The PenetraCone, a new robust field measurement device for determining the penetrability of cementitious grouts

摘要

One of the most crucial parameters for successful grouting is to ensure that the grout can penetrate the necessary apertures. For the most commonly used grout, cementitious grout, the available methods for determining the ability to penetrate apertures involves several measurements with different meshes or similar, which need to be evaluated. However, during the grouting process in the field there is rarely any time for evaluation and the most commonly used field method today stipulates a mesh width through which a certain volume need to pass. This implies that only an indirect measurement of the penetrability is performed. In order to perform direct and fast field measurements of the penetrability, a new, robust measuring device has been developed at Chalmers University of Technology in Gothenburg, Sweden. The device is named PenetraCone and the measuring part consists of a gap that is formed between two conical cylinders. The penetrability characteristics are measured by decreasing this gap as grout flows through. The gap is measured using a dial indicator gauge. Initial tests with the PenetraCone show that two characteristic gaps or widths can be evaluated. The width as the grout flow goes from continuous flow to dripping is termed b_(filter) and when the flow stops completely it is termed b_(stop). The parameter b_(filter) is related to the commencement of clogging or filtration of the cementitious grout. This means that for apertures larger than b_(filter) the cement passes unrestricted but for narrower apertures filtration will commence. This filtration process will occur in apertures down to b_(stop), which indicates the smallest aperture that the cement can pass through and for apertures below b_(stop) the cement will not penetrate at all. The device is easy to use and the tests show that consistent values are obtained. The accuracy seems good enough for use as a control of the penetrability of cementitious grouts in the field. For use in production, the PenetraCone should be placed on the grouting rig, after the mixer, so that direct measurements can be performed on the grout that will actually be used for grouting. By relating the measured parameters to the penetrability requirements, quick decisions regarding the quality of the grout can be made directly on the grouting rig.