Section A4.403.2 of Appendix A4 of the California Green Building Standards Code is adopted as a Mandatory measure for all Tier 1 and Tier 2 projects and is amended to read:
A4.403.2 Low Carbon Concrete Requirements.
A4.403.2.1 Purpose. The purpose of this chapter is to provide practical standards and requirements for the composition of concrete, as defined herein, that maintains adequate strength and durability for the intended application and at the same time reduces greenhouse gas emissions associated with concrete composition. This code includes pathways for compliance with either reduced cement levels or lower-emission supplementary cementitious materials.
A4.403.2.2 Definitions. For the application of this section the following definitions shall apply:
Concrete. Concrete is any approved combination of mineral aggregates bound together into a hardened conglomerate in accordance with the requirements of this code.
Environmental product declaration (EPD). EPDs present quantified environmental information on the life cycle of a product to enable comparisons between products fulfilling the same function. EPDs must conform to ISO 14025, and EN 15804 or ISO 21930, and have at least a "cradle to gate" scope (which covers product life cycle from resource extraction to the factory).
Upfront embodied carbon (embodied carbon). The greenhouse gasses emitted in material extraction, transportation and manufacturing of a material corresponding to life cycle stages A1 (extraction and upstream production), A2 (transportation), and A3 (manufacturing). Definition is as noted in ISO 21930 and as defined in the Product Category Rule for Concrete by NSF dated February 22nd, 2019. https://www.nsf.org/ newsroom_pdf/concrete_pcr_2019.pdf
A4.403.2.3. Compliance. Compliance with the requirements of this chapter shall be demonstrated through any of the compliance options in Sections 4.403.2.3.2 through 4.403.2.3.5:
Table A4.403.2.3 Cement and Embodied Carbon Limit Pathways
Cement limits for use with any compliance method A4.403.2.3.2 to A4.403.2.3.5 | Embodied Carbon limits for use with any compliance method A4.403.2.3.2 to A4.403.2.3.5 | |
Minimum specified compressive strength f’c, psi (1) | Maximum ordinary Portland cement content, lbs/yd3 (2) | Maximum embodied carbon kg CO2e/m3, per EPD |
up to 2500 | 362 | 260 |
3000 | 410 | 289 |
4000 | 456 | 313 |
5000 | 503 | 338 |
6000 | 531 | 356 |
7000 | 594 | 394 |
7001 and higher | 657 | 433 |
up to 3000 light weight | 512 | 578 |
4000 light weight | 571 | 626 |
5000 light weight | 629 | 675 |
Notes (1) For concrete strengths between the stated values, use linear interpretation to determine cement and/or embodied carbon limits. (2) Portland cement of any type per ASTM C150. |
A4.403.2.3.1 Allowable Increases.
(1) Cement and Embodied Carbon Limit Allowances. Cement or Embodied Carbon limits shown in Table A4.403.2.3 can be increased by 30% for concretes demonstrated to the Building Official as requiring high early strength. Such concretes could include, but are not limited to, precast, prestressed concrete; beams and slabs above grade; and shotcrete
(2) Approved Cements. The maximum cement content may be increased proportionately above the tabulated value when using an approved cement, or blended cement, demonstrated by approved EPD to have a plant-specific EPD lower than 1040 kg CO2e/metric ton. The increase in allowable cement content would be (1040/plant=specific EPD) %.
A4.403.2.3.2 Cement Limit Method - Mix. Cement content of a concrete mix using this method shall not exceed the value shown in the Table A4.403.2.3. Use of this method is limited to concrete with specified compressive strength not exceeding 5,000 psi.
A4.403.2.3.3 Cement Limit Method - Project. Total cement content shall be based on total cement usage of all concrete mix designs within the same project. Total cement content for a project shall not exceed the value calculated according to Equation A4.403.2.3.3.
Equation A4.403.2.3.3:
Cem proj < Cem allowed
where
Cem proj = Cem n v n and Cem allowed = Cem lim v n
and
n = the total number of concrete mixtures for the project
Cem n = the cement content for mixture n, kg/m3 or lb/yd3
Cem lim = the maximum cement content for mixture n per Table A4.403.2.3, kg/m3 or lb/yd3
v n = the volume of mixture n concrete to be placed, yd3 or m3
Applicant can use yd3 or m3 for calculation, but must keep same units throughout
A4.403.2.3.4. Embodied Carbon Method - Mix. Embodied carbon of a concrete mix, based on an approved environmental product declaration (EPD), shall not exceed the value given in Table A4.403.2.3.
A4.403.2.3.5. Embodied Carbon Method - Project. Total embodied carbon (EC proj) of all concrete mix designs within the same project shall not exceed the project limit (EC allowed) determined using Table A4.403.2.3 and Equation A4.403.2.3.5.
Equation A4.403.2.3.5:
EC proj < EC allowed
where
EC proj = EC n v n and EC allowed = EC lim v n
and
n = the total number of concrete mixtures for the project
EC n = the embodied carbon potential for mixture n per mixture EPD, kg/m3
EC lim = the embodied carbon potential limit for mixture n per Table A4.403.2.3, kg/m3
v n = the volume of mixture n concrete to be placed, yd3 or m3
Applicant can use yd3 or m3 for calculation, but must keep same units throughout.
A4.403.2.3.6. Enforcement.
As a condition prior to the issuance of every building permit involving placement of concrete, the permit applicant shall be required to submit a completed low-carbon concrete compliance form that shall be provided by and reviewed for compliance by the building department prior to issuing the permit.
As a condition of such building permits, and prior to approving construction inspections following placement of concrete, the permit applicant shall be required to submit batch certificates and/or EPDs provided by the concrete provider that demonstrate compliance with the low-carbon concrete compliance form on file with the building permit. The batch certificates and/or EPDs shall be reviewed for compliance by the building department prior to approving any further inspections.
When deviations from compliance with this section occur, the chief building official or his designee is authorized to require evidence of equivalent carbon reductions from the portions
of remaining construction of the project to demonstrate alternative compliance with the intent of this chapter.
For projects involving placement of concrete by, or on behalf of, a public works, parks, or similar department the director of such department, or his/her assignee, shall maintain accurate records of the total volume (in cubic yards) of all concrete placed, as well as the total compliant volume (in cubic yards) of all concrete placed, and shall report this data annually to the governing body in a form expressing an annual compliance percentage derived from the quotient of total compliant concrete volume placed divided by total concrete volume placed.
A4.403.2.3.7. Exemptions.
(a) Hardship or infeasibility exemption. If an applicant for a project subject to this chapter believes that circumstances exist that make it a hardship or infeasible to meet the requirements of this chapter, the applicant may request an exemption as set forth below. In applying for an exemption, the burden is on the applicant to show hardship or infeasibility. The applicant shall identify in writing the specific requirements of the standards for compliance that the project is unable to achieve and the circumstances that make it a hardship or infeasible for the project to comply with this chapter. Circumstances that constitute hardship or infeasibility may include, but are not limited to the following:
(1) There is a lack of commercially available material necessary to comply with this chapter;
(2) The cost of achieving compliance is disproportionate to the overall cost of the project;
(3) Compliance with certain requirements would impair the historic integrity of buildings listed on a local, state or federal list or register of historic structures as regulated by the California Historic Building Code (Title 24, Part 8).
(b) Granting of exemption. If the chief building official determines that it is a hardship or infeasible for the applicant to fully meet the requirements of this chapter and that granting the requested exemption will not cause the building to fail to comply with the California Building Standards Code, the chief building official shall determine the maximum feasible threshold of compliance reasonably achievable for the project. In making this determination, the chief building official shall consider whether alternate, practical means of achieving the objectives of this chapter can be satisfied. If an exemption is granted, the applicant shall be required to comply with this chapter in all other respects and shall be required to achieve the threshold of compliance determined to be achievable by the chief building official.
(c) Denial of exception. If the chief building official determines that it is reasonably possible for the applicant to fully meet the requirements of this chapter, the request shall be denied and the applicant shall be notified of the decision in writing. The project and compliance documentation shall be modified to comply with the standards for compliance.
(Ord. 5570 § 1 (part), 2022)