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TECHNICAL PAPER

and landed cost of SCM used in trial i, cost of test j, number of 3. INSIGHTS ON NEW MATERIALS AND
trials, number of tests, and data set k based on previous trials, ALTERNATIVE APPLICATIONS
respectively.
3.1 Food waste as nutrient media for
Key contribution: The mathematical equation demonstrates the bio-cementation
principles of macroeconomics in civil engineering applications
Food waste and cement manufacturing are two major
by introducing probability functions. The approach presents contributors to global carbon emissions . Literature shows that
[9]
a novel framework that, when fully evolved, can quantify the sequestering CO 2 in concrete can lower the carbon footprint
[9]
amount one can spend on research while ensuring profit. This and improve the properties of concrete . The conventional
will effectively encourage stakeholders to explore alternative strategies for carbon sequestration focus on captured CO 2 .
In a previous study, CO 2 released through the controlled
materials based on a quantified matrix.
decomposition of food waste was explored as an alternate route
[9]
for carbon sequestration in concrete . Here, food waste, along
Limitation: The mathematical equation was validated over a
with compatible non-pathogenic bacteria, is added to concrete.
small dataset, i.e., chemical composition of 30 different fly ashes, The bacteria will feed upon the food waste to release CO 2 ,
for the maximum replacement level without any strength loss. which is simultaneously sequestered by portlandite, as shown in
[9]
Full-scale validation across different SCMs for different material Figure 3 . The alternate route eliminates the need for trapping
characteristics has not been completed. Furthermore, in the CO 2 while replacing the commercially used nutrient media
[9]
during bio-cementation with upcycled food waste .
limited results, the model predicted a conservative success
rate, i.e., up to 8 % lower theoretical replacement level than the The study explored two major pathways for upcycling food
waste as nutrient media, i.e., powder form and pulp form . The
[9]
experimental optimum. In the present format, the SCMs will be
study showed high bacterial growth in powder-based nutrient
suggested at lower replacement levels, and further experiments media for E. Coli DH-5α. The solution was added in a mortar
will be needed to increase SCM utilisation to optimum by mixing water and bacteria immobilised on waste tyre rubber
[9]
replacement levels. fibre . The resulting microstructure showed that bacteria
addition resulted in a denser cement matrix and improved
2.3 New observations related to SCM interfacial transition zone (ITZ) around rubber fibres, as shown
in Figure 4. The resulting mortar increased the strength by
characterisation
over 80 % for mortar prepared with up to 2 % rubber. This is
significantly higher than previously reported works on bacterial
Previous studies also explored the application of different
mortars, with a maximum strength gain of about 60 % across
characterisation techniques on various SCMs [7,8] . Some of the all observed literature . The bacterial rubberised mortars
[9]
observations, with potential for improving further understanding also exhibited self-healing ability . It is hypothesised that
[9]
of the SCMs, have been summarised as follows: the higher strength gain may be a result of the smaller size of
E. Coli DH-5α. A smaller bacterial size will also be able to occupy
i Irregularly shaped particles exhibit higher pozzolanic smaller pores and occupy them through calcite precipitation,
reactivity than spherical particles when observing different resulting in a denser microstructure.
[8]
coal-based fly ashes . The study also demonstrated that the bacteria immobilised on
[9]
the surface of the rubber can strengthen the ITZ . The process
ii Raman spectroscopy can detect and quantify unburnt
of bacteria immobilisation can be extended to other wastes, like
carbon in different coal-based fly ashes, making detection plastic, for improved waste upcycling.
faster than loss on ignition testing .
iii Raman micrograph can identify particle distribution and
confirm the degree of blending between different siliceous
[7]
and calcareous powders .
It should be noted that these observations are based on a few
SCMs. As a result, these may be true for specific SCMs and may
not be a generalised observation. However, these observations
can improve the characterisation of SCMs and need further
exploration in future research. Figure 3: Carbon sequestration using food waste for bio-cementation

THE INDIAN CONCRETE JOURNAL | JANUARY 2026 69