Page 7 - Open-Access-Jan-2022

TECHNICAL PAPER

Table 2: Concrete mix design, values are given in kg/m 3

PARAMETER M20-Ref M20-RCA M10-Ref M10-RCA
Cement (OPC 53 Grade) 200 200 120 120
Fly ash 100 100 110 110
Natural aggregates 10/20 mm 593 593 558 558
Natural aggregates 4/10 mm 593 593 558 558
Crushed stone sand (CSS) 0/4 mm 791 396 914 -
RCA 0/2 mm - 396 - 914
Total water 204 211 206 222
Superplasticizer 2.40 2.40 1.84 1.84

split was 343 m for M20 and 151 m for M10. The former quality The results for CSS 0/4 mm are the monthly average (30
3
3
was used in the grade slab, whereas the lean concrete was used samples) and a grading within Zone I was obtained for the sieve
in miscellaneous structures (e.g., kerbs and walkways). A total sizes 0.6, 1.18 and 2.36. The quantity of particles smaller than
quantity of 268 tons of fine RCA was consumed in the pilot. The 75 µm was 10% (standard deviation = 1.8%). From the total
Indian standard for coarse and fine aggregate [IS: 383 (2016)] grading performance, the RCA 0/2 mm is considered suitable for
does in principle allow maximum 20% replacement of the fine the concrete mix design chosen in Table 2.
aggregates for reinforced concrete up to grade M25.
4.2 Aggregate properties of RCA 0/2 mm

4. RESULTS The aggregate properties determined are shown in Table 3.
The obtained results complied with all existing limits issued in
4.1 Particle grading IS: 383 (2016). The dissolved silica content and the reduction
in alkalinity were used to assess the alkali aggregate reactivity
The results from the sieve analyses are shown in Figure 3a and
(AAR). The obtained results indicated that the samples were
the grading complied with IS 383 (Zone II). The results for RCA innocuous in nature. Furthermore, low contents of chlorides
0/2 mm are comparable to earlier results on crushed concrete and sulphates were found in the fine RCA sample as well as
produced without washing, shown in Figure 3b . Furthermore, high particle density. The latter is in accordance with the good
[26]
the positive effect of washing can be seen on RCA 0/2 mm, as grade concrete (M40 and M45) used as the feedstock material.
the amounts of particles passing the 0.150 mm sieve were lower The determined WA for CSS 0/4 mm was 2.9 and 4.1% (monthly
than the dry-produced RCA. The quantity of fines (particle size average), which was lower than the RCA 0/2 mm. It can be
less than 75 µm) was 2.9%, which is in accordance with the sieve noted that the WA methods are connected with uncertainty and
analyses. the WA of the produced fine RCA will also vary. Furthermore,

(a) (b)
Figure 3: (a) Results from the sieve analysis of RCA 0/2 mm and CSS 0/4 mm (b) Sieve analysis of crushed concrete (RCA 0/3 mm)
produced with dry crushing process [26]

52 THE INDIAN CONCRETE JOURNAL | JANUARY 2022