British Standards and the use of recycled aggregate in concrete...Part 2: Specification for constituent materials and concrete Slide 8 Crushed concrete aggregate Recycled aggregate

Slide 1

British Standards and the use of recycled aggregate in concrete

Chris A Clear BSc PhD CEng MICE FIMMM FICT

Director BRMCAChair BSI Standards Committee Concrete Production and Testing, B/517/1

This webinar is funded by the Royal Academy of Engineering's Frontiers Champion Project.

23 February 2021 12:00

Slide 2

Eurocodes

European Standards are

British Standards

Slide 3

BS EN 206:2013+A1:2016 Concrete — Specification,performance, production and conformity

BS EN BS EN 933-11:2009 Tests for the geometrical properties of aggregates Part 11: Classification test for the constituents of coarse recycled aggregate

BS EN 12620:2002+A1:2008 Aggregates for concrete

BS EN 206:2013+A1:2016

3.1.2.14reclaimed washed aggregateAggregate gained by washing fresh concrete

3.1.2.15reclaimed crushed aggregateaggregate gained by crushing hardened concrete that has not been previously used in construction

Slide 4

Slide 5

5.2.3.3 Reclaimed aggregate(1) Reclaimed aggregate may be used as aggregate for concrete provided it is only used internally by the producer or a group of producers.(2) Reclaimed aggregate shall not be added in quantities greater than 5 % by mass of the total aggregate if they are undivided.(3) Where the quantities of the reclaimed washed aggregates are greater than 5 % by mass of the total aggregate, they shall be divided into separate coarse and fine aggregates and conform to EN 12620.(4) Where the quantities of the reclaimed crushed aggregates are greater than 5 % by mass of the total aggregate they shall be treated as recycled aggregates.

BS EN 206:2013+A1:2016

Slide 6

3.1.2.16recycled aggregateaggregate resulting from the processing of inorganic material previously used in construction

5.2.3.4 Recycled aggregates(1) Recommendations for the use of coarse recycled aggregates are given in Annex E.NOTE No recommendations for the use of fine recycled aggregate are given in this standard.

Annex A Initial tests(9) Where concrete containing recycled aggregates is to be produced, the need to carry out tests to determine the drying shrinkage, creep and modulus of elasticity shall be considered.

Annex E Recommendation for the use of aggregatesNOTE For the risk of alkali-silica reaction with recycled aggregates, see EN 12620:2002+A1:2008, G.3.2.

BS EN 206:2013+A1:2016

Slide 7

BS 8500-1:2015+A2:2019 Concrete –Complementary British Standard to BS EN 206 Part 1: Method of specifying and guidance for the specifier

BS 8500-2:2015+A2:2019 Concrete –Complementary British Standard to BS EN 206 Part 2: Specification for constituent materials and concrete

Slide 8

Crushed concrete aggregate

Recycled aggregate

recycled aggregateaggregate resulting from the processing of inorganic material previously used in construction

Slide 9

Recycling plant – visual assessment on each delivery

Concrete?Masonry?Soil?Glass?Other?Hazardous waste?

Material this clean only

comes from crushing

precast panels

Slide 10

Mobile plant: Crushing & screening

Slide 11

Fixed plant: crushing, air flow screening, washing?

Slide 12

Impurities in aggregates?Historic requirements – ‘Natural aggregates’ specified.

Constituent Limits Test methods Coal, silt and dust

Not to total more than: 1% by weight of coarse aggregate 3% by weight of sand 15% by weight of crushed stone fines (BS 882)

Washing and sieving (BS 812:Part 103)

Shell Not to exceed 20% by weight in aggregate coarser than 5 mm and finer than 10 mm 8% by weight in aggregate coarser than 10 mm

Hand extraction and weighing (BS 812: Part 106)

Acid soluble material

Unspecified Chemical analysis BS 812: Part 119

Slide 13

Determination of the volume of floating particles

1 Plunger2 Water level

Fines, due to increased water demand and likely presence of plaster dust

Acid-soluble sulfate (SO3)

Chloride

Floating material

BS EN 12620 Aggregates for concreteImpurities in aggregates, performance specification

Slide 14

BS EN 933-11:2009 Table 2 — Non-floating constituents of recycled aggregates

Constituent Description

Rc Concrete, concrete products, mortar Concrete masonry units

Ru Unbound aggregates, natural stone Hydraulically bound aggregate

Rb Clay masonry units (i.e. bricks and tiles) Calcium silicate masonry units Aerated non-floating concrete

Rg Glass

X

Other: Cohesive (i.e. clay and soil) Miscellaneous: metal (ferrous and non-ferrous). Non-floating wood, plastic and rubber Gypsum plaster

Slide 15

Aggregate standard - revision BS EN 12620:2002+A1:2008 Aggregates for concrete

BS EN 12620:2013 Aggregates for concrete(Published 31 May 2013,withdrawn 10 January 2014)

Recycled concrete aggregate (RCA) Crushed concrete aggregate (CCA)

Annex G (Informative) Guidance on the effects of some chemical constituents of aggregate on the durability of concrete in which they are incorporated G.3.2 Alkali-silica reaction with recycled aggregates

Annex C (informative) Guidance on the effects of some chemical constituents of aggregates on the durability of concrete in which they are incorporated C.3.2 Alkali-silica reaction with recycled aggregates (including manufactured glass)

The use of recycled aggregates can influence the suitability of the above precautions. In the case of recycled concrete aggregates, it will be necessary to ascertain that the original concrete does not contain reactive (or reacting) aggregate and, where the alkali content of the new concrete (or the cement therein) is being limited, the alkali content of the recycled concrete aggregates will need to be determined and taken into account. In the case of general recycled aggregates, it will be appropriate to regard the material as being a potentially reactive aggregate, unless it has been specifically established to be non-reactive. In both cases, the possibility of unpredictable compositional variability should be considered.

Slide 16

BS 8500-2 Requirements for coarse crushed concrete aggregate (CCA) A)

Properties BS EN 12620 size or category Description of category

Aggregate size d≥4 mm, D≥10 mm B) d/D

Maximum fines f4 ≤4% by mass of particles passing

the 0.063 mm sieve Maximum acid-soluble sulfate (SO3)

AS0,8 ≤0.8% by mass acid soluble

sulfate

Content of: concrete… Rc90 ≥90% by mass

Content of: concrete… hydraulically bound aggregate Rcu90 ≥90% by mass

Content of: Clay masonry units… Rb10- ≤10% by mass

Content of bituminous materials Ra5- ≤5% by mass

Content of other materials… gypsum plaster, and glass XRg1- ≤1% by mass

Floating material by volume FL2- ≤2 cm3/kg A) Where the material to be used is obtained by crushing hardened concrete of known composition that has not been in use, e.g. surplus precast units or returned fresh concrete, and not contaminated by storage or processing, the only requirements are for aggregate size, fines content, drying shrinkage and resistance to fragmentation. B) The designation accepts the presence of some particles which are retained on the upper sieve (oversize) and some which pass the lower sieve (undersize). For single size coarse aggregate with a specified maximum aggregate size of 40 mm, 20 mm, 14 mm and 10 mm the BS EN 12620 aggregate sizes are 20/40, 10/20, 6.3/14 and 4/10 respectively.

Coarse crushed concrete aggregate

Slide 17

BS 8500-2:2015+A2:20194.3.6 Coarse recycled aggregate (RA)Where coarse RA is specified, its use in concrete shall be assessed on a case-by-case basis taking into account its specific composition. The minimum requirements of coarse RA in accordance with BS EN 12620 shall be as given in Table 4.

When determining the maximum chloride and alkali content of concrete containing RA, the chloride and alkali content of coarse RA and its variability shall be established and taken into account.NOTE 1 Clean fine CCA is suitable for use in concrete. However, it is known that some concrete elements have been coated with gypsum plaster, and on crushing most of this gypsum plaster finishes in the fine CCA. This gypsum plaster is known to increase the sulfate content, which in turn can increase the risk of delayed ettringite formation (see BRE Information Paper IP11/01 [5]) and there are great difficulties in detecting localized high volumes of sulfate. In addition there is no information on possible stockpile segregation. For these reasons, the use of fine CCA is left to the project specification, which can take account of the particular source of CCA.

NOTE 2 Some fine RA might also be suitable for use in concrete, but because of the wide range of composition and lack of detailed information, generic requirements cannot be given at present. The comment in Note 1 on gypsum in fine CCA also applies to some sources of fine RA.

Slide 18

BS 8500-2 Requirements for coarse recycled aggregate A) (RA)

Properties BS EN 12620 size or category Description of category

Aggregate size d≥4 mm, D≥10 mm B) d/D

Maximum fines f4 ≤4% by mass of particles

passing the 0.063 mm sieve

Maximum acid-soluble sulfate (SO3) -C by mass acid soluble sulfate

Content of: concrete… RcNR No requirement

Content of: concrete… hydraulically bound aggregate RcuNR No requirement

Content of: Clay masonry units… RbNR No requirement

Content of bituminous materials Ra10- ≤10% by mass

Content of other materials… gypsum plaster, and glass XRg1- ≤1% by mass

Floating material by volume FL2- ≤2 cm3/Kg A) Where the material to be used is obtained by crushing hardened concrete of known composition that has not been in use, e.g. surplus precast units or returned fresh concrete, and not contaminated by storage or processing, the only requirements are for aggregate size, fines content, drying shrinkage and resistance to fragmentation. B) The designation accepts the presence of some particles which are retained on the upper sieve (oversize) and some which pass the lower sieve (undersize). For single size coarse aggregate with a specified maximum aggregate size of 40 mm, 20 mm, 14 mm and 10 mm the BS EN 12620 aggregate sizes are 20/40, 10/20, 6.3/14 and 4/10 respectively. C) The appropriate limit and test method needs to be determined on a case-by-case basis

Recycledaggregate and recycled fines

Difficult to use

due to case-b-

case assessment

and testing

Slide 19

The use of recycled concrete aggregate in structural concreteTransport Research Laboratory. AJJ Calder and CP Roberts. March 2005

• Density and compressive strength

• Dynamic modulus• ShrinkageUp to 20% of coarse crushed concrete aggregate does not significantly affect engineering properties.

Slide 20

BS 8500-2 Limitations on use: of Coarse CCA/RCA and RA

Type of aggregate Maximum

permissible strength classA

Maximum Permitted exposure classesB

Crushed Concrete Aggregate (CCA)

Recycled Concrete Aggregate (RCA)

C40/50

X0 XC1 XC2 XC3/4 XF1 DC-1

No risk of corrosion Very dry Wet, rarely dry Moderate humidity or cyclic wet and dry Moderate saturation without de-icing Non-aggressive ground only

Recycled Aggregate (RA)

Additional specification requirements and permitted applications to be assessed on a case-by-case basis

Notes A

B

CCA/RCA from clean precast units or crushed returned concrete of known composition can be used in any strength class With appropriate testing to ensure suitability for intended environment CCA/RCA may be used in other exposure classes

Limitations on use in concrete to BS 8500. Essentially any

proportion of

coarse aggregate

in benign

environments

may be specified

Slide 21

Limitations on use in Designated concretes concrete to BS 8500. BS 8500-2 Limitations on use of coarse CCA/RCAA in designated concretes

Designated concrete Example of Application Permitted proportion of coarse aggregate

CB6/8 to CB40/50 GEN0-GEN3

RC20/25 to R40/50 FND2 to FND3

PAV1-PAV2

Hardstanding, roadbase Trench fill, unreinforced Reinforced concrete Foundation in aggressive ground Pavement quality concrete

100% 100% 20% 0% 0%

A

It is possible for coarse recycled aggregate in designated concrete in accordance with the above limitations providing the specification for the material includes:

a) maximum acid soluble sulfate; b) method for determination of chloride content; c) classification with respect to alkali-aggregate reactivity; d) method for the determination of alkali content; and e) any limitations on the use in concrete

and that these issues have been addressed, documented and approved by the certification body.

Certification bodies

Slide 22

Recycled aggregate

New World Wildlife Fund Headquarters

Slide 23

C32/40 Piling concrete using 100% secondary aggregates

42,250 tonnes of secondary aggregate used instead of primary aggregates

Bloomberg Headquarters, Skanska.

Slide 24

Summary

Reclaimed washed aggregate – up to 5% unless otherwise specified

Reclaimed crushed concrete aggregate – up to 5% unless otherwise specified

Crushed concrete aggregate (CCA) also known as recycled concrete aggregate (RCA) - Where of known composition and generated from a clean source may be used as natural aggregate, otherwise limitations for strength class and exposure conditions.

Recycled aggregate (RA) May be used but homogenisation, sampling and testing required often precludes use.

Slide 25

Valedictory

Natural aggregates - readily available, tried and tested and may well have a lower carbon footprint than recycled aggregates.For every 100 tonnes of natural aggregates replaced by recycled aggregates for use in concrete, there are 100 tonnes of natural aggregates used for applications where recycled aggregates could have been used.