70 years of ASR with no end in sight? (Part 2)

12 Influence of the crystallite size on the X-ray peak [21]

13 Influence of the microstrain on the X-ray peak [21]

14 Characteristic quartz quintuplet (5-finger-peak) [22]

15 Structure types of strained quartz [25]

16 Medium-grained greywacke, light grey and white grains (clastic quartz) in the fine quartz matrix, Pol. ×

17 Typical rhyolite structure with large inset quartzes, Pol. ×

18 Particle size distribution determined on the basis of the EBSD orientation mapping of a strained quartz grain. About 20 % of the crystals have a size < 10 µm with a maximum of less than 500 nm (blue) [MÖSER, FIB]

19 EBSD orientation mapping with representation of the local distribution of the quartz crystals with a grain size < 10 µm. The colours correspond to the grain sizes in Fig. 18 [MÖSER, FIB]

20 Expansion during the concrete prism test (German fog chamber method) according to the Alkali Guideline, Part 3, with granodiorite aggregates (documented ASR-damage on a federal highway)

21 Schematic representation of the complex environmental impacts on outdoor elements

22 View into the climate simulation chamber (Feutron)

23 Temperature profile in the climate simulation chamber of the FIB for a complete cycle (21 days)

24 ASR performance test of a concrete composition for highway and airfield pavements containing granodiorite aggregates (documented ASR-damage on a federal highway)

25 ASR performance test of a concrete composition for airfield pavements containing andesite aggregates

26 ASR performance test of a concrete composition for highway and airfield pavements containing andesite aggregates

$27 ASR performance test of a concrete composition for highway and airfield pavements with one grain size fraction of gravel (Central Germany) and two fractions of diabase aggregates$

27 ASR performance test of a concrete composition for highway and airfield pavements with one grain size fraction of gravel (Central Germany) and two fractions of diabase aggregates

28 Core half (150 mm diameter, 250 mm length) for FIB cyclic climate storage prepared for exposure to de-icing salt

29 Influence of different amounts of fly ash, ground granulated blastfurnace slag and silica fume on the expansion during the mortar bar test according to ASTM C1260 [39]

30 Alkalis bonded in C-S-H phases depending on the C/S ratio [40]

31 Influence of a fly ash with a low content of CaO on the expansion due to ASR during the concrete prism test according to ASTM C1293 depending on the amount added [41]

Mikrofabric of concrete damaged by ASR

32 Influence of lithium (addition of 14 l/m³ of a 30 % LiNO₃ solution) on the expansion of concrete (with an alkali-reactive greywacke) exposed to a de-icer solution (potassium formate) during the FIB cyclic climate storage

33 Calculated species distribution at 25 °C in a saturated Ca(OH)₂ solution with addition of CH₃COOK (potassium acetate)

34 ASR damage to the 44-year old Hunderfossen Dam (Norway, 2008)

35 ASR damage to a 65-year old harbour facility (Norway, 2008)

Summary: The deleterious ASR in concrete is an extremely complex long-term reaction. The amount and condition of the quartz in the aggregates play the decisive role. The alkali-silica gel is capable of swelling only in a certain range of the CaO content. Thus, all cement admixtures, which bind the Ca(OH)₂ formed during the C₃S and C₂S hydration, help to avoid a deleterious ASR in concrete. If the currently available test methods, in particular the ASR performance test, are used consistently, a deleterious ASR can be avoided. Part 1 summarizes general mechanisms, ASR test methods and their pros and cons, part 2 gives in-depth information on specific research approaches, selected test methods and field cases of ASR-damaged structures.

4 ASR investigations at the FIB

A reliable evaluation of the ASR damaging potential of individual aggregates and project-specific concretes can be given, as matters stand at the moment, due to the combination of various, complementary investigations and test methods at the FIB [9, 28]. The following procedure is used at the FIB:

A preliminary evaluation of the reactivity of all aggregates (separately according to grain size fractions) that are intended to be used in a concrete is carried out by means of a mortar bar test, supported by petrographic and mineralogical investigations. Existing...