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TECHNICAL PAPER COLLECTOR’S EDITION

Table I : Properties of recycled aggregate and recycled aggregate concrete (RAC)

Author and year Properties of recycled concrete aggregate
Density, Water Crushing Abrasion Percentage reduction
kg/m 3 absorption, value, value, in strength of RAC
kg/m 3 percent percent compared to original
concrete
Malhotra (1976) 3 2500-2530 3.9-4.4 CA 18 26 10-20
7.9-9.6 FA

Buck (1976) 4 2590 2.3-4.5 CA - - -
BCSJ (1978) 15 1970-2140 3.6-8 CA 22 36.5 14-32
8.3-12 FA
Nixon (1978) 6 2430 CA - - - 20.0
Hasaba and others (1981) 7 2430 CA 7CA 23.0 HSC - 12.0
11 FA 24.6 LSC
- 7 - -
Wesche and Schulz (1982) 2 - - - 10.0
Hansen and Narud (1983) 8 2490 8.7-3.7 6-12 41.4HSC 22.0
22.4 LSC
Gerardu and Hendricks (1985) 9 8 5.0
Ravindrarajah and Tam (1985) 10 2440-2460 4.5-5.4 8-12 29 8-12
HSC - High strength concrete LSC - Low strength concrete

Tests on recycled aggregate concrete through compacting factor for original and
Ordinary Portland cement (43 grade) and natural recycled aggregate concrete. 32 cubes were cast
river sand passing IS sieve no.480, were used for for each of the four mix proportions using fresh
production of parent (reference) specimen and granite aggregate, out of which six each were for
recycled aggregate concretes. Crushed granite 7 and 14 day strength tests and twenty cubes were
having a maximum size of 25 mm was used as for 28-day strength test. Eighteen cubes were cast
coarse aggregate in the reference concrete. As a for each of the four proportions with three recycled
first step, in order to study the relative strength aggregates for carrying out compressive strength
characteristics of aggregates obtained from tests on six cubes at 7, 14 and 28-day for each mix.
recycled concrete and masonry, four nominal These amount to a total of 344 cubes for the first
mixes of concrete, viz., 1:1½:3, 1:2:4, 1:3:5 and 1:4:7 stage of investigation.
were produced using fresh granite aggregate and
the three types of recycled aggregates described In the second stage of investigation, a study
earlier. on use of recycled aggregate from concrete of
known strengths was attempted. The objective
In order to maintain uniform quality during of this study was to establish clearly as to what
concrete production, aggregates were pre-soaked extent the properties of parent concrete (from
in order to compensate the high water absorption which the recycled aggregate is made) influences
of recycled concrete and brick masonry aggregates. the strength of recycled aggregate concrete. For
The water requirement for each of the four nominal this purpose, 20 concrete cubes, made with fresh
mixes have been decided based on a compacting granite aggregate, that were available after 28-day
factor of around 0.85 (that is, a pre-decided low compression tests (that is, after establishing their
value to suit recycled concrete brick production). strengths) from the first stage of investigation
Properties of fresh concrete have been measured were used. The concrete cubes of each of the four

The Indian Concrete Journal | November 2018 77