Evaluation of thermal conductivity in air permeable concrete for dynamic breathing wall construction

Jim Min Wong, F. P. Glasser, M. S. Imbabi

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

Air permeable concrete (APC) is potentially useful as a dynamic insulator. The dynamic function is achieved by passing air through the material in the direction of heat flow to facilitate heat recovery. An APC sample of 200 mm length with 60% cement filling of large voids (between 0.5 and 5 mm), was tested between 5 and 10 Pa differential pressures; permeabilities were 0.28-0.32 m(2)/Pa h, confirming its suitability as a dynamic insulator. To characterise properties it is necessary to determine the static thermal conductivity, i.e., no air flow. A one-dimensional heat flow model for predicting the effective thermal conductivity (lambda(e)) of APC is developed using as variables the fractions of voids, aggregate and cement paste comprising the material. Measured values of lambda(e) were 0.7-1.4 W/m K. A theoretical model predicts and further improves the performance and formulation of APC. The water/cement ratio (w/c) also controls the lambda(e). Increasing w/c increases the volume of micropores, adding resistance to heat flow. (C) 2007 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)647-655
Number of pages9
JournalCement & Concrete Composites
Volume29
Issue number9
DOIs
Publication statusPublished - Oct 2007

Keywords

  • air permeable concrete
  • dynamic insulation
  • thermal conductivity
  • heat recovery
  • energy efficiency
  • uncertainty
  • systems
  • packing

Cite this