Home / Technical Resources / fire resistance ratings

Resources

Fire Resistance Ratings of Concrete Masonry Assemblies

  • September 2020

INTRODUCTION

Concrete masonry is widely specified for fire walls and fire barriers because concrete masonry is noncombustible, provides durable fire resistance, and is economical to construct. Chapter 7 of the International Building Code (IBC) (ref. 2) governs materials and assemblies used for structural fire resistance and fire-rated separation of adjacent spaces. This TEK is based on the provisions of Code Requirements for Determining Fire Resistance of Concrete and Masonry Construction Assemblies, ACI 216.1/TMS 216 (ref. 1) , which outlines a procedure to calculate the fire resistance ratings of concrete masonry assemblies. The 2014 edition of the ACI 216.1/TMS 216 is referenced in the 2015 IBC for concrete and masonry materials. This TEK is based on both prescriptive details and tables as well as the calculated fire resistance procedure, which is practical, versatile and economical. The calculation procedure allows the designer virtually unlimited flexibility to incorporate the excellent fire-resistive properties of concrete masonry into a design. Included are methods for determining the fire resistance rating of concrete masonry walls, columns, lintels, beams, and concrete masonry fire protection for steel columns. Also included are assemblies composed of concrete masonry and other components, including plaster and gypsum wallboard finishes, and multi-wythe masonry components including clay or shale masonry units.

METHODS OF DETERMINING FIRE RESISTANCE RATINGS

Because full-scale fire testing of representative test specimens is not practical in daily practice due to time and financial constraints, the IBC outlines multiple options for fire rating determination:

  • standardized calculation procedures, such as those in the ACI 216.1/TMS 216 and in Section 722 of the IBC;
  • prescriptive designs such as those in Section 721 of the IBC;
  • engineering analysis based on a comparison with tested assemblies;
  • third party listing services, such as Underwriters Laboratory; and
  • alternative means approved by the building official per Section 104.11 of the IBC.

Of these, the calculation method is an economical and commonly used method of determining concrete masonry fire resistance ratings. The calculations are based on extensive research, which established relationships between the physical properties of materials and the fire resistance rating. The calculation method is fully described in ACI 216.1/TMS 216 and IBC Section 722, and determines fire resistance ratings based on the equivalent thickness of concrete masonry units and the aggregate types used to manufacture the units. Private commercial listing services allow the designer to select a fire rated assembly that has been previously tested, classified and listed in a published directory of fire rated assemblies. The listing service also monitors materials and production to verify that the concrete masonry units are and remain in compliance with appropriate standards, which usually necessitates a premium for units of this type. The system also is somewhat inflexible in that little variation from the original tested wall assembly is allowed, including unit size, shape, mix design, constituent materials, and even the plant of manufacture. More information on listing services for fire ratings is provided in CMU-FAQ 015-23 (ref. 16).

For prescriptive designs, the IBC provides a series of tables that describes requirements of various assemblies to meet the fire resistance ratings specified. The last two options listed above require justification to the building official that the proposed design is at least the equivalent of what is prescribed in the code.

CALCULATED FIRE RESISTANCE RATINGS

Background

The calculated fire resistance method is based on extensive research and testing of concrete masonry walls. Fire testing of wall assemblies is conducted in accordance with Standard Test Methods for Fire Tests of Building Construction and Materials, ASTM E119 (ref. 3), which measures four performance criteria, as follows:

  • resistance to the transmission of heat through the wall assembly;
  • resistance to the passage of hot gases through the wall, sufficient to ignite cotton waste;
  • load-carrying capacity of loadbearing walls; and
  • resistance to the impact, erosion and cooling effects of a hose stream on the assembly after exposure to the standard fire.

The fire resistance rating of concrete masonry is typically governed by the heat transmission criteria. From the standpoint of life safety (particularly for fire fighters) and reuse, this failure mode is certainly preferable to a structural collapse endpoint, characteristic of many other building materials.

The calculated fire resistance rating information presented here is based on the IBC and ACI 216.1/TMS 216 (refs. 1, 2).

Equivalent Thickness

Extensive testing has established a relationship between fire resistance and the equivalent solid thickness of concrete masonry walls, as shown in Table 1. Equivalent thickness is essentially the solid thickness that would be obtained if the volume of concrete contained in a hollow unit were recast without core holes (see Figure 1). The equivalent thickness is determined in accordance with Standard Methods of Sampling and Testing Concrete Masonry Units, ASTM C140 (ref. 4), and is reported on the C140 test report. If the equivalent thickness is unknown, but the percent solid of the unit is, the equivalent thickness of a hollow unit can be determined by multiplying the percent solid by the unit’s actual thickness.

The equivalent thickness of a 100% solid unit or a solid grouted unit is equal to the actual thickness. For partially grouted walls where the unfilled cells are left empty, the equivalent thickness for fire resistance rating purposes is equal to that of an ungrouted unit. For partially grouted walls with filled cells, see the following section. Loadbearing units conforming to ASTM C90 (ref. 5) that are commonly available include 100% solid units, 75% solid units, and hollow units meeting minimum required face shell and web dimensions. Typical equivalent thickness values for these units are listed in Table 2.

Filling Cells with Loose Fill Material

If all cells of hollow unit masonry are filled with an approved material, the equivalent thickness of the assembly is the actual thickness. This also applies to partially grouted concrete masonry walls where all ungrouted cells are filled with an approved material.

Applicable fill materials are: grout, sand, pea gravel, crushed stone, or slag that comply with ASTM C33 (ref. 6); pumice, scoria, expanded shale, expanded clay, expanded slate, expanded slag, expanded fly ash, or cinders that comply with ASTM C331 (ref. 7); perlite meeting the requirements of ASTM C549 (ref. 8); or vermiculite complying with C516 (ref. 9).

Wall Assembly Fire Ratings

The fire resistance rating is determined in accordance with Table 1 utilizing the appropriate aggregate type used in the masonry unit and the equivalent thickness.

Units manufactured with a combination of aggregate types are addressed by footnote C, which may be expressed by the following equation (see also the blended aggregate example, below):

Blended aggregate example:

The required equivalent thickness of an assembly constructed of units made with expanded shale (80% by volume), and calcareous sand (20% by volume), to meet a 3-hour fire resistance rating is determined as follows. From Table 1:

Multi-Wythe Wall Assemblies

The fire resistance rating of multi-wythe walls (Figure 2) is based on the fire resistance of each wythe and the air space between each wythe using the following equation:

For multi-wythe walls of clay and concrete masonry, use the values in Table 3 for the brick wythe in the above equation.

Reinforced Concrete Masonry Columns

Concrete masonry column fire testing evaluates the ability of the column to carry design loads under standard fire test conditions. Based on a compendium of fire tests, the fire resistance rating of reinforced concrete masonry columns is based on the least plan dimension of the column as indicated in Table 4. The minimum required cover over the vertical reinforcement is 2 in. (51 mm).

Concrete Masonry Lintels

Fire testing of concrete masonry beams and lintels evaluates the ability of the member to sustain design loads under standard fire test conditions. This is accomplished by ensuring that the temperature of the tensile reinforcement does not exceed 1,100°F (593°C) during the rating period. The calculated fire resistance rating of concrete masonry lintels is based on the nominal thickness of the lintel and the minimum cover of longitudinal reinforcement (see Table 5). The cover requirements protect the reinforcement from strength degradation due to excessive temperature during the fire exposure period. Cover requirements may be provided by masonry units, grout, or mortar. Note that for 3 and 4 hour requirements, not enough cover is available for 6-in. (152 mm) masonry; however, if a special analysis indicates that the reinforcement is not necessary or not needed, such as when conditions for arching action are present, the cover requirements may be waived. See TEK 17-01D (ref. 11) for lintel design and conditions for arching action.

Control Joints

Figure 3 shows control joint details in fire-rated wall assemblies in which openings are not permitted or where openings are required to be protected. Maximum joint width is 1/2 in. (13 mm). Although these details are not directly in the IBC, they are included by reference in ACI 216.1/TMS 216.

In addition to these prescriptive fire resistance rated control joints, other control joints may be permitted in fire rated masonry walls. For example, the IBC and ACI 216.1/1/TMS 216 include provisions for ceramic fiber joint protection for precast panels, which are similar to concrete masonry walls in that both rely on concrete for fire protection, and both are governed by the ASTM E119 heat transmission criteria (see Figure 4). The first two categories of aggregate types in Table 1 would correspond to the carbonate or siliceous aggregate concrete curve and the last two aggregate categories of Table 1 would correspond to the semi-lightweight or lightweight concrete curve. For example, for an 8-in. (203-mm) limestone aggregate concrete masonry wall with a maximum control joint width of 1/2 in. (13 mm), a 1 in. (25 mm) thickness (measured perpendicular to the face of the wall) of ceramic fiber in the joint can be used in walls with fire resistance ratings up to 3 hours, while a 2 in. (51 mm) thickness can be used in the joints of a 4-hour wall.

Steel Columns Protected by Concrete Masonry

Fire testing of a steel column protected by concrete masonry evaluates the structural integrity of the steel column under fire test conditions, by measuring the temperature rise of the steel. The calculated fire resistance rating of steel columns protected by concrete masonry, as illustrated in Figure 5, is determined by:

Effects of Finish Materials on Fire Resistance Ratings

In many cases, drywall, plaster or stucco finishes are used on concrete masonry walls. While finishes are normally applied for architectural reasons, they can also provide additional fire resistance. The IBC and ACI 216.1/TMS 216 include provisions for calculating the additional fire resistance provided by these finishes.

Note that when finishes are used to achieve the required fire rating, the masonry alone must provide at least one- half of the total required rating and the contribution of the finish on the non-fire-exposed side cannot be more than one-half of the contribution of the masonry alone. This is to assure structural integrity during a fire. The finish material must also be continuous over the entire wall.

Certain finishes deteriorate more rapidly when exposed to fire than when they are on the non-fire side of the wall. Therefore, two separate tables are required. Table 7 applies to finishes on the non fire-exposed side of the wall, and Table 8 applies to finishes on the fire-exposed side. For finishes on the non-fire exposed side of the wall, the finish is converted to an equivalent thickness of concrete masonry by multiplying the finish thickness by the factor given in Table 7. The result, Tef, is then added to the concrete masonry wall equivalent thickness, Te, and used in Table 1 to determine the wall’s fire resistance rating (i.e., the equivalent thickness of concrete masonry assemblies, Tea = Te Tef).

For finishes on the fire-exposed side of the wall, a time (from Table 8) is assigned to the finish. This time is added to the fire resistance rating determined for the base wall and nonfire-exposed side finish, if any. The times listed in Table 8 are essentially the length of time the various finishes will remain intact when exposed to fire (i.e., on the fire-exposed side of the wall).

When calculating the fire resistance rating of a wall with finishes, two calculations are performed, assuming each side of the wall is the fire exposed side. The fire rating of the wall assembly is the lower of the two. Typically, for an exterior wall with a fire separation distance greater than 5 ft (1,524 mm), fire needs be considered on the interior side only

Installation of Finishes

Finishes that contribute to the total fire resistance rating of a wall must meet certain minimum installation requirements. Plaster and stucco are applied in accordance with the provisions of the building code without further modification. Gypsum wallboard and gypsum lath are to be attached to wood or metal furring strips spaced a maximum of 16 in. (406 mm) o.c., and must be installed with the long dimension parallel to the furring members. All horizontal and vertical joints must be supported and finished.

UNCONVENTIONAL AGGREGATES

In recent years, manufacturers of concrete masonry products have been exploring the use of alternative materials in the production of concrete masonry units. Some of these materials have not been evaluated using standardized fire resistance test methods or have been evaluated only to a limited degree. Such unconventional materials, which are typically used as a replacement for conventional aggregates, may not be covered within existing codes and standards due to their novelty or proprietary nature.

While test methods such as ASTM E119 define procedures for evaluating the fire resistance properties of concrete masonry assemblies, including those constructed using unconventional constituent materials, there has historically been no defined procedure for applying the results of ASTM E119 testing to standardized calculation procedures available through ACI 216.1/TMS 216. To provide consistency in applying the results of full scale ASTM E119 testing to established calculation procedures, CMHA has developed CMU-FAQ-013-23 (Ref. 15).

This guideline stipulates that when applying the fire resistance calculation procedure of ACI 216.1/TMS 216 to products manufactured using aggregate types that are not listed in ACI 216.1/TMS 216, at least two full scale ASTM E119 tests must be conducted on assemblies containing the unconventional material. Based on the results of this testing, an expression can be developed in accordance with this industry practice that permits the fire resistance of units produced with such aggregates to be calculated for interpolated values of equivalent thickness and proportion of non listed aggregate.

REFERENCES

  1. Code Requirements for Determining Fire Resistance of Concrete and Masonry Construction Assemblies, ACI 216.1- 14/TMS216-14. American Concrete Institute and The Masonry Society, 2014.
  2. International Building Code 2015. International Code Council, 2015.
  3. Standard Test Methods for Fire Tests of Building Construction and Materials, ASTM E119-16a. ASTM International, Inc., 2016.
  4. Standard Methods for Sampling and Testing Concrete Masonry Units, ASTM C140-16. ASTM International, Inc., 2016.
  5. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C90-16. ASTM International, Inc., 2016.
  6. Standard Specification for Concrete Aggregates, ASTM C33-16e1. ASTM International, Inc., 2016.
  7. Standard Specification for Lightweight Aggregates for Concrete Masonry Units, ASTM C331-14. ASTM International, Inc., 2014.
  8. Standard Specification for Perlite Loose Fill Insulation, ASTM C549-06(2012). ASTM International, Inc., 2012.
  9. Standard Specification for Vermiculite Loose Fill Thermal Insulation, ASTM C516-08(2013)e1. ASTM International, Inc., 2013.
  10. Steel Column Fire Protection, TEK 07-06A. Concrete Masonry & Hardscapes Association, 2009.
  11. ASD of Concrete Masonry Lintels Based on the 2012 IBC/2011 MSJC, TEK 17-01D. Concrete Masonry & Hardscapes Association, 2011.
  12. Standard Specification for Concrete Building Brick, ASTM C55 14a. ASTM International, Inc., 2014.
  13. Standard Specification for Calcium Silicate Brick (SandLime Brick), ASTM C73-14. ASTM International, Inc., 2014.
  14. Standard Specification for Prefaced Concrete and Calcium Silicate Masonry Units, ASTM C744-16. ASTM International, Inc., 2016.
  15. How is the fire resistance of a concrete masonry assembly calculated when using unconventional aggregates?, CMU-FAQ-013-23. Concrete Masonry & Hardscapes Association, 2023.
  16. What is the difference between fire resistance ratings for masonry assemblies obtained through IBC versus a listing service such as UL or FM?, CMU-FAQ-015-23. Concrete Masonry & Hardscapes Association, 2023.

Steel Column Fire Protection

  • August 2018

INTRODUCTION

Because of its inherent fire resistant properties, concrete masonry is often used as a non-structural fire protection covering for structural steel columns. Fire endurance of steel column protection is determined as the period of time for the average temperature of the steel to exceed 1,000 o F (538 o C), or for the temperature at any measured point to exceed 1,200 o F (649 o C) (ref. 1). These criteria depend on the thermal properties of the column cover and of the steel column (ref. 2). Using this technique, an empirical formula was developed to predict the fire endurance of concrete masonry protected steel columns (refs. 3, 4). This formula is presented in Figure 1, and is also included in the International Building Code (ref. 5)

Equivalent Thickness

Equivalent thickness is essentially the solid thickness that would be obtained if the volume of concrete contained in a hollow unit were recast without core holes (see Figure 2). The equivalent thickness is determined in accordance with Standard Methods of Sampling and Testing Concrete Masonry Units, ASTM C 140 (ref. 7), and is reported on the C 140 test report. Note that when all cells of hollow unit masonry are filled with an approved material, such as grout and certain loose fill materials, the equivalent thickness of the assembly is the actual thickness. For more detailed information, as well as typical equivalent thicknesses for concrete masonry units, see Fire Resistance Ratings of Concrete Masonry Assemblies, TEK 07-01D (ref. 8).

REFERENCES

  1. Standard Test Methods for Fire Tests of Building Construction and Materials, ASTM E 119-00. ASTM International, 2000.
  2. Lie, T. T. and Harmathy, T. Z. A Numerical Procedure to Calculate the Temperature of Protected Steel Columns Exposed to Fire, Fire Study No. 28, National Research Council of Canada, March 1972.
  3. Harmathy, T. Z. and Blanchard, J. A. C. Fire Test of a Steel Column of 8-in. H Section, Protected with 4-in. Solid Haydite Blocks, National Research Council of Canada, February 1962.
  4. Lie, T. T. and Harmathy, T. Z. Fire Endurance of Protected Steel Columns, ACI Journal, January 1974.
  5. 2006 International Building Code. International Code Council, 2006.
  6. Standard Method for Determining Fire Resistance of Concrete and Masonry Construction Assemblies, ACI 216.1-07/TMS 0216.1-07. American Concrete Institute and The Masonry Society, 2007.
  7. Standard Test Methods for Sampling and Testing Concrete Masonry Units and Related Units, ASTM C 140-02a. ASTM International, 2002.
  8. Fire Resistance Ratings of Concrete Masonry Assemblies, TEK 07-01D. Concrete Masonry & Hardscapes Association, 2018.

Determining the Recycled Content of Concrete Masonry Products

  • August 2018

INTRODUCTION

Sustainable development has been defined as development that meets the needs of the present without compromising the ability of future generations to meet their own needs (ref.1). This is often expressed as a holistic approach to building design, with the goal of optimizing environmental, economic and social impacts, from site selection through building operation and maintenance. A sustainable building optimizes resource management and operational performance, while minimizing risks to human health and the environment. As such, providing a sustainable building project encompasses far-reaching design decisions, and recognizes the interrelationships between virtually all elements and phases of the project.

A range of products and programs has been developed to help designers achieve a more sustainable built environment. Whether in the form of design guidelines for particular building types, or rating systems that step the design team through a series of design considerations, all aim to provide practical guidance for achieving the almost overwhelming goal of sustainability.

Referenced and in some cases mandated by some branches of the Federal government, as well as many state and local governments, the United States Green Building Council’s (USGBC) Leadership in Energy and Environmental Design (LEED®) has become perhaps the most widely used of these programs in recent years. LEED is a voluntary rating system designed to provide guidance as well as national third-party certification for defining what constitutes a “green” building.

Concrete masonry building and hardscape products can make a significant contribution to meeting LEED certification. This contribution is augmented by the recycled content potential of the companion products necessary for a concrete masonry wall, such as grout, mortar and reinforcement products.

Concrete masonry building and hardscape materials can contribute to earning credits in several LEED categories, including Sustainable Sites, Energy and Atmosphere, Materials and Resources and Innovation in Design. More detail on LEED strategies incorporating concrete masonry and hardscape materials is available in TEK 06 09C, Concrete Masonry and Hardscape Products in LEED 2009 and PAV-TEC-016-16, Achieving LEED Credits with Segmental Concrete Pavement (refs. 2, 3).

LEED includes specific rating systems for various applications. The information in this TEK is applicable to LEED for new construction, school, retail, and core and shell development (refs. 4-7).

For these LEED programs, Materials and Resources Credit 4: Recycled Content allows up to two LEED certification points for using materials with recycled content. The inert nature of concrete masonry lends itself well to incorporating recycled materials as cement replacements, as aggregates and as other constituents in the concrete mix. This TEK provides guidance on determining the recycled content of concrete masonry products for the purpose of earning LEED credit under the new construction, school, retail, and core and shell development LEED programs.

The LEED for Homes (ref. 8) recycled content credit differs from these other programs. Concrete masonry walls are eligible for recycled content credit under the LEED for Homes Materials and Resources Credit 2: Environmentally Preferable Products, provided the masonry contains at least 25% recycled content (post-consumer plus one-half pre-consumer, as described in the following sections). Note, however, that the National Association of Home Builders with the International Code Council has developed their own green building standard that has similar requirements (ref. 9). See www.nahbgreen.org for more information.

USE OF RECYCLED MATERIALS IN CONCRETE MASONRY AND HARDSCAPE UNITS

When concrete masonry products incorporate recycled materials, due consideration must be given to ensure that the use of these materials does not adversely affect the quality or safety of the units or construction. Note that some recycled materials may only be regionally available. Designers should work closely with concrete masonry manufacturers to substantiate recycled content.

Unit Specifications

Whether produced using recycled or virgin materials, concrete masonry products are required to meet the applicable ASTM unit specification (see Table 1). These standards contain minimum requirements that assure properties necessary for quality performance. For example, many concrete masonry units are required to conform to ASTM C90, Standard Specification for Loadbearing Concrete Masonry Units (ref. 11). ASTM C90 requirements include material requirements for aggregates, cementitious materials, and other constituent materials, physical requirements, finish and appearance requirements, and permissible variations in dimensions.

Aggregates, including recycled aggregates, for concrete masonry units are required to meet ASTM C33, Standard Specification for Concrete Aggregates, or C331, Standard Specification for Lightweight Aggregates for Concrete Masonry Units (refs. 19, 20), except that grading requirements do not have to be met. Aggregate characteristics governed include limits on deleterious substances and aggregate soundness.

Cements are required to meet ASTM C150 and supplemental cementitious materials such as fly ash must meet ASTM C618 (refs. 27, 28). In addition to cementitious materials and aggregates, the ASTM unit specifications also allow for the inclusion of “Other Constituents,” such as pigments, integral water repellents and finely ground silica. For a material to qualify for inclusion in a concrete masonry product under this provision, the material:

  • must have been previously established as suitable for use in the product, and
  • must either conform to applicable ASTM standards or be shown, via test or experience, not to be detrimental to the durability of the units or other masonry materials.

Fire Resistance Ratings

For construction requiring a fire resistance rating, the use of recycled aggregates may impact the method used to determine the hourly rating, because concrete masonry fire resistance ratings vary with the aggregate type(s) used to manufacture the units. Concrete masonry fire ratings can be determined by: model building code prescriptive tables (ref. 21), a standard calculation method as provided in Section 721 of the International Building Code (IBC) (ref. 21) and the ACI/TMS 216 (ref. 22); testing in accordance with ASTM E 119, Standard Test Methods for Fire Tests of Building Construction and Materials (ref. 23); commercial listing services; and deemed-to comply assemblies included in some building codes. These tools also include ways to increase a wall system’s fire resistance rating through careful placement of additional materials.

Currently, the standard calculation procedure applies to the following aggregate types: expanded slag, pumice, expanded clay, expanded shale, expanded slate, limestone, cinders, aircooled slag, calcareous gravel, and siliceous gravel. When units are made with a combination of these aggregates, the fire rating is determined by interpolation (see ref. 23 for more detail). When aggregate types other than those listed above are used, the fire resistance rating is determined using a method other than the standard calculation procedure.

TEK 07-01D, Fire Resistance Rating of Concrete Masonry Assemblies (ref. 24) contains a detailed discussion of concrete masonry fire ratings. Additional considerations for recycled aggregates which are not listed in the standard calculation procedure are their stability, safety and load-carrying ability when subjected to fire.

LEED MATERIALS & RESOURCES CREDIT 4: RECYCLED CONTENT

By increasing the demand for products that incorporate recycled materials, the Recycled Content credits are intended to reduce the environmental and societal impacts associated with extracting and processing virgin materials.

LEED awards 1 point to projects that demonstrate that the total amount of a project’s recycled content exceeds 10% based on both weight and the total building product costs. An additional point is awarded if the recycled content reaches 20%. Also, if the recycled content reaches 30%, a third point can be earned as an Innovation & Design credit.

LEED refers to the International Organization for Standardization (ISO) for the definition of what constitutes recycled content, and for the basis of determining the percentage – i.e., weight (ref. 25). Recycled materials are those materials diverted from the solid waste stream, either during the manufacturing process (pre-consumer) or after their intended use (post-consumer). The recycled content for LEED credit is determined as the sum of all post-consumer recycled content plus one-half of the pre-consumer recycled content.

To claim this credit, the LEED NC Reference Guide suggests establishing a project goal for recycled content materials, and dentifying product suppliers who can achieve this goal. The following sections describe how concrete masonry and hardscape products can contribute to recycled content goals.

Pre-Consumer Recycled Content

Pre-consumer (post-industrial) content as defined by the LEED v2.2 reference manual is “material diverted from the waste stream during the manufacturing process. Excluded is reutilization of materials such as rework, regrind or scrap generated in a process and capable of being reclaimed within the same process that generated it (Source ISO 14021). Examples in the pre-consumer category include planer shavings, plytrim, sawdust, chips, bagasse, sunflower seed hulls, walnut shells, culls, trimmed materials, print overruns, over-issue publications, and obsolete inventories.” (refs. 4, 25) It is important for the producer to work with the material suppliers to determine which materials can be considered recycled and which cannot. It is important for the producer to have documentation from the material supplier stating that a material is considered recycled for the purposes of contributing to LEED certification.

Post-Consumer Recycled Content

Post-consumer recycled content is consumer waste that can no longer be used for its intended purpose. The official LEED definition of a post-consumer material is “material generated by households or by commercial, industrial and institutional facilities in their role as end users of the product which can no longer be used for its intended purpose. This includes returns of materials from the distribution chain (ref. 26). Examples of materials in this category include construction and demolition debris, materials collected through curbside and drop off recycling programs, broken pallets (if from a pallet refurbishing company, not a pallet-making company), discarded products (e.g. furniture, cabinetry and decking) and urban maintenance waste (leaves, grass clippings, tree trimmings, etc.) (refs. 4, 25).

As with pre-consumer materials, a producer should work with the material supplier to document that the materials being used are specifically documented as post-consumer recycled material for the purposes of contributing to LEED certification.

DETERMINING RECYCLED CONTENT

The LEED recycled content credit(s) is based on the recycled content percentages, based on the total value of all permanently installed materials on the project. Note that mechanical, electrical and plumbing components are excluded from this total, as are specialty items such as elevators. In determining the percentages of recycled content, the contribution from concrete masonry and hardscape products is added to the contribution from other building components.

The following sections describe the procedure for determining the recycled content of a particular product, then combining all such data to determine the overall recycled content percentage for the project. The percentages are based on both weight and cost, as described below.

For a Product

The producer is responsible for reporting the percentages of reconsumer and post-consumer recycled content for each product sold. If the producer supplies other products in addition to block such as reinforcement, mortar, etc., the producer should also document the recycled percentages in each of these products and report them to the contractor who purchased them.

The percentages are based on weight, as follows:

As an aid to the producer, CMHA has developed a simple spreadsheet to calculate these percentages (see Figure 1). Figure 1 illustrates the process of determining the weights of all constituent materials; determining the total weight; then determining the percent by weight of each recycled material. The total pre-consumer and post consumer percentages are simply the sum of the individual material percentages in each category.

Note that Figure 1 includes an alternate calculation, applicable to concrete products only. This alternate calculation is described below.

For a Product: Alternate Calculation per LEED for New Construction and Major Renovations

LEED for New Construction and Major Renovations, Version 2.2 and the LEED Reference Guide for Green Building Design and Construction, 2009 Edition (ref. 5, 26) provide an alternate method to calculate and report the recycled content for concrete products that use supplementary cementitious materials (SCMs), such as fly ash or ground blast furnace slag cement. This alternate method allows the recycled content calculation to be based on only the cementitious materials, rather than on all materials in the concrete mix. This alternate method helps offset the fact that the recycled content calculation is based on weight, and SCMs are typically very low in weight. For concrete mixes with SCMs as the only recycled content, this alternate method will result in a higher recycled content value than the conventional approach. For concrete mixes that incorporate both SCMs and other recycled materials, the manufacturer may want to evaluate the percent recycled content using both methods to determine which method yields the best result.

The basic calculation is the same as that described in the previous section, except:

  • when determining the percent post-consumer and percent pre consumer recycled content, divide by the total weight of the cementitious materials only, and
  • when determining the recycled content value, multiply the percent recycled content by the total value of the cementitious materials only.

Use of the alternative calculation method requires that the value of the cementitious materials be used in place of the total value of the product when the LEED project team determines the value of the recycled content. The producer would likely benefit from describing this value as a percentage of the value of the whole product and not as a monetary figure. When requested, the producer should report this value to the direct customer and not to a third party.

For the Project as a Whole

Based on information from the product suppliers, the design team determines the recycled content value for the project as a whole as follows:

  1. For each product, the percent recycled content is determined as the percent post-consumer (reported by the supplier) plus one-half of the percent pre-consumer. For the example in Figure 1, the percent recycled content for the concrete masonry units is 17.9% + 1/2(37.1%) = 36.5%
  2. For each product, the recycled content value is determined as the percent recycled content multiplied by the total product cost for the project. For the hypothetical project referenced in Figure 1, if the total cost of the concrete masonry units is $90,000, the recycled content value of the concrete masonry units is 0.365($90,000) = $32,805. It is important to note that the cost used in this calculation is the amount paid to the producer or the contractor for the product. It is not the cost of the individual materials that constitute the concrete masonry or hardscape product. The product cost should be supplied by the contractor. It is the contractor’s responsibility to separate their labor charges from the material charges.
  3. For the project as a whole, the recycled content percentage is determined as the sum of the recycled content values of each product, divided by the total cost of all of these products. If this total recycled content percentage is 10% or higher, the project earns one LEED point; if it is 20% or higher the project earns two LEED points. Projects with recycled content percentages of 30% or more may be eligible for an additional Innovation in Design point.

CONCRETE MASONRY UNITS RETURNED FROM A JOB SITE

Unused concrete masonry units returned to the manufacturer from a job site are considered under Materials and Resources Credit 2: Construction Waste Management. Under Credit 2, the building project with unused materials can earn LEED point(s) for returning those materials, and hence diverting them from a landfill. If subsequently used on another project, the recycled content of the units as manufactured is reported to the contractor or design team, as for unused concrete masonry products.

REFERENCES

  1. Standard Terminology for Sustainability Relative to the Performance of Buildings, ASTM E2114-06a. ASTM International, Inc., 2006.
  2. Concrete Masonry and Hardscape Products in LEED 2009, TEK 06-09C, Concrete Masonry & Hardscapes Association, 2009.
  3. Achieving LEED Credits with Segmental Concrete Pavement, PAV TEC-016-16, Concrete Masonry & Hardscapes Association, 2016.
  4. LEED for New Construction and Major Renovations, Version 2.2, 3rd ed. U. S. Green Building Council, 2005.
  5. LEED for Schools for New Construction and Major Renovations, Version 2007. U. S. Green Building Council, 2007.
  6. LEED for Retail: New Construction and Major Renovations, Version 3. U. S. Green Building Council, 2008.
  7. LEED Green Building Rating System for Core and Shell Development, Version 2.0. U. S. Green Building Council, 2006.
  8. LEED for Homes Rating System. U. S. Green Building Council, 2008.
  9. NAHB Model Green Home Building Guidelines. National Association of Home Builders, 2006.
  10. Standard Specification for Concrete Brick, ASTM C55-06e1. ASTM International, 2006.
  11. Standard Specification for Loadbearing Concrete Masonry Units, ASTM C90-06b. ASTM International, Inc., 2006.
  12. Standard Specification for Nonloadbearing Concrete Masonry Units, ASTM C129-06. ASTM International, 2006.
  13. Standard Specification for Prefaced Concrete and Calcium Silicate Masonry Units, ASTM C744-05. ASTM International, 2005.
  14. Standard Specification for Concrete Facing Brick, ASTM C1634-06. ASTM International, 2006.
  15. Standard Specification for Solid Concrete Interlocking Paving Units, ASTM C936-08. ASTM International, 2008.
  16. Standard Specification for Concrete Grid Paving Units, ASTM C1319-01(2006). ASTM International, 2006.
  17. Standard Specification for Dry-Cast Segmental Retaining Wall Units, ASTM C1372-04e2. ASTM International, 2002.
  18. Standard Specification for Concrete Masonry Units for Construction of Catch Basins and Manholes, ASTM C139-05. ASTM International, 2005.
  19. Standard Specification for Concrete Aggregates, ASTM C33-07. ASTM International, Inc., 2007.
  20. Standard Specification for Lightweight Aggregates for Concrete Masonry Units, C331-05. ASTM International, Inc., 2005.
  21. International Building Code, International Code Council. 2006 and 2009 editions.
  22. Code Requirements for Determining Fire Resistance of Concrete and Masonry Construction Assemblies, ACI 216.1-07/TMS 216-07. American Concrete Institute and The Masonry Society, 2007.
  23. Standard Test Methods for Fire Tests of Building Construction and Materials, ASTM E119-08a. ASTM International, Inc., 2008.
  24. Fire Resistance Rating of Concrete Masonry Assemblies, TEK 07-01D, Concrete Masonry & Hardscapes Association, 2018.
  25. Environmental Labels and Declarations – Self-Declared Environmental Claims (Type II Environmental Labeling), ISO 14021-1999. International Organization for Standardization, 1999.
  26. LEED Reference Guide for Green Building Design and Construction, 2009 Edition. U.S. Green Building Council, 2009.
  27. Standard Specification for Portland Cement, ASTM C150-07. ASTM International, 2007.
  28. Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use in Concrete. C618-08a. ASTM International, 2008.