1. INTRODUCTION
⌅Basaltic
rocks are used as concrete aggregates in many countries owing to their
local abundance and their propensity to improve concrete strength and
quality (11. Korkanç, M.; Tugrul, A. (2004) Evaluation of selected basalts from Niğde, Turkey, as source of concrete aggregate. Eng. Geol. 75 [3-4], 291-307. https://doi.org/10.1016/j.enggeo.2004.06.015.
).
However, the role that basalts play in alkali-silica reactions (ASR)
remains poorly understood. Researchers disagree as to whether basalts
should be considered non-reactive (22. Shayan, A.; Quick, G.W. (1988) An alkali-reactive basalt from Queensland, Australia. Int. J. Cem. Comp. Lightw. Conc. 10 [4], 209-214. https://doi.org/10.1016/0262-5075(88)90050-4.
, 33.
Šťastná, A.; Nekvasilová, J.C.; Přikryl, R.; Šachlova, Š. (2019)
Microscopic examination of alkali-reactive volcanic rocks from the
Bohemian Massif (Czech Republic). 3rd International Conference on
Sustainable Construction Materials and Technologies (SCMT 2013), Kyoto,
Japan, 10.
) or reactive (4-64.
Ólafsson, H. (1992) Alkali-silica reactions - Icelandic experience. In:
The alkali silica reaction in concrete, ed. R. N. Swamy, 208-222. ISBN
0-203-03663-8.
5. Reis, M.O.; Silva, H.S.; Silva, A.S. (1996)
Ocorrência de reacções alcalis inerte em Portugal. Estudos de Casos.
Betão Estrutural 1996, LNEC, Lisboa: pp 14 (in Portuguese).
6.
Madsen, L.; Rocco, C.; Falcone, D.; Locati, F.; Marfil, S. (2019)
Alkali-silica reactivity of basaltic aggregates of Mesopotamia
Argentina: case studies. Bull. Eng. Geol. Environ. 78, 5495-5509. https://doi.org/10.1007/s10064-019-01470-w.
).
The potential alkali reactivity of basalts varies from one geological
context to another and even between samples within the same geological
area. According to Fernandes et al. (77.
Fernandes. I.; Ribeiro, M.A.; Broekmans, M.A.T.M.; Sims, I. (2015)
Petrographic Atlas. Characterisation of aggregates regarding potential
reactivity to alkalis. RILEM 219-ACS AAR-1.2. RILEM TC 219-ACS
Recommended Guidance AAR-1.2, for Use with the RILEM AAR-1.1
Petrographic Examination Method. RILEM Guideline, Springer, 196. ISBN
978-94-017-7383-6
), this might be due to the regional
geological history of a rock and the presence of both reactive and
innocuous varieties of the same type of rock stemming from subtle
differences in their mineralogical composition and/or texture.
In the literature, the reactivity of basaltic rocks is usually associated with the presence of volcanic glass (8-148. Wakizaka, Y. (2000) Alkali-silica reactivity of Japanese rocks. Develop. Geo. Eng. 84, 293-303. https://doi.org/10.1016/S0165-1250(00)80024-3.
9.
Wigum, B.J.; Björnsdóttir, V.D.; Olafsson, H.; Iversen, K. (2007)
Alkali-aggregate reaction in Iceland - New test methods, VGK-Hönnun
Consulting Engineers, 74.
10. Marfil, S.; Locati, F.; Maiza, P.;
Lescano, L. (2013) Basaltic rocks from Argentina used in concrete
structures. In: Wu & Qi (eds). Global View of Engineering Geology
and the Environment. 253-258. ISBN 978-1-138-00078-0.
11. Munhoz,
F.A.; Kihara, Y.; Ncotto, M.A. (2008) Effect of mineral admixtures on to
the mitigation of alkali-silica reaction in concrete. 13th International Conference on Alkali-Aggregate Reaction in Concrete, 16-19 June, Norway, 9.
12.
Katayama, T.; St John, D.A.; Futagawa, T. (1989) The petrographic
comparison of rocks from Japan and New Zealand-Potential reactivity
related to interstitial glass and silica minerals. In: Okada, K,
Nishibayashi, S.; Kawamura, M. (editors), Proceedings of the 8th International Conference on Alkali-Aggregate Reaction (ICAAR). Kyoto, Japan, 537-542.
13.
RILEM AAR-1.1 (2016) Detection of potential alkali-reactivity - Part 1:
Petrographic examination method. In: Nixon, P.J., Sims, I. (editors):
RILEM recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures. RILEM State-of-the-art Report 17,
35-60.
14. Korkanç M.; Tuğrul, A. (2005) Evaluation of selected basalts from the point of alkali-silica reactivity. Cem. Concr. Res. 35 [3], 505-512. https://doi.org/10.1016/j.cemconres.2004.06.013.
), devitrified volcanic glass (1313.
RILEM AAR-1.1 (2016) Detection of potential alkali-reactivity - Part 1:
Petrographic examination method. In: Nixon, P.J., Sims, I. (editors):
RILEM recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures. RILEM State-of-the-art Report 17,
35-60.
), different types of reactive silica (e.g., chalcedony, opal, and microcrystalline and cryptocrystalline silica) (8-138. Wakizaka, Y. (2000) Alkali-silica reactivity of Japanese rocks. Develop. Geo. Eng. 84, 293-303. https://doi.org/10.1016/S0165-1250(00)80024-3.
9.
Wigum, B.J.; Björnsdóttir, V.D.; Olafsson, H.; Iversen, K. (2007)
Alkali-aggregate reaction in Iceland - New test methods, VGK-Hönnun
Consulting Engineers, 74.
10. Marfil, S.; Locati, F.; Maiza, P.;
Lescano, L. (2013) Basaltic rocks from Argentina used in concrete
structures. In: Wu & Qi (eds). Global View of Engineering Geology
and the Environment. 253-258. ISBN 978-1-138-00078-0.
11. Munhoz,
F.A.; Kihara, Y.; Ncotto, M.A. (2008) Effect of mineral admixtures on to
the mitigation of alkali-silica reaction in concrete. 13th International Conference on Alkali-Aggregate Reaction in Concrete, 16-19 June, Norway, 9.
12.
Katayama, T.; St John, D.A.; Futagawa, T. (1989) The petrographic
comparison of rocks from Japan and New Zealand-Potential reactivity
related to interstitial glass and silica minerals. In: Okada, K,
Nishibayashi, S.; Kawamura, M. (editors), Proceedings of the 8th International Conference on Alkali-Aggregate Reaction (ICAAR). Kyoto, Japan, 537-542.
13.
RILEM AAR-1.1 (2016) Detection of potential alkali-reactivity - Part 1:
Petrographic examination method. In: Nixon, P.J., Sims, I. (editors):
RILEM recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures. RILEM State-of-the-art Report 17,
35-60.
), and swelling clay minerals that are alteration products of volcanic glass (1010.
Marfil, S.; Locati, F.; Maiza, P.; Lescano, L. (2013) Basaltic rocks
from Argentina used in concrete structures. In: Wu & Qi (eds).
Global View of Engineering Geology and the Environment. 253-258. ISBN
978-1-138-00078-0.
, 1212.
Katayama, T.; St John, D.A.; Futagawa, T. (1989) The petrographic
comparison of rocks from Japan and New Zealand-Potential reactivity
related to interstitial glass and silica minerals. In: Okada, K,
Nishibayashi, S.; Kawamura, M. (editors), Proceedings of the 8th International Conference on Alkali-Aggregate Reaction (ICAAR). Kyoto, Japan, 537-542.
). Some authors have described problems in concrete related to basalt use (66.
Madsen, L.; Rocco, C.; Falcone, D.; Locati, F.; Marfil, S. (2019)
Alkali-silica reactivity of basaltic aggregates of Mesopotamia
Argentina: case studies. Bull. Eng. Geol. Environ. 78, 5495-5509. https://doi.org/10.1007/s10064-019-01470-w.
, 8-128. Wakizaka, Y. (2000) Alkali-silica reactivity of Japanese rocks. Develop. Geo. Eng. 84, 293-303. https://doi.org/10.1016/S0165-1250(00)80024-3.
9.
Wigum, B.J.; Björnsdóttir, V.D.; Olafsson, H.; Iversen, K. (2007)
Alkali-aggregate reaction in Iceland - New test methods, VGK-Hönnun
Consulting Engineers, 74.
10. Marfil, S.; Locati, F.; Maiza, P.;
Lescano, L. (2013) Basaltic rocks from Argentina used in concrete
structures. In: Wu & Qi (eds). Global View of Engineering Geology
and the Environment. 253-258. ISBN 978-1-138-00078-0.
11. Munhoz,
F.A.; Kihara, Y.; Ncotto, M.A. (2008) Effect of mineral admixtures on to
the mitigation of alkali-silica reaction in concrete. 13th International Conference on Alkali-Aggregate Reaction in Concrete, 16-19 June, Norway, 9.
12.
Katayama, T.; St John, D.A.; Futagawa, T. (1989) The petrographic
comparison of rocks from Japan and New Zealand-Potential reactivity
related to interstitial glass and silica minerals. In: Okada, K,
Nishibayashi, S.; Kawamura, M. (editors), Proceedings of the 8th International Conference on Alkali-Aggregate Reaction (ICAAR). Kyoto, Japan, 537-542.
, 1515.
Lindgård, J.; Grelk, B.; Wigum, B.J.; Trägårdh, J.; Appelqvist, K.;
Holt, E.; Ferreira, M.; Leivo, M. (2017) Nordic Europe. In: Sims, I. and
Poole, A. (ed). Alkali-aggregate reaction in concrete: A World review.
CRC Press/Balkema. Taylor & Francis Group, London, UK, 277-320.
). Severe ASR problems were observed in Iceland during the 1970s (1616.
Guðmundsson, G.; Ólafsson, H. (1996) Silica fume in concrete - 16 years
of experience in Iceland, in: A. Shayan (ed.). Alkali-Aggregate
Reaction in Concrete, Proceedings of the 10th International Conference, Melbourne, Australia, 1996, 562-569.
) arising from the use of reactive aggregates with high rhyolitic content and altered basalts (77.
Fernandes. I.; Ribeiro, M.A.; Broekmans, M.A.T.M.; Sims, I. (2015)
Petrographic Atlas. Characterisation of aggregates regarding potential
reactivity to alkalis. RILEM 219-ACS AAR-1.2. RILEM TC 219-ACS
Recommended Guidance AAR-1.2, for Use with the RILEM AAR-1.1
Petrographic Examination Method. RILEM Guideline, Springer, 196. ISBN
978-94-017-7383-6
), the use of some unwashed sea-dredged material (1616.
Guðmundsson, G.; Ólafsson, H. (1996) Silica fume in concrete - 16 years
of experience in Iceland, in: A. Shayan (ed.). Alkali-Aggregate
Reaction in Concrete, Proceedings of the 10th International Conference, Melbourne, Australia, 1996, 562-569.
) together with high-alkali cements, and adverse environmental conditions (1515.
Lindgård, J.; Grelk, B.; Wigum, B.J.; Trägårdh, J.; Appelqvist, K.;
Holt, E.; Ferreira, M.; Leivo, M. (2017) Nordic Europe. In: Sims, I. and
Poole, A. (ed). Alkali-aggregate reaction in concrete: A World review.
CRC Press/Balkema. Taylor & Francis Group, London, UK, 277-320.
, 1717. Guðmundsson, G.; Ólafsson, H. (1999) Alkali-silica reactions and silica fume, 20 years of experience in Iceland. Cem. Concr. Res. 29 [8], 1289-1297. https://doi.org/10.1016/S0008-8846(98)00239-7.
).
Petrographic
characterization is considered the first essential step in assessing
the potential alkali reactivity of concrete aggregates (1818.
ASTM C294 (2012). Standard descriptive nomenclature for constituents of
concrete aggregates. Annual Book of ASTM Standards, The American
Society for Testing and Materials, Philadelphia, USA, 11.
), as stated in the RILEM AAR-0 test standard (1919.
RILEM AAR-0 (2016) RILEM Recommended test method AAR-0. Outline guide
to the use of RILEM methods in the assessment of the alkali-reactivity
potential of aggregates. In: Nixon, P.J.; Sims, I. (eds): RILEM
recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures, RILEM State-of-the-Art Reports 17,
Springer, 5-34. https://doi.org/10.1007/978-94-017-7252-5_2.
).
Petrographic analysis of aggregates allows classification in terms of
reactivity based on the presence of potentially reactive mineralogical
phases. An aggregate is categorized into one of three classes according
to RILEM AAR- 1.1 (1313.
RILEM AAR-1.1 (2016) Detection of potential alkali-reactivity - Part 1:
Petrographic examination method. In: Nixon, P.J., Sims, I. (editors):
RILEM recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures. RILEM State-of-the-art Report 17,
35-60.
): Class I (very unlikely to be
alkali-reactive); Class II (alkali reactivity uncertain); and Class III
(very likely to be alkali-reactive). Lindgård et al. (2020.
Lindgård, J.; Nixon, P.J.; Borchers, I.; Schouenborg, B.; Wigum, B.J.;
Haugen, M.; Akesson, U. (2010) The EU “PARTNER” Project - European
standard tests to prevent alkali reactions in aggregates: final results
and recommendations. Cem. Concr. Res. 40 [4], 611-635. https://doi.org/10.1016/j.cemconres.2009.09.004.
)
indicated that the petrographic method can produce results relatively
quickly and is generally effective in identifying reactive materials.
For fine-grained rocks, such as volcanic rocks, optical microscope
analysis usually requires the use of complementary methods such as X-ray
diffraction and scanning-electron microscopy to identify reactive
components.
Final classification as either innocuous or
potentially alkali-reactive depends on which laboratory expansion test
is used to assess an aggregate. The most common such tests are the
accelerated mortar bar test (AMBT-80ºC) (ASTM C 1260 (2121.
ASTM C 1260 (2014) Standard test method for potential alkali reactivity
of aggregates (mortar bar method). Annual Book of ASTM Standards, The
American Society for Testing and Materials, Philadelphia, USA, 4.
) or RILEM AAR-2 (2222.
RILEM AAR-2 (2016) RILEM Recommended test method: AAR-2-Detection of
potential alkali-reactivity-Accelerated mortar-bar test method for
aggregates. In: Nixon, P.J.; Sims, I. (editors): RILEM recommendations
for the prevention of damage by alkali-aggregate reactions in new
concrete structures, RILEM State-of-the-Art Reports 17, Springer, 61-77. https://doi.org/10.1007/978-94-017-7252-5_4.
)), the concrete prism test (CPT-38ºC) (ASTM C 1293 (2323.
ASTM C 1293 (2020) Standard test method for determination of length
change due to alkali silica reaction. Annual Book of ASTM Standards. The
American Society for Testing and Materials, Philadelphia, USA, 6.
) or RILEM AAR-3 (2424.
RILEM AAR-3 (2016) RILEM Recommended test method AAR-3. Detection of
potential alkali-reactivity - 38ºC. Test method for aggregate
combinations using concrete prisms. In: Nixon, P.J. and Sims, I. (eds):
RILEM recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures, RILEM State-of-the-Art Reports 17,
Springer, 79-97, 2016. https://doi.org/10.1007/978-94-017-7252-5_5.
)), and the accelerated concrete prism test (CPT-60ºC) (RILEM AAR-4.1 (2525.
RILEM AAR-4.1 (2016) RILEM Recommended test method: AAR-4.1-Detection
of potential alkali-reactivity - 60 °C test method for aggregate
combinations using concrete prisms. In: Nixon, PJ, Sims, I (editors):
RILEM recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures, RILEM State-of-the-Art Reports 17,
Springer, 99-116. https://doi.org/10.1007/978-94-017-7252-5_6.
)).
Although the AMBT is useful as a rapid test, there is no consensus as
to the validity of the results it furnishes, especially when compared to
the results of petrography and those obtained from the CPT (2626.
Feng, X., Clark, B. (2012) Correlations between laboratory tests
methods for potential alkali silica reactivity of aggregates. In:
Drimalas, T.; Ideker, J.H.; Fournier, B. (eds.): Proceedings of the 14th
International Conference on Alkali-Aggregate Reaction, Austin, USA, 9.
). Positive experiences using the AMBT have been reported in the EU “PARTNER” project (2020.
Lindgård, J.; Nixon, P.J.; Borchers, I.; Schouenborg, B.; Wigum, B.J.;
Haugen, M.; Akesson, U. (2010) The EU “PARTNER” Project - European
standard tests to prevent alkali reactions in aggregates: final results
and recommendations. Cem. Concr. Res. 40 [4], 611-635. https://doi.org/10.1016/j.cemconres.2009.09.004.
)
and in inter-laboratory trials conducted under the International Union
of Laboratories and Experts in Construction Materials, Systems and
Structures (RILEM). Gadea et al. (2727.
Gadea, J.; Soriano, J.; Martín, A.; Campos, P.L.; Rodríguez, A.; Junco,
C.; Adán, I., Calderón, V. (2010) The alkali-aggregate reaction for
various aggregates used in concrete. Mater. Construcc. 60 [299], 69-78. https://doi.org/10.3989/mc.2010.48708.
)
also reported positive results using the AMBT, and concluded that it is
a simple and reliable way to determine the reactivity of an aggregate.
However, Nixon and Fournier (2828.
Nixon, P., Fournier, B. (2017) Assessment, testing and specification.
In: Sims, I. and Poole A. (ed.) Alkali-aggregate reaction in concrete: a
world review (1st ed.). CRC Press Chapter 2, 33-61.
) noted that, for a wide range of aggregates, namely the slow/late-reactive aggregates as identified in (2020.
Lindgård, J.; Nixon, P.J.; Borchers, I.; Schouenborg, B.; Wigum, B.J.;
Haugen, M.; Akesson, U. (2010) The EU “PARTNER” Project - European
standard tests to prevent alkali reactions in aggregates: final results
and recommendations. Cem. Concr. Res. 40 [4], 611-635. https://doi.org/10.1016/j.cemconres.2009.09.004.
),
the 14-day AMBT can be erroneous and misleading compared to the more
accurate and realistic one-year concrete prism test (CPT-38ºC). In work
by Ramos (2929.
Ramos, V. (2013) Characterization of the potential reactivity to
alkalis of Portuguese aggregates for concrete. PhD thesis, Faculty of
Sciences of the University of Porto and University of Aveiro, Portugal,
417.
) and Ramos et al. (3030.
Ramos, V. Fernandes, I.; Santos Silva, A.; Soares, D.; Fournier, B.;
Leal, S.; Noronha, F. (2016) Assessment of the potential reactivity of
granitic rocks - Petrography and expansion tests. Cem. Concr. Res. (86), 63-77. https://doi.org/10.1016/j.cemconres.2016.05.001.
),
slow/late-reacting aggregates were tested using different methods
including the AMBT extended to 28 days, the CPT-38ºC, and the
accelerated concrete prism test (CPT-60ºC). The authors concluded that
the AMBT gave false-negative results for the granite, basalt, and
limestone samples tested and led to some aggregate classifications that
disagreed with those arising from the petrographic method. Moreover,
while the CPT-38ºC and CPT-60ºC tests are well-correlated, the AMBT
shows poor correlation with both concrete prism tests. Therefore, care
should be exercised in using the ASTM C 1260 (2121.
ASTM C 1260 (2014) Standard test method for potential alkali reactivity
of aggregates (mortar bar method). Annual Book of ASTM Standards, The
American Society for Testing and Materials, Philadelphia, USA, 4.
) to assess the potential alkali-reactivity of slow/late-reacting aggregates.
Over
recent decades, suggestions have been made for overcoming these
discrepancies in aggregate classification, namely by extending the
duration of the tests and/or applying more conservative (lower)
reactivity thresholds, particularly for slow/late-reactive aggregates (31-3531.
Alaejos, P.; Lanza, V.; Bermúdez, M.A.; Velasco, A. (2014)
Effectiveness of the accelerated mortar bar test to detect rapid
reactive aggregates (including their pessimum content) and slowly
reactive aggregates. Cem. Concr. Res. 58, 13-19. https://doi.org/10.1016/j.cemconres.2014.01.001.
32. Shayan, A. (2007) Field evidence for inability of ASTM C 1260 limits to detect slowly reactive Australian aggregates. Aust. J. Civ. Eng. 3 [1], 13-26. https://doi.org/10.1080/14488353.2007.11463917.
33.
Shayan, A.; Morris, H. (2001) A comparison of RTA T363 and ASTM C 1260
accelerated mortar bar test methods for detecting reactive aggregates. Cem. Concr. Res. 31 [4], 655-663. https://doi.org/10.1016/S0008-8846(00)00491-9.
34.
Hooton, R.D.; Rogers, C.A. (1992) Development of the NBRI rapid mortar
bar test leading to its use in North America. In: Poole, A.B. (ed).
Proceedings of the 9th International Conference on Alkali-Aggregate Reaction, London, UK, 461-467.
35.
Santos-Silva, A.; Braga-Reis, M.O. (2000) Avaliação da reactividade aos
álcalis dos agregados para betão. Encontro Nacional de Betão
Estrutural, Faculdade de Engenharia da Universidade do Porto, Portugal
(in Portuguese), 23-32.
). More recently, Santos Silva et al. (3636.
Santos-Silva, A.; Fernandes, I.; Soares, D.; Custódio, J.; Bettencourt
Ribeiro, A., Ramos, V.; Medeiros, S. (2016) Portuguese experience in ASR
aggregate assessment. In: IBRACON Eds., Proceedings of the 13th International Conference on Alkali-Aggregate Reactivity in Concrete, São Paulo, Brazil, 10.
) recommended that basaltic aggregates be evaluated by applying the CPT with an extended test period of two years.
The aim of the present study is to examine the potential alkali-silica reactivity of basaltic rocks from locations around the world using petrographic characterization methods, the AMBT, and the CPT to determine which methods are best for classifying aggregates of this type.
2. MATERIALS AND METHODS
⌅Volcanic aggregates from twelve countries were tested in this study. Most of the aggregates originated from quarrying operations and consisted of basaltic rocks. Aside from basalts in the strict sense of the term, including trachybasalts, basanites, trachyandesite, basaltic andesite, and trachyte, additional rocks were also assessed for comparative purposes. These rocks included two andesites (from Japan and Turkey) and one rhyolite (from Mozambique). The aggregates were obtained from different regions and geological settings, and were represented by either a single sample (Brazil, Canada, Japan, Mozambique, Norway, and Turkey) or more than one sample (the Canary Islands (Spain), Iceland, New Zealand, the Azores Archipelago (Portugal), and the Hawaiian Archipelago (United States of America)). Table 1 shows the label assigned to each sample.
| Country | Rock | Label | Country | Rock | Label | Country | Rock | Label |
|---|---|---|---|---|---|---|---|---|
| Brazil | Basalt | BRAZ | Portugal (Azores) |
Basanite | SMA-SM1 | Portugal (Azores) |
Mugearite | FLO-SM2 |
| Canada | CAN | SMA-SM2 | Hawaiite | CRV | ||||
| Iceland | Gravel | ICL1 | Potassic trachybasalt | SMG-SM1 | Spain (Canary Islands) |
Basanite | CANY1 | |
| ICL2 | SMG-SM2 | CANY2 | ||||||
| Basalt | ICL3 | Basalt | SMG-SM3 | Turkey | Andesite | TK | ||
| Gravel | ICL4 | Trachyte | TER-SM1 | USA (Hawaii Islands) |
Basalt | HW1 | ||
| Japan | JAP | Basalt | TER-SM2 | HW2 | ||||
| Mozambique | Rhyolite | MOZ | Hawaiite | GRA-SM1 | HW3 | |||
| New Zealand | Basanite | NZ1 | Basalt | SJO-SM1 | Mugearite | HW4 | ||
| Basalt | NZ2 | Basalt | PIC-SM1 | Basalt | HW5 | |||
| Basalt | NZ3 | Hawaiite | FAI-SM1 | HW6 | ||||
| Norway | Basalt | NOR | Benmoreite | FLO-SM1 | HW7 |
In addition to the quarried aggregates, basaltic sands from the Hawaiian Islands (HW7 sand) and from Iceland (ICL1 fine sand, ICL1 coarse sand, ICL3 sand, and ICL4 sand) were assessed by the AMBT and the CPT. These sands were mixed with non-reactive coarse (high-purity limestone) aggregates in order to evaluate their behaviour in the CPT.
A
different set of methods was used to better understand the potential ASR
of the volcanic rocks considered in this study. In accordance with
RILEM AAR-0 (1919.
RILEM AAR-0 (2016) RILEM Recommended test method AAR-0. Outline guide
to the use of RILEM methods in the assessment of the alkali-reactivity
potential of aggregates. In: Nixon, P.J.; Sims, I. (eds): RILEM
recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures, RILEM State-of-the-Art Reports 17,
Springer, 5-34. https://doi.org/10.1007/978-94-017-7252-5_2.
),
examination using a petrographic/polarizing microscope was the first
method used to evaluate the potential alkali reactivity of the
aggregates. The main objective of this petrographic study was to
identify potentially reactive forms of silica in the samples studied. In
volcanic aggregates, these forms include volcanic glass, tridymite,
cristobalite, microcrystalline quartz, opal, chalcedony (1313.
RILEM AAR-1.1 (2016) Detection of potential alkali-reactivity - Part 1:
Petrographic examination method. In: Nixon, P.J., Sims, I. (editors):
RILEM recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures. RILEM State-of-the-art Report 17,
35-60.
), and clay minerals (1010.
Marfil, S.; Locati, F.; Maiza, P.; Lescano, L. (2013) Basaltic rocks
from Argentina used in concrete structures. In: Wu & Qi (eds).
Global View of Engineering Geology and the Environment. 253-258. ISBN
978-1-138-00078-0.
, 1414. Korkanç M.; Tuğrul, A. (2005) Evaluation of selected basalts from the point of alkali-silica reactivity. Cem. Concr. Res. 35 [3], 505-512. https://doi.org/10.1016/j.cemconres.2004.06.013.
).
Potentially reactive forms of silica may be present at the
sub-microscopic level, especially in volcanic rocks. In order to examine
certain areas of the samples in more detail and to complement the
petrographic study, two other methods were used: (a) scanning-electron
microscopy-energy-dispersive X-ray spectrometry (SEM/EDS) and (b)
electron probe microanalysis (EPMA). Bulk-rock chemical analyses were
performed at Activation Laboratories Ltd. in Canada using the lithium
metaborate/tetraborate fusion-inductively coupled plasma (ICP) method
and the inductively coupled plasma-mass spectrometry (ICP/MS) method.
Chemical classification was performed on all aggregates with the
exception of ICL1, ICL2, and ICL4 because of their diverse materials
(polymictic gravel). Together with the petrographic analysis, these
analyses provide complementary information about the rock composition.
Petrographic
studies were conducted on conventional thin sections using an Olympus
CX31 polarizing microscope in order to identify the aggregate materials’
mineralogical and textural characteristics and the potentially reactive
forms of silica present (77.
Fernandes. I.; Ribeiro, M.A.; Broekmans, M.A.T.M.; Sims, I. (2015)
Petrographic Atlas. Characterisation of aggregates regarding potential
reactivity to alkalis. RILEM 219-ACS AAR-1.2. RILEM TC 219-ACS
Recommended Guidance AAR-1.2, for Use with the RILEM AAR-1.1
Petrographic Examination Method. RILEM Guideline, Springer, 196. ISBN
978-94-017-7383-6
, 1818.
ASTM C294 (2012). Standard descriptive nomenclature for constituents of
concrete aggregates. Annual Book of ASTM Standards, The American
Society for Testing and Materials, Philadelphia, USA, 11.
).
A number of photomicrographs were captured using an Olympus SC100
camera. Notably, the point counting described in RILEM AAR-1.1 (1313.
RILEM AAR-1.1 (2016) Detection of potential alkali-reactivity - Part 1:
Petrographic examination method. In: Nixon, P.J., Sims, I. (editors):
RILEM recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures. RILEM State-of-the-art Report 17,
35-60.
) was not performed owing to the (fine) size of
the minerals present in the samples. As the very fine grains of
extrusive rocks can present a challenge to mineral identification under
the polarizing microscope, other techniques such as EPMA and SEM/EDS
were used on carbon-coated, polished thin sections. Quantitative
geochemical data were obtained by EPMA performed at Université Laval,
Québec, Canada, where a CAMECA SX-100 electron microprobe was used for
samples from Brazil, Canada, Spain, Hawaii, Iceland, Japan, Mozambique,
Norway, and Turkey. Only certain samples from the Azores (SMG-SM1,
TER-SM1, and TER-SM2) were analysed by SEM/EDS. Semiquantitative
geochemical EDS analyses of phases in the SMG-SM1 and TER-SM2 samples
were performed in Japan by Kawasaki Geological Engineering. For the
TER-SM1 sample, this was also done at the Materials Centre of the
University of Porto in Portugal (Centro de Materiais da Universidade do
Porto - CEMUP) using EDS (JEOL JSM-6301F SEM with a Noran Voyager EDS:
15 kV, 15-mm working distance, 60-s collection time, and 30% dead-time).
The potential alkali reactivity of the aggregates considered was
further evaluated using the AMBT and the CPT. Different accelerated
mortar bar test series were performed as part of this study: (a) 29
mixes at Université Laval, Québec, Canada, and (b) 13 mixes at the
National Laboratory for Civil Engineering (Laboratório Nacional de
Engenharia Civil, LNEC), Lisbon, Portugal, within the scope of the ReAVA
and IMPROVE research projects. The mortar mixtures at Université Laval
were prepared in accordance with the CSA A23.2-25A standard (3737.
CSA A23.2-25A (2014) Test method for detection of alkali-silica
reactive aggregate by accelerated expansion of mortar bars. Canadian
Standards Association, Mississauga, Ontario, Canada, 425-433.
) and incorporated a general use (GU) Portland cement with an alkali content of 0.94% Na2Oequiv, while tests performed at LNEC followed the ASTM 1260 standard (2121.
ASTM C 1260 (2014) Standard test method for potential alkali reactivity
of aggregates (mortar bar method). Annual Book of ASTM Standards, The
American Society for Testing and Materials, Philadelphia, USA, 4.
) using cement type CEM I 42.5 R (3838.
EN 197-1 (2011) Cement. Composition specifications and conformity
criteria for common cements. Brussels: European Committee for
Standardization (CEN), 38.
) with 0.86% Na2Oequiv. and a water/cement (w/c) ratio of 0.47. In all cases, the bars were
immersed in a 1N NaOH solution at 80°C and length-change measurements
were taken at regular intervals for up to 28 days (3737.
CSA A23.2-25A (2014) Test method for detection of alkali-silica
reactive aggregate by accelerated expansion of mortar bars. Canadian
Standards Association, Mississauga, Ontario, Canada, 425-433.
).
The 29 mixes prepared in Canada included samples NOR, CAN, BRAZ, CRV,
JAP, MOZ, NZ1, NZ2, NZ3, CANY1, CANY2, TK, HW1, HW2, HW3, HW4, HW5, HW6,
HW7, HW7 sand, ICL1, ICL1 fine sand, ICL1 coarse sand, ICL2, ICL3, ICL3
sand, ICL4, ICL4 sand, and GBS (sand from Iceland). The control used
was Spratt aggregate: a highly reactive siliceous limestone aggregate
from Ontario, Canada. The mixes prepared in Portugal included aggregate
samples from the different islands of the Azores Archipelago: SMA-SM1,
SMA-SM2, SMG-SM1, SMG-SM2, SMG-SM3, TER-SM1, TER-SM2, GRA-SM1, SJO-SM1,
PIC-SM1, FAI-SM1, FLO-SM1, FLO-SM2.
An additional CPT series was
conducted for this study: (a) 30 mixes at Université Laval and (b) 13
mixes at the LNEC, within the scope of the ReAVA and IMPROVE research
projects. For the CPT, an extra mix with coarse and fine aggregates from
the same source (HW7-CA+FA) was prepared at Université Laval. The CPT
series at Université Laval were conducted in accordance with the CSA
A23.2-14A standard (3939.
CSA A23.2-14A (2014) Potential expansivity of aggregates; procedure for
length change due to alkali-aggregate reaction in concrete prisms.
Canadian Standards Association, Mississauga, Ontario, Canada, 246-256.
) (equivalent to ASTM C 1293 (2323.
ASTM C 1293 (2020) Standard test method for determination of length
change due to alkali silica reaction. Annual Book of ASTM Standards. The
American Society for Testing and Materials, Philadelphia, USA, 6.
)) and incorporated a GU Portland cement with an alkali content of 0.94% Na2Oequiv. A cement content of 420 kg/m3 and a w/c ratio of 0.43-0.44 were used in all mixtures. The aggregate
grading consisted of three equal-mass portions of 5-10 mm, 10-14 mm and
14-20 mm size fractions. NaOH was added to the mix water in order to
raise the total alkali content in the mix to 1.25% (by cement mass);
i.e., a total concrete alkali content of 5.25 kg/m3. The CPT performed at the LNEC followed RILEM AAR-3 (2424.
RILEM AAR-3 (2016) RILEM Recommended test method AAR-3. Detection of
potential alkali-reactivity - 38ºC. Test method for aggregate
combinations using concrete prisms. In: Nixon, P.J. and Sims, I. (eds):
RILEM recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures, RILEM State-of-the-Art Reports 17,
Springer, 79-97, 2016. https://doi.org/10.1007/978-94-017-7252-5_5.
).
The concrete mixes were prepared with the same cement used for the AMBT
and with fine and coarse aggregates from the same origin (< 22.4
mm). A cement-to-aggregate ratio of 0.25 and a w/c ratio of 0.45 were
used in the 13 mixes. A total cementitious material content of 440 kg/m3 was used in those mixtures and NaOH was added to the mix water in order
to raise the total alkali content in the mix to 1.25% (by cement mass);
i.e., a total concrete alkali content of 5.50 kg/m3.
In all Université Laval and LNEC test series, the test prisms were stored at 38oC and R.H. > 95% and length-change measurements were taken regularly over the specified one-year test period.
3. RESULTS
⌅3.1. Petrography and complementary techniques
⌅Petrographic characterization in terms of basic composition indicated similarities between the samples. In general, relatively large, conspicuous crystals (phenocrysts) of olivine, pyroxene, and plagioclase were present in various proportions. The groundmass was mainly fine-grained with intergranular texture and was formed of the same mineral assemblage plus apatite and opaque minerals. The latter sometimes showed a skeletal form when present as phenocrysts. Olivine was absent from the groundmass in a few samples. Some samples contained chlorite, either together with zeolites (ICL1, ICL2) or alone (CAN and NOR - Figure 1a and b). Zeolites were present in samples SMA-SM1, CANY1 and ICL1. The presence of these two minerals was confirmed by EPMA. Additionally, quartz was recognised by the same analysis in samples ICL1, ICL2, and NOR. Microcrystalline quartz was detected by SEM/EDS in TER-SM1. Using EPMA, a silica material was identified in the BRAZ sample, and optical properties examined using a petrographic microscope suggested the presence of quartz between green celadonite minerals (Figure 1c). Clay minerals were also detected by EMPA in samples BRAZ, CAN, and ICL2. Petrographic microscope examination showed that volcanic glass was present in almost half of the samples (Figures 1d-g). For each sample, the presence of volcanic glass was also confirmed by EPMA; results are shown in Table 2. Depending on the sample, glass appeared to various extents, varied in colour, and ranged from a dark to a lighter, brownish appearance. Notably, the NZ1 sample contained some whitish fragments between the darker volcanic particles. Under the microscope, these whitish particles were revealed to be fine-grained chert with microcrystalline forms of silica and tectonite with deformation structures mainly composed of microcrystalline quartz.
| Samples | BRAZ | CAN | ICL1 | ICL2 | ICL3 | ICL4 | MOZ | HW1 | HW5 | HW6 | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| SiO2 % | 53.89 | 97.68* | 54.13 | 73.35 | 43.05 | 49.47 | 52.10 | 71.64 | 79.12 | 62.77 | 77.37 |
| TiO2 % | 0.02 | 0.00 | 0.13 | 0.10 | 0.04 | 1.93 | 1.47 | 0.10 | 0.66 | 0.33 | 0.83 |
| Al2O3 % | 2.56 | 0.55 | 10.45 | 15.02 | 8.25 | 14.45 | 2.00 | 15.32 | 12.55 | 22.14 | 12.10 |
| MgO % | 6.23 | 0.00 | 4.08 | 0.05 | 16.38 | 7.11 | 13.26 | 0.01 | 0.04 | 0.04 | 0.05 |
| CaO % | 0.00 | 0.08 | 0.26 | 0.50 | 1.42 | 11.74 | 19.06 | 0.27 | 2.98 | 4.47 | 1.80 |
| MnO % | 0.02 | 0.00 | 0.08 | 0.05 | 0.09 | 0.19 | 0.39 | 0.00 | 0.01 | 0.02 | 0.00 |
| FeO % | 20.09 | 0.29 | 18.08 | 0.81 | 20.62 | 13.23 | 13.77 | 0.29 | 0.62 | 0.99 | 1.73 |
| Na2O % | 0.02 | 0.19 | 0.12 | 6.26 | 0.32 | 0.84 | 0.34 | 1.69 | 3.77 | 7.31 | 4.44 |
| K2O % | 9.01 | 0.08 | 8.36 | 3.96 | 0.58 | 0.17 | 0.02 | 7.98 | 0.23 | 2.45 | 0.81 |
| Total % | 92.20 | 98.86 | 95.72 | 100.11 | 90.76 | 99.27 | 102.42 | 97.32 | 99.97 | 100.52 | 99.31 |
From a macroscopic perspective, the natural (rounded) gravel aggregates ICL1, ICL2, and ICL4 presented different textures and the frequent presence of shells. Under the microscope, differences were apparent between these gravel aggregates from Iceland and the other samples. The former included a mixture of rock fragments of different origins: mainly basalts, metabasalts (metamorphic derivatives of basaltic rocks), some rhyolites, and a few highly altered plutonic rocks (probably altered gabbro). The fragments of these mixtures showed textures similar to those of the other basaltic samples in this study with the same mineral assemblage. Volcanic glass and devitrified volcanic glass appeared scattered in the groundmass and featured a rusty colour, probably due to palagonite (Figures 1d and f). The fragments of metabasalts exhibited peculiar features: pore spaces were filled with zeolites with surrounding chlorite. There were also fragments of dacites in ICL4 with a very fine-grained groundmass containing phenocrysts of plagioclase. The rhyolite fragments present in gravels ICL1 and ICL2 featured a fine-grained groundmass with quartz and feldspar as the dominant minerals.
The two investigated andesites (Figure 1h) were very similar. Both were porphyritic with plagioclase phenocrysts, pyroxene, and some olivine. The groundmass of TK was composed of volcanic glass and plagioclase. Volcanic glass appeared to be absent in the JAP sample, though it did contain an unidentified silica form (possibly tridymite). The rhyolite (MOZ) was aphyric (Figure 1i) and contained microcrystalline silica. The groundmass appeared to be banded with lighter and darker areas. According to the EPMA analysis, both areas consisted of volcanic glass.
EDS analyses were
performed on three samples from the Azores (SMA-SM1, SMG-SM2, and
TER-SM1). For volcanic glass, the EDS results showed SiO2 content of 58% and 55% for SMG-SM1 and TER-SM2, respectively. The
interstitial silica detected in the TER-SM1 sample was confirmed as
microcrystalline quartz (4040.
Medeiros, S.; Katayama, T.; Zanon, V.; Fernandes, I.; Silva, A.S.;
Nunes, J.C.; Miranda, V.; Soares, D. (2012) Assessment of the potential
alkali-reactivity of volcanic aggregates from Azores Islands. In:
Drimalas, T.; Ideker, J.H. and Fournier, B. (eds.). Proceedings of the
12th International Conference on Alkali-Aggregate Reactivity in Concrete, Austin, Texas, USA, 10.
).
Table 2 summarizes EPMA results for presumed volcanic glass in samples where this material was identified initially by petrography. These identifications were positive except in the BRAZ sample, where high SiO2 content revealed by EPMA indicated quartz instead. Several analyses were performed for each section within each sample. One set of EPMA data is provided per geological setting with the exception of the BRAZ sample, where a second column shows the analysis of quartz. Note that no petrographic characterization was performed on the sands or in the control aggregates (Spratt aggregate and GBS sand) since this study focused on coarse aggregates.
3.2. Expansion tests
⌅The 14- and 28-day AMBT expansion results for the aggregates investigated in this study are presented in Figure 2. The Canadian standard CSA A23.2-27A (4141.
CSA A23.2-27A (2014) Test methods and standard practices for concrete -
Standard practice to identify degree of alkali-reactivity of aggregates
and to identify measures to avoid deleterious expansion in concrete.
Canadian Standards Association, Mississauga, Ontario, Canada, 439-451.
) states that an expansion of >0.15% after 14 days indicates a potentially reactive aggregate. ASTM Standard Guide C1778 (4242.
ASTM C 1778 (2020) Standard guide for reducing the risk of deleterious
alkali-aggregate reaction in concrete. The American Society for Testing
and Materials, Philadelphia, USA, 11
) considers that
14-day mortar bar expansions of <0.10% represent innocuous
aggregates, in most cases. Aggregates that generate mortar bar
expansions of >0.10% are considered potentially deleterious; the CPT
is then recommended to confirm reactivity. In ASTM C 1260 (2121.
ASTM C 1260 (2014) Standard test method for potential alkali reactivity
of aggregates (mortar bar method). Annual Book of ASTM Standards, The
American Society for Testing and Materials, Philadelphia, USA, 4.
),
it is stated that an expansion of >0.20% after 14 days indicates
potentially deleterious behaviour while expansions of <0.10%
generally suggest innocuous behaviour. Expansions between 0.10% and
0.20% correspond to aggregates that fall into either category based on
field performance: some innocuous while others deleterious.
The
AMBT results at the end of the 14-day period showed that samples BRAZ,
ICL1 fine sand, ICL4, ICL4 sand, JAP, MOZ, NZ3, TK, HW1, HW3, HW5, HW6,
HW7, and HW7 sand were potentially reactive since their expansion values
ranged from 0.22 to 0.98%. Samples ICL3 and TER-SM1 presented values
corresponding to aggregates that can be either innocuous or potentially
reactive. The rest of the samples showed expansion values <0.10% and
were therefore considered non-reactive, including SMA-SM1, SMA-SM2,
SMG-SM1, SMG-SM2, SMG-SM3, TER-SM2, GRA-SM1, SJO-SM1, PIC-SM1, FAI-SM1,
FLO-SM1, FLO-SM2, CRV, CAN, ICL2, NZ1, NZ2, CANY1, CANY2, HW2, and HW4.
The results of the AMBT for the majority of the Azores samples are
presented in Medeiros et al. (4040.
Medeiros, S.; Katayama, T.; Zanon, V.; Fernandes, I.; Silva, A.S.;
Nunes, J.C.; Miranda, V.; Soares, D. (2012) Assessment of the potential
alkali-reactivity of volcanic aggregates from Azores Islands. In:
Drimalas, T.; Ideker, J.H. and Fournier, B. (eds.). Proceedings of the
12th International Conference on Alkali-Aggregate Reactivity in Concrete, Austin, Texas, USA, 10.
).
The one-year concrete prism expansion results for the various aggregates investigated in this study are illustrated in Figure 3. The Canadian standard CSA A23.2-27A (3232. Shayan, A. (2007) Field evidence for inability of ASTM C 1260 limits to detect slowly reactive Australian aggregates. Aust. J. Civ. Eng. 3 [1], 13-26. https://doi.org/10.1080/14488353.2007.11463917.
) and ASTM Standard Guide C1778 (4242.
ASTM C 1778 (2020) Standard guide for reducing the risk of deleterious
alkali-aggregate reaction in concrete. The American Society for Testing
and Materials, Philadelphia, USA, 11
) state that an
aggregate inducing an expansion of <0.040% (cited as 0.04% for the
ASTM standard) is considered non-reactive and may be used in concrete
without any further testing for ASR. On the other hand, both standards
consider that a one-year concrete prism expansion greater than or equal
to this critical value indicates a reactive aggregate and that
preventive measures are required if the aggregate is to be used in
concrete construction. On the basis of trials conducted on aggregate
combinations of known field performance from various parts of the world,
RILEM AAR-3 (2424.
RILEM AAR-3 (2016) RILEM Recommended test method AAR-3. Detection of
potential alkali-reactivity - 38ºC. Test method for aggregate
combinations using concrete prisms. In: Nixon, P.J. and Sims, I. (eds):
RILEM recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures, RILEM State-of-the-Art Reports 17,
Springer, 79-97, 2016. https://doi.org/10.1007/978-94-017-7252-5_5.
)
recommends that test results (usually measured after 12 months) of
<0.05% be considered as likely indicating non-expansive materials.
The CPT showed that two samples from Iceland (ICL1, which contained both
coarse and fine aggregate, and ICL4), ICL4 sand, JAP, TK, and HW7 sand
were considered reactive at the end of the one-year period, with
expansion values ranging from 0.13 to 0.34%. The rest of the samples
were considered non-reactive according to the CPT. The results of the
CPT for the Azores samples are presented in Medeiros et al. (4040.
Medeiros, S.; Katayama, T.; Zanon, V.; Fernandes, I.; Silva, A.S.;
Nunes, J.C.; Miranda, V.; Soares, D. (2012) Assessment of the potential
alkali-reactivity of volcanic aggregates from Azores Islands. In:
Drimalas, T.; Ideker, J.H. and Fournier, B. (eds.). Proceedings of the
12th International Conference on Alkali-Aggregate Reactivity in Concrete, Austin, Texas, USA, 10.
).
4. DISCUSSION
⌅The petrographic study showed that almost half of the samples contained volcanic glass. Other forms of potentially reactive material were also identified, such as devitrified volcanic glass in ICL1, ICL2, and BRAZ, and micro- to cryptocrystalline silica in TER-SM1 and in ICL4. Furthermore, the presence of tridymite and cristobalite was observed in ICL2 and ICL3, and tridymite was also observed in JAP. In addition, clay minerals were recognized in two samples: BRAZ and ICL2.
Volcanic
glass is an amorphous material that results from rapidly cooling magma;
its usual composition ranges from 40 to 77 wt% SiO2. The volcanic glass analysed by EPMA for the different aggregates showed a range of SiO2 content from 43.05 to 79.16% SiO2. According to Katayama et al. (1212.
Katayama, T.; St John, D.A.; Futagawa, T. (1989) The petrographic
comparison of rocks from Japan and New Zealand-Potential reactivity
related to interstitial glass and silica minerals. In: Okada, K,
Nishibayashi, S.; Kawamura, M. (editors), Proceedings of the 8th International Conference on Alkali-Aggregate Reaction (ICAAR). Kyoto, Japan, 537-542.
), volcanic glass is highly reactive when its SiO2 content is >65% (rhyolitic glass); however, andesitic glass (57-63 wt% SiO2 (4343.
Le Maitre, R.W.; Streckeisen, A.; Zanettin, B.; Le Bas, M.J.; Bonin,
B.; Bateman, P.; Bellieni, G.; Dudek, A.; Efremova, S.; Keller, J.;
Lameyre, J.; Sabine, P.A.; Schmid, R.; Sørensen, H.; Wooley, A.R. (2002)
Igneous rocks. A classification and glossary of terms. Recommendations
of the International Union of Geological Sciences, Subcomission on the
Systematics of Igneous Rocks. In: Le Maitre, R.W. (ed). Cambridge
University Press, 236.
)) can be considered less
reactive or even non-reactive. The same authors have mentioned that even
basalts and andesites can include rhyolitic glass despite being,
respectively, basic and intermediate rocks. The presence of reactive
volcanic glass with an SiO2 content of >50% has also been reported by Korkanç and Tugrul (11. Korkanç, M.; Tugrul, A. (2004) Evaluation of selected basalts from Niğde, Turkey, as source of concrete aggregate. Eng. Geol. 75 [3-4], 291-307. https://doi.org/10.1016/j.enggeo.2004.06.015.
) in some basalts from Turkey. Furthermore, RILEM AAR-1.1 (1313.
RILEM AAR-1.1 (2016) Detection of potential alkali-reactivity - Part 1:
Petrographic examination method. In: Nixon, P.J., Sims, I. (editors):
RILEM recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures. RILEM State-of-the-art Report 17,
35-60.
) describes volcanic glass as a potentially
alkali-reactive constituent of different rock types usually occurring as
rhyolitic glass or hydrated rhyolitic glass. Additionally, devitrified
volcanic glass is considered potentially alkali-reactive (1313.
RILEM AAR-1.1 (2016) Detection of potential alkali-reactivity - Part 1:
Petrographic examination method. In: Nixon, P.J., Sims, I. (editors):
RILEM recommendations for the prevention of damage by alkali-aggregate
reactions in new concrete structures. RILEM State-of-the-art Report 17,
35-60.
, 4444.
Falikman, V.R.; Rozentahl, N.K. (2017) Russian Federation. In: Sims I
and Poole A (ed) Alkali-aggregate reaction in concrete: A world review.
CRC Press/Balkema. Taylor & Francis Group, London, UK, 433-466.
). According to some authors, swelling clay minerals are also deleterious (1010.
Marfil, S.; Locati, F.; Maiza, P.; Lescano, L. (2013) Basaltic rocks
from Argentina used in concrete structures. In: Wu & Qi (eds).
Global View of Engineering Geology and the Environment. 253-258. ISBN
978-1-138-00078-0.
, 1212.
Katayama, T.; St John, D.A.; Futagawa, T. (1989) The petrographic
comparison of rocks from Japan and New Zealand-Potential reactivity
related to interstitial glass and silica minerals. In: Okada, K,
Nishibayashi, S.; Kawamura, M. (editors), Proceedings of the 8th International Conference on Alkali-Aggregate Reaction (ICAAR). Kyoto, Japan, 537-542.
), as they result from the alteration of volcanic glass (1212.
Katayama, T.; St John, D.A.; Futagawa, T. (1989) The petrographic
comparison of rocks from Japan and New Zealand-Potential reactivity
related to interstitial glass and silica minerals. In: Okada, K,
Nishibayashi, S.; Kawamura, M. (editors), Proceedings of the 8th International Conference on Alkali-Aggregate Reaction (ICAAR). Kyoto, Japan, 537-542.
).
In general, from the point of view of petrography, samples that contain
deleterious constituents are regarded as potentially reactive. Some of
the samples, especially those from Iceland (ICL1) and the Hawaiian
Islands (HW1, HW5, and HW6), contained volcanic glass with high SiO2 content in basaltic aggregates (63-79%). This merits further
investigation; these high values might be due to the presence of some
form of silica in the groundmass (4545.
Medeiros, S.; Fernandes, I.; Fournier, B.; Nunes, J.C.; Ramos, V.
(2020) Hawaiian and Azorean volcanic aggregates: a preliminary study of
the potential alkali silica reaction. Bull. Eng. Geol. Environ. 80, 8949-8960. https://doi.org/10.1007/s10064-019-01702-z.
).
Regarding the AMBT, Korkanç and Tugrul (1414. Korkanç M.; Tuğrul, A. (2005) Evaluation of selected basalts from the point of alkali-silica reactivity. Cem. Concr. Res. 35 [3], 505-512. https://doi.org/10.1016/j.cemconres.2004.06.013.
)
studied basalts from Turkey in which the presence of volcanic glass
with acidic-intermediate character showed expansions of >0.10%. Wigum
et al. (99.
Wigum, B.J.; Björnsdóttir, V.D.; Olafsson, H.; Iversen, K. (2007)
Alkali-aggregate reaction in Iceland - New test methods, VGK-Hönnun
Consulting Engineers, 74.
) studied several Icelandic
basaltic aggregates and showed that most of them were considered
deleterious at the end of 14 days of expansion. According to Marfil et
al. (1010.
Marfil, S.; Locati, F.; Maiza, P.; Lescano, L. (2013) Basaltic rocks
from Argentina used in concrete structures. In: Wu & Qi (eds).
Global View of Engineering Geology and the Environment. 253-258. ISBN
978-1-138-00078-0.
), if a basalt contains clay
minerals that are expansive, then they may increase the expansion
observed in the AMBT. The same authors have reported that the presence
of volcanic glass and clay minerals are associated with the expansion
measured in the mortar bars. Madsen et al. (66.
Madsen, L.; Rocco, C.; Falcone, D.; Locati, F.; Marfil, S. (2019)
Alkali-silica reactivity of basaltic aggregates of Mesopotamia
Argentina: case studies. Bull. Eng. Geol. Environ. 78, 5495-5509. https://doi.org/10.1007/s10064-019-01470-w.
)
have put forth the same opinion. On one hand, there is generally a
direct relationship between the results of the AMBT and the content of
volcanic glass plus clay minerals. On the other hand, Menéndez et al. (4646.
Menéndez, E.; García-Roves, R.; Aldea, B.; Puerto, E.; Recino, H.
(2021) Study of the alkali-silica reaction rate of Spanish aggregates.
Proposal of a classification based in accelerated mortar bars tests and
petrographic parameters. Mater. Construcc. 71 [344], e263. https://doi.org/10.3989/mc.2021.13421.
)
reported that a Spanish basalt containing quartz with straight
extinction (but in low proportion) did not show any reactivity according
to the AMBT. In the present study, the classifications of most samples
considered between potentially reactive to reactive according to the
AMBT were supported by petrographic analysis results. However, there
were some exceptions: CAN, ICL2, NZ3, NOR, and TER-SM2. Only a few
samples were considered reactive according to all the presented
assessment methods. These samples included JAP and TK, which were used
as controls, as well as Spratt aggregate and GBS, for which the
reactivity was already known. The basaltic samples that were classified
as reactive according to all methods were: ICL1 coarse and fine sand,
ICL4, ICL4 sand, and HW7 sand.
Notably, the mixture HW7 CA+FA
(coarse aggregate plus fine aggregate from the same source) was found to
be non-reactive according to the CPT, while the HW7 sand was reactive
according to the same test (including a very high one-year expansion of
0.32%). This result merits further analysis. An interesting result
contrary to expectations was that the MOZ rhyolite sample was considered
non-reactive according to the CPT. According to Wigum (4747.
Wigum, B.J. (2012) Assessment and development of performance tests for
alkali aggregate reaction in Iceland. In: Drimalas, T.; Ideker, J.H.;
Fournier, B. (eds.). Proceedings, 14th International Conference on Alkali-Aggregate Reactions in Concrete, Austin, Texas, 10.
),
high amounts of reactive sand in Iceland may be responsible instead of
the gravels (coarse fraction) for the high degree of expansion observed
in the CPT. However, experience from an outdoor field exposure site
shows the opposite trend for the same materials (4747.
Wigum, B.J. (2012) Assessment and development of performance tests for
alkali aggregate reaction in Iceland. In: Drimalas, T.; Ideker, J.H.;
Fournier, B. (eds.). Proceedings, 14th International Conference on Alkali-Aggregate Reactions in Concrete, Austin, Texas, 10.
).
In the present study, alkali reactivity occurred in the sand fractions
rather than in the coarse aggregate fractions in Icelandic and Hawaiian
samples. Different field exposure sites have been established in the US
and in Europe. One of these sites (since 2011) is located at the
University of Hawaii at Manoa, Hawaii, with 30 concrete blocks cast
mainly using local basaltic aggregates in various mixtures. Only one of
these basaltic aggregates showed signs of ASR expansion and cracking in
the field study: a basalt not used for concrete manufacture (4848.
Robertson, I.; Shen, L. (2018) Field evaluation of concrete using
Hawaiian aggregates for alkali silica reaction. In: International
Conference on Concrete Repair, Rehabilitation and Retrofitting (ICCRRR
2018). MATEC Web of Conferences 199 [10], 03005. https://doi.org/10.1051/matecconf/201819903005.
).
Figure 4 plots the results of the 14-day AMBT along with the one-year CPT expansion results; yellow dots represent aggregates containing volcanic glass. Four zones are labelled in the figure as I, II, III, and IV. Most of the samples fell into zone I, classified as innocuous according to both tests. Samples categorized within zone II showed excessive expansion in the AMBT but were not considered reactive according to the limits established for the CPT. The samples in zone III were classified as potentially reactive according to both the AMBT and the CPT. Significantly, none of the aggregates fell into zone IV, in which CPT and AMBT results would suggest, respectively, potentially reactive and innocuous. These results show that the mortar bar test is more sensitive to the presence of volcanic aggregates than the CPT, causing a number of samples to fall into zone II (i.e. “false-positive”). The latter are less problematic than “false negative” results, which would be located in zone IV. Overall, in their evaluation of the potential alkali reactivity of aggregates, the CPT and AMBT were in agreement for 78% of the cases evaluated in this study (i.e., results that fell into zones I or III).
Table 3 summarizes the results obtained for all samples and methods applied in this study.
| Samples | Country | Chemical Classification | Potentially reactive forms of silica identified by petrographic characterization | AMBT expansion, % | CPT expansion, % (1 year) | |
|---|---|---|---|---|---|---|
| 14 days | 28 days | |||||
| BRAZ | Brazil | Basalt | Volcanic glass, devitrified volcanic glass, clay minerals | 0.48 | 0.55 | -0.01 |
| CAN | Canada | Basalt | Volcanic glass | 0.02 | 0.03 | 0.01 |
| Spratt | Limestone | * | 0.39 | 0.71 | 0.17 | |
| ICL1 | Iceland | Gravel (basalts, metabasalts, rhyolite) | Volcanic glass, devitrified volcanic glass, tridymite and cristobalite | 0.44 | 0.58 | 0.02 |
| ICL1 fine sand | Sand | * | 0.46 | 0.64 | 0.20 | |
| ICL1 coarse sand | Sand | * | 0.34 | 0.48 | 0.25 | |
| ICL2 | Gravel (basalts, metabasalts rhyolites) | Volcanic glass, devitrified volcanic glass, clay minerals, tridymite and cristobalite | 0.05 | 0.08 | 0.01 | |
| ICL3 | Basalt | Volcanic glass | 0.10 | 0.20 | 0.01 | |
| ICL3 sand | Basalt | * | 0.13 | 0.20 | -0.01 | |
| ICL4 | Gravel (basalts, dacite, gabbro?) | Volcanic glass, devitrified volcanic glass, microcrystalline silica | 0.57 | 0.75 | 0.13 | |
| ICL4 sand | Sand | * | 0.63 | 0.92 | 0.34 | |
| GBS sand | Basalt | * | 0.30 | 0.40 | 0.05 | |
| JAP | Japan | Andesite | Tridymite | 0.79 | 1.30 | 0.24 |
| MOZ | Mozambique | Rhyolite | Volcanic glass and microcrystalline silica | 0.22 | 0.36 | 0.00 |
| NZ1 | New Zealand | Basanite | Volcanic glass | 0.009 | 0.01 | 0.01 |
| NZ2 | Basalt | - | 0.04 | 0.03 | 0.02 | |
| NZ3 | Basalt | Volcanic glass | 0.58 | 0.67 | 0.03 | |
| NOR | Norway | Basalt | - | 0.07 | 0.17 | 0.00 |
| SMA-SM1 | Portugal (Azores Islands) |
Basanite | - | 0.02 | 0.02 | 0.02 |
| SMA-SM2 | Basanite | - | 0.01 | 0.01 | 0.02 | |
| SMG-SM1 | Potassic trachybasalt | - | 0.02 | 0.02 | 0.02 | |
| SMA-SM2 | Potassic trachybasalt | - | 0.02 | 0.03 | 0.04 | |
| SMG-SM3 | Basalt | - | 0.02 | 0.02 | 0.02 | |
| TER-SM1 | Trachyte | Volcanic glass Micro- to cryptocrystalline silica |
0.13 | 0.17 | 0.02 | |
| TER-SM2 | Basalt | Volcanic glass | 0.02 | 0.01 | 0.03 | |
| GRA-SM1 | Hawaiite | - | 0.01 | 0.01 | 0.03 | |
| SJO-SM1 | Basalt | - | 0.01 | 0.01 | 0.03 | |
| PIC-SM1 | Basalt | - | 0.00 | 0.00 | 0.03 | |
| FAI-SM1 | Hawaiite | - | 0.01 | 0.01 | 0.02 | |
| FLO-SM1 | Benmoreite | - | 0.01 | 0.01 | 0.01 | |
| FLO-SM2 | Mugearite | - | 0.01 | 0.01 | 0.01 | |
| CRV | Hawaiite | - | 0.02 | 0.02 | 0.01 | |
| CANY1 | Spain (Canary Islands) | Basanite | - | 0.01 | 0.01 | 0.01 |
| CANY2 | Basanite | - | 0.02 | 0.01 | 0.02 | |
| TK | Turkey | Andesite | Volcanic glass | 0.98 | 1.62 | 0.14 |
| HW1 | USA (Hawaiian Islands) | Basalt | Volcanic glass | 0.77 | 1.13 | 0.02 |
| HW2 | Basalt | - | 0.07 | 0.07 | 0.01 | |
| HW3 | Basalt | Volcanic glass | 0.82 | 1.58 | 0.03 | |
| HW4 | Mugearite | - | 0.03 | 0.02 | 0.02 | |
| HW5 | Basalt | Volcanic glass | 0.45 | 1.05 | 0.02 | |
| HW6 | Basalt | Volcanic glass | 0.02 | 0.02 | 0.02 | |
| HW7 | Basalt | Volcanic glass | 0.90 | 1.25 | 0.01 | |
| HW7 sand | Basalt | * | 0.50 | 1.04 | 0.32 | |
| HW7 CA+-FA | Basalt | Volcanic glass | - | - | 0.01 | |
5. CONCLUSIONS
⌅The main objective of this study was to assess the potential alkali-silica reactivity of a wide range of basaltic aggregates from distinct parts of the world using different test methods. The main conclusions from the above investigations are as follows:
-
Petrographic characterization identified volcanic glass as the main constituent responsible for potential alkali-silica reactivity in almost half of the samples. Other deleterious species were also identified, such as clay minerals, micro- to cryptocrystalline silica, tridymite, and cristobalite;
-
EPMA showed high SiO2 content in volcanic glass present in the basaltic aggregates from Iceland (ICL1) and the Hawaiian Islands (HW1, HW5 and HW6);
-
According to the AMBT, twelve samples were considered potentially reactive according to measurements taken at the end of the 14-day testing period: one from Brazil (BRAZ), five samples from Iceland (ICL1, ICL4, ICL1 sand, and ICL4 coarse and fine sands), one from Japan (JAP), one from Mozambique (MOZ), one from New Zealand (NZ3), one from Turkey (TK), and six from the Hawaiian Islands (HW1, HW3, HW5, HW6, and HW7, including HW7 sand). However, most of the samples were classified as non-reactive by this method;
-
CPT results showed that the majority of the samples were non-reactive, with the exception of four samples from Iceland (ICL1, both aggregate and fine aggregate, and ICL4, both coarse and fine sand), Japan (JAP), Turkey (TK), and one from the Hawaiian Islands (HW7 sand);
-
The samples from Japan and Turkey were considered reactive according to all methods, as expected. This was due to their intermediate character. However, the sample from Mozambique was considered non-reactive in spite of being a rhyolite with volcanic glass;
-
Basaltic samples considered reactive according to all methods were: ICL1, coarse and fine sand, and ICL4, both aggregate and sand, both samples from Iceland, and HW7 sand from the Hawaiian Islands;
-
Most of the tested sands seem to be responsible for reactivity as observed in the CPT;
-
There was clear evidence that the AMBT overestimated the reactivity of many basalts, which probably indicates that this method is too conservative to evaluate reactivity in basalts.
According to the literature on this subject, the presence of volcanic glass and silica minerals is known to influence the potential alkali reactivity of volcanic rocks. In this work, the intermediate to acidic character of volcanic glass and the presence of silica minerals identified in petrographic studies seemed to dictate the potential reactivity of the aggregates studied.
However, the results obtained show that much work remains to be done in order to clarify the potential alkali reactivity of basaltic rocks. Future work will extend the duration of the CPT, and a gel pat test will be performed for further clarification. Furthermore, examining samples from real concrete structures or outdoor exposure sites could help to understand the reactivity of various types of basalt.