Page 118 - ICJ Jan 2023

TECHNICAL PAPER COLLECTOR’S EDITION

Table 5. Permitted exposures (shown highlighted) for: (a) RCA concrete in BS 8500-2 and (b)
for RA concrete prior to revisions to BS 8500-2 in 2003
Exposure description (a) RCA (b) RA
Severity of exposure Severity of exposure

X0 No risk of corrosion or attack XO XO

XC Corrosion induced by carbonation XC-1 XC-2 XC-3 XC-4 XC-1 XC-2 XC-3 XC-4

Corrosion induced by
XD XD-1 XD-2 XD-3 XD-1 XD-2 XD-3
chlorides
Corrosion induced by chlorides
XS XS-1 XS-2 XS-3 XS-1 XS-2 XS-3
(seawater)
XF Freeze/thaw attack XF-1 XF-2 XF-3 XF-4 XF-1 XF-2 XF-3 XF-4

DC Sulfate attack DC-1 DC-2 DC-3 DC-4 DC-1 DC-2 DC-3 DC-4

proved difficult for most producers to produce composition of the proposed RA. The additional
RCA from demolition waste in the UK; although requirements include:
it is recognised that practices differ elsewhere.
Therefore, whilst the use of RCA is permitted by 1. Maximum acid-soluble sulfate.
BS 8500-2, there is insufficient material produced
in the UK to make an impact on the use of natural 2. Method for determination of the chloride
aggregates. content.
3. Classification with respect to alkali-
Table 6. Performance-related requirements aggregate reactivity.
for recycled aggregate H in JIS A 5021:2005
4. Method for determination of the alkali
Property Coarse RA Fine RA
content.
Oven-dry density ≥ 2500 kg/m 3 ≥ 2500 kg/m 3
5. Limitations on use in concrete.
Water absorption ≤ 3.0% ≤ 3.5%
Japanese (JIS) practice
Abrasion ≤ 35
The Japanese approach differs to that in Europe
Material passing 75 mm ≤ 1.0% ≤ 7.0%
sieve in that they have recognised that composition
% of solid volume for ≥ 55 ≥ 57 of recycled aggregate does not necessarily
evaluation of particle reflect performance capability. Consequently,
shape the standards for recycled aggregate in Japan
Chloride ions ≤ 0.04% ≤ 0.04% require measurement and conformity of
physical properties of the recycled aggregate in
In contrast, the range of material quality falling addition to limits for the amounts of deleterious
within the band known as RA is potentially very substances. The Japanese Standards Association
variable, and thus the specification for RA in BS are introducing specifications for three standards
8500-2 has been supplemented by additional of recycled aggregate for concrete. JIS A 5021,
provisions in the project specification based on the established in 2005, is the standard for high-quality
recycled aggregate (H )for concrete, in which the

The Indian Concrete Journal | November 2018 119