength and thus easier removal of surface layers by water jet. Concrete mixtures with basalt aggregate demonstrate higher resistance against water jet penetration regardless thermal loading compared to mixture with standard granodiorite aggregate. Presence of polypropylene fibres has substantial influence on concrete strength properties, however only marginal impact on resistance against water jet penetration. [Copyright &y& Elsevier]

The concrete samples with various erosion states simulating road or bridge damage were disintegrated by pure continuous water jets generated from pressure 380 MPa and by pulsing water jets generated from low pressure 30 MPa. The erosion states of samples were prepared applying several laboratory techniques simulating the concrete aging under the conditions corresponding to the use in practice. The influence of the erosion state on the disintegration rate was tested because water jet techniques are very effective in selective disintegration of damaged concrete without significant erosion of the unbroken concrete unlike pneumatic drills or other impacting machines usually used for such a work. The comparison of both the depth of penetration and the ratio of volume disintegration regarding the input power is performed. All results are discussed regarding their application in practice and further development of special routings. [ABSTRACT FROM AUTHOR]