RILEM TC 275 - Moisture Buffer Value of vegetal concrete - Results of round-robin testing

Abstract The moisture buffering characterization of bio-based building materials and products is investigated to accurately define a test methodology, as previous studies have shown some discrepancies and difficulties for comparison. An industrial hemp concrete was selected. The applicability of the NORDTEST protocol, with complementary details, was assessed by two round robin tests (RRT) with seven participating laboratories to achieve robustness and validation. The first RRT specified a method for previously conditioning the specimens and identified that: the exchange surface widely impacted the MBV results; a lower MBV was found for molded surface; the moisture flux direction versus the compaction direction did not show a high impact on the results; climatic chambers with Peltier technology are less efficient in desorption phase; the impact of air velocity was not highlighted, as the air velocity was similar in all labs; the test can be performed with vertical or horizontal exchange surfaces. For the second RRT, the conditioning protocol was reduced and simplified but complementary details were provided: the exchange surface was molded and the moisture flux was perpendicular to the compaction direction; the necessity to well remove dust before sealing was emphasized; more caution was taken when sealing the other specimen surfaces. This RRT confirmed that the exchange surface finishing widely affects the MBV results and the less efficiency of climate chambers with Peltier technology. Moreover, it underlined the effect of air velocity. The results obtained following this more detailed protocol were comparable between laboratories, suggesting their robustness to assess MBV of bio-based products.