COST Action FP 1303 Cooperative Performance Test Instructions for participants

Transcription

1 COST Action FP 1303 Cooperative Performance Test Instructions for participants by Christian Brischke, Miha Humar, Linda Meyer, Stig Bardage, and Jan Van den Bulcke July 2014

2 Content 1 Background and objectives Principle set up Documentation Exposure conditions Selection of exposure site Documentation of exposure site Documentation of exposure conditions Documentation of unforeseen incidents Assessment and evaluation Decay Discoloration CIE L*a*b* color measurements - colorimeter CIE L*a*b* color measurements simplified approach Surface disfigurement due to mould and staining fungi Corrosion Intermediate assessments Final evaluation Crack formation Moisture content and temperature (only Version A) MC monitoring equipment Read out of data loggers Battery check / replacement Trouble-shooting Measurement intervals - summary References

3 1 Background and objectives Cost Action FP 1303 Performance of bio-based building materials has successfully started in October 2013 and is looking forward to an ambitious program during the upcoming 3.5 years. Among this a collaborative field test is planned. As we have learned from earlier actions it is valuable to start with such cooperative activities as early as possible in the life of the action. This allows harvesting results within the run-time of the action and will initiate lively discussions during the upcoming workshops and meetings. A Cooperative Performance Test has been organized in the frame of this action as decided during the first workshop in Paris. The idea is to distribute a fairly simple test set up among as many places in Europe as possible to collect performance data under the full range of climatic conditions to be expected. Furthermore performance shall be considered in its manifold meaning, i. e. optical, aesthetical, moisture and functional performance and durability. In contrast to traditional Round Robin tests aiming on comparative evaluation and validation of results from different test labs, this initiative aims on collecting performance data under climatically different exposure conditions. Therefore it will be required to provide weather data from the respective test sites to allow establishing relationships between climate conditions and the following measurands, which shall be evaluated regularly: Decay Discoloration Development of mould and other staining fungi Corrosion Formation of cracks Moisture performance (if data logging device is included) The results expected from this cooperative performance test will contribute to a better understanding of performance aspects of bio-based materials in the building sector under the influence of geographical and climatic differences. Furthermore it will enable the participants to estimate their own location in terms of exposure severity and performance to be expected. 3

4 2 Principle set up A folding table with boards made from three different materials (i. e. Norway spruce, English oak and thermally modified Norway spruce) serves as easy shippable and ready-to-use test object (Fig. 1). The boards are fixed with partly stainless and partly ordinary steel screws. The table is available in three different versions: Version A: Performance table with the three materials mounted; including data logging device for recording temperature and wood MC (8 channels) Version B: Performance table with 3 materials mounted, no data logger Version C: Performance table, blank rig for testing extra materials according to personal/regional preferences (delivered only in addition to version A or/and B) Fig. 1. Performance folding table. 4

5 3 Documentation All results and all other relevant data will be requested in an Excel sheet template that has been delivered with this performance table. Results and documentation reports will be requested regularly. In return the overall results will be summarized, presented and circulated regularly as well. 4 Exposure conditions 4.1 Selection of exposure site Please choose for your performance table an exposure location that meets the following requirements: Typical free exposure (avoid canopies and vicinity to buildings and other shading elements) Use your standard test site (if available) to allow for further comparison with your running tests Make sure that the performance table is safe (against vandalism, thievery, storm, and other catastrophes, which might occur at your place) The table should be fixed to the ground. Therefore angle steel can be used. Steel box with dataloggers can be positioned below the table or on the nearby holder. There are several mounting options available. Be sure to prevent leaking. 4.2 Documentation of exposure site Please provide the following information of your exposure site: Geographical position (GPS coordinates) Height above sea level Photographs (preferably immediately after exposure) showing the performance table and the surrounding showing the four compass directions 5

6 4.3 Documentation of exposure conditions For interpretation of the results from your performance table detailed information about the respective exposure conditions are needed. In particular the weather parameters corresponding to the exposure period are requested. Please provide daily data for the following parameter (tables to fill in are provided in the enclosed Excel file). Precipitation Average air temperature Minimum air temperature Maximum air temperature Average relative humidity If available also the following parameters would be valuable: Wind speed Wind direction Global irradiance Please use the closest weather station, which might be an official, private or even your own station. 4.4 Documentation of unforeseen incidents In case there is an unforeseen incident, which might have an effect on the performance of your test table, it should be reported even if there is no evidence that it had any impact. 6

7 5 Assessment and evaluation 5.1 Decay The specimens should be inspected once a year regarding the onset and progress of decay. Therefore the screws should be loosened and the specimens removed from the rig to allow inspection from all sides. Decay shall be assessed by visual inspection combined with a pick-test using a pointed knife. The knife should be pricked into the specimens and pulled out again to inspect the surface strength as well as the fracture depth and splinter characteristics for the rating pursuant to EN 252 (1989). The rating scheme according to EN 252 (1989) is shown in Table 1. Table 1: Decay rating scale according to EN 252 (2012) Rating Classification Definition 0 No attack No change perceptible by the means at the disposal of the inspector in the field. If only a change of colour is observed, It shall be rated 0. 1 Slight attack Perceptible changes, but very limited in their intensity and their position or distribution: changes which only reveal themselves externally by superficial degradation, softening of the wood being the most common symptom. 2 Moderate attack Clear changes: softening of the wood to a depth of at least 2 mm over a wide surface (covering at least 10 square centimetres) or by softening to a depth of at least 5 mm over a limited surface area (covering less than 1 square centimetre). 3 Severe attack Severe changes : marked decay in the wood to a depth of at least 3 mm over a wider surface (covering at least 25 square centimetres) or by softening to a depth of at least 10 mm over a more limited surface area. 4 Failure Impact failure of the stake in the field. 7

8 Additionally, on the basis of visible characteristics the type of decay should be identified. Information how to distinguish the main decay types (brown rot, white rot, soft rot and tunnelling bacteria) can be found in CEN/TS (2005) Annex D. Typical examples of the main decay types are shown in Fig. 3 and Fig. 2. Fig. 2: Left: Beech. Failure after 0.5 years exposure. Visual inspection showed typical signs of white rot: whitish discoloration, long-fibred splinter, fibred fracture. Right: Southern yellow pine. Failure after 0.5 years exposure. Visual inspection showed typical signs of brown rot: brownish discoloration, brittle/cubical splinter, cross-checking texture 8

9 Fig. 3: European ash. Failure after 0.5 years exposure. Visual inspection showed typical signs of soft rot: shell-shaped splinter, attack on the outer wood shell, clean fracture. 9

10 5.2 Discoloration CIE L*a*b* colour measurements - colorimeter Colour measurements should be recorded at three points on the upper surface of each specimen with a colorimeter. The measuring points are marked on each specimen through cross lines. The positions are centrally between the long sides of the specimens and 30 mm from the end-grain and in the middle of the specimen as shown in Fig. 4. Fig. 4. Positions for measuring L*a*b* colour values. The measurements are taken in L*a*b coordinates, as established by the Commision Internationale de Enluminure (CIE) in 1976, where L* determines the lightness, a* and b* determine the chromatic coordinates on the green-red and blue-yellow axis, respectively. First measurement will be performed at University Ljubljana before shipment of the specimens. Second measurement to determine initial values should be performed immediately upon the delivery of the table (= before exposure and storage in the lab). The measurements should be conducted every week during the first six weeks of exposure, every 4 weeks during the first six months, and later on twice a year. Measurements should be determined on the dry surface, at least 2 hours after the last rainfall. In case that there is snow or ice on the table, measurements should be postponed. To determine colour changes over time the distance in colour space ΔE shall be determined according to Equation 1: Equation 1: Distance in colour space ΔE ; ΔE = distance in color space [-] ; L* = lightness [-] ; a* = chromatic coordinate of the red-green axis [ ] ; b* = chromatic coordinate of the yellow-blue axis [ ] 10

11 5.2.2 CIE L*a*b* colour measurements simplified approach This is a straightforward procedure for imaging the surface of the samples, either with the table standing up or in folded position, using a standard camera. Following are needed: 1. Semi-automatic camera; 2. Calibration target: -> reflective Fuji Calibration Target, 13x18 cm (5x7"); 3. Constant and evenly distributed lighting using e.g. fluorescent lights and canvas or a closed box. A possible set-up is shown in Fig. 5. Fig. 5. Possible set-up for imaging the surface of the table (yellow = position of fluorescent lights). Two fluorescent lights are positioned at the edges of a frame consisting of two plywood panels fitted in two triangular supports each. Make sure that the table surface is illuminated properly. The two open sides of the box, as well as the top surface, are covered 11

12 with canvas. The camera is positioned at the top of the box in a holder such as illustrated in detail in Fig. 9. Fig. 6. Detailed view on the camera holder. The table is put either upright but most probably in folded position to enable full view of the table surface as well as the reflective target; the latter is put next to the table at the same height of the table surface. The samples are not in perfect horizontal position when the table is folded, thus it needs to be levelled properly. The settings of the camera depend on the model available. If possible, shoot in highest resolution with autostabilizer and auto-focus on. An example of a dummy table with dummy target is shown in Fig. 7. Fig. 7. Dummy table with dummy target. The procedure described above is one example of several other possibilities. The frame with canvas can be replaced with a closed black box with fluorescent lights inside; the set-up can even be simpler when a large cylinder is made with wire mesh and covered with canvas, on top of which a panel is put with fluorescent lights attached to it and a 12

13 hole for the camera. Naturally, more professional approaches are possible as well. Just ascertain to 1. use the same set-up for every picture; 2. create diffuse light without too much specular reflection; 3. use the calibration target. 5.3 Surface disfigurement due to mould and staining fungi For easy evaluation of surface disfigurement due to fungal growth use the following criteria adapted from EN 152:2011 (Determination of the protective effectiveness of a preservative treatment against blue stain in wood in service Laboratory method), Assessment of the test specimen surface, with some modification to even accommodate the evaluation of disfigurement caused by mould fungi. Examine the upper surface of the test specimens visually for the presence of mould and staining fungi. Evaluate the upper and lower surface (underside) of the samples as follows (Table 2): Table 2: Fungal disfigurement rating scale Rating Classification Definition 0 no disfigurement No surface disfigurement can be detected visually on the surface. 1 Slight disfigurement The surface exhibits only a few individual small colonies none larger than 1.5 mm in width and 4 mm in length. 2 Moderate disfigurement The surface is colonized up to a maximum of one third of the total area. 3 Severe disfigurement More than one third of the surface area is colonised. Additional document in the form of images of the samples taken at the evaluation occasion is desirable. 13

14 The assessment shall only be based on the flat surfaces of the test specimens. Difficulties may arise in distinguishing development of blue-stain on certain types of darkly coloured finish. 5.4 Corrosion Corrosion shall be assessed according to the adopted procedure described by Jermer and Andersson (2005). Each fastener is washed in ethanol and weighed before being fixed in the wood sample. There will be two types of fasteners used, galvanized and stainless steel screws Intermediate assessments In parallel with the visual assessment of fungal decay the fasteners will be inspected regarding corrosion. All fasteners on the upper surface should be removed and inspected visually according to the rating scheme presented in Table 3. Table 3: Assessment of corrosion attack (Jermer and Andersson 2005) Rating Description Definition 0 No attack 1 Insignificant attack <5 % of surface attacked 2 Slight attack 5-50 % of surface attacked 3 Serious attack % of surface attacked 4 Completely attacked >95 % of surface attacked Final evaluation After 3 years of exposure, fasteners should be replaced with new ones. The old ones should be analysed according to the following procedure. The metal loss is calculated and expressed as metal loss (%) and as depth of corrosion (mm). In order to determine the metal loss and depth of corrosion the corrosion products had to be eliminated. Thus 14

15 the fasteners will be pickled, cleaned and then weighed. Pickling and cleaning will be performed as follows: 1.) 5 min pickling in Clark s solution: Concentrated hydrochloric acid with an additive of 20 g/l antimony oxide and 20 g/l stannic chloride 2.) 2 min cleaning in hot water 3.) 10 s rinsing in hot running water 4.) Drying with a clean paper tissue 5.) Dipping for 30 s in 96 % ethanol 6.) Drying with a clean paper tissue 7.) Storage for at least one hour in a desiccator. To equalize the temperature, storage shall be done in the same room as the weighing Equation 2: Metal loss due to corrosion [%] ; MeL= metal loss [%] ; minitial = initial mass of screws [g] ; mpickled = mass after pickling [g] Equation 3: Corrosion depth [mm] ; dcorrosion= depth of corrosion [mm] ; øinitial = initial diameter [mm] ; øpickled = diameter after pickling [mm] In case that you face difficulties in performing the described task, you can send the fasteners to: Miha Humar, University of Ljubljana, Biotechnical faculty, Jamnikarjeva 101, SI1000 Ljubljana, Slovenia. 15

16 5.5 Crack formation The formation of cracks on the upper surface of the specimens shall be determined. Therefore the following three measures need to be recorded: Total crack length (total length of cracks with length of more than 5 mm) Number of cracks (longer than 5 mm) Mean maximum crack width The length of cracks can be easily determined using a ruler. For measuring the crack width a crack measuring gauge (Fig. 8) should be used. The maximum width of each single crack (longer than 5 mm) shall be recorded to determine the mean maximum crack width. NOTE: the sides and the lower surface of the specimens will not be considered. Fig. 8. Crack measuring gauge. Specimens shall be inspected regarding the formation of cracks before exposure (initial state) and then every 3 months. 16

17 5.6 Moisture content and temperature (only Version A) MC monitoring equipment Version A of the performance table is equipped with moisture content sensors, a Thermofox datalogger and a connected gigamodule for electrical resistance measurements and recordings (full batteries included). Data loggers have to be connected with the test specimens. Electrodes are fixed to the wood with insulated fasteners as shown in Fig. 9. Therefore, the moisture content is recorded only in the central part of the specimen. Fig. 9. Isolated fasteners (left) used for fixing electrodes on wood specimens (right). Black cables are mounted for moisture content measurements; red cables are used for temperature measurements. There are 8 electrodes mounted to the wood. First three in the spruce, wood, second three in the thermally modified wood, and the last two in the English oak. Temperature is measured and recorded in the least dense (thermally modified Norway spruce) and the most dense material only (English oak). 17

18 Fig. 10. Mounting of the electrodes for MC measurements to gigamodule. Fig. 11. Mounting of the electrodes for temperature measurements to Thermofox. 18

19 Performance table and the moisture logging device are send in the same parcel. Setting up the table requires two persons in order to avoid potential damage of the cables! Prior to exposure, remove the Styrofoam from the box; check the cables and their position to the data logger and gigamodule. Black cables should be mounted to gigamodule, while red ones should be mounted to Thermofox. Be sure, to have the the doors of the steel box closed. Prior exposure check if all holes are sealed. The cables have to be on the bottom part of the steel box. Key for the steel box is fixed to the box with self-adhesive tape. Figure 12: Parcel with performance table and steel box with data logging device NOTE: Do not change the settings! The data logger is recording electrical resistance in 10logOhm and temperature, which can be translated to wood moisture content (formula is provided in corresponding Excel files). 19

20 Fig. 13. Steel box should be positioned below the table on two EN 252 specimens, or on the T shaped holder. There are several mounting options available. 20

21 5.6.2 Read out of data loggers Reading out the data loggers requires software SoftFOX. The SoftFOX analysis software has been specially developed for Microsoft Windows and can be used under Windows 98, NT, Me, 2000, XP, Vista, 7 and newer. The latest version of software can be downloaded from Scanntronik web page: Fig. 14. User interface of the SoftFOX software. The devices can be connected to a computer via an USB interface cable which is included in the delivery of the gigamodule (Fig. 15). Each logging device is recording the following parameters: 8 x moisture content (i. e. electrical resistance) and 2 x temperature, twice per day. 21

22 Fig. 15. USB interface for connecting PC and Thermofox datalogger. Retrieving data: 1. Disconnect the gigamodule from the Thermofox. 2. Connect the cable to the port Computer/Schalter. Start the Softfox program 3. Press the bat button on Status bar 4. Press menu Toolbox / Transfer data 5. Press menu File / Save project as (design name as location and date; Ljubljana_ tf2) 6. Export project as.xls file (design name as location and date; Ljubljana_ xls) 7. Press menu Options / Delete datalogger memory 8. Disconnect the Thermofox from the computer 9. Connect the gigamodule again 22

23 Fig. 16. Mounting/un-mounting of the gigamodule to the steel box Fig. 17. Position of the gigamodule and data-logger in steel box 23

24 5.6.3 Battery check / replacement There are two sets of batteries, one in the data logger (Themofox) and one in the gigamodule. The life span of the batteries should be between 12 and 18 months Thermofox If the BAT indicator appears on display, the batteries (2 AAA) should be replaced at least, when the indicator remains for a longer period of time. Pay attention to the correct polarity when inserting the new batteries (Fig. 18). After inserting the new batteries, the Thermofox reports with a friendly HI on the display. The status of the batteries can be read through the SoftFOX Software as well (Fig. 18). Fig. 18. The batteries on the back side of the Thermofox data logger 24

25 Fig. 19. Status bar of the SoftFOX software. Battery indicator is resolved on the lower part of the status bar Gigamodule The gigamodule is powered by six standard Mignon-AA batteries. If necessary, the batteries can be exchanged at any time by the user so that every measurement can start immediately without delay. The status of the batteries is resolved from the 2 system status LED. If the LED flashes rhythmically every two seconds, the batteries are OK. If the LED flashes every five seconds, the system is still functional, but the batteries should be exchanged as soon as possible. 25

26 Fig. 20. Position of the flashlight on the upper part of the Gigamodule. Fig. 21. Position of batteries in the gigamodule. 26

27 5.6.4 Trouble-shooting In case of the problems please read the supplemented instructions, or contact Miha Humar or Christian Brischke 27

28 6 Measurement intervals - summary The schedule for measurements and assessment given in Table 4 should be followed: Table 4. Assessment schedule for performance tests. Test/Assessment Period Interval Decay full every 6 months Mould / stain first 6 months every 4 weeks from month 7 on every 6 months Crack formation full every 3 months Colour measurements first 4 weeks every week first 6 months every 4 weeks from months 7 on every 6 months Corrosion visual full every 6 months Corrosion final after 3 years - MC recordings (read out of data logger) full every 3 months 7 References CEN/TS (2005) Durability of wood and wood-based products - Determination of the natural durability of solid wood against wood-destroying fungi, test methods - Part 2: Soft rotting micro-fungi. EN 252 (2012): Field test method for determining the relative protective effectiveness of a wood preservative in ground contact. Jermer J, Andersson B-L (2005) Corrosion of fasteners in heat-treated wood progress report after two years exposure outdoors. The International Research Group on Wood Protection. Document-No. IRG/WP