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. 2014 Apr 11;7(4):3002-3020.
doi: 10.3390/ma7043002.

A Procedure to Measure the in-Situ Hygrothermal Behavior of Earth Walls

Pierre-Antoine Chabriac  1   2 , Antonin Fabbri  3 , Jean-Claude Morel  4 , Jean-Paul Laurent  5 , Joachim Blanc-Gonnet  6
Affiliations

A Procedure to Measure the in-Situ Hygrothermal Behavior of Earth Walls

Pierre-Antoine Chabriac et al. Materials (Basel). .

Abstract

Rammed earth is a sustainable material with low embodied energy. However, its development as a building material requires a better evaluation of its moisture-thermal buffering abilities and its mechanical behavior. Both of these properties are known to strongly depend on the amount of water contained in wall pores and its evolution. Thus the aim of this paper is to present a procedure to measure this key parameter in rammed earth or cob walls by using two types of probes operating on the Time Domain Reflectometry (TDR) principle. A calibration procedure for the probes requiring solely four parameters is described. This calibration procedure is then used to monitor the hygrothermal behavior of a rammed earth wall (1.5 m × 1 m × 0.5 m), instrumented by six probes during its manufacture, and submitted to insulated, natural convection and forced convection conditions. These measurements underline the robustness of the calibration procedure over a large range of water content, even if the wall is submitted to quite important temperature variations. They also emphasize the importance of gravity on water content heterogeneity when the saturation is high, as well as the role of liquid-to-vapor phase change on the thermal behavior.

Keywords: cob; dielectric constant; full scale experiments; hygrothermal behavior; rammed earth; water content measurement.

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Conflict of interest statement

The authors declare no conflict of interest

Figures

Figure 1.
Figure 1.
Operating principle of a TDR (Time-Domain Reflectometry) probe.
Figure 2.
Figure 2.
Particle-size distribution.
Figure 3:
Figure 3:
Comparison between the volumetric water contents obtained by weighing (θreference) and from the probes CS650 (θBL−CS650) and CS616 (θBL−CS616) calibrated with the bilinear relation.
Figure 4.
Figure 4.
Side view and top view of the implementation of CS616 and CS650 probes in the rammed earth wall placed in a sealed box.
Figure 5.
Figure 5.
Evolution of (up) volumetric water content and (down) temperature of the wall.
Figure 6.
Figure 6.
Deviation Δθ on the values of volumetric water content between the CS616 and CS650 probes located respectively on the left and right sides 50cm high.
Figure 7.
Figure 7.
Volumetric water content depending on the height in the wall.
Figure 8.
Figure 8.
Focus on the temperature within the wall and within the boxes during (A) a drying stage and (B) a forced drying stage.
See this image and copyright information in PMC

References

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