Page 117 - ICJ Jan 2023

TECHNICAL PAPER COLLECTOR’S EDITION

2. Manufactured aggregates, are of mineral Constituent Content (% by mass) Category
origin resulting from industrial process
involving thermal or other modification, and < 50 Rcu Declared
No requirement Rcu NR
3. Recycled aggregates, result from the
Rb ≤ 10 Rb
processing of inorganic material previously 10
used in construction. However, BS EN ≤ 30 Rb 30
12620 provides no guidance on how these ≤ 50 Rb 50
different aggregates may be used. > 50 Rb Declared

In 2008, an amendment was made to BS EN 12620 No requirement Rb NR
to introduce a number of categories for coarse Ra ≤ 1 Ra
recycled aggregate based on the proportions of 1-
≤ 5 Ra 5-
unbound stone (Ru), crushed concrete (Rc), crushed
masonry (Rb), bituminous material (Ra), glass (Rg), ≤ 10 Ra 10-
floating material (FL) and other constituents (X). FLs + FLns ≤ 1 FLtotal 1
This is shown in Table 4. ≤ 3 FLtotal 3

FLns ≤ 0.01 FLns 0.01
Table 3. Examples of types of recycled and
secondary aggregate in the UK ≤ 0.05 FLns 0.05

Secondary ≤ 0.1 FLns 0.1
Recycled X+Rg ≤ 0.2 XRg
Manufactured Natural 0.2
≤ 0.5 XRg 0.5
Recycled Recycled glass Slate
concrete Blast furnace slag aggregate ≤ 1 XRg 1
aggregate (RCA) Steel slag China clay
Recycled Pulverized fuel-ash sand
aggregate (RA) Incinerator bottom Colliery spoil BS 8500-2 which defines the constituent materials
Recycled asphalt ash Oil drill that may be used in concrete in the UK permits the
Recycled asphalt Sewage sludge ash cuttings
planings Furnace bottom ash use of all aggregates conforming to BS EN 12620,
Spent railway Used foundry sand including recycled and manufactured aggregates.
8
ballast Spent oil shale
Recycled plastic However, it classifies recycled aggregates
recycled tyres
differently to that of BS EN 12620 as RCA and RA.
Table 4. Categories for constituents of coarse
RA in BS EN 12620: 2008 RCA is obtained from crushing demolished
Constituent Content (% by mass) Category concrete structures, discarded precast elements
and unused hardened concrete, and by definition
Rc ≥ 90 Rc 90
(BS 8500-2) it must be predominately composed
≥ 70 Rc 70 of concrete (at least 83.5% by mass) with no more
< 70 Rc Declared than 5% masonry. Because of the lower proportion
No requirement Rc NR of masonry, the performance characteristics of

Rc+Ru ≥ 90 Rcu 90 RCA are regarded as better than those of RA and
consequently there are fewer restrictions on
≥ 70 Rcu 70
their use in concrete (Table 5). However, because
≥ 50 Rcu 50 of this restriction on masonry content, it has

118 The Indian Concrete Journal | November 2018