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Session 1359

EXPERIMENTAL SETUP OF A LOW DIFFERENTIAL PRESSURE PERMEABILITY APPARATUS FOR CONCRETE SAMPLES

Kevin J. Renken, George T. Abraham University of Wisconsin-Milwaukee

Abstract

This paper presents the results of a mechanical engineering senior design project that was carried-out in the Radon Reduction Technology Laboratory at the University of Wisconsin-Milwaukee (UWM). The objective of the student's project was to design, setup and test an experimental apparatus to measure the air permeability coefficient of concrete samples under low pressure differences (∆p ~ 5 - 10 Pa) that emulate residential indoor radon gas entry by advection. Details of the innovative experimental setup and procedures, the experimental data as well as the educational experience of the undergraduate student who worked on the project are described.

Introduction

Concrete is a porous material that easily allows radon gas to flow through it by the transport mechanisms of advection and diffusion. The permeability of concrete describes its ability to act as a barrier to gas movement when a pressure gradient exists across the concrete. For concrete with high permeability, pressure effects dominate diffusion effects resulting in radon gas advection as the major transport mechanism. There have been a number of studies pertaining to the advective flow of radon gas through concrete as well as the measurement of the permeability coefficient of air in concrete, but there exists little experimental data on the permeability coefficient of concrete for very low pressure differences. The majority of studies have documented permeability coefficients at differential pressures beyond the scope of advective radon entry problems in residential construction (i.e., ∆p ~ 5 - 10 Pa). Permeability measurements under specified high-pressure difference conditions have been found not to scale linearly to the small pressure differences of interest. This nonlinearity for large pressure differences normally leads to an underestimate of the flow velocity at low pressure difference conditions and hence, a large variance in the permeability value.1

The research goal of the UWM College of Engineering and Applied Science Radon Reduction Technology Laboratory (www.uwm.edu:80/Dept/radon/) is to investigate the phenomena of radon gas transport and entry dynamics with respect to innovative radon mitigation techniques. One of our current projects is the automated measurement of concrete permeability at low pressures utilizing control technology and state-of-the-art instrumentation. This study was initiated by a senior design project in the fall of 1999. Since then the laboratory has provided important data to the radon technology community on the air permeability coefficients of various concrete samples subjected to constant low-pressure differences between 0 - 10 Pa (0 - 6.90 x 10-2 psi).

Proceedings of the 2001 American Society for Engineering Education Annual Conference & Exposition Copyright  2001, American Society for Engineering Education

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Renken, K., & Abraham, G. (2001, June), Experimental Setup Of A Low Differential Pressure Permeability Apparatus For Concrete Samples Paper presented at 2001 Annual Conference, Albuquerque, New Mexico. 10.18260/1-2--9260