In these day the high performance concrete is one the important material, despite it should be environment friendly.
HPC and UHPC generally contain a higher amount of cement than conventional concrete, which increases their embodied energy and CO2 emissions. The same is true for steel fibers. However, they allow to construct slender and lightweight structures, which may result e.g. in less concrete in the foundation and lower emissions due to transportation of material. Use of HPC could also become more sustainable when the increased concrete durability allows reducing maintainance. Whether HPC/UHPC or other, more conventional solutions are more sustainable, should however be decided case by case by performing a specific Life Cycle Assessment (LCA)
You can find a very interesting example of LCA about concrete bridges in this paper, by Prof. Habert of ETH Zurich (who should also be on Research Gate): Habert, G., Arribe, D., Dehove, T., Espinasse, L., & Le Roy, R. (2012). Reducing environmental impact by increasing the strength of concrete: quantification of the improvement to concrete bridges. Journal of Cleaner Production, 35, 250-262.
By using sufficient amount of steel vibers in UHPC, sustainable lightweight concrete constructions are now possible.
HPC and UHPC generally contain a higher amount of cement than conventional concrete, which increases their embodied energy and CO2 emissions. The same is true for steel fibers. However, they allow to construct slender and lightweight structures, which may result e.g. in less concrete in the foundation and lower emissions due to transportation of material. Use of HPC could also become more sustainable when the increased concrete durability allows reducing maintainance. Whether HPC/UHPC or other, more conventional solutions are more sustainable, should however be decided case by case by performing a specific Life Cycle Assessment (LCA)
You can find a very interesting example of LCA about concrete bridges in this paper, by Prof. Habert of ETH Zurich (who should also be on Research Gate): Habert, G., Arribe, D., Dehove, T., Espinasse, L., & Le Roy, R. (2012). Reducing environmental impact by increasing the strength of concrete: quantification of the improvement to concrete bridges. Journal of Cleaner Production, 35, 250-262.
To assess sustainability, it is essential to consider all the variables (economic, social, technical, legal, even geopolitical)
Sustainability
Material Requirements
The use of UHPC may translate to savings in the total materials required for the design of various structures. Although UHPC has a higher cement content per cubic yard than normal concrete, structural members typically require fewer cubic yards of material, and as a result, the total quantity of cement used is about the same or perhaps even less for UHPC design solutions than those from normal concrete (Walraven 2002). Walraven also estimates that the total amount of aggregates, in which he includes both fine and coarse aggregates, used in structural members may be decreased by 30 percent with the use of UHPC compared to normal concrete. (Note that the amount of coarse aggregates is reduced 100 percent.) Racky (2004), in his own study, determined that while the cement content in UHPC may be as much as twice that in normal concrete, the amount of UHPC required for a large column application was only 44 percent of the normal concrete alternative, which supports Walraven’s hypothesis.Fly ashes used in UHPC can also be obtained as by-products from the power industry. By employing material that would otherwise be wasted, UHPC represents a step towards sustainability. The use of more mineral components and powders in place of cement for concrete applications is a step toward sustainability and helps to meet the sustainability mandates that may soon be implemented by some government agencies (Aïtcin 2000).
Lifecycle
Although too few applications of UHPC currently exist to allow a reliable comparison with normal concrete for average life-cycle durations and costs, most researchers agree the excellent durability properties of UHPC should increase the longetivity of structures while minimizing maintenance costs (Racky 2004; Blais and Couture 1999). Aïtcin (2000) notes that unlike normal concrete, UHPC can be recycled several times before being used as granular road base. This recyclability is attributed to the fact that not all of the cement in UHPC is hydrated during hardening, and unhydrated cement is therefore available for future reactions.
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