PSI - Issue 37

João Custódio et al. / Procedia Structural Integrity 37 (2022) 644–651 João Custódio et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Considering the data obtained so far with the two methods – semi-adiabatic and isothermal conduction (Table 3), an estimation of the Q 41,EN196-9 and Q 120,EN196-9 values can be made from the Q 168,EN 196-11 value. If one uses the estimated values, Q 41,EN196-9/196-11 = 317 J/g and Q 120,EN196-9/EN196-11 = 332 J/g, in the abovementioned methodology, the maximum estimated temperature, reached by a concrete applied at a temperature of 24.4 ºC, would be 70.8 ºC. This estimation differs from the measured temperature by less than 2 ºC (3 %), also in a conservative manner, thus showing an interesting result. Once all heat of hydration determinations, indicated in Table 1, are completed, the estimation of Q 41,EN196-9/196-11 and Q 120,EN196-9/EN196-11 will be refined. This approach could be useful in situations when only data from the isothermal conduction calorimetry method are available, for instance, due to time constraints or even due to the amount of cement sample available for testing. 4.3. Concrete potential ISR reactivity Testing results of swelling records for each concrete specimen, during the first 180 days of readings according to LPC test method no. 66, are presented in Fig. 5.

0.36

Specimen 3 Specimen 2 Specimen 1 LPC no. 66

0.32

0.28

0.24

0.20

0.16

0.12 Expansion (%)

0.08

0.04

0.00

0

30

60

90 120 150 180 210 240 270 300 330 360

Time (days)

Fig. 5. Results obtained in the expansion tests.

In this test method, a concrete mixture design / heating combination is considered suitable for use if one of the following criteria is met: Criterion 1 – (a) average longitudinal deformation of 3 specimens is less than 0.04 % and no individual value exceeds 0.06 % at 12 months; and (b) monthly variation in average longitudinal deformation for 3 specimens, measured as of the 3rd month, is below 0.004 %; Criterion 2 – (a) if individual longitudinal deformation of 3 specimens lies between 0.04 % and 0.07 % after 12 months, it is necessary to extend the test up to 15 months; and (b) monthly variation in average longitudinal deformation for 3 specimens measured as of the twelfth month is less than 0.004 %, and cumulative variation between twelfth and fifteenth months is below 0.006 %. As it can be seen from Fig. 5, the expansion attained at 180 days of testing already surpasses the values indicated in the LPC test method no. 66 criteria, meaning that this concrete mixture, with the associated curing temperature regime, is susceptible to the deleterious development of ISR. Thus, according to LNEC Specification E 461 (LNEC, 2021), if this concrete was to be used in a structure with massive concrete elements and categorised into risk category R3, the level of precaution P3 requires that the concrete temperature during the hydration process does not surpass 65 ºC. 4. Conclusions This paper analysed and discussed the data already available from an ongoing study that aims at more adequately prevent the deleterious development of ISR on new concrete structures. In this study, heat of hydration determinations were conducted to several cement samples, of the types normally used on massive structures or structures with massive elements, with two currently available standardized test methods