alkali-silica reaction guidance for recycled aggregate in concrete

7/31/2019 Alkali-Silica Reaction Guidance for Recycled Aggregate in Concrete

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Aggregate Research Programme/Final Report

Alkali-Silica Reaction Guidance forRecycled Aggregate in Concrete

This report summarises the outcomes of a comprehensive researchproject investigating the effect of recycled aggregates (RAs) on the riskof alkali-silica reaction (ASR) in concrete carried out over 4.5 years.

Project code: MRF 108-001 ISBN: 1-84405-411-XResearch date: August 2008 - January 2009 Date: January 2009


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Front cover photograph: Processing of recycled aggregates (Courtesy of Commercial Recycling, Wimbourne)

WRAP and the University of Dundee believe the content of this report to be correct as at the date of writing.While steps have been taken to ensure accuracy, WRAP cannot accept responsibility or be held liable to anyperson for any loss or damage arising out of or in connection with this information being inaccurate, incomplete ormisleading. For more detail, please refer to WRAPs Terms & Conditions on its web site: www.wrap.org.uk

Published by

Waste & Resources The Old Academy Tel: 01295 819 900 Helpline freephone

Action Programme 21 Horse Fair Fax: 01295 819 911 0808 100 2040

Banbury, Oxon E-mail: [email protected]

OX16 0AH


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ASR Testing on Recycled Aggregates 2

Contents

1.0 Introduction ................................................................................................................................ 51.1 Background ....................................................................................................................... 51.2 Overall Aim and Objectives of the Project ............................................................................. 5

2.0 Experimental Programme ........................................................................................................... 52.1 Phase 1: Classification of RA Components using Rapid Tests .................................................. 62.2 Phase 2: Concrete Expansion Tests (BS 812-123, 38oC) ......................................................... 72.3 Phase 3: Unsheltered External Exposure Site Tests ................................................................ 72.4 Phase 4: Optical Microscopy Assessment .............................................................................. 7

3.0 Test Materials and Assessment Methodologies ......................................................................... 73.1 Materials ........................................................................................................................... 7

3.1.1 Concrete Constituents ............................................................................................ 73.1.4 Laboratory-Produced RAs ........................................................................................ 83.1.5 Site-Produced RAs ................................................................................................. 10

3.2 Test Methods .................................................................................................................... 103.2.1 Bulk Oxide Analysis ............................................................................................... 103.2.2 RA Alkali Release (RILEM/CANMET) ........................................................................ 103.2.3 Mortar Expansion (ASTM C1260) ............................................................................ 123.2.4 Concrete Expansion Tests (BS 812-123, carried out at 38oC and 60oC) ....................... 123.2.5 Unsheltered External Exposure Site Tests and Optical Microscopy Assessment ............ 13

4.0 Phase 1: Classification of RA Components Using Rapid Tests ................................................. 144.1 RA Alkali Release (RILEM/CANMET) .................................................................................... 144.2 Mortar Expansion (ASTM C1260)......................................................................................... 144.3 Concrete Expansion Tests (BS 812-123, carried out at 60oC) ................................................. 21

4.3.1 Reactivity ............................................................................................................. 214.3.2 Alkali Release ....................................................................................................... 27

5.0 Phase 2: Concrete Expansion Tests (BS 812-123, 38oC) ......................................................... 295.1 Reactivity ......................................................................................................................... 29

5.1.1 Fine RA ................................................................................................................ 295.1.2 Coarse RA ............................................................................................................ 29

5.2 Alkali Release .................................................................................................................... 295.3 Additional Tests................................................................................................................. 34

5.3.1 Demolition Materials .............................................................................................. 345.3.2 High Expansion / High Alkali Release Materials ........................................................ 345.3.3 Combination with High Reactivity Aggregates .......................................................... 34

6.0 Phase 3: Unsheltered External Exposure Site Tests ................................................................ 407.0 Phase 4: Optical Microscopy Assessment ................................................................................ 418.0 Conclusions and Practical Implications.................................................................................... 559.0 References ................................................................................................................................ 57


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Executive Summary

This report describes the work of an investigation carried out to examine the influence of recycled aggregate (RA) on

damaging alkali-silica reaction (ASR) in concrete. The experimental programme was carried out in 4 phases. Phase 1

was concerned with identifying, by rapid tests, RAs with a tendency to (i) release alkalis in concrete, which may

contribute to damaging ASR and (ii) exhibit reactive properties. A range of materials, including masonry units, concrete,plaster, road planings and demolition waste were collected and examined for these effects using the RILEM/CANMET

(alkali release) and ASTM C1260 mortar (aggregate reactivity) test methods. The alkali release tests indicate that for

the range of materials, greatest alkali release occurred in masonry units (clay bricks and concrete blocks). Alkali release

from concrete was less than that of the masonry units by typically more than 50%. Demolition waste (concrete and

bricks), while giving similar effects to recently produced material, generally released less alkali. Slate and plasterboard

released least alkali of the RAs tested. The reactivity tests, carried out with the RAs in mortar, indicate that all materials

exhibited expansions of < 0.1 %, (ie innocuous, according to the standard), thereby suggesting little reactivity and risk

of damaging ASR.

A selection of materials from these tests, including masonry units, concrete, mortar, road planings and demolition waste

were used in concrete to replace sand or gravel in a low reactivity aggregate combination (North Fife sand and gravel)

and examined for reactivity, in terms of expansion, using the BS 812-123 test (high alkali content, 7.0 kg/m3), but at a

temperature of 60oC. The results indicate that in almost all cases over the 12 week test period, expansions of less than0.07% were obtained. The exception to this was road planings, which had expansions more than double those of the

other materials tested. Tests under similar conditions on concrete with an alkali content of 5.4 kg/m3 using RA to

replace sand in a normal reactivity aggregate combination (Trent Valley sand and gravel) were carried out to examine

the effect of alkali release from RA. These were designed to establish whether the RA reactivity and their alkali release

would give greater expansion than the normal reactivity aggregate combination. In all cases, except for road planings,

the RAs gave lower expansions than this, with all expansions being less than 0.11% at 12 weeks. A chemical test to

examine for ASR gel in road planing specimens, although inconclusive, suggested that the high expansion may not have

been due to ASR.

In Phase 2, parallel expansion tests, on the same concretes used in Phase 1, were carried out for reactivity and alkali

release using the BS 812-123 method at 38oC for more than 3 years (186 weeks). The results of these tests showed

general agreement with the 60o

C tests in terms of the expansion rankings of the test concretes. It was noted that theroad planings gave similar expansions to the other concretes for both reactivity and alkali release tests in this case. In

the reactivity tests at 52 weeks, all concretes had expansions of less than 0.06% indicating low reactivity. There were

only minor increases in these in the 100+ weeks that measurements were continued for thereafter. In the alkali release

tests, the control concrete (with the normal reactivity aggregate combination) and that with recycled concrete aggregate

previously showing signs of ASR in service (Montrose Bridge concrete) gave greatest expansions of 0.13 and 0.10% at

52 weeks, respectively. The other concretes had expansions of 0.07% or less at this time. Only minor increases in

expansion were noted with these concretes in the test period thereafter.

In Phase 3, expansion tests were carried out on large blocks (500 x 250 x 200 mm) at a local unsheltered external

exposure site, with bricks, road planings and RCA as fine aggregate. These indicate insignificant expansions at 3 years

for both reactivity and alkali release test concretes.

In Phase 4, optical microscopy was carried out on small cores taken from Phase 2 samples exhibiting greatest

expansions, and all of those from Phase 3, to examine for the presence of alkali-silica gel and associated damage.

These indicate that the maximum rim thickness for alkali-silica gel observed around aggregate particles was 14 m, with

most samples giving rims of < 10 m. The microscopy suggests insignificant effects with regard to concrete damage

caused by ASR.

Overall, the results indicate that RAs can contribute alkali to concrete, which was greatest with masonry units. The RAs

when tested in concrete replacing sand or gravel in a low reactivity aggregate combination were found to give low

reactivity. Greatest expansions tended to occur with materials containing reactive aggregates, or which have shown

signs of ASR in their previous applications, e.g. in recycled concrete aggregate. The combination of alkali release and

the reactivity of the RAs when replacing fine aggregate in a normal reactivity aggregate combination gave less expansion

than the control (normal reactivity aggregate combination) concrete.


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Acknowledgements

The Authors would like to acknowledge the advice given in the early part of the project (Phase 1) by representatives of

the following organisations, Waste and Resources Action Programme, Brick Development Association Ltd, Castle Cement

Ltd, Concrete Block Association, Davis Langdon LLP, Gifford and Partners Ltd, H + H Celcon Ltd, Quarry Products

Association, RMC Materials (UK) Ltd and STATS Ltd (who were members of the Project Steering Committee).Mr P Livesey (Castle Cement Ltd) is thanked for his input and discussions in the preparation of this report.


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1.0 Introduction

1.1 BackgroundThe 2003 amendment to BS 8500-2 [1] introduced changes to the provisions to resist damaging alkali-silica reaction

(ASR) in concrete, when recycled concrete aggregate (RCA) and recycled aggregate (RA) are used. The requirementswith respect to RCA were relaxed, with its classification being changed from high reactivity aggregate to normal

reactivity. In addition, a safe assumed alkali contribution from RCA was introduced. However with RA, the new

provisions made it more difficult to use these materials.

Indeed, the British Standards Institution (BSI) was unable to draft provisions for resistance to ASR with RA, given its

very wide range of potential compositions. Consequently, BS 8500-2 [1] requires specifications to include:

Reactivity classification of RA

Alkali contribution from RA

This may be possible when a particular source of RA is to be used, but it is a significant deterrent to the general use of

RA. Moreover, as BS 8500-2 [1] does not contain a full specification for RA, it cannot be included in the permitted

constituent materials for designated concretes.

Coverage of the effect of RA on ASR in the l iterature is limited and there is little information on individual components.

Furthermore, this also indicates differences in behaviour between studies. For example, it has been found that the use

of bricks as fine aggregate, may suppress ASR due to their pozzolanic properties [2]. However, other work suggests

that these components do not appear to reduce the risk of damage [3]. For RCA, it is usually the aggregate used in

recycled concrete that is the main concern [4, 5]. Given the general lack of information and the obstacles highlighted

above, there is a need to examine this issue and to provide appropriate guidance.

The Concrete Technology Unit (CTU), University of Dundee, have carried out several research projects investigating the

use of RCA and RA in construction [5 - 16]. This report describes a four phase investigation to examine the effect of

recycled aggregate on the risk of ASR in concrete. In Phase 1, rapid tests to measure alkali release of RA materials and

their reactivity (expansion) when used in mortar and concrete were carried out to provide an initial assessment of ASRrisk. In Phase 2, parallel expansion tests on concrete using the British Standard method (BS 812-123 [17]) were made.

Phase 3 involved expansion tests at an unsheltered external exposure site (large samples; 500 x 250 x 200mm) on

selected concretes. Phase 4 used optical microscopy to examine for the presence of damaging alkali-silica gel in

concretes tested in Phases 2 and 3. The practical implications of the research were also explored.

1.2 Overall Aim and Objectives of the ProjectThe main aim of this study was to examine, by experimental means, the risk of ASR in concrete for the range of RAs

available, or likely to become available in concrete construction. The project objectives were as follows:

i.

To define the range of compositions of RA and identify whether they release alkalis within an alkali solutionand/or exhibit expansion in a cementitious system. This was intended to establish materials that require

detailed investigation.

ii. To test components that exhibit expansion, in concrete mixes, to determine the level of reactivity.iii. To test components that release alkalis, in concrete mixes, to quantify their influence on the ASR process.iv. To develop guidance on the classification of different RAs and alkali limits in relation to damaging ASR.

2.0 Experimental Programme

The experimental programme was divided into four main phases, carrying out (i) rapid tests to examine alkali release

and reactivity of RA materials, (ii) BS 812-123 [17] concrete tests on RA materials, (iii) unsheltered external exposuresite tests on selected concretes and (iv) optical microscopy to examine for the presence of alkali-silica gel in the

concretes tested during (ii) and (iii).


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Initially a search of the literature was carried out to identify available RAs for testing and to obtain information on their

composition, in particular the presence of reactive silica and likelihood of alkali release. A range of materials were

obtained thereafter for testing including concrete, bricks, blocks and demolition waste. Initial alkali release and mortar

reactivity experiments were carried out on these, in order to identify which materials were likely to represent a risk in

relation to ASR and required further investigation.

The reactivity of various RAs was examined by using these to replace fine or coarse aggregate components in a lowreactivity (aggregate) combination in BS 812-123 [17] concrete mixes (high alkali content). The test procedure

described in this standard was also followed, but at an elevated temperature (60oC), with expansion measurements

carried out for 12 weeks. The alkali contribution of the various RAs was considered using the same exposure conditions

and test procedure, but with RA replacing fine aggregate in a normal reactivity (aggregate) combination. In this case,

the alkali level in concrete was sufficient to cause measurable ASR expansion (for the normal reactivity combination

aggregate) and the test would determine whether the alkali release / reactivity of the RA increased this.

A parallel set of concrete tests (reactivity and alkali release) was carried out using BS 812-123 [17] test conditions

(38oC). Further work using these tests with additional material samples was initiated to address some of the issues

raised in the earlier data generated. In addition, large-scale test specimens were cast with selected materials (covering

both reactivity and alkali release concretes described above) for exposure at a local external site. Optical microscopy

was also carried out to examine for alkali-silica gel in the 38o

C and external exposure tests.

The different phases of the experimental programme are described in greater detail below.

2.1 Phase 1: Classification of RA Components using Rapid Tests

To ensure the study was comprehensive, attempts were made to include all available RAs being used, or likely to be

used in concrete construction in the near future. Reference to the literature, AggRegain Website and discussions with

the steering committee members, lead to the formulation of the following list of materials for inclusion in the project:

Concrete (including that containing reactive aggregates)

Bricks (clay and calcium silicate)

Lightweight concrete blocks

Masonry units containing waste materials

Road (asphalt) planings

Mortar

Plasterboard

Slate

Material samples were obtained from both (i) recently manufactured products and (ii) locally demolished

structures/elements. On receipt, the RA samples were crushed to the required size for the various tests and for

determination of their bulk oxide composition using X-ray fluorescence spectrometry (XRFS).

Alkali release was examined using the RILEM/CANMET test [18], which provides a measure of alkali release in alkali

solution, i.e. corresponding to the pore fluid chemistry of concrete. Alkali-silica reactivity was assessed using theASTM C1260 standard [19], which is a rapid test to assess ASR risk of aggregate. These tests and conditions were

selected in order to enable a rapid assessment to be made.

Testing of RA in concrete followed the BS 812-123 method [17], but at 60oC, with expansion tests up to 12 weeks. It

was intended that testing would focus on RA components used during the RA alkali release / mortar reactivity tests in

Phase 1, where results suggested potential ASR risk. The RAs were used both as fine and coarse aggregate, with a

Na2Oeq in concrete of 7.0 kg/m,controlled by the cement content. Tests with different RA levels (as fine aggregate) to

examine if there was a pessimum proportion of reactive material were also carried out. The aggregate combination

used (components of which RA replaced) in the control concrete was of low reactivity (North Fife sand and gravel) [4].

Similar concrete tests at 60oC were carried out to establish alkali contributions from RA components and their influence

on ASR. The aggregate combination (the sand of which RA replaced) in the control concrete in these tests was of

normal reactivity (Trent Valley sand and gravel). A Na2Oeq in concrete of 5.4 kg/m, controlled by the cement content,sufficient to cause measurable expansion ([20] was used, with alkali contributions from RA ignored in this calculation. If

alkali was released from RA, the expansion would be greater than the control, assuming it was of similar reactivity.


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2.2 Phase 2: Concrete Expansion Tests (BS 812-123, 38oC)Given there can be limitations associated with high temperature testing with regard to ASR behaviour in practice [21],

test series were initiated using the industry accepted BS 812-123 method [17] at 38oC and high humidity. This work

used the same materials and mixes as for the reactivity and alkali release tests made at 60oC and involved periodic

measurements of expansion for up to approximately 3.5 years (186 weeks, ie beyond the 52 weeks required by the

standard [17] or 104 weeks for greywacke aggregates as per BRE Digest 330 [4]) to examine for any long-term effects.

As data was generated, further tests were set up to address some of the issues that these raised. This included testing

of, (i) demolition materials from 4 sites to examine the effect of RA material variability (as fine and coarse aggregate in

concrete), (ii) further RA samples for those showing high reactivity (expansion) / alkali release in the earlier tests

including, road planings and brick and (iii) combinations of RA samples showing similar effects to (ii) in the earlier tests,

including, road planings, brick and recycled concrete, with aggregate likely to have high reactivity (borosilicate glass) as

fine aggregate.

2.3 Phase 3: Unsheltered External Exposure Site TestsIn addition to the tests at 38

o

C, large concrete samples (500 x 250 x 200 mm) were also cast with selected RA materials(road planings, bricks and RCA) using reactivity and alkali release concrete mixes (as above). These had fixed reference

studs attached for expansion testing and were located at a local unsheltered external exposure site. Tests on these

were continued for up to 3 years.

2.4 Phase 4: Optical Microscopy AssessmentOptical microscopy was carried out on small cores removed from the test concretes to assess for the presence of alkali-

silica gel and cracking. The concretes considered were (i) those exposed to 38oC exhibiting greatest expansions at the

conclusion of testing (Phase 2) and (ii) all externally exposed samples (Phase 3).

3.0 Test Materials and Assessment Methodologies

3.1 Materials3.1.1 Concrete Constituents

Portland Cement (PC)

Two Portland cements (PCs) were obtained for inclusion in the test programme. For the ASTM C1260 mortar tests, PC

with a Na2Oeq of 0.6% (low alkali; PC1) was used. For the concrete tests, PC with a Na2Oeq of 1.0% (high alkali; PC2)

was used, thus allowing the alkali content to be readily controlled in the test mixes. The physical and chemical

properties of these materials are given in Table 1.

Natural Aggregates

Two natural aggregates were used for the concrete tests during the experimental programme and were chosen to

provide low and normal reactivity aggregate combinations, according to BRE Digest 330 [4]. These were a North Fife

gravel (10 and 20 mm) and sand, classified as low reactivity and a Trent Valley gravel (10 and 20 mm) and sand,

classified as normal reactivity. Table 2 gives the physical and chemical properties of these materials.

Borosilicate Glass

Borosilicate glass, from laboratory waste and household glassware was used in selected test mixes as a fine aggregate.

This was treated at a processing plant and its physical and chemical properties are also given in Table 2.


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Table 1 Physical and chemical properties of Portland cements used (manufacturers data)

PORTLAND CEMENT

Physical Properties PC1 PC2

Fineness, m/kg 350 360

Loss-On-Ignition, % by mass 0.9 2.5Particle Density, kg/m 3140 3150

Compressive Strength, N/mm

28 day 59.5 52.0

Setting Time, min

Initial 125 130

Soundness, mm 0.6 1

Chemical Properties

Bulk Oxide, % by mass

SiO2 20.8 21.3

Al2O3 5.0 4.9

Fe2O3 2.9 3.3

CaO 63.5 65.0Cl- 0.0 0.1

Na2Oeq 0.6 1.0

Bogue Composition, % by mass

C2S 19.0 15.0

C3S 55.0 61.0

C3A 8.3 7.0

C4AF 8.9 10.0

3.1.4 Laboratory-Produced RAs

Bricks

Commercial bricks from four sources (3 clay (Brick 1, 2 and 3) and a calcium silicate) were used. Bricks 1 and 3 were

obtained locally, while Brick 2 and the calcium silicate brick were sourced from national suppliers.

Blocks/Bricks Containing Waste

Concrete blocks containing incinerator bottom ash aggregate (IBAA), as a total replacement of lightweight aggregate,

were obtained from a national supplier.

Lightweight Concrete Blocks

Recently manufactured (aerated) lightweight concrete blocks were obtained from a national supplier. These blocks hada density of 620 kg/m and a 7-day compressive strength of 4.0 N/mm.

Mortar

A mortar (Designation 1) was produced in the laboratory using mixes given in the BS 5628 [22]. The mortar was mixed,

using PC1, cured to 28 days in water at 20oC before crushing. This was only used selectively in the concrete tests.

Plasterboard

A recently produced gypsum plasterboard was obtained for use as fine aggregate in the alkali release and mortar

reactivity tests. This is subsequently referred to as plaster.


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Table 2 Properties of test aggregates

PROPERTY

AGGREGATE COMBINATION

Normal Reactivity* Low Reactivity* Borosilicate

Glass

Sand 10 mm 20 mm Sand 10 mm 20 mm Sand

Physical Properties

Shape, visual - Rounded - Rounded -

Surface texture, visual - Smooth - Smooth -

Particle density 2.65 2.65 2.64 2.63 2.59 2.59 2.42

Water absorption, %

Lab. dry to SSD

Oven dry to SSD

Oven dry to 10 min

0.4

0.6-

0.6

-

0.2

0.6

-

0.2

0.5

0.6

-

1.3

-

1.0

1.2

-

1.0

-

-

-

Grading, % passing by mass

37.5 mm -- -- 100 -- -- 100 n/t

20 mm -- -- 86 -- -- 92

14 mm -- -- 3 -- 100 45

10 mm 100 100 1 100 93 96.3 mm 99 21 0.3 99 17 2

5 mm 96 6 0.2 84 1 2

2.36 mm 84 0.6 -- 70 1 1

1.18 mm 78 -- -- 56 -- 1

600 m 72 -- -- 36 -- --

300 m 22 -- -- 7 -- --

150 m 1 -- -- 1 -- --

75 m -- -- -- 1 -- --

Bulk Oxide Composition, % by mass

SiO2 91.5 93.6 92.5 78.5 68.7 63.7 68.2

Al2O3 5.8 3.5 5.1 8.4 12.6 15.0 5.3

Fe2O3 0.5 1.4 0.5 3.3 4.9 5.0 0.1CaO 0.2 0.3 0.4 1.9 2.9 4.6 2.3

MgO 0.5 0.0 0.1 1.9 2.9 3.2 0.1

P2O5 0.0 0.0 0.0 --- --- --- 0.0

TiO2 0.2 0.2 0.3 0.6 0.8 0.9 0.0

SO3 0.0 0.1 0.2 --- --- --- 0.2

K2O 1.2 0.8 0.7 1.5 1.8 1.5 1.7

Na2O 0.0 0.0 0.2 1.4 2.4 2.2 6.1

MnO 0.1 0.1 0.1 0.1 0.1 0.1 0.0

Cl- 0 0 0 0 0 0 0

*In accordance with BRE Digest 330 [4], - not applicable, -- all passing / not passing,

n/t particle size distribution not tested, --- not detected

Recycled Aggregate Concrete

Concretes containing low (L) and normal reactivity (N) aggregate combinations were cast in the laboratory with PC1 and

cured for 28 days in water at 20C before use. Different target (cube) strengths were considered, i.e. 25 and 50 N/mm2

(25N and 50N) to determine the effect of variable alkali (cement) content (25NN indicates 25 N/mm concrete with

normal reactivity aggregate, etc). Concretes containing fly ash (FA, 30%) and ground granulated blastfurnace slag

(GGBS, 50%) as additions, known to reduce the risk of ASR, were also examined (in 50 N/mm2 concrete, with the low

reactivity aggregate combination).


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3.1.5 Site-Produced RAs

Recycled Aggregates

A range of materials were obtained from recently demolished structures/elements. All materials were crushed using a

jaw crusher and graded to meet the requirements of the test being carried out, or mix they were being used in. In the

case of the concrete tests, this was similar to the grading or size of the aggregate being replaced.

Demolition Waste

Samples of demolition waste were collected from two sites processing recycled material. Initially a total of five materials

were obtained, namely, 3 concrete samples, including a lightweight concrete, and 2 brick samples. Concrete from

Montrose Bridge (NE Scotland), built during the 1930s (recently demolished, and known to be suffering from ASR) was

also used. Additional samples of RA were later sourced from four sites (Brechin, Dundee, Dundee - 1 and Bristol) for

inclusion in the test programme.

Road Planings

Two road planings samples (Road Planings and Road Planings - 1) were obtained from a local supplier, which had been

recovered (at different times) for recycling and sized to 5, 10 and 20 mm. No details of the material history or

composition were available but the material came from the Tayside area and was likely to use local aggregate sources

(most commonly crushed whinstone).

Slate

Roofing slate was obtained locally from recently demolished housing. This was used as fine aggregate in alkali release

and mortar reactivity tests.

3.2 Test Methods3.2.1 Bulk Oxide Analysis

The bulk oxide analysis of the RAs was determined using a Philips MagiX sequential fluorescence spectrometer (XRFS)with a Rhodium source (the instrument has 10 analysing crystals to cover all elements, with the mA/kV settings of thetube adjusted to best suit the range being analysed) coupled with an auto sampler. Each material was ball-milled andthe fine powder compressed into a standard pellet for analysis.

The bulk oxide analyses of all RA test materials are given in Table 3

3.2.2 RA Alkali Release (RILEM/CANMET)

The alkali release test used was a method developed by RILEM/CANMET [18], which is a procedure for evaluating thealkali contribution of components in concrete. As there was no information on aggregate grading, the materials for this

test were graded as described in the ASTM C1260 Standard [19] for the ASR mortar expansion test (Table 5).

A 25 g sample of each material was placed in a sealed container with 100 ml of either 1N potassium hydroxide (KOH) or

1N sodium hydroxide (NaOH) solution. The container was placed in an oven at a temperature of 80oC for 14 days and

agitated twice a day. At this time, the solutions were filtered and stored until testing.

The K+ and Na+ concentrations of each solution were measured using atomic absorption spectrometry (AAS). This

method enables concentrations of metallic species in solution to be determined.


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Table 3 Bulk oxide composition of RA test materials

MATERIALBULK OXIDE, % by mass

CaO Si2O3 Al2O3 Fe2O3 MgO MnO TiO2 K2O Na2O P2O5 Cl- SO3 Na2Oe

Brick 1 2.9 56.7 17.0 7.5 2.9 0.1 1.0 3.4 1.5 0.2 0.0 0.0 3.7

Brick 2 0.6 57.0 21.0 8.7 1.6 0.2 1.1 2.3 0.5 0.2 0.0 0.0 2.0

Brick 3 2.6 57.9 16.8 7.6 3.0 0.1 1.0 3.6 1.8 1.2 0.0 0.0 4.2

Calcium SilicateBrick

20.8 53.2 6.7 4.2 0.7 0.1 0.4 2.2 0.5 0.1 0.3 0.1 1.9

LightweightConcrete Block

19.8 35.2 17.7 10.9 1.4 0.1 0.9 2.1 0.7 0.3 0.4 1.5 2.1

IBA Block 39.9 24.9 9.8 5.6 1.2 0.1 0.9 1.6 1.1 0.6 0.4 3.1 2.2

25 NL Concrete 38.1 41.7 6.2 2.6 1.6 0.1 0.5 1.1 0.6 0.1 0.0 0.8 1.9

25 NN Concrete 30.9 41.1 7.6 4.0 2.3 0.1 0.6 1.4 1.1 0.1 0.0 0.8 2.1

50 NL Concrete 27.9 45.2 8.3 4.0 2.2 0.1 0.8 1.6 1.2 0.1 0.0 0.6 2.3

50 NN Concrete 38.8 40.8 4.3 2.6 1.3 0.0 0.4 1.2 0.5 0.1 0.0 1.0 1.3

DemolitionConcrete 1

10.5 52.7 14.8 6.6 4.2 0.1 1.3 2.2 2.4 0.3 0.1 0.4 3.8

DemolitionConcrete 2

16.4 55.7 10.7 4.8 1.6 0.1 0.7 2.0 1.5 0.2 0.0 0.5 2.8

Demolition

Brick 1

3.0 57.5 20.8 8.3 0.9 0.6 1.3 1.1 0.2 0.1 0.0 0.0 0.9

DemolitionBrick 2

1.5 39.9 17.2 5.0 0.7 0.1 1.0 1.3 0.2 0.1 0.0 0.1 1.1

DemolitionLightweightConcrete

22.4 33.8 19.7 5.7 1.1 0.1 1.2 0.4 0.2 0.3 0.0 1.3 0.5

Mortar 38.6 37.5 6.7 4.2 0.7 0.1 0.4 2.2 0.5 0.1 0.3 0.1 1.5

Road Planings 6.1 52.6 13.1 6.3 3.6 0.1 1.3 1.7 2.2 0.4 0.1 0.7 3.3

Road Planings -1 8.9 64.0 9.9 4.9 2.5 0.1 0.5 2.0 1.9 0.2 0.0 0.9 3.2

Slate 2.5 63.9 19.3 6.9 2.3 0.1 0.9 3.0 1.8 0.1 0.0 0.1 1.3

Plaster 40.0 0.4 0.3 0.1 0.0 0.0 0.0 0.1 0.0 0.1 0.0 45.3


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3.2.3 Mortar Expansion (ASTM C1260)

Preparation of Materials

Prior to mixing, the aggregate to be tested was crushed to achieve similar grading to that specified in ASTM C1260 [19],

see Table 4 and dried in laboratory air (20C, 55% RH).

Table 4 Grading of aggregate used in RILEM/CANMET alkali release and ASTM C1260 mortar tests

PARTICLES PASSING, % by mass

4.75 mm 2.36 mm 1.18 mm 600 m 300 m 150 m

100 90 65 40 15 0

Mix Proportions

The proportions used for the mortar mixes to determine aggregate reactivity were those given in the standard, see Table

5.

Table 5 Batch proportions used in ASTM C1260 mortar tests

BATCH QUANTITIES, gw/c RATIO

PC1 Aggregate Water*

440 990 205 0.47

* De-ionised water

Casting of Test Specimens

The mortar was prepared, as described in the standard, using a 5 litre capacity planetary mixer, and specimens cast into

steel moulds (3 No. 25 x 25 x 300 mm for each mix) and cured for 24 hours, under a tentage of damp hessian and

plastic sheeting at 20C, 95% RH, prior to demoulding.

Test Procedure

The ASTM C1260 test involves measuring the expansion of test specimens daily over a 16 day period: immersion in

water at 80C for 1 day and 1N NaOH solution at 80C for a further 14 days. Expansion was calculated as that occurring

during the 14 days in alkali solution.

3.2.4 Concrete Expansion Tests (BS 812-123, carried out at 38oC and 60oC)

Concrete Constituent Mix Proportions

BS 812-123 [17] prescribes test concrete mixes on a percentage by volume basis, as follows, PC 22.2%; water 22.8%;

sand 16.5%; 10 mm 16.5%; 20 mm 22.2%. These were used for both Phase 1 and 2, with the mix proportions

determined by mass, by taking account of the particle densities of the constituents (including each of the RAs tested).

As an example, the mix proportions used for the control mix are given in Table 6.

In the case of alkali-release tests, the cement content (540 kg/m3) was fixed to give the required alkali content and the

water content adjusted to maintain the w/c at the BS 812-123 [17] level. Thereafter, the aggregate contents were

derived using the BRE Method for the design of normal mixes [23]. The mix proportions of the control mix for this are

also given in Table 6.


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Table 6 Mix proportions for concrete expansion tests (control concretes)

MIX*

MIX PROPORTIONS, kg/m

w/c Na2OeqPC2 Water

Aggregates

20 mm 10 mm Fine

Reactivity 700 230 575 430 435 0.33 7.0

Alkali-release 540 180 780 395 505 0.33 5.4

*Consistence Class S2 (small dosage of superplasticizer added as required to achieve workability)

Preparation of Test Specimens

All aggregates/RA components in this stage of the work were used after oven drying at 105C to constant mass and

cooling in a desiccator. Prior to use, the RAs were crushed to achieve similar size/grading to the material they replaced.

Calculation of batch quantities involved adjustment to the water content to allow for absorption. As prescribed in the

standard, for fine aggregate water absorption from oven-dry to saturated-surface dry (SSD) was allowed for, whilst for

10 and 20 mm aggregates the water absorbed in 10 minutes was used.

Concrete was prepared, and 4 No. 75 x 75 x 300 mm prisms cast for each of the exposure conditions and cured (20C,

95% RH), as described in the standard. Specimens were demoulded 24 hours after casting, prior to preconditioning and

initiation of testing.

Expansion Measurements

The BS 812-123 test involves periodically measuring expansion of the 75 x 75 x 300 mm specimens during storage in

moist air at 38C (RH >95%). In this study, the tests were carried out according to BS 812-123, but with exposure

temperatures of both 60C (Phase 1) and 38oC (as given in the Standard, Phase 2) used. Immediately after demoulding,

length measurements of the concrete specimens were taken and they were wrapped in moist cloth and plastic sheeting

(which was kept in place throughout the test) and then sealed in air-tight containers above water (RH > 95%). Initially,

the specimens and containers were stored at 20C, prior to transfer at the age of 7 days to the 60C and 38o

C rooms.

Initial expansion measurements were taken and then subsequent tests made at 1, 2, 4, 6, 8, 10 and 12 weeks for those

at 60oC and weekly to 4 weeks and then at 13, 26, 39 and 52 weeks and at regular intervals thereafter for those in the

38oC exposure. In both cases, the specimens were located in a room at 20C for 24 hours, prior to testing length

change. Immediately after testing, the specimens were returned to their containers and appropriate temperature control

room for continued exposure.

BRE Digest 330 [4] provides guidance on the interpretation of BS 812-123 [17] tests at 7.0 kg/m Na2Oeq (38oC) with

regard to aggregate reactivity / expansion risk (based on 52 week expansion), see Table 7. The literature indicates that

the onset of cracking on specimen surfaces may be noted when expansion exceeds a level of 0.05% [21].

Table 7 BS 812-123 Concrete prism test, suggested criteria for interpretation (BSI WG B/502/6/10) [4]

Expansion for up to 12 months,

% of initial length at 7 days

Classification for the aggregate

combination testedAggregate type

> 0.20 Expansive Normal reactivity

0.10 to 0.20 Possibly expansive Normal reactivity> 0.05 to 0.10 Probably non-expansive Low reactivity

0.05 Non-expansive Low reactivity

3.2.5 Unsheltered External Exposure Site Tests and Optical Microscopy Assessment

Details of the external exposure tests and optical microscopy assessment carried out on selected materials and samples

are given in Sections 6.0 and 7.0, respectively.


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4.0 Phase 1: Classification of RA Components Using Rapid Tests

The objectives of Phase 1 of the experimental programme were to carry out tests to identify, by rapid means, RA

materials that may represent a risk in terms of ASR. These tests:

i.

established the levels of alkali released from RAs following the method developed by RILEM/CANMET [18].ii. determined the level of reactivity of the various RAs using the rapid mortar expansion ASTM C1260 test method

[19].

iii. examined reactivity of various materials and the influence of their alkali contribution with regard to ASR inconcrete at 60oC and high humidity

4.1 RA Alkali Release (RILEM/CANMET)The sodium (Na+) and potassium (K+) concentrations for each of the test materials and the alkali released in terms of

Na2Oeq using the RILEM/CANMET test [18], by atomic absorption spectrometry are given in Table 8. The alkali released

is also compared in Figures 1 to 4 for bricks and blocks, concrete, demolition waste and the range of other materials

tested respectively.

For the various materials, released alkali levels increased in the following general order, slate, plaster, road planings,

concrete, bricks and blocks.

With the exception of calcium silicate brick (which released alkali levels of around 0.15% Na2Oeq by mass), the RAs

releasing greatest alkali were recently produced bricks and blocks, which were between 0.47% and 0.61% Na2Oeq by

mass. Bricks from demolition waste had alkali contents of 0.21% and 0.40% Na2Oeq by mass. These were lower than

those recently produced, suggesting differences in compositions and/or production techniques, or possible leaching of

alkalis during service. The alkalis in the bricks may be due to quantities of sodium or potassium present, which are likely

to be in the form of potassium or sodium sulfate. The alkalis in the lightweight concrete blocks will be mainly sourced

from the Portland cement.

Concretes recently produced in the laboratory (PC) and from the demolition waste had alkali contents of between

approximately 0.15 and 0.20% Na2Oeq by mass. Differences between low and high strength concretes were minor and

there were essentially no differences between concretes containing low and normal reactivity aggregates.

In line with their coverage in guidance documents [4], the alkali release of GGBS concrete was lower than that of the

others, while perhaps surprisingly, given its known alkali contribution to concrete [20], the FA concrete was higher (at

0.27% Na2Oeq). The alkali levels of the demolition concrete were slightly lower than those of the laboratory produced

materials, again possibly reflecting constituent material differences or leaching during service.

The results of the other materials indicate similar alkali release levels for road planings to those of concrete, suggesting

that Portland cement may have been used as a filler in the material. The slate and plaster had the lowest levels of the

materials tested of 0.1% Na2O

eqby mass or less.

Comparisons of the total Na2Oeq from XRF tests and those from the RILEM/CANMET [18] alkali release tests are also

given in Table 8. The results indicate that the clay bricks (both recently produced and from demolition waste),

lightweight and IBAA blocks gave the highest relative alkali release, in most cases, in excess of 20%. The recently

produced concretes were generally between 10 and 15%, while those of the demolition waste concretes were around

5%. The calcium silicate brick, slate and road planings all released less than 10% of their total alkali contents.

4.2 Mortar Expansion (ASTM C1260)The results obtained from the mortar expansion ASTM C1260 [19] tests to 14 days are given in Figures 5 to 8. A

comparison between the 14 day results for all materials is given in Table 9 and Figure 9, where the various classes for

quantifying the risk of ASR, according to the ASTM C1260 test method standard are shown. It should be noted that with

this test the alkali content of the solution used is relatively high, such that variations in alkali release between materials


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Table 8 Alkali release results for RAs using RILEM/CANMET test method

MATERIALCONCENTRATION, % by mass of solids

K Na Na2Oe % of Total Na2Oe

Brick 1 0.61 0.11 0.61 16.3

Brick 2 0.51 0.05 0.47 23.4

Calcium Silicate Brick 0.06 0.09 0.16 8.2

Lightweight Concrete Block 0.33 0.16 0.47 22.7

IBAA Block 0.38 0.22 0.60 27.7

FA Concrete 0.08 0.16 0.27 -

GGBS Concrete 0.05 0.05 0.10 -

25 NL Concrete 0.11 0.09 0.20 10.8

25 NN Concrete 0.10 0.08 0.18 9.0

50 NL Concrete 0.10 0.09 0.19 8.7

50 NN Concrete 0.12 0.08 0.20 15.5

Demolition Concrete 1 0.07 0.08 0.15 4.0

Demolition Concrete 2 0.07 0.06 0.14 5.0

Demolition Brick 1 0.23 0.02 0.21 22.8

Demolition Brick 2 0.38 0.07 0.40 38.3

Demolition Lightweight Concrete 0.04 0.04 0.08 16.7

Road Planings 0.02 0.10 0.15 4.6

Slate 0.06 0.02 0.07 5.7

Plaster 0.07 0.03


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0.0

0.2

0.4

0.6

0.8

1.0

FA Concrete GGBS Concrete 25 NL Concrete 25 NN Concrete 50 NL Concrete 50 NN Concrete

ALKALIRELEASE,

%b

ymassofsolids

Figure 2 Alkali release of recycled concretes using RILEM/CANMET test method

0.0

0.2

0.4

0.6

0.8

1.0

Demolition Concrete 1 Demolition Concrete 2 Demolition Brick 1 Demolition Brick 2 Demolition Lightweight

Concrete

ALKAL

IRELEASE,

%b

ymassofsolids

Figure 3 Alkali release of demolition waste using RILEM/CANMET test method


18/60


0.0

0.2

0.4

0.6

0.8

1.0

Road Planings Slate Plaster

ALKALIRELEASE,

%b

ymassofsolids

Figure 4 Alkali release of other RA materials using RILEM/CANMET test method

is unlikely to influence the results and significant expansions will reflect the presence of reactive components in the

aggregates.

In line with expected behaviour, there was a gradual increase in expansion for the various mortars with time (Figures 5

to 8). However, in most cases, by the end of the test period, the expansion development appeared to level off. In

addition, for all RAs, expansions measured by 14 days were all less than 0.06%, indicating that they were all in the

innocuous region, according to ASTM C1260, suggesting low risk of ASR.

Comparisons between bricks and blocks indicate that greatest expansions were recorded in Brick 1 and 2, with

expansions of around 0.05%. The calcium silicate brick gave an expansion of 0.036%, while the lightweight concrete

and IBAA blocks gave expansions of 0.022 and 0.039%, respectively. The expansions of the demolition bricks were

slightly lower than those of the recently produced bricks.

The results obtained for the tests on recycled concrete indicate that these gave a similar range of expansions to those

noted for the masonry units. In this case, least expansion was obtained in the FA and GGBS concretes of around

0.025%. Little difference was found in the tests between low and high strength concretes and between concretes with

normal and low reactivity aggregate combinations. The latter is slightly surprising, but may reflect variations in

quantities of aggregate/paste present in the mortars following crushing to the required grading, between samples.

Indeed, reference to the bulk oxide composition in Table 3 indicates that CaO is higher and SiO2 lower than would be

expected, based on the concrete mix proportions and hence that the concretes (used as RAs) may be paste rich. This

suggests that the characteristics of the concrete and crushing method may influence the composition of RA and

potentially, therefore, impact on ASR. The demolition concretes fell within the range of results for those produced in the

laboratory.

As with the alkali release tests, the road planings gave similar type expansions to those of the recycled concrete as

aggregate. Slate and plaster were at the lower end of the expansions measured for the range of materials examined.


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0.14

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0.18

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0 2 4 6 8 10 12 14 16

TIME, days

EXPANSION,

%o

finitiallength

Brick 1 Brick 2 Calcium Silicate Brick Lightweight Concrete Block IBAA Block

Exposure, 80oC 1N NaOH

Figure 5 Expansion development of mortar containing bricks and blocks (ASTM C1260 test method)

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0.04

0.06

0.08

0.10

0.12

0.14

0.16

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0 2 4 6 8 10 12 14 16

TIME, days

EXP

ANSION,

%o

finitiallength

25NL Concrete 25NN Concrete 50NL Concrete 50NN Concrete PFA Concrete GGBS Concrete

Exposure, 80oC 1N NaOH

Figure 6 Expansion development of mortar containing concrete (ASTM C1260 test method)


20/60


21/60


Table 9 14 day ASR expansion test results (ASTM C1260 test method)

MATERIAL14 DAY EXPANSION,

% of initial length

Brick 1 0.050

Brick 2 0.053

Calcium Silicate Brick 0.036

Lightweight Concrete Block 0.022

IBAA Block 0.039

FA Concrete 0.025

GGBS Concrete 0.024

25 NL Concrete 0.053

25NN Concrete 0.053

50 NL Concrete 0.045

50 NN Concrete 0.048

Demolition Concrete 1 0.030

Demolition Concrete 2 0.036Demolition Brick 1 0.032

Demolition Brick 2 0.046

Demolition Lightweight Concrete 0.044

Road Planings 0.036

Slate 0.023

Plaster 0.028

0.00

0.05

0.10

0.15

0.20

0.25

0.30

Brick

1

Brick

2

Calci

umSilic

ateBr

ick

Ligh

twei

ghtC

oncr

eteBl

ock

IBAA

Blo

ck

FACon

cret

e

GGBS

Con

cret

e

25NL

Conc

rete

25NN

Con

cret

e

50NL

Conc

rete

50NN

Conc

rete

Dem

oliti

onCon

cret

e1

Dem

oliti

onCon

cret

e2

Dem

oliti

onBric

k1

Dem

oliti

onBric

k2

Dem

oliti

onLig

htw

eigh

tCon

cret

e

Road

Pla

ning

sSl

ate

Plaste

r

14DAYEXPANSION,

%o

finitiallength Potentiall deleterious*

Further testin re uired*

Innocuous*

* ASTM limits at 14 days

Figure 9 Comparative behaviour of RAs using ASTM C1260 test method


22/60


4.3 Concrete Expansion Tests (BS 812-123, carried out at 60oC)4.3.1 Reactivity

It was initially intended, in the planning of the test programme, that results from the early tests of Phase 1 would be

used to identify materials that represent a risk in terms of alkali release and expansion with respect to ASR. However, itwas clear that there were only small differences between materials for both tests. It was, therefore, decided that, with

the exception of slate and plaster, samples of the other material types examined would be considered in the expansion

tests carried out on concrete.

The main objective of this part of the work was to examine the reactivity of RA in concrete. Details of the materials

tested during this work are given in Table 10. In all cases, the alkali content of the test concretes was 7.0 kg/m3,

controlled through the cement content.

The majority of the tests included RA as fine aggregate. In these concretes the following RAs were used, Brick 1, 50 NN

concrete, Montrose Bridge concrete, lightweight concrete blocks, IBAA blocks, demolition waste, mortar and road

planings. These replaced all of the fine aggregate (in the low reactivity aggregate combination) of the control concrete.

Tests using RAs to examine the effect of (i) RA as coarse aggregate, using, Brick 1, 50 NN concrete and demolition

waste (i.e. replacing coarse aggregate in the (low reactivity aggregate combination) control concrete), and (ii) RA

content (as fine aggregate) using Brick 1 and IBAA blocks (i.e. replacing different portions of fine aggregate (in the low

reactivity aggregate combination) control concrete)

Table 10 RA materials used in Phase 1 concrete reactivity tests (7.0 kg/m3 Na2Oeq concrete)

RECYCLED AGGREGATE*

RA CONTENT OF AGGREGATE

FRACTION,

by mass

RA as FINE aggregate(combined with coarse aggregate)

50NN Concrete 100%Brick 1 100%

Lightweight Concrete Block 100%

Road Planings 100%

Mortar 100%

IBAA Block 100%

Demolition Waste 100%

Montrose Bridge Concrete 100%

Control -

RA as COARSE aggregate (combined with fine aggregate)

50NN Concrete 100%

Brick 1 100%

Demolition Waste 100%RA as FINE aggregate (combined with a mix of coarse and fine aggregate)

Brick1 25%

Brick1 50%

IBAA Block 25%

IBAA Block 50%

* RA combined as indicated with coarse or fine aggregate (or a mix of these) of the low reactivity aggregate

combination (North Fife sand and gravel)

Fine RA

The results showing the expansion development obtained for the range of materials in the 60

o

C exposure using RA at100% of the fine aggregate are given in Figure 10, whilst the 12 week results from these tests are plotted in Figure 11.

The results indicate that in all cases there was an increase in expansion with time, but at a gradually reducing rate.


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0 2 4 6 8 10 12 14TIME, weeks

EXPANSION,

%o

finitiallen

gth

Control Road Planings Brick 1 50NN Concrete

Demolition IBAA Blocks Lightweight Concrete Blocks Montrose Bridge Concrete

Exposure: 60oC, RH > 95%

Alkali content, 7.0 kg/m

Low reactivity aggregate

Fine aggregate replacement

Figure 10 Expansion development for concrete containing RA as FINE aggregate

(60oC - reactivity test)

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

0.20

Control 50NN

Concrete

Lightweight

Concrete

Block

Road Planings Demolition

Waste

Montrose

Bridge

Concrete

Brick 1 IBAA Block

12WEEK

EXPANSION,

%o

finitiallength

Exposure: 60o

C, RH > 95%Alkali content, 7.0 kg/m



Figure 11 12 week expansion for concrete containing RA as FINE aggregate



24/60


The expansion ranking for the materials at 12 weeks, lowest to highest was Brick 1, IBAA block, demolition waste,

control, lightweight concrete block, Montrose Bridge concrete, 50 NN concrete and road planings. In the majority of

cases, the concretes exhibited expansions of less that 0.07% compared to their initial length, by the conclusion of the

tests. The exception to this was the road planings, which had expansions more than double those of the other

concretes.

It is unclear whether the high expansion of road planings was caused by ASR, or some other effect. For example, roadsurface courses can comprise greywacke aggregates or similar, which may be susceptible to ASR. The test temperature

could also have influenced the volume stability of the aggregate, although high expansions were not observed in the

ASTM C1260 tests. In order to examine this further, it was decided to use a chemical test method on one of the road

planing test specimens to establish the presence of ASR products or not. The technique used was the dual staining

method described by Guthrie and Carey [24], where the abundance and distribution of potassium and calcium

(chemically distinct ASR gel products) is identified.

One of the ASR test prisms was sawn in half and then rinsed with de-ionised water. It was then treated with the

staining solutions in the following sequence:

rinse - sodium cobaltinitrate treatment rinse rhodamine B treatment - rinse

After rinsing, stained regions can be observed (yellow potassium, and pink calcium) and are normally concentrated

at the paste / aggregate interfaces and cracks if ASR is occurring.

The results of this test indicate minor yellow staining and uniform distribution of pink staining. While not conclusive,

these suggest that ASR is unlikely to be occurring.

Overall the results indicate that (with the exception of road planings) IBAA blocks, Brick 1 and demolition waste all had

lower expansions than the control, while those containing normal reactivity aggregate (50NN concrete), lightweight

concrete block and that with aggregate known previously to have exhibited ASR (Montrose Bridge concrete) were only

0.01 to 0.02% higher.

Coarse RA

The expansion results from tests on selected materials carried out with 100% replacement of coarse aggregate with RA

are given in Figures 12 and 13. The results are similar to those obtained for the corresponding tests with fine RA, in

terms of expansion development with time, and ranking of the various materials. This is despite greater quantities of

(coarse) RA in these concretes. The results suggest that little or no effect of particle size in relation to ASR damage.

RA Content

The results obtained on selected RAs (Brick 1 and IBAA blocks) tested to examine the effect of aggregate content in

concrete and whether there is a pessimum proportion with respect to ASR are given in Figures 14 and 15. The 12 week

results are compared in Figures 16 and 17.

The data indicate, for both materials, that the low expansions found for the tests with 100% RA were also noted for the25 and 50% levels tested, and these were essentially indistinguishable at the different RA levels, suggesting that there is

no pessimum proportion.


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0 2 4 6 8 10 12 14

TIME, weeks

EXPANSION,

%o

finitiallength

Control Brick 1 50NN Concrete Demolition Waste




Coarse aggregate replacement

Figure 12 Expansion development for concrete containing RA as COARSE aggregate


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0.18

0.20

Control 50NN Concrete Demolition Waste Brick 1

12WEEK

EXPANSION,

%o

finitiallength


Alkali content, 7.0 kg/mLow reactivity aggregate


Figure 13 12 week expansion for concrete containing RA as COARSE aggregate



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TIME, weeks

EXPANSION,

%o

finitiallength

Control 25% Brick 50% Brick 100% Brick





Figure 14 Expansion development for concrete containing different levels of Brick 1 as FINE aggregate


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0 2 4 6 8 10 12 14

TIME, weeks

EX

PANSION,

%o

finitiallength

Control 25% IBAA Block 50% IBAA Block 100% IBAA Block





Figure 15 Expansion development for concrete containing different levels of IBAA as FINE aggregate



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Control 25% Brick 1 50% Brick 1 100% Brick 1

12WEEKEXPANSION,

%o

finitiallengt

h





Figure 16 12 week expansion for concrete containing different levels of Brick 1 as FINE aggregate


0.00

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0.08

0.10

0.12

0.14

0.16

0.18

0.20

Control 25% IBAA Block 50% IBAA Block 100% IBAA Block

12WEEK

EXPANSION,

%o

finitiallength




Figure 17 12 week expansion for concrete containing different levels of IBAA as FINE aggregate



28/60


4.3.2 Alkali Release

This work was concerned with establishing alkali contributions from RA to the ASR process. Details of the materials

tested during this part of the work are given in Table 11.

In all cases, tests used RA to replace the fine aggregate of the normal reactivity aggregate combination control. The

alkali content of the test concretes was 5.4 kg/m3 controlled through the cement content, which related work has shown

[20] is sufficient to cause measurable expansion due to ASR with the aggregate combination being used. Therefore, any

alkali contribution from the RA, should lead to increased expansions compared to the control, assuming it has similar

reactivity to the aggregate it replaces.

Table 11 RA materials used in Phase 1 concrete alkali release tests (5.4 kg/m3 Na2Oeq concrete)

RECYCLED AGGREGATE*

RA CONTENT OF AGGREGATE

FRACTION,

by mass

RA as FINE aggregate(combined with coarse aggregate)50NN Concrete 100%

Brick 1 100%

Lightweight Concrete Block 100%

Road Planings 100%

Mortar 100%

IBAA Block 100%

Demolition Waste 100%

Montrose Bridge Concrete 100%

Control -

* RA combined as indicated with coarse aggregate of the normal reactivity aggregate

combination (Trent Valley gravel)

The results obtained from the tests to examine the influence of alkali release from the RAs on the expansion due to ASR

are given against time in Figure 18. A comparison of the 12 week results is made in Figure 19.

The results indicate that the general behaviour, noted previously in Section 4.3.1 of increasing expansion with time was

also noted. While in some cases, expansion rates reduced with exposure period, in others, particularly those at higher

expansion levels, it remained approximately constant during the 12 week test period, suggesting expansion would

continue beyond the conclusion of the tests.

The concrete showing greatest expansion was (as with the reactivity tests) that of road planings. The expansion ranking

for the other materials from lowest to highest was Brick 1, demolition waste, 50 NN concrete, IBAA block, Montrose

Bridge concrete, mortar, lightweight concrete block and the control, which was just lower than that of the road planings.

The expansions noted were, in the main, slightly greater than in Phase 1, reflecting the combination of RAs with normal

reactivity coarse aggregate (albeit with a lower alkali content). With the exception of the control, road planings and

lightweight concrete block, which had expansions of between approximately 0.11% and 0.14% at 12 weeks, in the

majority of cases, expansions at the test conclusion were less than 0.08%.

The results therefore suggest that the combined effect of alkali release and reactivity of the RAs used (excluding road

planings) gave less expansion than that of the (normal reactivity aggregate combination) control concrete mixes.


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0 2 4 6 8 10 12 14

TIME, weeks

EXPANSION,

%o

finitiallen

gth

Control Road Planings Brick 1

50NN Concrete Demolition IBAA Blocks

Lightweight Concrete Blocks Mortar Montrose Bridge Concrete



Normal reactivity aggregate


Figure 18 Expansion development of concrete containing RA as FINE aggregate

(60oC - alkali-release test)

0.00

0.02

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0.08

0.10

0.12

0.14

0.16

0.18

0.20

Control 50NN

Concrete

Lightweight

Concrete

Block

Road

Planings

Demolition

Waste

Montrose

Bridge

Concrete

Brick 1 IBAA Block Mortar

12WEE

KEXPANSION,

%o

finitiallength

Exposure: 60

o

C, RH > 95%Alkali content, 5.4 kg/m



Figure 19 12 weeks expansion of concrete containing RA as FINE aggregate

(60o

C - alkali-release test)


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5.0 Phase 2: Concrete Expansion Tests (BS 812-123, 38oC)

5.1 Reactivity5.1.1 Fine RA

The results showing the expansion development for the range of materials in the 38oC reactivity tests (Na2Oeq ,

7.0 kg/m3), with RA replacing the fine aggregate of the low reactivity aggregate combination are given in Figure 20,

whilst the 52 week results from these tests are compared in Figure 21.

The results indicate gradual increases in expansion with time for all materials. It was noted that the ranking obtained at

52 weeks broadly followed that of the 60oC tests, (ie, least to highest Brick 1, IBAA block, demolition waste, control,

road planings, lightweight concrete block, Montrose Bridge concrete and 50NN concrete). With the exception of

Montrose Bridge concrete and 50NN concrete, the expansions at 52 weeks for all other materials (Brick 1, IBAA block,

demolition waste, control, road planings and lightweight concrete block) were less than 0.05%, indicating that these

materials are of low reactivity and non-expansive according to the BRE Digest 330 classification [4]. Montrose Bridge

and 50NN concretes had expansions between 0.05 and 0.06% and were therefore in the low reactivity and probably

non-expansive class [4]. The results also suggest that the effects noted at 60oC for road planings were probably not due

to ASR.

While, there was a general levelling off of results beyond 52 weeks, the changes in expansion with time indicate some

differences between materials. Indeed, by 186 weeks the ranking order, least to highest was road planings, lightweight

concrete block, 50NN concrete, control, IBAA block, Brick 1, Montrose Bridge concrete and demolition waste, and

expansions were all between approximately 0.06% and 0.09%. While all still gave relatively low expansions, this

indicates some differences in reaction rates between materials with time.

5.1.2 Coarse RA

The corresponding expansion results with coarse RA in concrete at 38oC are given in Figures 22 and 23. As noted for

fine RA, these gave gradual increases in expansion over the test period. The ranking of the concretes in this case, from

lowest to highest expansion was demolition waste, control, bricks and 50 NN concrete. All of the test concretes at 52weeks were in the low-reactivity and non-expansive class according to BRE Digest 330 (< 0.05%) [4]. By the end of the

test period all of the test concretes had expansions of between 0.05 and 0.08%, with 50NN concrete slightly higher. As

noted at 60oC, similar results were obtained for the RA as fine and coarse aggregate.

5.2 Alkali ReleaseThe corresponding tests carried out on concretes at 38oC to 52 weeks and beyond for alkali release are given in

Figures 24 and 25. In this case, the control was that taken from a related study [20] with the same aggregates and

alkali content (and similar mix proportions to those used in the current study). In these tests, the ranking from lowest

to highest expansion was as follows, Brick 1, demolition waste, lightweight concrete blocks, road planings, IBAA block,

50NN concrete, Montrose Bridge concrete and the control. This indicates some difference compared to thecorresponding tests at 60oC. Indeed, the road planings at 38oC gave expansions in the middle of the range for the RA

materials and not significantly higher, as noted at 60oC. In this case at 52 weeks, Brick 1, lightweight concrete block

and demolition waste all exhibited expansions of less than 0.05%, while, road planings, IBAA block, and 50 NN concrete

were between 0.05 and 0.10 % and Montrose Bridge concrete marginally above 0.10% and the control 0.13%. The

results from the tests at both temperatures indicate that expansions were less than that of the control. In the tests

carried out to 186 weeks, the expansions for all materials, with the exception of Montrose Bridge concrete, were less

than 0.10%.

In order to examine the influence of alkali contribution from the RAs used, the RA alkali release (from Phase 1) was

plotted against the expansions recorded at 60oC and 38oC at 12 and 52 weeks respectively and this is shown in

Figure 26. The results indicate that there appears to be no noticeable effect of alkali release on expansion and those

materials, which release alkali, do not when replacing fine aggregate in the normal reactivity combination increase this

beyond that of the control concrete. The relationship between 60oC and 38oC testing regimes is shown in Figure 27 and

indicates that while there is general agreement between these, the expansions do not have a strong correlation.


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Lightweight Concrete Blocks Montrose Bridge Concrete





Figure 20 Expansion development for concrete containing RA as FINE aggregate

(38oC reactivity test)

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Figure 22 Expansion development for concrete containing RA as COARSE aggregate


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Figure 23 52 week expansion for concrete containing RA as COARSE aggregate



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Figure 24 Expansion development of concrete containing RA as FINE aggregate

(38oC alkali-release test)

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Brick 1, 60oC Lightweight Concrete Block, 38oC Lightweight Concrete Block, 60oC

IBAA Block, 38oC IBAA Block, 60oC Demolition Waste, 38oC

Demolition Waste, 60oC Road Planings, 38oC Road Planings, 60oC

50NN Concrete, 38oC 50NN Concrete, 60oC

Figure 26 Relationship between alkali release of RAs and 12 and 52 week expansion for RA

as FINE aggregate in concrete (38oC and 60oC - alkali release tests)

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EXPANSIONAT12WEEKS(60OC),%

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Alkali content, 5.4 kg/mNormal reactivity aggregate


Road Planings

Figure 27 Relationship between concrete expansions for 38oC (52 week) and 60oC (12 week) test regimes


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5.3 Additional Tests

5.3.1 Demolition Materials

In order to examine the effect of material variability of combined RAs, demolition material was obtained from four sites

(Brechin, Dundee, Dundee -1 and Bristol) and used in reactivity tests. The concretes tested had a Na2O

eqof 7.0 kg/m,

with RA used as both fine and coarse aggregate (replacing these in the low reactivity aggregate combination). The

expansion development of these is shown in Figures 28 and 29 respectively.

The results indicate that by 52 weeks, the majority of RAs had expansions less than the BRE Digest 330 [4] limit of

0.05% for non-expansive / low reactivity aggregates (Figures 30 and 31). By 130 weeks all specimens had expansions

of less 0.08%. There was very little difference in behaviour between fine and coarse RAs in concrete, although the

rankings changed slightly. The results also gave general agreement with those described above with the other RA

materials.

5.3.2 High Expansion / High Alkali Release Materials

Additional samples of material exhibiting either high expansion or alkali release were obtained, (i.e. road planings and

brick) and used as fine aggregate (replacing this in the low and normal reactivity aggregate combinations) in concrete

with Na2Oeq of 7.0 kg/m and 5.4 kg/m. The results from these tests are shown in Figures 32 and 33.

The tests with road planings indicate that at both alkali contents and aggregate combinations, the results were generally

similar at around 0.05 to 0.06% at 52 weeks. By 104 weeks, expansions were between 0.06 and 0.08%, with the newer

sample (Road Planings -1) giving slightly higher expansion in the 7.0 kg/m concrete.

The tests with Bricks 1 and 3 in concrete with Na2Oeq of 7.0 kg/m and 5.4 kg/m indicate that while Brick 1 had

expansions of around 0.025 and 0.03% at 52 weeks, Brick 3 was around 0.06%. While Brick 1 exhibited only minor

changes at subsequent test ages, Brick 3 increased to levels of around 0.08% by 104 weeks. Chemically Brick 3 had a

slightly higher alkali content than Brick 1, but the two bricks were otherwise similar. These differences in expansion

between bricks are unlikely to have any practical significance.

5.3.3 Combination with High Reactivity Aggregates

In these tests coarse RA found in the earlier work to exhibit relatively high reactivity (expansions) or to release alkalis

(i.e. road planings, brick and recycled concrete) were combined with fine aggregate (borosilicate glass) which in previous

studies has given high expansions with respect to ASR [25]. These were tested in concrete with Na2Oeq of 7.0 kg/m

and 5.4 kg/m with the coarse aggregate of the low and normal reactivity combinations also tested. The results from

these tests are shown in Figures 34 and 35.

These indicate that at 52 weeks all alkali contents / aggregate combinations gave expansions of between 0.05 and

0.08% by 52 weeks. For both tests the concrete containing the coarse aggregate of the low and normal reactivitycombinations were similar and had higher expansions than the RAs considered. It also appeared that in considering the

reactivity of the borosilicate glass, this lay somewhere between the North Fife and Trent Valley aggregates (and was not

as reactive (expansive) as expected).

It is apparent that between 52 and 104 weeks, there were further increases in expansion of about 0.02 to 0.03%, but all

were 0.10% or less by 104 weeks.


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Figure 28 Expansion development of concrete containing demolition materials as FINE aggregate


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Figure 29 Expansion development of concrete containing demolition materials as COARSE aggregate



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Figure 30 52 weeks expansion of concrete containing demolition materials as FINE aggregate


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Figure 31 52 weeks expansion of concrete containing demolition materials as COARSE aggregate



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Figure 32 Expansion development for high reactivity / high alkali release materials as FINE aggregate



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Figure 33 Expansion development for high reactivity / high alkali release materials as FINE aggregate



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Glass aggregate


Figure 34 Expansion development for glass FINE / RA COARSE aggregate concretes


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Figure 35 Expansion development for glass FINE / RA COARSE aggregate concretes

(38oC alkali-rele

alkali-silica reaction guidance for recycled aggregate in concrete

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