Introducing a New Method for Measuring Internal Stability of Microfine Cement Grouts

In some cases, permeation grouting can be a very cost effective soil improvement technique. Recently, the use of fine grained (microfine) cement has improved the performance of cement grouts by reducing bleeding and widening the range of soils that can be penetrated by grout. In this paper, an experimental study is conducted to evaluate the current practice for determining suspension grout stability. To do so, the performance of microfine cements over a range of water-to-cement ratios is evaluated and compared to its measured stability. First, traditional bleed column stability tests were performed on the different grout mixes. Then, a new method of determining grout stability while in motion is introduced, and its results are compared to the traditional bleed test results. Finally, constant flow permeation tests were performed through a two-foot long rigid wall permeameter using the different mixes. Lastly, the unconfined compressive strength of the grouted sand was measured as function of the distance from the injection point and the results were used to evaluate the efficiency of both grout stability methods in determining the filtration of the grout as it permeates through a porous medium. This paper presents data and preliminary results for the new stability test. Further results incorporating the use of lower water to cement ratio grouts and additives such as superplasticizers are to follow.