City of Austin Resource Center for the Homeless High Volume Fly Ash Concrete Innovation Credit Introduction: We are proposing the following innovation credit for a project which will be using site-cast concrete for piers, caps, grade beams, slab on grade, floors, tilt-up walls, retaining walls, and site concrete. Will LEED award an innovation credit for the following: Intent: Diminish the life cycle CO2 emissions associated with site-cast concrete by replacing large quantities portland cement with fly-ash. Requirements: Replace 40% by volume portland cement with fly ash on average for all site-cast concrete used on the project including piers, caps, grade beams, slab, floors, tilt-up walls, retaining walls and site concrete. Submittals: Provide a spreadsheet with the following information for all site-cast concrete. Total volume of concrete placed for each mix design. Total percentage of cement for each mix design (portland + fly ash). Amount of Portland cement and fly ash used by volume in each mix design. Percentage of fly ash by volume of total cementatious material for each mix design. Compressive strength for each mix design. Weighted average percentage of fly ash by volume for all site cast concrete. This weighted average will be based on the amount (in cubic yards) of concrete placed for each mix design, and must be greater than or equal to 40% to achieve this credit. Design Approach: Work with local engineers and suppliers to optimize the mix design for each application with replacement of portland cement with fly ash, with a total project average of 40% replacement, while not increasing the total percentage of cement in the concrete design mix.
An innovation point will be awarded for reducing total Portland cement content of cast-in-place concrete. In order to obtain this innovation credit point, the following requirements must be met: A minimum of 40% reduction of CO2 by weight for all cast-in-place concrete must be demonstrated against standard baseline mixes. Applicant must demonstrate that cast-in-place concrete makes up a significant portion of the work on the project - a point will not be awarded for negligible quantities in relation to the total work. For purposes of this credit, the following must be applied: One pound of Portland cement is equivalent to one pound of CO2. Baseline mixes shall be standard, 28-day strength regional mix designs. Temperature range shall be accounted for and documented. Documentation for cold weather mix designs shall include temperature on day of pour. Pozzolans allowed for displacement of Portland cement are fly ash, ground granulated blast furnace slag (ggbfs), silica fume, and rice hull ash. Required Documentation: Total cubic yards of cast-in-place concrete for project. Standard 28-day strength concrete mix designs from the concrete producer, in accordance with ACI 301, for each concrete mix required for project (2500 psi, 3000 psi, 5000 psi, etc.) and quantity of Portland cement for each mix in pounds per cubic yard. Quantity of Portland cement reduced and/or replaced for each mix in pounds per cubic yard. Temperature on day of pour if cold weather mix is used. Calculation demonstrating that a minimum 40% average reduction has been achieved over standard concrete mix designs for the total of all cast-in-place concrete. Example: Structural requirements call for all cast-in-place concrete to meet a minimum strength of 4000 psi at 28 days. The standard mix design for this concrete in the area of the project is 564 pounds of Portland cement per cubic yard of concrete. In order to achieve a 40% reduction of CO2 by weight, the following measures could be employed individually or in combination: Increase number of days required to achieve strength requirement; 4000 psi concrete at 90 days requires less Portland cement than 4000 psi at 28 days. Replace a portion of the Portland cement with a pozzolanic material. In the example, Portland cement content per cubic yard must be reduced by 225.6 pounds to meet the credit requirement. Let\'s assume that by modifying the 28-day strength requirement to 90 days, Portland cement could be reduced by 100 pounds per cu. yd. An additional 125.6 pounds of Portland cement could be replaced with Class F fly ash to satisfy the requirement for a 40% CO2 reduction. Applicable Internationally.