Page 5 - ICJ Feb Openaccess 2026

TECHNICAL PAPER

can be attenuated by replacing the M-sand with CandD waste is conducted for a detailed analysis of the effect of the RFA on
by which the carbon footprint can be efficiently reduced. This the concrete internal structure, viewing how these features affect
adoption is not only sustainable but also cost effective as their overall durability and longterm service life. The purpose of this
cost is about 30-40 % less in terms of cost compared to natural research is to determine how RAC can be more suitable and
[3]
aggregates . Thus, it can be a green initiative to include these resilient in construction applications by considering these critical
aggregates in conventional concrete and achieve desirable factors . However, the reason for this decrease was also clearly
[9]
characteristics in optimum proportions. The RA, despite being investigated in the microstructure study by researcher, which was
a beneficial alternative, have inferior quality, which is why the weak interfacial bond development between the aggregate
[4]
they are limited in structural applications . The performance and the cement matrix . The research tried to understand the
[10]
characteristics of RA concrete directly depend upon the crushing performances of concrete with the RFA in terms their durability
process of producing RA and the amount of old mortar that characteristics. Results showed that RFA could lower surface
adheres. Higher water absorption and increased porosity enable electrical resistivity and resistance to chloride penetration by
these aggregates to provide weaken interfacial transition significantly, with high RFA replacements of 30 % or more. On
zone (ITZ) in the concrete matrix. As a result, these factors the other hand, RFA incorporation resulted in increase in CO 2
collectively degrade the structural integrity, the durability and permeability of concrete. This increased porosity was analysed
the mechanical properties of RAC to such a degree that it has through mercury intrusion porosimetry (MIP) by the presence
proved difficult to match the performance of the conventional of old adhered mortar and large voids in the RFA, which had an
[5]
concrete . adverse effect on the durability of the concrete . This paper
[11]
The corrosion process thus is now even more complex due to also subjected the RAC concrete to wetting-drying cycles to
poor resistance to the ingression of harmful substances, which accelerate the process of penetration of chlorides into concrete.
affects the durability of the produced concrete causing an earlier Complete replacements of RCA increased the chloride value to
onset of corrosion and subsequently affecting its service life. All 40 % compared to the nominal mix due to its higher porosity
of these show that a proper understanding of the behaviour and for same w/c ratio and higher penetration was observed due
[12]
performance of RA is essential to adopting them in structural to capillary suction and Cl- ions diffusion . In this article the
concrete. Previous studies indicate that a great amount of RA authors calculated the eventual effect on service life from the
has been used by several countries in recent years to make chloride migration tests by using Fick’s second law diffusion
transition from being only in research into practical use. Though coefficient was obtained using the Nernst-Plank equation and
these applications are applied to lower quality infrastructure the prediction was made both experimentally and by Duracon
projects, such as pavements, shoulders, dams, gutters, and software. It was found that with increasing substitution levels of
bridge foundations. Biswal et al., further contributed to this RA with increasing w/c ratio, the Cl ions take much time to travel
area by proposing a concrete mix design of fly ash and ground through the cover thickness, thereby increasing the diffusion
granulated blast furnace slag (GGBS) along with RA replacement coefficient. The results showed a reduction in service life of
as an alternative to natural aggregate, which is sustainable and about 40 % for concretes with 100 % RCA and about 22 % for
potentially applicable to broader application. Concrete with 50 % RCA .
[13]
30 % fly ash replacement showed less strength whereas 50 %
GGBS replacement showed good long-term results . The loss This study introduces an innovative approach to increasing
[6]
of rheological characteristics over different time intervals was concrete sustainability through the use of RFA as 50 % and
observed in this study at complete replacements of fine RA to 100 % fine aggregate replacement in standard and high strength
[7]
natural aggregates observed from the stress growth test and concrete mixes. Research on RFA have yielded promising
flow curve test and was because of high-water absorption of performance, but there is still much room to investigate the
recycled sand. The authors investigated the effect of recycled combinations with secondary materials like fly ash and GGBS,
coarse aggregates at different percentage replacements and which may potentially improve performance even further.
observed a deterioration of strength up to a maximum of 25 % Valuable information regarding the resilience of these mixes
which was attributed to higher absorption and porosity of RA. may come from expanding durability tests such as acid attack
This phenomenon increased with the proportions of RA and resistance. Further on, a cost analysis would also be useful to
the optimum replacement was 10 % . Using laboratory testing find out the cost effectiveness of RFA based concrete. The
[8]
to evaluate the rheological properties, mechanical strength, findings of this study are expected to go some way towards
and durability of fine RAC and performance under chloride ensuring a more ecofriendly and economical concrete
ingress, this study provides a comprehensive evaluation of the production approach, thereby supporting the implementation of
performance of fine RAC. In addition, a microstructural analysis sustainable construction practice.

26 THE INDIAN CONCRETE JOURNAL | FEBRUARY 2026