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Round Robin Test 2008. Frost Resistance of Clay Units. Part 1: Report.

In 2009, the Technical Specification CEN TS 772-22 shall be proposed as EN 722-22 and submitted to formal vote. The publication of a TS (Technical Specification) let the possibility to each country to acquire experience during 3 years. In order to justify the Belgian position of the commission NBN E125 concerning this vote and in the frame of the discussion led in 2005 in the context of the ‘WG laboratories' led by BCCA, the Belgian Building Research Institute (BBRI) has organised a ‘Round Robin Test' on the frost resistance of an anonymous type of clay unit. This ‘Round Robin Test' is part of a larger pre-normative research entitled ‘Frost Resistance of Clay Masonry Units and Mortars' of BBRI and the Belgian Ceramic Research Centre (BCRC) subsidized by the FPS Economy. In this research, beyond the comparison of the severity of the Belgian and European ‘approach', mechanical inspection methods were investigated to quantify the frost damage. The objectives of this ‘Round Robin Test' are threefold. First of all, the severity of the European approach is compared to the Belgian one which has shown to be suitable. Keeping the same level of confidence on the quality is important for the sector. Secondly, the feasibility of quantitative inspection methods to detect frost damage is studied. Two methods were analyzed in the ‘Round Robin Test'. The first one is the determination of the resonance frequency on bricks to calculate the loss of dynamic elasticity modulus. This non-destructive method is applied on the same bricks before and after frost. The second one is the determination of the cohesion strength of the stretcher face of bricks. For this destructive method, two series of specimens are compared (one is tested before frost and one after frost). These inspection methods could contribute to objectify the occurring frost damage which is until now only based on visual inspection. In this report, before discussing the results of the ‘Round Robin Test' itself, the validation of both quantitative inspection methods is explained. Finally, the results of the participating laboratories are compared both based on the visual qualitative inspection of the bricks after frost as on the statistical analysis of quantitative properties (water absorption before frost test, resonance frequency, cohesion strength). These analyses provide a tool to each laboratory to evaluate themselves in comparison to the others in the context of quality management (recognition or accreditation).

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