Equipment and Procedure Description

Improvements in test methodology and characterisation of long-term flexure behaviour of fibre-reinforced concrete

“…Figure 39. Square panel creep frames examples: (up-left) single-specimen lever arm frame [192]; (up-right) single-specimen hydraulic frame [188,]; (down) multispecimen hydraulic frame [195] maximum CMOD reached in the pre-cracking stage CMODpri elastic CMOD recovery when the pre-cracking test unloading process ends CMODprd residual CMOD 10 minutes after unloading in the pre-cracking stage CMODci instantaneous CMOD immediately after reaching the reference load CMODci 10' short-term CMOD deformation 10 minutes after reaching the reference load CMODci 30' short-term CMOD deformation 30 minutes after reaching the reference load CMODci…”

“…Therefore, both short-and long-term tests are usually controlled by deflection. However, some laboratories reported studies [195] with both deflection and crack opening measurements in long-term tests, as seen in Figure 38. LVDT transducers were located below the square plate after the pre-cracking test, crossing the primary crack to assess crack opening evolution.…”

“…However, significant differences were noticed in pre-cracking level and load level parameters. On the one hand, the pre-cracking level ranges from 2 to 3 mm deflection reported in square panels [63,188,190,193,195] and 1 to 13 mm deflection in round panels [185,186]. This fact is explained by the target of each methodology; square panel procedures aim to characterise the long-term behaviour of FRC material in SLS, whereas round panel procedure is focused on assessing the safety factor of cracked structures when large cracks appear in ULS.…”

“…Although the reported load level referred to the residual strength ranges from 40 to 100%, the most used load level is 60%.Although in both flexure and tensile creep test, the use of the multi-specimen setup is extended, in the case of panel creep tests, the use of single-specimen setup is, so far, the most extended setup due to the challenging stacking procedure of cracked specimens. To date, only one laboratory reported creep tests in a multi-specimen setup [195], testing two superposed specimens simultaneously. However, this setup forced them to invert upper specimens generating a more complex procedure.…”

“…Depending on the laboratory, creep tests were conducted on controlled or uncontrolled environmental conditions. Although creep tests on square panels were usually reported in uncontrolled conditions [187,[190][191][192][193], Kaufman [188] and two participants of the RILEM Round-Robin Test [195] carried out in constant temperature and humidity. Square panel creep tests carried out in Rio de Janeiro were conducted in a climate-controlled chamber, whereas creep tests carried out by Versuchsstollen Hagerbach were conducted in the underground Hagerbach Test Gallery, as seen in Figure 42.…”