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TECHNICAL PAPER

Table 3: Time to corrosion initiation comparing Table 4: Key predictions considered in LIFE365
manual and LIFE365 values service life modelling

MIXES CALCULATED VALUE OF IT IT FROM LIFE 365 PREDICTION / PARAMETER IMPORTANCE IN SERVICE
LIFE ANALYSIS
SCC 24.76 32.9
Time to Corrosion Initiation Main output – years until chloride
SCCFRA50 14.5 22.3 (it) concentration at rebar depth reaches
SCCFRA100 9.76 s16.7 critical threshold.
HSSCC 40.8 48.2 Cover Depth Effect Shows that increasing cover thickness
significantly delays corrosion initiation.
HSSCCFRA50 28.7 36.8
Diffusion Coefficient (Dapp) Core input – higher D → faster chloride
HSSCCFRA100 20.5 28.7 ingress → shorter service life.
Exposure Severity (Surface Models mild, severe, and extreme
Manual calculation of it for the cover thickness of 40 mm Chloride, Cs) chloride environments for realistic field
assuming Cl th = 0.05 % by weight of concrete and C s = 1 % by conditions.
weight of concrete (for extreme exposure) are carried out and Total Service Life Combines initiation time (it) + constant
found to be similar to values obtained from LIFE 365 as shown in propagation period (≈ 6 years) to give
Table 3. overall service life prediction.
x 2
it = 2
–1
4D c [erf (1– Cl th )] 4. The increase of average pore size and total porosity of
C s
The predicted period to corrosion initiation from LIFE 365 concrete, along with poor properties of old mortar and
was higher compared to the calculated values based on Fick’s ITZ, reduced the resistance to chloride ingress when RFA
second law error function solutions. was incorporated.

The table 4 shows model LIFE365 predicts the time at which 5. Chloride resistance decreased with increasing substitution
corrosion begins by modelling chloride ingress on the basis of rates, as observed from all durability test methods, and
diffusion coefficient, surface chloride concentration, and cover M30-100 exhibited the lowest risk of corrosion
depth. It takes into consideration exposure severity to capture 6. The prediction of service life from LIFE365 showed that it
actual field conditions and included a propagation period to is mainly governed by concrete cover depth, surrounding
estimate total service life. The predictions provide sufficient environmental conditions, and the concrete diffusion
assessment of durability and maximized design of concrete coefficient.
buildings that last longer.
7. It was found that the diffusion coefficient decreased with
7. CONCLUSIONS a decrease in the w/c ratio of concrete, and the diffusion
coefficient for RA-based concretes was higher than that for
1. The impact on fresh and hardened properties of concrete natural aggregate-based concretes.
is more significant at higher replacement proportions of
RFA, which is attributed to the parent material, shape, 8. The deterioration of service life was predicted to be higher
texture, high porosity, high water absorption, and old for complete replacements and standard grade mixes
adhered mortar. among the combinations studied; the error between
2. A decreasing trend for passing ability was observed; predicted and calculated values from Fick’s law was
however, other workability properties like slump flow and negligible due to assumptions in LIFE365, and it was
V-Funnel flow time showed good flow and filling ability concluded that the standard mix had poorer performance
even at 100 % replacement. compared to the high strength mix, while 50 % RFA
incorporation showed slightly better strength, durability,
3. When incorporated, the RFA negatively affected the and service life, making it adaptable for structural
mechanical properties of concrete relative to the control
mix, with a maximum strength loss of about 19 % in purposes.
standard strength mixes and 22.4 % in high strength 9. Concluding on these findings, it is suggested that 50 %
mixes. According to IS: 456 (2000) (Clause 16, Acceptance replacement of RFA could be adopted safely in non-
Criteria), such reductions are substantial because the prestressed reinforced concrete members with moderate
resultant strengths are less than the acceptable codal to severe exposure conditions as long as sufficient cover
thresholds, thus making the mixes non-conforming and thickness (not less than 40 mm) and small w/c ratio
emphasize the real-world consequences of such loss in (not more than 0.40) are observed. Other precautions,
strengths. as adequate pre-soaking of RFA, addition of auxiliary

38 THE INDIAN CONCRETE JOURNAL | FEBRUARY 2026