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TECHNICAL PAPER

3.2 Concrete Mix Design 4.2 Fresh and Hardened concrete Properties
The concrete recipes used are shown in Table 2. In the 4.2.1 Slump and spreading
recipe with RCA, 37% of the natural coarse aggregate was
replaced by RCA 10/20 mm. Static calculations performed by The results are shown in Table 3. It can be seen that no major
responsible consultant (Reinertsen Engineering ANS) showed differences in the consistency were found between the reference
that a replacement of 40% RCA did not have any detrimental and the concrete with RCA up to 60 minutes.
consequences.
table 3: Consistency measurements of concrete
table 2: Concrete mix design for reference and during 0-60 minutes retention time
concrete with RcA consIs- UnIt c35-n (rEfErEncE) c35-r
tEncy
MAtErIAl UnIt c35-n c35-r 0 30 60 0 30 60
(rEfErEncE) Slump mm 140 - 75 210 190 175

Sand 0/4 mm (machined) kg/m 3 305 297 Spreading mm 350 - 320 520 490 375
Sand 0/8 mm kg/m 3 776 749
4.2.2 Density and air content
Coarse aggregates 12/16 mm kg/m 3 847 494
The density and air content were determined immediately after
RCA 10/20 mm kg/m 3 - 269
mixing, see Table 4. In addition, the density at 28 days hardening
Cement (CEM II/A-V) a kg/m 3 319 341 is shown. It can be seen that the density of C35-R was slightly
Plasticizing agent (Scancem LP) kg/m 3 2 3 lower than the reference, as expected due to the lower density
of the recycled aggregates.
Water kg/m 3 179 191
Effective w/b ratio kg/m 3 0.57 0.57 table 4: Density and air content
a RCA is treated as alkali reactive and low alkali cement from ProPErtIEs UnIt c35-n (rEfErEncE) c35-r
Norcem AS was used
Density (fresh) kg/m 3 2484 2424
Density (28 days) kg/m 3 2436 2383
4. ResUlts
Air content % 1.8 1.7
4.1 Material Properties of RcA
The results obtained from the testing of the RCA are shown in 4.2.3 Compressive strength and modulus of
Table 2. The RCA mainly contained crushed concrete. However, elasticity
a fraction of 4.6% brick was found in addition to insignificant The compressive strength development results are given
amounts of asphalt (less than 1%). The other material properties in Table 5. The concrete with RCA obtained a compressive
were complying to proposed limits at the time of construction.
strength of 91% of the reference strength. A tendency of slightly
decreased strength was obtained, as expected. However, the
table 2: Results from the material testing of RcA concrete fulfilled the designed strength. The average modulus
10/20 mm given as arithmetic mean ± 1 standard of elasticity (EC) for C35-R was found to be lower than the
deviation (n = 3-6) reference.
ProPErtIEs UnIt c35-r
table 5: compressive strength and modulus
Material fractions; concrete and stone % 95 ± 1.7
of elasticity (ec) given as arithmetic mean ± 1
Material fractions; bricks % 4.6 ± 1.3 standard deviation (n = 3-4)
Material fractions; asphalt % 0.4 ± 0.4 PArAMEtEr cUrIng UnIt c35-n c35-r
tIME (rEfEr-
Surface dried density (ρ ) g/cm 3 2.52 ± 0.03
ssd EncE)
Oven dried density (ρ ) g/cm 3 2.41 ± 0.04
rd Compressive strength 7 days MPa 31 ± 5.4 28 ± 2.6
Water absorption % 4.52 ± 0.76 28 days MPa 44 ± 5.2 40 ± 2.7
Chloride content mg/kg 21 ± 8 Modulus of elasticity 7 days GPa 24 ± 0.8 22 ± 1.1
Sulphate content mg/kg 95 ± 19 28 days GPa 28 ± 0.5 25 ± 1.0

32 The IndIan ConCreTe Journal | SepTember 2019