Specifications

Natural Pozzolan
Metakaolin
Rice Husk Ash
Publicity
Cost and availability
Scheduling
Applications (roads, roller-compacted, slabs, precast, cast-in-place)
Weather
Health/Environmental impact

Specifications

Question:

I work for a company that is interested in sustainable building. We would like to incorporate EcoSmart concrete into our specifications. Can you recommend a course of action?

Answer:

EcoSmart may be able to help you revise your specifications. Send your specific request to information@ecosmart.ca and we will assist you or put you in touch with someone who can help.

Natural Pozzolan
Question:
Has EcoSmart done any research on the use of natural pozzolan as a supplementary cementing material?

Answer:

A report entitled "The Potential Use of the Natural Pozzolans in British Columbia as Supplementary Cementing Materials" is available in the EcoSmart knowledge base.

Metakaolin

Question:
Has EcoSmart done any research on the use of metakaolin as a supplementary cementing material?

Answer:

A report entitled "Metakaolin Study: Pre-Feasibility Review of the Potential for Developing Metakaolin from Oil Sands Operations for Use in Concrete" is available in the EcoSmart knowledge base.

Rice Husk Ash
Question:
Can you provide me with some information on rice husk ash?

Answer:
A report entitled "Concrete Incorporating Rice Husk Ash: Compressive Strength and Chloride-Ion Penetrability" is available in the EcoSmart knowledge base.

Publicity
Question:
Would EcoSmart be interested in writing an article for my publication? Can I use information from your case study reports for my thesis/other publication? Can EcoSmart provide me with some case study images?

Answer:

The EcoSmart Foundation is interested in publicizing its progress. Please email information@ecosmart.ca with your specific request, including a description of your publication. Many of the works in our knowledge base are in the public domain, and you are free to use this information so long as you give credit appropriately. Items that are in the public domain are clearly marked.

Cost and Availability
Question:
I am presently negotiating a contract and would like to use the concrete/supplementary cementing materials described on your website. Is it available in my area? Where can I purchase it and how much does it cost?

Answer:

EcoSmart does not sell concrete or supplementary cementing materials. To purchase EcoSmart concrete, you will need to work with a materials engineer and your local concrete suppliers. You should specify a mix that optimizes Portland cement replacement with supplementary cementing materials (SCM) such as fly ash, silica fume, and slag.

The cost of EcoSmart concrete mixes is comparable to conventional mixes, although it varies by project and application. EcoSmart has completed a number of case studies, available in our knowledge base, where concrete mixes were typically less expensive. However, there may be cost implications for the contractor if the contractor is not knowledgeable about using EcoSmart concrete, since it may exhibit somewhat different plastic and hardening properties, e.g. reduced bleeding, increased setting time, and slower strength gain.

Scheduling
Question:
I'm working on a tight schedule - how will the stripping time be affected by using a higher volume of supplementary cementing materials in the concrete mix?

Answer:

The strength development of concrete incorporating high volumes of supplementary cementing materials (SCMs) is slower than that of conventional concrete. This retarding effect will be enhanced in cooler days. Nevertheless, in normal temperature conditions, strength development should not affect stripping time.

In the cases where higher early-age strength levels are required for stripping, several options exist:

• The schedule of stripping has to be adjusted
• The proportions of the mixture have to be optimized for higher early-age strength by adjusting different parameters such as the cementitious materials content, the proportion of SCMs, the water-to-cementitious materials ratio, the use of superplasticizer and acccelerator.
• The design stripping strength may need to be re-evaluated by the structural engineer on the project
• The insitu concrete strength may need to be measured more precisely by using insitu tests, e.g. Lok test or maturity test

Applications

Question:
Can EcoSmart concrete be used in slabs, precast and poured in place concrete? What are the best applications for EcoSmart concrete?

Answer:

The EcoSmart concept means optimizing the percentage of supplementary cementing materials (SCMs) in concrete to be used in any particular application while meeting technical and constructibility requirements; consequently, EcoSmart concrete can be used for almost any type of application.

The optimum replacement of Portland cement by SCM will differ depending on the application and the ambient temperature during the concrete pour, but it will be higher for applications where high early-age strength are not needed and when ambient temperatures are above 10 degrees celsius.

The best applications for EcoSmart concrete are mass elements and applications where low permeability is required for durability. Minor adjustments to the finishing, placing, and curing practices may be required to get full benefits from the use of EcoSmart concrete.

Weather
Question:
How does EcoSmart concrete perform when poured in hot or cold weather?

Answer:

In general, it is easier to get full benefits of EcoSmart concrete in hot weather. Higher temperatures accelerate the strength development and may result in significantly higher early age strengths. On the other hand, the use of large amount of fly ash as cement replacement will reduce significantly the heat development in mass concrete elements which is very advantageous against thermal crack development.

The use of high percentages of SCMs may delay the setting of the concrete and this may be an advantage in hot weather conditions for finishing purposes. In hot weather conditions, when SCMs are used in combination with low water-to-cementitious materials ratio (a recommended combination for EcoSmart concrete), care should be taken to prevent premature surface drying (plastic shrinkage) of horizontal surfaces due to insufficient bleeding water, which otherwise provides a safety factor against drying, but is not in itself desirable for concrete.

Health/Environmental Impact
Question:

I am concerned with worker safety. Does fly ash require special handling?

Answer:

The handling of fly ash and other supplementary cementing materials requires the same type of safety protection as that required for handling cement. For information on health issues related to fly ash, see the EPRI feature report "Coal Ash: Its Origin, Disposal, Use and Potential Health Issues" available in the EcoSmart knowledge base.

Question:
Does fly ash contain radon or toxic materials that leach from concrete?

Answer:

A recent report by the Environmental Protection Agency (EPA) indicates that the use of typically-occurring fly ash in concrete does not constitute a significantly different radiation risk than the risk from the cement it replaces, and neither of these is significantly different from the radiation risk posed by common soil. The report "Cement and Concrete Containing Fly Ash: Guideline for Federal Procurement" is available on the EPA's website.

Fly ash contains minor traces of toxic elements as does Portland cement. According the the Electric Power Research Institute (EPRI), studies have shown that even where some leaching of trace elements from coal ash has occurred, its effects did not pose public health risks. For more information, see the report "Coal Ash: Its Origin, Disposal, Use and Potential Health Issues".