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TECHNICAL PAPER
6.2.2 Global Warming Potential (the EDIs for the worst-case transportation scenarios are also
displayed in Figure 3). In general, the results in Table 5 show
The incorporation of industrial by-products in concrete (i.e. that even with differences in transportation distance ranging
SCMs) have environmental benefits, especially in the impact up to approximately 1470 km for a given mix design, the
category of global warming potential, which has been widely difference between the LCA results calculated with the best case
accepted as a major sustainability issue facing the concrete
industry. As shown in Figure 4, the global warming potential transportation distance and the LCA results calculated with the
of concrete generally decreases as the increase of cement worst case transportation distance is less than 3% in all cases.
replacing level by SCMs [28] . In this study, all the concrete mixes
with SCMs achieve lower EDIs than the control mix in the 7. sUMMARy AND CONCLUsIONs
analysis scenario of weighting scheme 1, as presented in Figure This paper presents an LCA of six concrete mix designs. The
3. When the weighting scheme is changed from 1 to 3, namely base mix design is 100% GU. Variables to this include the use
the weighting of global warming potential is changed from 0.25 of GUL cement as well as the use of SCMs, namely SL, FA and
to 0.7, mix designs with a higher cement replacement level by SF). A functional unit which incorporates both compressive
cement replacing materials (including FA, SL and limestone) strength and RCP as an indicator of durability, was used in this
achieve a greater decrease in EDIs. These results prove that analysis. Four environmental impacts were analyzed, and Gabi 6
the model built in this study aligns with the benchmarks built in software package was used. A sensitivity analysis was conduced
recent studies. to evaluate the effect of different weighting schemes and
transportation distance on the EDI.
£Óä FA SL The conclusions of this paper are relevant to LCA practitioners
££ä
or researcher conducting environmental modelling cement and
£ää
L> Ü>À} «ÌiÌ> À>Ì ¯® VÀiÌi ÜÌ
- É VÀiÌi ÜÌ
ÕÌ - ® ä concrete materials. The key findings based on LCA model and
assumptions in this paper are:
nä
Çä
The mix designs containing SCMs and limestone cement
•
Èä
(GU-25SL, GUL-25SL, GU-8SF-25SL, GU-10FA, GUL-10FA)
have EDIs that are lower than one when normalized to
xä
the base case (100GU), indicating a lower environmental
{ä
disturbance compared to the base case. This is because in
Îä
these mix designs, there is significant (at least 10%) cement
Óä
ä £ä Óä Îä {ä xä Èä Çä nä replacement. As cement is the most environmentally
- Ài«>ViiÌ iÛi ¯®
intensive component of concrete, cement replacement is
Figure 4: Effect of supplementary cementing materials on the global an effective way to decrease the life cycle environmental
warming potential of concrete [28] .
disturbance of concrete products.
6.2.3 Transportation • The only mix design containing SF as cement replacement,
Due to the high potential for variability in transportation namely, GU-8SF-25SL, has an environmental disturbance
distances, the sensitivity of the EDI results to changes in indicator far inferior to the other materials: EDI = 0.08
transportation distances was studied. The best transportation compared to the next lowest value of EDI = 0.60 (for
scenarios for SL, FA, SF and aggregates are 76 km, 332 km, mix design GU-25SL). Although the replacement rate
145 km and 80 km, respectively. Table 5 shows the percentage for SF is not as high (8%) as for other SCMs (10-25%), SF
difference in EDI results between the best-case and worst- can significantly and positively influence strength and
case transportation scenarios for the purposes of comparison permeability.
table 5: sensitivity analysis results for best-case and worst-case transportation scenarios (percentage
difference)
100Gu Gu-25Sl Gul-25Sl Gu-8SF-25Sl Gu-10FA Gul-10FA
EDI for Best-Case Transportation 1 0.67 0.58 0.08 0.83 0.85
EDI for Worst-Case Transportation 1 0.69 0.60 0.08 0.84 0.87
% Difference between Best- and Worst-Case Transportation 0 -1.7 -2.2 -2.9 -1.4 -1.8
The IndIan ConCreTe Journal | FeBruarY 2020 15
