PARTNER Petrographicatlas Version060701

PETROGRAPHIC ATLAS OF THE POTENTIALLY ALKALI-REACTIVE

ROCKS IN EUROPE (Version 010706)

PARTNER Copyright PARTNER-project-GRD1-CT-2001-40103 All rights reserved.

G. Lorenzi, J. Jensen, B. Wigum

In collaboration with: S.Guédon, M.Haugen, E.Schaefer, T.Sibbick, U.Akesson, A. Buendia & S. Goralczyk

PARTNER-Petrographicatlas-version060701

PETROGRAPHIC ATLAS OF THE POTENTIALLY ALKALI-REACTIVE ROCKS

IN EUROPE (Version 010706)

I. Foreword. ....................................................................................................................................................................................3 II. Introduction ...............................................................................................................................................................................3 III. Method .....................................................................................................................................................................................4 1. Sedimentary rocks ......................................................................................................................................................................5

1.1 Siliceous rocks......................................................................................................................................................................6 1.1.1 Flint - Chert ...................................................................................................................................................................6 1.1.2 Sandstone ......................................................................................................................................................................9 1.1.3 Siltstone.......................................................................................................................................................................12 1.1.4 Greywacke...................................................................................................................................................................13

1.2 Carbonate rocks..................................................................................................................................................................15 1.2.1 Limestone ....................................................................................................................................................................16

2. Metamorphic rocks...................................................................................................................................................................20 2.1 Gneiss.................................................................................................................................................................................21 2.2 Metaquartzite-metagreywacke ...........................................................................................................................................23 2.3 Phyllite ...............................................................................................................................................................................25 2.4 Mylonite .............................................................................................................................................................................26 2.5 Cataclasite ..........................................................................................................................................................................28 2.6 Hornfels.............................................................................................................................................................................29

3. Igneous rocks............................................................................................................................................................................30 3.1 Basalt and volcanic glass....................................................................................................................................................31 3.2 Rhyolite ..............................................................................................................................................................................32 3.3 Granite................................................................................................................................................................................33 3.4 Granodiorite .......................................................................................................................................................................34 3.5 Porphyritic diorite ..............................................................................................................................................................35

4. Regional Experience.................................................................................................................................................................36 4.1 Sweden ...............................................................................................................................................................................36 4.2 Denmark.............................................................................................................................................................................37 4.3 Norway...............................................................................................................................................................................38 4.4 Belgium ..............................................................................................................................................................................40

References ....................................................................................................................................................................................42


I. Foreword. A wide variety of concrete aggregate types in common use across Europe, particularly those with a siliceous composition, can be vulnerable to attack by the alkaline pore fluid in concrete. This alkali silica reaction can cause, in wet conditions, the deterioration of the concrete. Alkali-reactive aggregates have been investigated for many years and as a result different test methods have been developed. Unfortunately, such tests are, in some cases, only relevant for specific materials within a country. The PARTNER project, supported by the fifth European Framework Program, has mapped the known types of reactive aggregates throughout Europe based on laboratory and field experience. During the project a state of the art report has been produced and several testing methods have been evaluated such as: the RILEM AAR-1 petrographic method, RILEM AAR-2 accelerated mortar bar test, the RILEM AAR-3 and AAR-4 concrete tests. These laboratory tests have been validated by field tests under different climates. Overall, the project provides the basis for a unified European testing methodology to evaluate and classify the alkali reactivity of aggregates in concrete. This petrographic atlas, which covers the European alkali silica reactive concrete aggregates, has been produced as part of the PARTNER project.

II. Introduction The aim of this petrographic atlas of the potentially alkali-reactive rocks in Europe is to assist geologists who work in the field of the concrete degradations and in particular in the field of the alkali-silica reactions. It is not possible, in only one atlas, to describe every type of concrete alkali-reactive aggregate from Europe. In particular, some aggregates like the sands and the gravels, often contain several different rock types. For these reasons, this atlas has been based on the parent rocks rather than on the aggregates. The rocks are firstly classified under their origin (sedimentary, metamorphic or igneous) using the international nomenclatures; secondly, they have been grouped under families of similar species. For each rock family, a general description is given in the header including the most particular characteristics of the different rock species from different countries. The reactive components are emphasized within the descriptions and, when possible, within the pictures which illustrate the type of aggregate. Despite the fact that this atlas is not exhaustive, it is nevertheless representative of the majority of the European alkali-reactive rocks. It is important to bear in mind several points: - Firstly, if some rock types are reactive, it doesn’t necessary mean that all the rocks of the same family are reactive too: e.g. some sandstone or granite are reactive but not all the sandstones or granites!

- Secondly, the reactivity of an aggregate in a particular concrete will depend on the cement type used, on the alkali content in the concrete and the presence of water combined with the exposure effects by structural design. It will also depend on the content of the rock type in the aggregate.

- Some aggregates exhibits a pessimum effect, which is the phenomena that when a certain amount of aggregate is reached in the concrete the expansion is at its maximum and larger amounts of aggregate leads to less expansion. Because of the pessimum effect a greater proportion of the particular rock type may not necessarily lead to greater reactivity.


III. Method Petrography, the systematic description of rocks (and concretes) in thin sections, is a basic investigative tool for geologists worldwide. Thin sections are slices of rock/concrete ground down to a thickness of about 30 microns. Usually, the size of the sample to be studied is 50 x 40 x 0,030 mm but larger thin-sections can be prepared. The 30 microns thickness is standard and is necessary for the minerals to become translucent and in order to study the birefringence of the minerals by which they can be identified. The thin sections can be studied under a polarized microscope in varying modes of transmitted light: plane polarized light (PPL), cross-polarized light (XPL) and fluorescent light (FL). The fluorescent mode is obtained by first vacuum-impregnating the sample with an epoxy resin containing a yellow fluorescent dye, and then inserting two filters in the light path of a halogen lamp: an excitation band pass filter (with a maximum transmission of 400 nm) and a suppression long pass filter (with a maximum transmission of 500-550 nm). This mode makes the petrographic technique especially suitable for the study of porosities and microcracking. The result, in PPL view, is a sample embedded in a impregnation resin coloured in yellow, and, in FL view, a sample showing a differential porosity: the more porous the sample, the more intense the yellow-green colour (the non porous particles are nearly black or opaque).


1. Sedimentary rocks 1.1.Sedimentary rocks.

1.1.1. Flint – chert. 1.1.2. Sandstone. 1.1.3. Siltstone. 1.1.4. Greywacke.

1.2. Carbonate rocks. 1.2.1. Limestone.


1.1 Siliceous rocks 1.1.1 Flint - Chert

The term flint is generally used as a synonym of chert. They are rocks consisting of silica in the form of micro- or cryptocrystalline quartz. Primary flint or chert is mainly composed of silica in the form of siliceous organisms such as diatoms, radiolaria and sponges, and secondary flint or chert is calcite minerals in the limestones with silica. Dense flint may contain varying amounts of carbonates which range from small to larger crystals, occuring either individually or within specific areas of the rock. The fluorescence microscopy (FL) doesn’t reveal any porosity. Chalcedony is another form of flint consisting of feathered crystals of microquartz. The porosity of the porous chalcedony and porous flints is revealed by using fluorescent microscopy. Opaline flint consists of isotropic hydrated silica (opal) with varying amounts of associated carbonates. When the carbonate is the major constituent of the rock, it makes the identification of the opaline flint difficult in such rock types. However the fluorescent microscopy can help by revealing the higher porosity of the opaline flint material. The opaline flint in these rocks is constantly black in XPL and bordeaux red in XPL with gypsum plate inserted. 1.1.1-1: Dense flint composed of cryptocrystalline quartz in the center of the photo. The grains are embedded in a yellow impregnation epoxy resin. (PPLx20, picture is 5,8mm wide) 1.1.1-2: (XPLx20, picture is 5,8mm wide).

1.1.1-1 1.1.1-2

1.1.1-3: (XPLGx20, picture is 5,8mm wide). 1.1.1-4. FL reveals the lack of porosity. (FLx20, picture is 5,8mm wide).

1.1.1-3 1.1.1-4

1.1.1-5: Porous flint composed of cryptocrystalline quartz. (PPLx40, pictures are 2,9mm wide) 1.1.1-6: (XPLx40, pictures are 2,9mm wide)

1.1.1-5 1.1.1-6


1.1.1-7: (XPLGx40, pictures are 2,9mm wide) 1.1.1-8: FL reveals a high porosity. (FLx40, pictures are 2,9mm wide)

1.1.1-7 1.1.1-8

1.1.1-9: Grain of opaline flint. (PPLx40, pictures are 2,9mm wide) 1.1.1-10: (XPLx40, pictures are 2,9mm wide)

1.1.1-9 1.1.1-10

1.1.1-11: XPLG with the particular bordeaux colour. (XPLGx40, pictures are 2,9mm wide) 1.1.1-12. FL reveals a high porosity. (FLx40, pictures are 2,9mm wide)

1.1.1-11 1.1.1-12

1.1.1-13: Flints containing varying amounts of carbonates. (PPLx40, pictures are 2,9mm wide) 1.1.1-14: (XPLx40, pictures are 2,9mm wide)

1.1.1-13 1.1.1-14

1.1.1-15: Flints containing varying amounts of carbonates. (PPL x40, pictures are 2,9mm wide) 1.1.1-16: Flint containing carbonates as shown by the creamy colours in this photo. (XPL x40, pictures are 2,9mm wide)

1.1.1-15 1.1.1-16


1.1.1-17: Opaline flint (PPL x40, pictures are 2,9mm wide) 1.1.1-18: Opaline flint (XPL x40, pictures are 2,9mm wide)

1.1.1-17 1.1.1-18

1.1.1-19: Opaline flint (XPLGx40, pictures are 2,9mm wide) 1.1.1-20: Opaline flint (FL x40, pictures are 2,9mm wide)

1.1.1-19 1.1.1-20


1.1.2 Sandstone Sandstones are terrigenous rocks derived from clastic sediments derived from the weathering of pre-existing rocks. These rocks are composed of quartz, feldspar and rock fragments. A matrix makes up the cementing agent for the particles; this latter can be fine-grained and composed of clay minerals or it may be a secondary cement, such as silica or carbonates. The sandstones are classified according to the amount of these components, the amount of the matrix (up or less than 15 %) and the grain size. The main reactive sandstones found in Europe are sandstones with an argillaceous matrix. The recrystallisation of particular minerals (e.g. secondary biotite) and the lineation of some areas of the clayey matrix suggest some degree of low grade metamorphism affecting all these rocks. It’s widely accepted that the reactive components are mainly the very fine-grained sedimentary quartz (micro-cryptocristalline grains) embedded within the clayey matrix. Particular sandstones with an opaline matrix have also been found to be reactive. 1.1.2-1: Fine sandstone with rounded grains cemented partly with recrystallized silica and partly with a cryptocrystalline matrix. (PPLx40, picture is 2,9mm wide). 1.1.2-2: Detail showing the cryptocrystalline matrix. (XPLx100, picture is 1,15mm wide).

1.1.2-1 1.1.2-2

1.1.2-3: Same view of the matrix with the potentially reactive cryptocrystalline quartz. (XPLGx100, picture is 1,15mm wide).

1.1.2-3

1.1.2-4: Very fine sandstone with spots of secondary biotite resulting from a low grade metamorphism; the grains are cemented with a very fine argillaceous matrix. (PPLx40 picture is 2,9mm wide). 1.1.2-5: Same view. The argillaceous matrix acts as a support framework to the potentially micro-cryptocrystalline quartz. (XPLx40, picture is 2,9mm wide).

1.1.2-4 1.1.2-5


1.1.2-6: Detail of 1.1.2.4 showing the fine matrix and biotites. (PPLx100, picture is 1,15mm wide). 1.1.2-7: Same view. (XPLx100, picture is 1,15mm wide).

1.1.2-6 1.1.2-7

1.1.2-8: Medium grained sandstone with rounded clastic grains cemented with a crypto-crystalline clayey matrix. (PPLx20, picture is 5,8mm wide). 1.1.2-9: Same view as 1.1.2.8 (XPLx20, picture is 5,8mm wide).

1.1.2-8 1.1.2-9

1.1.2-10: Medium grained sandstone showing a shistosity affecting the rich-clay matrix layers. (PPLx20, picture is 5,8mm wide). 1.1.2-11: Same view as picture 1.1.2.10. (XPLx20, picture is 5,8mm wide).

1.1.2-10 1.1.2-11 1.1.2-12: Sand grain of opaline sandstone. The grain is embedded in a yellow impregnation epoxy resin. (PPLx20, picture is 5,8mm wide). 1.1.2-13: Same view under fluorescent light showing the high porosity.

1.1.2-12 1.1.2-13


1.1.2-14: Close up detail of 1.1.2.12 showing the different components : siliceous needles and other silica sponge debris and glauconite in an opaline matrix (PPLx40, picture is 2,9mm wide). 1.1.2-15: Same view. (XPLx40, picture is 2,9mm wide).

1.1.2-14 1.1.2-15

1.1.2-16: Same view as 1.1.2.15 (XPLGx40, picture is 2,9mm wide).

1.1.2-16


1.1.3 Siltstone

The siltstones are terrigeneous rocks derived from fine-grained clastic sediments, in which the grain size ranges between 0,0039 and 0,0625mm. They are generally enriched in clay minerals. Like for the sandstone and greywackes, it is widely accepted that the reactive components are mainly the very fine-grained quartz embedded within the clayey matrix. 1.1.3-1: Siltstone : fine grains of quartz and altered feldspars embedded in a argillaceous matrix enriched with opaque oxide minerals. (PPLx40, picture is 2,9mm wide). 1.1.3-2: Same view. (XPLx40, picture is 2,9mm wide).

1.1.3-1 1.1.3-2

1.1.3-3: Homogeneous siltstone containing quartz, chlorite, pyrite, muscovite, calcite and clay minerals (sericite), all cemented together by fine silica and a little calcite. (PPLx40, picture is 2,9mm wide). 1.1.3-4: Same view. (XPLx40, picture is 2,9mm wide).

1.1.3-3 1.1.3-4


1.1.4 Greywacke

Greywacke is a generic term relating to the mode of formation and is generally a complete jumble of particle types with different sizes and shapes cemented by a clayey matrix and like for the sandstone and siltstones, it is widely accepted that the reactive components are mainly the very fine-grained quartz embedded within the clayey matrix. 1.1.4-1: Fine-grained greywacke showing potentially reactive fine quartz and a lot of secondary biotite grains embedded within a clayey matrix. (PPLx40, picture is 2,9mm wide). 1.1.4-2: Same view. (XPLx40, picture is 2,9mm wide).

1.1.4-1 1.1.4-2

1.1.4-3: Poorly sorted greywacke. (PPLx40, picture is 2,9mm wide). 1.1.4-4: Same view. (XPLx40, picture is 2,9mm wide).

1.1.4-3 1.1.4-4

1.1.4-5: Fine-grained greywacke partly cemented with calcite (PPLx40, picture is 2,9mm wide). 1.1.4-6: Same view. (XPLx40, picture is 2,9mm wide).

1.1.4-5 1.1.4-6

1.1.4-7: Grain of fine greywacke showing shistosity. (PPLx20, picture is 5,8mm wide). 1.1.4-8: Detail. (PPLx40, picture is 2,9mm wide).

1.1.4-7 1.1.4-8


1.1.4-9: Same view showing the uniform orientation of the clay minerals composing the matrix. (XPLGx40, picture is 2,9mm wide).

1.1.4-9

1.1.4-10: Poorly sorted greywacke with coarse quartz and altered feldspar grains (sericite) and showing a schistosity. (PPLx20, picture is 5,8mm wide). 1.1.4-11: Same view pointing out the sericite grains. (XPLx20, picture is 5,8mm wide).

1.1.4-10 1.1.4-11

1.1.4-12: Close up view showing the microcrystalline matrix and the sericite. (XPLx100, picture is 1,15mm wide).

1.1.4-12

1.1.4-13: Medium sorted greywacke with very fine to medium coarse grains embedded within the clayey matrix. (PPLx20, picture is 5,8mm wide). 1.1.4-14: Same view emphasizing the secondary biotite. (XPLx20, picture is 5,8mm wide).

1.1.4-13 1.1.4-14


1.2 Carbonate rocks


1.2.1 Limestone Limestones are sedimentary rocks consisting mainly of calcite with variable amounts of dolomite. They are primarly made up of allochems (ooids, bioclasts, pelloids,…) and terrigenous elements (quartz, clays, rock debris). They are classified by comparing the proportions of carbonate mud (micrite), sparry calcite (sparite), and the allochems. The alkali-reactive limestones can be divided into two groups: - The silicified limestones: these rocks are usually packstones, wackestones or mudstones; they are mostly fine dark-grey argillaceous limestones often including fossils debris, some detrital quartz grains and showing some silification. The reactive silica is found under the form of diagenetic micro-cryptocristalline quartz or chalcedony and partially replaces the calcite within the fossils; It can also be found as discrete cryptocrystalline masses within the matrix, or as an infilling to some voids. Often, this limestone type shows dolomitization. The dark colour is usually due to the organic matter. White varieties of such a type of rocks, with less organic matter, are usually found to be reactive too. - Non-silicified limestones : this rock type is similar to the silicified limestone (fine dark-grey argillaceous limestone often with fossils debris and dolomitization), but showing no silicifications. The reactive silica is found, after a specific type of chemical attack, as very fine detrital quartz grains embedded within the argillaceous matrix. Of course, this type of very fine detrital quartz dust can also be found within the silicified limestones. 1.2.1-1: Silicified wackestone with many fossils debris such as echinoids, brachiopods, with a very thin layers of dark organic matter and clays. (PPLx 20, picture is 5,8mm wide). 1.2.1-2. Same limestone: coarse piece of shell completely silicified. (PPLx 20, picture is 5,8mm wide).

1.2.1-1 1.2.1-2

1.2.1-3 & 1.2.1-4: Same views : the calcite of the shell is replaced by the potentially reactive microquartz which is revealed by its low first-order interference colours. (XPL, XPLGx20, pictures are 5,8mm wide).

1.2.1-3 1.2.1-4

1.2.1-5: Grain of a silicified micritic limestone : the grain is embedded in a yellow impregnation epoxy resin. (PPLx20, picture is 5,8mm wide). 1.2.1-6: Detail showing microfossils embedded in a micritic matrix. (PPLx40, picture is 2,9mm wide).

1.2.1-5 1.2.1-6


1.2.1-7 & 1.2.1-8: Same views showing the potentially reactive microsilica within the matrix (low 1’st order interference colours). (XPL, XPLGx40, pictures are 2,9mm wide).

1.2.1-7 1.2.1-8

1.2.1-9: Grain of a silicified sparitic limestone containinga white area of silica. (PPLx20, picture is 5,8mm wide). 1.2.1-10: Same view showing the silicification with some chalce-dony. (XPLx20, picture is 5,8mm wide).

1.2.1-9 1.2.1-10

1.2.1-11: Same view as 1.2.1.10 with gypsum plate inserted. (XPLGx20, picture is 5,8mm wide).

1.2.1-11

1.2.1-12: Silicified micritic limestone with spherulites embedded in the fine matrix. (PPLx40, picture is 2,9mm wide). 1.2.1-13: Same view showing the silicifications of the spherulites. (XPLGx40, picture is 2,9mm wide).

1.2.1-12 1.2.1-13

1.2.1-14: Silicified packestone with a lot of coarse fossils debris now partly silicified. (PPLx20, picture is 5,8mm wide). 1.2.1-15: Same view showing the silicifications. (XPLx20, picture is 5,8mm wide).


1.2.1-14 1.2.1-15 1.2.1-16: Micritic microfacies of the same limestone with fine sized silicifications. (PPLx20, picture is 5,8mm wide). 1.2.1-17: Same view showing the silicifications impregnating the matrix. (XPLx20, picture is 5,8mm wide).

1.2.1-16 1.2.1-17

1.2.1-18: Same view as 1.2.1-17 showing the silicifications impregnating the matrix. (XPLGx20, picture is 5,8mm wide).

1.2.1-18

1.2.1-19: Silicified wackestone with lighter colured uniform areas of silica. (PPLx20, picture is 5,8mm wide). 1.2.1-20: Same view showing chalcedony. (XPLx20, picture are 5,8mm wide).

1.2.1-19 1.2.1-20

1.2.1-21: Same view as 1.2.1.20 showing chalcedony. (XPLGx20, picture are 5,8mm wide).

1.2.1-21


1.2.1-22: View under the SEM of the polished surface of a silicified limestone gently attacked with hydrochloric acid: A fine net of reactive diagenetic silica is clearly visible. To be compared with picture 1.2.1-26. (Picture is 180 µm wide).

1.2.1-22 1.2.1-23

1.2.1-23, 24 & 25: Different microfacies of a highly reactive limestone without silicifications. (PPLx20, x40, x20).

1.2.1-24 1.2.1-25

1.2.1-26 : View under the SEM of the polished surface of a reactive limestone non-silicified limestone which has been gently attacked with hydrochloric acid: there is no diagenetic silica net, but only small amounts of clay are visible. To be compared with picture 1.2.1-22. (Picture is 160 µm wide).

1.2.1-26


2. Metamorphic rocks

2.1. Gneiss. 2.2. Metaquartzite – metagreywacke. 2.3. Phyllite. 2.4. Mylonite 2.5. Cataclasite 2.6. Hornfels


2.1 Gneiss The term “ gneiss” covers a multitude of banded rocks formed during high-grade regional metamorphism of either sedimentary or igneous rocks. These rocks contain a large number of different minerals in variable amounts, but often they are composed of quartz, feldspars, micas and mafic minerals. Generally, gneiss are not reactive, but when micro- or cryptocrystalline quartz are present, they might be potentially reactive. Often strained quartz is a sign of potential reactivity, which might be because it is associated with complex metamorphic suturing and development of microquartz crystals, which is potentially reactive. 2.1-1: General view of a grain of gneiss embedded in a yellow epoxy resin. (PPL x40, picture is 2,9mm wide). 2.1-2: Same view as 2.1-1. (XPL x40, picture is 2,9mm wide.

2.1-1 2.1-2 2.1-3: View of area of microcrystalline quartz in a gneiss. (XPL x100, picture is 1,15mm wide). 2.1-4: General view of micro-crystalline quartz and strained quartz. (XPL x40, picture is 2,9mm wide).

2.1-3 2.1-4

2.1-5: Detailed view of microcrystalline quartz and strained quartz. (XPL x100 picture is 1,15mm wide).

2.1-5

2.1-6: General view of microcrystalline quartz and strained quartz in another grain of gneiss. (XPL x40, picture is 2,9mm wide). 2.1-7: Detailed view of microcrystalline quartz and strained quartz (XPL x100, picture is 1,15mm wide).

2.1-6 2.1-7


2.1-8: Other area in the gneiss (XPL x40, picture is 2,9mm wide). 2.1-9: Microquartz in layer of mica (XPL x100, picture is 1,15mm wide).

2.1-8 2.1-9


2.2 Metaquartzite-metagreywacke Metaquartzite (or quartzite) is a hard metamorphic rock, which was originally a sandstone : under the metamorphism conditions, the original grains have recrystallized along with the former cementing material to form an interlocking mosaic of crystals, mainly quartz and feldspars. Minor amounts of former cementing materials, iron oxide, carbonate and clay, are often recrystalized and have migrated under the pressure to form streaks and lenses within the quartzite. All original textures and structures have usually been erased by the metamorphism. Often, quartzite shows stress features, such as foliation, strained quartz,etc. Generally, quartzite is not reactive but when micro- or cryptocrystalline quartz are present they might be reactive. Metagreywacke has also been found to be reactive. A metagreywacke is a metamorphic rock, which was originally a greywacke. The terms orthoquartzite/quartzite are also used to refer to quartz-arenite (sandstone with more than 95% of quartz) cemented primarily with secondary silica giving a well-imbricated grains structure. 2.2-1: General view of a fine quartzite. (PPL x40, picture is 2,9mm wide). 2.2-2: Same view as 2.5.1. (XPL x40, picture is 2,9mm wide).

2.2-1 2.2-2

2.2-3: Detailed view showing the strained quartz embedded in a matrix of potentially reactive microquartz and mica. (XPL x100, picture is 1,15mm wide). 2.2-4: Same view as 2.5.3. (XPLG x100, picture is 1,15mm wide).

2.2-3 2.2-4

2.2-5: General view of a metaquartzite grain showing strained quartz intergrown with microquartz., (XPL x40, picture is 2,9mm wide). 2.2-6: Detail of the previous photo. (XPL x100, picture is 1,15mm wide).

2.2-5 2.2-6


2.2-7: General view of another metaquartzite grain showing strained and deformed quartz and microquartz. (XPL x40, picture is 2,9mm wide). 2.2-8: Detail view of the pre-vious photo. (XPL x100, picture is 1,15mm wide).

2.2-7 2.2-8

2.2-9: General view of a fine quartzite. (XPL x40, picture is 2,9mm wide). 2.2-10: Another view of the same sample. (XPLG x40, picture is 2,9mm wide).

2.2-9 2.2-10

2.2-11: Detailed view showing the elongated quartz and the potentially reactive microquartz, with some associated layers of muscovite. (XPL x100, picture is 1,15mm wide). 2.2-12: Metagreywacke with finely grained clastic quartz and feldspar components within a dark grey microcrystalline siliceous matrix, considered as potentially reactive. The argillaceous brown-reddish layers form a less pronounced cleavage. (XPLx200, picture is 0.60 mm length).

2.2-11 2.2-12


2.3 Phyllite Phyllite is a metamorphic rock form intermediate between slate and schist. It consists of platy minerals that are larger than those in slate, but still too small to be clearly discernable to the naked eye in terms of grain size. Similar in appearance to slate, it is distinguished from slate by a glossy sheen compared to the dull appearance of slate. It usually exhibits cleavage, but not with the regularity of slate. The rock is often wavy/folded with a great amount of mica. The rock sometimes has a high content of quartz, and when the grain size is less than 60 µm the rock is potentially reactive. Carbonate is sometimes visible in the rock, too. The mica minerals are nearly parallel oriented, and give the rock a schistosity. The reactive minerals are crypto-microcrystalline quartz. 2.3-1: Phyllite : the rock is wavy/foliated with a large proportion of micas and chlorites. (PPLx40, picture is 1.2 mm wide). 2.3-2: Detailed view. (PPLx100, picture is 1.2 mm wide).

2.3-1 2.3-2

2.3-3: Biotite-quartz slate. Finegrained quartz-rich rock with biotite (XPL).

2.3-3

2.3-4: Quartz-phyllite : this wavy/foliated rock contains a large amount of fine and micro-cryptocrystalline quartz grains. (PPLx40, picture is 3.2 mm wide).

2.3-4

2.3-5: Same view. (XPLx40, picture is 3.2mm wide). 2.3-6: Detailed view showing the potentially reactive micro-cryptocrystalline quartz. (XPLx100, picture is 1.2 mm wide).

2.3-5 2.3-6


2.4 Mylonite Mylonite is a foliated (and usually lineated) fine-grained dynamic metamorphic rock of local occurence, which shows evidence for strong ductile deformation. The term is purely structural and gives no indication of the mineralogy of the rock. Thus, a mylonite can be of any rock type and mylonite zones can be found in rocks of all ages and can be of almost any scale. Mylonites have two types of constituents, matrix and porphyroclasts. The matrix is composed of the more ductile platy elements of the rock and of micro- cryptocrystalline minerals, such as quartz minerals. This part of the rock appears almost fluid while the porphyroclasts are the more brittle elements of the rock. A true mylonite will be composed of 10-50% porphyroclasts. The different mylonite types are classified in the literature as followed: primary, secondary, protomylonite, ultramylonite, blastomylonite, layered mylonite and hyalomylonite. The classification is based mainly on the degree of metamorphism and secondarily on the matrix/porphyroclasts ratio. The reactive minerals are crypto-microcrystalline quartz and stressed quartz grains of different sizes within the matrix. . 2.4-1: General view of a mylonite : deformed rock with stressed porphyroclasts of feldspars and quartz. (XPL x20, picture is 5,8mm wide). 2.4-2: Detailed view of porphyroclasts embedded in a micro-cryptocrystalline matrix including the potentially reactive quartz. (XPL x40, picture is 2,9mm wide).

2.4-1 2.4-2

2.4-3: Same view as 2.4-2. (XPLG x40, picture is 2,9mm wide). 2.4-4: Other view of the porphyroclasts and thin layers of mica within the matrix. (XPL x40, picture is 2,9mm wide).

2.4-3 2.4-4

2.4-5, -6: Sericitic gneiss with heterogeneous deformation under retrograde metamorphic conditions of green schist facies. Center: strongly deformed quartz with sutured grain boundaries and undulatory extinction; bottom right: microshear zone with fine granoblastic quartz grains; upper half: sericitic lenses formed from instable plagioclase; dark central grain: potassic feldspar. (XPLx40, picture is 3.85 mm wide).

2.4-5 2.4-6


2.4-7: Another mylonite grain embedded in a yellow epoxy resin : general view showing the porphyroclasts of different sizes. (PPL x40, picture is 2,9mm wide). 2.4-8: Same view as 2.4-5. (PPL x40, picture is 2,9mm wide).

2.4-7 2.4-8

2.4-9: Detailed view of the porphyroclasts and the micro-cryptocrystalline matrix including the potentially reactive quartz grains. (XPL x40, picture is 2,9mm wide).

2.4-9

2.4-10, 11, 12 : General view of another type of mylonite (mylonite/cataclasite) : deformed porphyroclasts embedded in a micro-cryptocrystalline matrix. The dark zones are enriched in organic matter which has migrated under the pressure. (PPL, XPL, XPLG x20, pictures are 5,8mm wide).

2.4-10 2.4-11

2.4-12

2.4-13, 14: Detailed view of the porphyroclasts and the recrystallised clayey matrix including the potentially reactive cryptocrystalline quartz. (XPL, XPLG x100, pictures are 1,15mm wide).

2.4-13 2.4-14


2.5 Cataclasite A cataclasite is a rock, which only has undergone mechanical breakage without showing the plastic deformation and flowage as seen in the mylonites. The rock is brittle deformed and contains randomly distributed and oriented clasts of assorted size from the original rock embedded in a matrix of crypto- to microcrystalline minerals: this matrix contains varying amounts of quartz which lead to the reactivity of the rock. 2.5-1: General view of a cataclasite: coarse sized rock debris embedded in a fine-grained matrix. (PPL x20, picture is 5,8mm wide). 2.5-2: Same view as 2.5.1. (XPL x20, picture is 5,8mm wide).

2.5-1 2.5-2

2.5-3: Detailed view of rocks debris of different sizes embedded within a micro- cryptocrystalline matrix rich in potentially reactive quartz. (XPL x40, picture is 2,9mm wide). 2.5-4: Same view as 2.5.3. (XPLG x40, picture is 2,9mm wide).

2.5-3 2.5-4


2.6 Hornfels Hornfels is a fine-grained rock formed by contact metamorphism. It is characterised by a fine-grained matrix without preferred orientation, in which phenocrysts or clasts can be embedded. Reactive hornfels is found as a rock where the matrix is composed largely of sericite and including potentially reactive micro-cryptocrystalline quartz grains and some feldspars. 2.6-1: Hornfels: general view showing the elongated brow-nish biotite minerals in a very fine-grained groundmass. (PPLx20, picture is 5.2 mm wide). 2.6-2: Same view. (XPLx20, picture is 5.2 mm wide).

2.6-1 2.6-2

2.6-3: Detailed view: the rock mainly consists of quartz, fedspar, biotite and pyroxene. (XPLx100, picture is 1.2 mm wide). 2.6-4: Another view of the same hornfels. (PPLx20, picture is 5.2 mm wide).

2.6-3 2.6-4

2.6-5: Same view: due to the very fine grains, the minerals are hard to be identified. (XPLx20, picture is 5.2 mm wide). 2.6-6: Detailed view showing some potentially reactive micro- and cryptocrystalline quartz grains. The blue minerals are chlorites. (XPLx100, picture is 1.2 mm wide).

2.6-5 2.6-6


3. Igneous rocks

3.1. Basalt and volcanic glass. 3.2. Rhyolite. 3.3. Granite. 3.4. Granodiorite. 3.5. Porphyritic microdiorite.


3.1 Basalt and volcanic glass In the most generalised definition basalts are fine-grained mafic rocks with essential augite, plagioclase and opaque minerals. Basalts are subdivided into tholeiitic basalts and alkali olivine basalts on the basis of the presence or absence of accessory olivine, quartz and low-ca pyroxenes. Olivine tholeiite is almost a fresh silica-undersaturated basalt with no quartz minerals. Tholeiite is oversaturated with silica, which is present as cristobalite and quartz in the groundmass. Basaltic andesite contains nearly 10% of rhyolitic interstitial glass with trace amounts of cristobalite 3.1-1: Tholeiitic basalts Plagioclase with brown glass (palagonite) in between. (PPL, picture is 1,37mm wide). 3.1-2: (XPL, picture is 1,37mm wide).

3.1-1 3.1-2

3.1-3: Tholeiitic basalts Same as above, but brown glass more altered (palagonisation) and coarser grains (XPL, picture is 1,37mm wide). 3.1-4: (XPL, picture is 1,37mm wide).

3.1-3 3.1-4

3.1-5: Volcanic glass Palagonite with minor amounts of feldspar phenocrysts. (PPL, picture is 0,685mm wide). 3.1-6: (XPL, picture is 0,685mm wide).

3.1-5 3.1-6


3.2 Rhyolite A rhyolite is an acid volcanic rock generally containing phenocrysts of quartz and alkali-rich feldspar in a fine-grained or glassy groundmass. Many rhyolites are wholly glassy and some have a high proportion of glass. 3.2-1: Rhyolite: Fine-grained groundmass containing reactive cryptocrystalline quartz. (PPL, picture is 0,69mm wide). 3.2-2: (XPL, picture is 0,69mm wide).

3.2-1 3.2-2


3.3 Granite Granite is the coarse-grained equivalent to rhyolite. Granitic rocks should in general not be regarded as alkali reactive, however microstructural properties due to deformation such as strain lamellas and sub-grain development, which may enhance the suitability for reaction. A second type of ASR in granites can be derived from partial kaolisation of the k-feldspars, which creates micro-crystalline quartz as a bi-product. This quartz can produce an extremely large volume of ASR-gel. 3.3-1: Granite with myrmekitic texture. (XPL, picture is 1,37mm wide). 3.3-2: Granite with strain lamellas. (XPL, picture is 1,37mm wide).

3.4-1 3.4-2

3.3-3: Granite with sub-grain development. (XPL, picture is 1,37mm wide).

3.4-3


3.4 Granodiorite Granodiorite is typically intermediate colored with a subequal mixture of light colored sodium plagioclase/quartz, and dark colored amphibole and biotite. Orthoclase may be present in small amounts. Generally granodiorite is not reactive but when micro- or cryptocrystalline quartz are present they might still be potentially reactive. 3.4-1: Granodiorite. (PPL, picture is 2,75mm wide). 3.4-2: (XPL, picture is 2,75mm wide).

3.3-1 3.3-2


3.5 Porphyritic diorite Porphyritic quartz-rich microdiorite (or dacitic/andesitic metaporphyry) : intrusive rock showing a porphyritic texture with coarse crystals of less than 1 cm size embedded within a fine matrix. The main coarse crystals are plagioclases phenocrysts often weathered into epidotes and/or secondary clay minerals. The chlorites minerals are secondary minerals coming from amphiboles transformation. All these minerals are embedded in a fine-grained matrix composed of micro-cryptocrystalline potentially reactive quartz and feldspars. 3.5-1: Porphyritic quartz-rich microdiorite showing phenocrysts of plagioclases weathered into epidotes embedded in a fine-grained matrix including potentially reactive micro-cryptocrystalline quartz. (PPLx20, picture is 6 mm wide). 3.5-2: Porphyritic quartz-rich microdiorite (XPLx20, picture is 6 mm wide)

3.5-1 3.5-2

3.5-3: Porphyritic quartz-rich microdiorite. Additional view showing green spots of second-dary chlorite and plagioclase altered to sericite, all embedded in a microcrystalline matrix. (PPLx20, picture is 6 mm wide) 3.5-4: Porphyritic quartz-rich microdiorite. (XPLx20, picture is 6 mm wide)

3.5-3 3.5-4


4. Regional Experience

4.1 Sweden Examples of reactive rocks from the same Swedish 0-8 gravel. 4.1-1: Greywacke (XPL) 4.1-2: Mylonite (XPL)

4.1-1 4.1-2

4.1-3: Phyllite (XPL) 4.1-4: Siltstone (XPL)

4.1-3 4.1-4

4.1-5: Strained quartzite (XPL).

4.1-5


4.2 Denmark Examples of reactive Danish aggregates as they appear in concrete. 4.2-1: Opaline flint. Opaline flint, which has reacted and caused cracking of the surrounding concrete. (PPL, picture is 5,3mm wide). 4.2-2: Opaline flint. (FL, picture is 5,3mm wide).

4.2-1 4.2-2

4.2-3: Opaline flint. Opaline flint, which has reacted and caused internal cracking and filling of adjacent pores with gel from ASR. (PPL, picture is 5,3mm wide). 4.2-4: Opaline flint. (FL, picture is 5,3mm wide).

4.2-3 4.2-4

4.2-5: Opaline flint. Opaline flint, which has reacted and caused cracking of the surroundingconcrete. (PPL, picture is 5,3mm wide). 4.2-6: Opaline flint. (FL, picture is 5,3mm wide).

4.2-5 4.2-6

4.2-7: Flint. Dense flint with porous area that has reacted. (XPL, picture is 5,3mm wide). 4.2-8: Flint. (FL, picture is 5,3mm wide).

4.2-7 4.2-8


4.3 Norway Examples of reactive Norwegian aggregates as they appear in concrete. 4.3-1: ASR within a mylonite aggregate: cracks through the aggregate containing ASR gel. (PPLx20, picture is 4,7 mm wide). 4.3-2: Same view showing the micro- cryptocrystalline matrix (PPLx20, picture is 4,7 mm wide).

4.3-1 4.3-2

4.3-3: Detailed view showing the ASR gel filling cracks at the edge of the aggregate. (PPLx100, picture is 0,9 mm wide).

4.3-3

4.3-4: ASR within sandstone aggregates: the cement paste and the aggregate are cracked. (PPLx20, picture is 4,7 mm wide). 4.3-5: Detailed view: the cracks through the aggregates and the cement paste are filled with ASR gel. (PPLx100, picture is 0,9 mm wide).

4.3-4 4.3-5

4.3-6: Other detailed view showing the potentially reactive micro-cryptocrystalline quartz cement surrounding the larger clastic grains. (PPLx20, picture is 5.5 mm wide).

4.3-6


4.3-7: ASR within a greywacke aggregate: airvoids with ASR gel. (PPLx20, picture is 4,7 mm wide). 4.3-8: Same view under cross-polarized light. (XPLx20, picture is 4,7 mm wide).

4.3-7 4.3-8

4.3-9: Detailed view: fine cracks, through the upper part of the greywacke aggregate, containing ASR gel. (PPLx40, picture is 2,4 mm wide). 4.3-10: Same view, under cross-polarized light, highlighting the potentially reactive micro-cryptocristalline matrix of the greywacke. (XPLx20, picture is 4,7 mm wide).

4.3-9 4.3-10

4.3-11: ASR with a rhyolite aggregate: cracks through the aggregate containing ASR gel at the edge of the aggregate. (PPLx20, picture is 4,7 mm wide). 4.3-12: Same view under cross-polarized light: very fine-grained matrix with some large crystals of felspars (left side). (XPLx20, picture is 4,7 mm wide).

4.3-11 4.3-12

4.3-13: Detailed view showing the ASR gel filling cracks at the edge of the aggregate. (PPLx100, picture is 0,9 mm wide).

4.3-13


4.4 Belgium Examples of reactive Belgian aggregates as they appear in concrete. 4.4-1: ASR in a concrete containing a dense flint. (PPLx40, picture is 3.1 mm wide). 4.4-2: Same view, under fluorescent light: the reactive flint does not yet show any porosity but is strongly cracked. (x40, picture is 3.1 mm wide).

4.4-1 4.4-2

4.4-3: ASR in a concrete with a Porphyritic quartz-rich microdiorite. (PPLx20, picture is 6.2 mm wide). 4.4-4: Same view, XPL. (x20, picture is 6.2 mm wide).

4.4-3 4-4-4

4.4-5: Detailed view showing the cracks passing through the porphyry grain and filled with ASR gel. (PPLx100, picture is 1.2 mm wide). 4.4-6: ASR in a concrete containing grains of lower Carboniferous silicified limestone. (PPLx20, picture is 6.2 mm wide).

4.4-5 4.4-6

4.4-7: Detailed view of the ASR gel. (PPLx100, picture is 1.2 mm wide). 4.4-8: ASR in a concrete with two reactive aggregate particles: a siltstone (on the right) and a porphyry (on the left). (PPLx40, picture is 3.1 mm wide).

4.4-7 4.4-8


4.4-9: Same view under XPL. (x40, picture is 3.1 mm wide). 4.4-10: Detailed view showing cracks filled with ASR gel and passing from the reactive grain into the surrounding cement paste. (PPLx100, picture is 1.2 mm wide).

4.4-9 4.4-10

4.4-11: ASR developed in a concrete with a sandstone (lightly metamorphic). (PPLx100, picture is 1.2 mm wide). 4.4-12: Same view, XPLG. (x100, picture is 1.2 mmwide).

4.4-11 4.4-12


References 1. Adams, A.E., MacKenze, W.S. and Guilford, C., 1994. Atlas of sedimentary rocks under the

microscope. Longman, Harlow. 2. Bates, R. L. and Jackson, J.A., 1980. Glossary of Geology, American Geological Institute,

Virginia. 3. Hoinkes, G. and Hauzenberger, C. A., 2005. Metamorphic rocks. Classification, nomenclature and

formation, in Encyclopedia of Geology, Elsevier, Oxford. 4. MacKenzie, W.S., Donaldson, C.H. and Guilford, C., 1982. Atlas of the igneous rocks and their

textures. Longman, Harlow. 5. MacKenzie, W.S. and Guilford, C., 1986. Atlas of rock-forming minerals in thin section.

Longman, Harlow. 6. Yardley, B.W.D., MacKenzie, W.S. and Guilford, C., 1990. Atlas of the metamorphic rocks and

their textures. Longman, Harlow. 7. Lorenzi, G., Guédon-Dubied, S., Antenucci, D., 2001. The status of the reactive silica in the

limestones susceptible to the alkali-silica reaction: contribution of petrographic and SEM techniques. Proceedings of the 8th Euroseminar on Microscopy applied to Building Materials, Athen.

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