Dear Adeyemi, you have a good point about how long we will have fly ash available in sufficient quantities for replacing cement. Even if pond ash is used, still it's inadequate in the long term given the ever increasing quantities of cement being consumed. Also availability of fly ash at a suitable location for its economical use also can be a challenge. Given all of these issues which also affects geopolymers, material like LC3 cement is being pursued aggressively by researchers led by Prof Karen Scrivner and he collaborators. Lime Calcined Clay Cement is made from the same abundantly available raw materials as Cement but at a.much lower embodied energy. You may find it of interest. We are currently developing ECC using LC3 materials. We will be publishing the results soon.

Hi Adyemi;

Sustainability of ECC has been a challenge right from the early days when it was composed of a large amount of Portland Cement (much higher than normal concrete). Subsequently with use of high volume fly ash, the composition has become increasingly more Eco-friendly to the extent that not only is it comparable to ordinary concrete, but can be better in terms of Life Cycle Costs.

In our group here at HKUST, we are doing some work to make ECC more sustainable by use of high volume fly ash as well as recycled PET fibers. You can see some of the publications at https://www.researchgate.net/project/Sustainable-Structural-Concrete-with-Ultrahigh-Volume-Fly-Ash Evaluation of cost, embodied energy and carbon footprint of each component is the key in our approach. We have not yet done full life cycle analysis.

Hope this is of some help.

Regards;

Dhanada

The sustainability becomes the major aim and concern in present scenario as the issues related are immense. The OPC is considered as the most energy expensive material after steel and one of the major contributor of global CO2 emission (7%). It uses huge amount of lime stones for its making, hence developments are taking place to make cement industries greener. High volume replacement of clinker by flyash and GGBS(ground granulated blast furnace slag) are the most recent trends towards sustainability. Yet, this much is not enough, the Engineered Cementatious Composites (ECC) have to more sustainable, I am talking about Geopolymer Concre, a concrete without cement. Extensive research work has been done on geopolymer, in some part of the globe its being used. Yet it have to come to the front, more research is needed for deep understanding regarding the material and which will eventually help to develop a customize standard code for geopolymer.

We are working on geopolymer concrete, you can see our published article- Article An Overview of Current Research Trends in Geopolymer Concrete

Thank you

Regards

Thank you Dhanada Kanta Mishra , great work you're doing. It will be great to also consider the supply reservoir of fly ash, and if large amount of it will still be produced as waste in the coming years

However, I still have strong issues with fly ash. Though most developing countries still use coal to generate power, but with more global sustainable awareness most of these coal plants will be decommissioned in the next few years to decade.

Do you think there's other material with sufficient deposits that can sustain the supply market for ECC in the coming years?

Thank you Shaswat Das

I differ from that statement that "OPC is considered as the most energy expensive material after steel and one of the major contributor of global CO2 emission (7%) " - If you compare the embodied energy and carbon of OPCcompared to other building materials, it is lower. The only reason for the high contribution of OPC to the world's anthropogenic carbon emission is as a result of large amount of OPC used.

ECC is quite different from geopolymers and alkali activated materials. And in my experience with this two materials, it is hard to get a ductile composite when alkali activation is formed due to the brittle nature of the aluminosilicate gel

cement is the binder that binds FA and CA. but cement is the main cause for the deterioration in concrete system than other ingredients of concrete. more over cement is the prime material which affects the environment than other materials that use in construction industry. replacing the cement in concrete will make the sustainable concrete industry. most of the industrial wastes are pozzolanic materials in which very fine or ultra fine pozzolanic materials can be used to replace the cement.

Adeyemi Adesina Thanks for the clarification. I do agree with you, that we cant get a material which have good ductility from geopolymers & alikali-activated materials. Then what do you suggest? What kind of ECC you need? I mean the engineering properties.

Thank you

ECC with low cement content and if possible waste products used as fibers and aggregates in the ECC

Dear Adeyemi, you have a good point about how long we will have fly ash available in sufficient quantities for replacing cement. Even if pond ash is used, still it's inadequate in the long term given the ever increasing quantities of cement being consumed. Also availability of fly ash at a suitable location for its economical use also can be a challenge. Given all of these issues which also affects geopolymers, material like LC3 cement is being pursued aggressively by researchers led by Prof Karen Scrivner and he collaborators. Lime Calcined Clay Cement is made from the same abundantly available raw materials as Cement but at a.much lower embodied energy. You may find it of interest. We are currently developing ECC using LC3 materials. We will be publishing the results soon.

I'd suggest moving to ternary cement blends. Using slag and PFA with limestone would help to keep a low clinker factor in the binder, without using up excessive PFA and slag (which as others have said are no longer readily available in sufficient quantities).

Please check reference below.. hope it will be helpful for you… Regards…

https://pdfs.semanticscholar.org/66c2/cf5472afd23c53170ea665f14864970ebfa5.pdf

In my opinion, the key of the sustainablity of ECC is stable ECC performance

Ultimately, sustainability is a local issue.  What is sustainable for me, in Ottawa, will be very different than for someone in a little town outside Nairobi.  For any given setting, do your have access to the materials from within the community (scale flexible, but at least the size of the urban and rurals that support it)?  If the resident of Nairobi needs fly-ash from Canada, it isn't sustainable.

The second question becomes can the ecological services of that local community provide sufficient ecological services to absorb the wastes of the processes used to create the product?  And does the community have the skills to do the work? 

If any of those questions is 'no', then the product isn't sustainable there.  It might be fine somewhere else, and so as a researcher, after you've found a great product, you then may have to go out and find the setting where it would be greatest.

So the major way to improve the sustainability of ECC is to assess it in it's local setting.