MEASURING PERMEABILITY OF CONCRETE - THE CHALLENGES AND SOLUTIONS IN THE RESEARCH EXPERIENCE

The objective of this research is to measure the permeability of concrete using the recently developed hollow dynamic pressurization (HDP) technique. While the outline of the research was as straightforward as preparing plain cement paste samples in accordance to the mix design standards and testing them using the HDP experimental setup, several hardships and challenges were encountered during this process. Two different batches of cement paste with water to cement (w/c) ratio of 0.40 and 0.50 were prepared to understand the impact of w/c on affecting permeability measurements. The first challenge in the experiment was to figure out a way to prepare hollow samples using standard solid molds. The next task was to demold the sample without damaging its core. Since permeability of the samples is expected to be around nanometer scale at early ages, setting up the test without flaws was a critical step to obtain accurate measurements. The extremely sensitive nature of the linear variable differential transformers (LVDT's) used to track the displacements over a length of time required utmost care in handling. Further, since the test was carried out at high pressure levels, depressurizing at the end of the test had to be done with high degree of skill and care, for sudden drop in pressure levels would result in leaks and spillage apart from damaging the sample. The lessons learnt in dealing with the aforementioned problems faced during the process of completing this research are elaborated in detail in this paper.