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Synchronizing clocks at Armageddon

Synchronizing clocks at Armageddon. Moira Wilson School of Mechanical, Aerospace and Civil Engineering, The University of Manchester. RHX Some scientific observations and issues. Team RHX: Moira Wilson Chris Hall Margaret Carter Ceren Ince Bill Hoff One microbalance.

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Synchronizing clocks at Armageddon

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  1. Synchronizing clocks at Armageddon Moira Wilson School of Mechanical, Aerospace and Civil Engineering, The University of Manchester Megiddo 2010

  2. RHX Some scientific observations and issues Team RHX: Moira Wilson Chris Hall Margaret Carter Ceren Ince Bill Hoff One microbalance Megiddo 2010

  3. Basis of method is “moisture expansion” Megiddo 2010

  4. Moisture induced expansion is of concern to builders and civil engineers because it gives rise to strain. Rule of thumb: bricks should not be used for about 2 weeks after firing. (i.e. when they have finished expanding (Ha!)) Megiddo 2010

  5. The lime mortar accommodated strain. Modern cement mortars do not, so expansion joints are specified in design codes. Moisture expansion in structural masonry • Old brick masonry • (before ~ 1950) does • not have expansion joints. Megiddo 2010

  6. How big are these effects? EXPANSION: 1 km of wall will expand by ~ 1 m over 200 y Megiddo 2010

  7. FILM OF BRICK GAINING MASS Megiddo 2010

  8. Of most interest • Moisture expansion was known to be REVERSIBLE • (but no agreement on the temperature • required to do this) • The moisture expansion was accompanied by • an increase in mass (but only 1 set of data • in the literature from 1962). (No point in engineering) Megiddo 2010

  9. The Manchester and Edinburgh work time¼ law (2003) Megiddo 2010

  10. Discovery of the (time)1/4 law: (2003) Megiddo 2010

  11. (2003) Megiddo 2010

  12. Discoveryof the (time)1/4 law: 120 year old brick 1900 year old brick 20 year old brick Fresh brick (2003) Megiddo 2010

  13. Effect of environmental conditions (i) Megiddo 2010

  14. Effect of environmental conditions (ii) SATURATED DRY Megiddo 2010

  15. 1 day 16 days Expansion versus t1/4 Mass gain versus t1/4 Discovery of the 2 stage process: (2005) Megiddo 2010

  16. TIME 1/4 The t1/4 law means that equal amounts of expansion or mass gain occur in the time intervals 1, 16, 81, 256 etc seconds / minutes/ years after firing. These correspond to 14, 24, 34, 44 etc seconds / minutes/ years. If we plot mass gain or expansion against t1/4 we get a straight line. Megiddo 2010

  17. EUREKA! The older the brick, the bigger it is. It gets bigger and heavier at a precisely defined rate Could the new rate law be exploited to produce a dating method for fired clay ceramics?? Megiddo 2010

  18. 1 Measure initial length (L) or mass (m) L,m Expansion 4. Age of sample 3. Extrapolate stage II data 2. Measure early time mass or expansion following reheating L,mo ta1/4 t1/4 Principle of the dating method Megiddo 2010

  19. Fresh Reheat 1 Reheat 2 1 day Expansion in fresh/reheated brick Linear fits to Stage 2 data: (F) ε= 0.93×10-5t1/4 + 2.77×10-5 (R1) ε= 0.45×10-5t1/4 + 3.67×10-5 (R2) ε= 0.33×10-5t1/4 + 2.45×10-5 Systematic reduction in Stage II gradient on repeated reheating Megiddo 2010

  20. Same 2 stage process observed 16 days Started looking at mass gain again: FORM of data same as expansion data - scattery. Why? Megiddo 2010

  21. Freshly fired brick y = 0.0039x + 0.0205 Same brick reheated 270 days y = 0.004x + 0.0248 7 days Is the mass gain reversible? Megiddo 2010

  22. Initial mass of 39 week old brick 1281.6 1281.4 1281.2 Extrapolated Stage II data 1281.0 1280.8 Stage II data Mass (g) 1280.6 14 days 1280.4 1280.2 1280.0 1279.8 1279.6 5 10 15 20 25 Time1/4 (min1/4) The first “dating” experiment Predicted age of 49 weeks. Megiddo 2010

  23. The first dating trial A B A × 1.33 = B (mean over all trials) Calculated date too young 1,957 Years Megiddo 2010

  24. The first dating trial All dates came out wrong- BY THE SAME AMOUNT Megiddo 2010

  25. A B 1,957 Years The DATA Megiddo 2010

  26. The microbalance: The next step… Allows us to weigh 5 g pieces of brick under tightly controlled conditions to 0.1µg. (1/10 of a millionth of a gram). Megiddo 2010

  27. Vastly improved quality of data. Speed of data acquisition. Absolute confirmation of the t1/4 law The data 10 days NO SCATTER!!!!!! (WHY?) Megiddo 2010

  28. Putting the microbalance through its paces Megiddo 2010

  29. Arrhenius plot This shows that we have a chemical reaction going on ……… and that it’s TEMPERATURE DEPENDENT! Megiddo 2010

  30. AND All samples in 1st dating trial were measured at ~25 OC! • → Stage II gradients were too steep (temp too high), • → Extrapolated Stage II data intersected line of initial mass too soon • → Age of sample too young EUREKA! (again) • Scattery data due to temperature fluctuations • over course of measurement period • First dating experiment worked because the brick had been sitting in the lab for 39 weeks – and the mass gain measurements following heating were carried out at the same temp (~ 25 OC) (2008) Megiddo 2010

  31. Second dating trial Gradient = 0.2 min-1/4 Megiddo 2010

  32. yippee! AND THEN … Started to get some REALLY good results Megiddo 2010

  33. EEK! AND THEN … We dated a Roman brick to March 2008! (i.e. 8 months old) Megiddo 2010

  34. NOW WHAT? AND THEN … We dated a MEDIEVAL brick to 1942! (i.e. 66 years old) – the “Canterbury Tale”… Megiddo 2010

  35. Eventually…the “line of knowns” REPLICATE VALUES (yrs) 330 321 333 308 307 50 person-years of effort for 6 data points! Megiddo 2010

  36. Improved methodology Megiddo 2010

  37. Solid line: freshly-fired at 800ºC; □: following reheating at 500ºC. Some other nice microbalance results Megiddo 2010

  38. NEW RESULTS: 1. Samian ware Megiddo 2010

  39. Mass gain measured at 11 deg C and 30% RH following reheating at 500 deg C Samian ware AGE = 1950 years Megiddo 2010

  40. Samian ware Plot of gradient segments: Megiddo 2010

  41. 25ºC 20ºC 15ºC Samian ware Mass gain at different temperatures: Megiddo 2010

  42. Samian ware ln r = 1.6383 r = 0.1943 mg/hr1/4 Sample dates to 1943 years 25ºC 20ºC 15ºC 11ºC Megiddo 2010

  43. Samian ware 11ºC and 50 % RH BOTH DATE TO ~ 1950 years old 11ºC and 30 % RH Megiddo 2010

  44. 2. Saxon loom-weight Mass gain measured at 11 deg C and 30% RH. Gradient stabilised after 7 days Megiddo 2010

  45. RESULTS RHX age: 1159 years (= 850AD) Assigned age: 5th century 8th century OR 9th century Conclude 9th century Megiddo 2010

  46. 2. Megiddo: RHX4 S7 2 1 Mass gain measured at 19 deg C and 30% RH. Megiddo 2010

  47. 2 1 2 1 1 Megiddo 2010

  48. The “Piasetzky Effect” 3. Megiddo Plot of gradients vs number of data points: Megiddo 2010

  49. Now have 2 sets of anomalous results: Megiddo 2010

  50. BET specific surface area results: SAMPLE SURFACE AREA mm^2/g Megiddo 2010

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