Field site tests were carried out to assess the reliability of the tests developed by RILEM and some regional tests to evaluate the alkali-reactivity potential of aggregates (eight tests were included). One hundred concrete cubes made with 13 different European aggregate combinations were stored on eight different European field sites to compare their expansions with the laboratory test results. All highly reactive aggregate combinations caused significant expansion of concrete cubes within the first six years on all field sites from Norway to Spain. These and the non-reactive aggregate combinations were correctly identified with all laboratory tests. Concrete cubes with moderately reactive aggregate combinations expanded very slowly and mainly in the outdoor exposure sites with warm climate conditions. The RILEM test method AAR-4.1 (60°C accelerated concrete prism test) and the Norwegian concrete prism test at 38°C seem to be best suited to identity the potential reactivity of moderately reactive aggregate combinations.
Se realizaron pruebas de campo para evaluar la fiabilidad de los ensayos desarrollados por RILEM y algunos ensayos regionales para evaluar la reactividad alcalina potencial de los áridos (se incluyeron ocho ensayos). Se almacenaron 100 cubos de hormigón fabricados con 13 combinaciones diferentes de áridos europeos, en ocho emplazamientos europeos distintos, para comparar sus expansiones con los resultados de las pruebas de laboratorio. Todas las combinaciones de áridos altamente reactivos provocaron una expansión significativa de los cubos de hormigón durante los primeros seis años en todos los emplazamientos de campo, desde Noruega hasta España; éstas y las combinaciones de áridos no reactivos se identificaron correctamente con todas las pruebas de laboratorio. Los cubos de hormigón con combinaciones de áridos moderadamente reactivos se expandieron muy lentamente y principalmente en los lugares de exposición exterior con condiciones climáticas cálidas. El método de ensayo RILEM AAR-4.1 (ensayo acelerado de prisma de hormigón a 60°C) y el ensayo de prisma de hormigón noruego a 38°C parecen ser los más adecuados para identificar la reactividad potencial de las combinaciones de áridos moderadamente reactivos.
The European “PARTNER” project (2002-2006) had the overall objective of establishing a unified test procedure for evaluating the potential alkali-reactivity of aggregates across the different European economic and geological regions (
Test method | Brief outline of method |
---|---|
RILEM AAR-2 |
Mortar bars made with the aggregate and a reference high alkali cement are stored in 1M NaOH at 80ºC and their expansion monitored over a 14 days period. Two alternative prism sizes are used; 25x25x285 mm3 (AAR-2.1) or 40x40x160 mm3 (AAR-2.2). |
RILEM AAR-3 |
Expansion test for 12 months. Wrapped concrete prisms, (75±5)x(75±5)x (250±50) mm3, made with the aggregate and a reference high alkali cement (1.25% ± 0.05% sodium oxide equivalent) are stored in individual containers in a constant temperature room at 38°C and measured at 20°C. This wrapped version was withdrawn by RILEM TC 219-ACS in 2010. A revised test procedure without wrapping was published in 2016 ( |
RILEM AAR-4.1 |
Expansion test for 20 weeks. Concrete prisms, (75±5)x(75±5)x(250±50) mm3, made with the aggregate and a reference high alkali cement (1.25% ± 0.05% sodium oxide eq.) are stored in individual containers within a reactor at 60°C and measured at 20°C. |
Draft RILEM AAR-4 Alt. |
Accelerated expansion test for 20 weeks. Wrapped concrete prisms, (75±5)x(75±5)x (250±50) mm3, made with the aggregate and a reference high alkali cement (1.25% ± 0.05% sodium oxide equivalent) are stored in individual containers in a constant temperature room at 60°C and measured at 20°C. This draft wrapped version of the 60°C accelerated concrete prism test (ACPT) was withdrawn by RILEM TC 219-ACS in 2010. |
German concrete method ( |
Test duration of 270 to 273 days. Concrete prisms (100x100x500 mm3) and one cube (300 mm3) are stored in a fog chamber at 40°C with measurements taken immediately with no cooling down period. The expansion of concrete prisms and the maximum crack width on the cube are determined. |
Norwegian concrete prism method ( |
Accelerated expansion test for 12 months. Concrete prisms (100x100x450 mm³) made with the aggregate and a reference high alkali cement are stored in individual containers in a room at 38°C and 100% relative humidity and measured at 20°C. |
TI-B51 - The Danish mortar bar test ( |
Mortar bars made with the aggregate are stored in saturated NaCl solution at 50°C and their expansion is monitored for 52 weeks. |
The Danish Chatterji method ( |
The degree of reaction between silica in the aggregate and KCl is determined by measuring the alkalinity after 24 hours reaction compared to a non-reactive standard. |
All aggregates were also analysed petrographically according to RILEM AAR-1 within the “PARTNER” project (
To evaluate the reliability of different laboratory test methods, concrete cubes were produced with the same concrete mixture as used in the prisms for the accelerated laboratory testing. The concrete cubes with 300 mm lateral length were stored at different outdoor exposure sites in Europe. The expansion and the maximum crack width were determined periodically at approximately the same temperature (15°C) in spring and autumn.
Thirteen aggregate combinations (of the 22 aggregate types included in the laboratory test program) were selected with the purpose of covering most types of reactive aggregates throughout Europe and with respect to mineralogical properties and alkali-reactivity (
non-reactive aggregates (green),
moderately reactive aggregates that react in timescales of 15 to 50 years (yellow) and
highly reactive aggregates that react in timescales of 5 to 20 years (red).
The former classes for “slowly” and “normally” reactive aggregates in (
The former RILEM standard cement CEM I 42,5 R provided by NORCEM AS, Norway was used for preparing the concrete. The total alkali content of the cement was 1.26 mass% Na2O-equivalent.
Concrete was made with 440 kg/m³ cement, and the water to cement ratio was 0.50. The air content was approximately 1.5 vol.-%; no air-entraining agent was added to the concrete mix. In case of inappropriate workability of the concrete (slump < 20 mm) a superplasticizer was added. In accordance with the RILEM test method AAR-3 and AAR-4.1 the aggregate combination consisted of one of the following (see
the fine and coarse test aggregates (C + F);
the fine test aggregate combined with non-reactive coarse aggregate (F + NRC);
the coarse test aggregate combined with non-reactive fine aggregate (C + NRF).
Sample number | Origin | Aggregate details | Combinations * | Reported reactivity in structures |
---|---|---|---|---|
F1 | France (Seine Valley) | Gravel with flint | C + NRF | Non-reactive. |
F2 | France | Non-reactive limestone | C + F | Non-reactive |
It2 | Italy (Piemont region) | Gravel with quartzite and gneiss | C + F | Moderately reactive, damage between 15 to 50 years |
N2 | Norway (South-East) | Sandstone | C + NRF | |
N4 | Norway (South-East) | Gravel with sandstone and catacl. rocks | C + F | |
S1 | Sweden | Gravel with porphyritic rhyolite | C + F | |
P1 | Portugal | Silicified limestone | C + NRF | |
B1(RF)* | Western Belgium | Silicified limestone | C + F | Highly reactive, damage between 5 to 20 years |
B1 | C + NRF | |||
D2 | Denmark | Sea-dredged sand semi-dense flint | F + NRC | |
N1 | Norway (middle) | Cataclasite | C + NRF | |
G1 | Germany (Upper Rhine Valley) | Crushed gravel with siliceous limestone and chert | C + NRF | |
UK1 | United Kingdom | Greywacke | C + F | |
* C = coarse aggregate |
The aggregate fractions were combined in proportions of 30 mass-% fines (0 to 4 mm) and 70 mass-% coarse aggregates: 30 mass-% 4 to 10 mm and 40 mass-% 10 to 20 mm.
Two concrete cubes with 300 mm lateral length were produced for each field site and each aggregate combination (
Aggregate | Reactivity | Borås Forest | Borås Highway | Trondheim | Brevik | Watford | Düsseldorf | Milan | Valencia |
---|---|---|---|---|---|---|---|---|---|
|
Non-reactive | F1-Wa | F1-Mi | ||||||
|
F2-BF | F2-BH | F2-Br | F2-Du | F2-Va | ||||
|
Moderately reactive | IT2-Br | IT2-Mi | ||||||
|
N2-Br | N2-Wa | |||||||
|
N4-Br | N4-Du | N4-Mi | ||||||
|
P1-BF | P1-Mi | |||||||
|
S1-BF | S1-BH | S1-Br | S1-Du | S1-Va | ||||
|
Highly reactive | B1(RF)-BF | B1(RF)-BH | B1(RF)-Br | B1(RF)-Du | B1(RF)-Va | |||
|
B1-BF | B1-Tr | B1-Wa | B1-Mi | B1-Va | ||||
|
D2-BF | D2-BH | D2-Tr | D2-Wa | D2-Va | ||||
|
G1-BF | G1-Tr | G1-Du | G1-Mi | |||||
|
N1-BF | N1-BH | N1-Tr | N1-Wa | N1-Du | N1-Va | |||
|
UK1-BF | UK1-BH | UK1-Tr | UK1-Wa | UK1-Va |
At the different field sites, each institute that participated in this research installed two pairs of reference studs into the top surface and into the two adjacent side faces, before the cubes were exposed outdoors. Most laboratories pre-drilled holes before gluing the studs. All cubes were stored in the same direction in relation to the four cardinal points to minimize deviations between the labs resulting from different exposure to direct solar radiation (
During exposure, one cube was stored with its base in a tray filled with water and the other was exposed only to ambient rainfall (
The dimensions of the cubes at the top surface and two adjacent side faces as well as the crack width were determined periodically (first 2½ years every three months, afterwards every half year). Some laboratories have only measured once a year. The measurements were conducted at the field site at temperatures around 15°C and preferably in periods with rather stable temperatures over a 24-hour period and with limited sunshine. The mean expansions of the three side faces are presented in
All highly reactive aggregates expanded within the first six years at the four field sites and showed high expansions from 0.3% to 1.6% after 15 years. In the mild and warm climates of Düsseldorf, Germany (Du) and Milan, Italy (Mi) the expansion rates decreased after some years, whereas in cold climates like Trondheim, Norway (Tr) (
The cubes with the moderately reactive aggregates expanded considerably slower with expansions of about 0.09% to 0.22% after 15 years.
The cubes with the non-reactive aggregate F2 neither expanded at any field site nor showed significant cracking. However, the Damage Rating Index (DRI) determined on polished sections and qualitative damage assessment performed on thin sections revealed that an alkali-silica reaction (ASR) occurred to a small extent (
For the following laboratory-field-correlations, the mean laboratory test results of all participating laboraties were used. Some results were excluded in the case they turned out to be unreliable and if the laboratory was unexperienced with the test method.
Both versions of the AMBT (AAR-2.1 and AAR-2.2) were able to reliably distinguish between non- and highly reactive aggregates (
The concrete prism test methods AAR-3 and AAR-4.1 were effective in distinguishing between the non- and highly reactive aggregates (
Looking at the moderately reactive aggregates, the two versions of RILEM test method AAR-4.1 were detecting its reactivity potential more reliably, if the limit value of 0.03% after 20 weeks as proposed in (
As for RILEM AAR-3 and AAR-4.1, the German and the Norwegian concrete test methods were able to distinguish between non- and highly reactive aggregates (
Compared with AAR-3 and the German method, the Norwegian CPT had the best match with the field performance of the cubes. It correctly displayed the alkali-reactivity potential of the three tested moderately reactive aggregates, even for the very slowly reacting S1. This can probably be attributed to the bigger prisms (100 x 100 x 450 mm³) and less alkali leaching compared to AAR-3 (75 x 75 x 250 mm³) (
In the Danish mortar bar test TI-B51, the expansion after 20 and 52 weeks is used for classifying aggregates into three alkali-reactivity classes. The names of the classes below are used in
Non-reactive: Expansion <0.04% after 20 weeks
Moderately reactive: Expansion <0.1% after 20 weeks and >0.1% after 52 weeks
Highly reactive: Expansion >0.1% after 20 weeks
The TI-B51 was able to show successfully the reactivity potential of the non-reactive F1 and all highly reactive aggregates, but underestimated the reactivity potential of the moderately reactive aggregates N2, P1, IT2 and S1 (
The result of the Danish Chatterji method is a calculated Δ-value that is shown in
The European “PARTNER” project (2002-2006) evaluated the reliability of four RILEM concrete prism tests and four regional test methods to assess the alkali-reactivity potential of aggregates. In addition, field site tests with concrete cubes produced with 13 different aggregate combinations were carried out for comparison with the laboratory results. After about 15 years of outdoor exposure, the main conclusions from this research are as follows:
None of the two non-reactive aggregates showed any signs of ASR in the outdoor exposure sites.
Highly reactive aggregate combinations caused significant expansion of concrete cubes at the field sites in Norway, Germany and Italy within the first six years of storage.
All five moderately reactive aggregate combinations (timescale of reaction 15 to 50 years based on field experience) showed signs of damaging ASR.
Once a deleterious ASR has occurred frost could probably further damage the concrete.
The field site tests confirm that all laboratory tests correctly identified highly reactive and non-reactive aggregate combinations. However, of the RILEM test methods, AAR-4.1 seems to be best suited to identity the potential reactivity of moderately reactive aggregate combinations. The results confirm the limit value of 0.03% after 20 week instead of 15 weeks.
The Norwegian concrete prism test at 38°C was also reliably identifying the moderately reactive aggregate combinations, probably due to reduced alkali leaching of the prims compared to RILEM AAR-3.
The authors wish to thank their colleagues and partners who were running the field site tests and providing their results:
Karin Appelquist (RISE Research Institutes of Sweden, Borås, Sweden) Mario Berra (Ricerca sul Sistema Energetico - RSE S.p.A., Milan, Italy) Jürgen Bokern (formerly Verein Deutscher Zementwerke e. V., Düsseldorf, Germany) Linus Brander (RISE Research Institutes of Sweden, Borås, Sweden) Sigrun Kjær Bremseth (Norcem AS, Brevik, Norway) Magnus Döse (RISE Research Institutes of Sweden, Borås, Sweden) Giorgia Faggiani (Ricerca sul Sistema Energetico - RSE S.p.A., Milan, Italy) Simon Lane (Building Research Establishment Ltd (BRE), Watford, UK) Lotta Liedberg (RISE Research Institutes of Sweden, Borås, Sweden) Angel M. López Buendía (Asociación de Investigación de Industrias de la Construcción (AIDICO), - Paterna (Valencia) SPAIN) Pilar Martí Martí (Asociación de Investigación de Industrias de la Construcción (AIDICO), Paterna (Valencia) SPAIN) Esperanza Menéndez Méndez (Consejo Superior de Investigaciones Científicas (CSIC), Spain) Björn Schouenborg (RISE Research Institutes of Sweden, Borås, Sweden)
Conceptualization: P. Nixon; Data curation: I. Borchers; Formal analysis: I. Borchers; Funding acquisition: P. Nixon; Investigation: I. Borchers, J. Lindgård, M. Berra, J. Bokern, S. K. Bremseth, G. Faggiani; Methodology: P. Nixon, J. Bokern, I. Borchers, J. Lindgård; Project administration: J. Bokern, I. Borchers, J. Lindgård; Resources: I. Borchers; Software: I. Borchers; Validation: I. Borchers, J. Lindgård; Visualization: I. Borchers; Writing, original draft: I. Borchers; Writing, review & editing: I. Borchers, J. Lindgård, C. Müller.