FIRE RESISTANCE RATINGS OF CONCRETE MASONRY ASSEMBLIES. TEK 7-1C Fire Resistance (2009) Related TEK: 2-6, 5-8B, 7-6A

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1 n information erie from the national authority on concrete maonry technology FIRE RESISTNCE RTINGS OF CONCRETE MSONRY SSEMBLIES TEK 7-C Fire Reitance (009) INTRODUCTION Concrete maonry i widely pecifi ed for fi re wall and fi re barrier becaue concrete maonry i noncombutible, provide durable fi re reitance, and i economical to contruct. Chapter 7 of the International Building Code (IBC) (ref., ) govern material and aemblie ued for tructural fire reitance and fire-rated eparation of adjacent pace. Thi TEK i baed on the proviion of Code Requirement for Determining Fire Reitance of Concrete and Maonry Contruction emblie, CI 6./TMS-06 (ref. ) (hereafter referred to a the Standard), which outline a procedure to calculate the fire reitance rating of concrete maonry aemblie. The 997 edition of the Standard i referenced in the 00 and 006 IBC for concrete and maonry material. The current edition of the Standard, publihed in 007, contain only minor change from the 997 edition and i referenced in the 009 IBC. IBC ection 7. through 7.5 are nearly identical to the proviion of the Standard. Thi TEK i baed on both precriptive detail and table a well a the calculated fi re reitance procedure, which i practical, veratile and economical. The calculation procedure allow the deigner virtually unlimited fl exibility to incorporate the excellent fi re-reitive propertie of concrete maonry into the deign. Included are method for determining the fi re reitance rating of concrete maonry wall, column, lintel, beam, and concrete maonry fi re protection for teel column. lo included are aemblie compoed of concrete maonry and other component, including plater and gypum wallboard fi nihe, and multi-wythe maonry component including clay or hale maonry unit. METHODS OF DETERMINING FIRE RESISTNCE RTINGS Becaue full-cale fi re teting of repreentative tet pecimen i not practical in daily practice due to time and financial contraint, the IBC outline multiple option for alternative for fi re rating determination: tandardized calculation procedure, uch a thoe in the Standard and in Section 7 of the IBC, precriptive deign uch a thoe in Section 70 of the IBC, engineering analyi baed on a comparion with teted aemblie, and third party liting ervice, uch a Underwriter Laboratory, alternative mean approved by the building offi cial per Section 04. of the IBC. Of thee, the calculation method i an economical and commonly ued method of determining concrete maonry fi re reitance rating. The calculation are baed on extenive reearch, which etablihed relationhip between the phyical propertie of material and the fi re reitance rating. The calculation method i fully decribed in the Standard and IBC Section 7, and determine fi re reitance rating baed on the equivalent thickne of concrete maonry unit and the aggregate type ued in their manufacture. Private commercial liting ervice allow the deigner to elect a fi re rated aembly that ha been previouly teted, claifi ed and lited in a publihed directory of fi re rated aemblie. The liting ervice alo monitor material and production to verify that the concrete maonry unit are and remain in compliance with appropriate tandard, which uually neceitate a premium for unit of thi type. The ytem alo i omewhat infl exible in that little varia- Related TEK: -6, 5-8B, 7-6 Keyword: calculated fi re reitance rating, column, control joint, equivalent thickne, fi re reitance rating, fi re wall, lintel, multi-wythe wall, pecifi cation, teel column protection NCM TEK 7-C

2 tion from the original teted wall aembly i allowed, including unit ize, hape, mix deign, contituent material, and even the plant of manufacture. For precriptive deign, the IBC provide a erie of table that decribe requirement of variou aemblie to meet the fi re reitance rating pecifi ed. The lat two option lited above require jutifi cation to the building offi cial that the propoed deign i at leat the equivalent of what i precribed in the code. 5% olid unit in. (94 mm) 4.04 in. (0 mm) the equivalent thickne i 4.04 inche (0 mm) CLCULTED FIRE RESISTNCE RTINGS Background The calculated fi re reitance method i baed on extenive reearch and teting of concrete maonry wall. Fire teting of wall aemblie i conducted in accordance with the Standard Tet Method for Fire Tet of Building Contruction and Material, STM E9 (ref. 4), which meaure four performance criteria, a follow: reitance to the tranmiion of heat through the wall aembly, reitance to the paage of hot gae through the wall, uffi cient to ignite cotton wate, load-carrying capacity of loadbearing wall, and reitance to the impact, eroion and cooling effect of a hoe tream on the aembly after expoure to the tandard fi re. The fi re reitance rating of concrete maonry i typically governed by the heat tranmiion criteria. From the tandpoint of life afety (particularly for fi re fi ghter) and alvageability, thi failure mode i certainly preferable to a tructural collape endpoint, characteritic of many other building material. The equivalent thickne (a olid unit with the ame amount of material) of thi particular unit i 4.04 in. (0 mm). Figure Equivalent Thickne Table Equivalent Thicknee of Concrete Maonry Unit, in. (mm) Nominal Baed on Baed on width, in. typical percent olid (mm) hollow unit (75%) (00%) 4 (0).7 (69) [7.8].7 (69).6 (9) 6 (5). (79) [55.0] 4. (07) 5.6 (4) 8 (0) 4.0 (0) [5.0] 5.7 (45) 7.6 (9) 0 (54) 4.5 () [46.] 7. (8) 9.6 (44) (05) 5. (9) [44.0] 8.7 ().6 (95) 4 (56) 5.5 (9) [40.] 0. (59).6 (45) 6 (406) 6.0 (5) [8.4].7 (97) 5.6 (96) Value in bracket [ ] are percent olid value baed on typical two-core concrete maonry unit. Table Fire Reitance Rating Period of Concrete Maonry emblie (ref.,, ) ggregate type in the Minimum required equivalent thickne, in. (mm), for fire reitance rating, hour, B concrete maonry unit C 4 /4 / /4 /4 / /4 /4 / /4 /4 / Calcareou or iliceou gravel Limetone, cinder or unexpanded lag Expanded clay, hale or late Expanded lag or pumice Fire reitance rating between the hourly fi re reitance rating period lited may be determined by linear interpolation baed on the equivalent thickne value of the concrete maonry unit. The requirement of STM C55, STM C7, STM C90 or STM C744 (ref., 4, 6, 5) hall apply. Include equivalent thickne of fi nihe where applicable: ee ection Effect of Finihe on Fire Reitance Rating. B Where combutible member are framed into the wall, the thickne of olid material between the end of each member and oppoite wall face, or between member et in from oppoite ide, mut be at leat 9% of thickne hown. C Minimum required equivalent thickne correponding to the hourly fi re reitance rating for unit made with a combination of aggregate hall be determined by linear interpolation baed on the percent by volume of each aggregate ued in the manufacture. NCM TEK 7-C

3 The calculated fi re reitance rating information preented here i baed on the IBC and the Standard (ref.,, ). Equivalent Thickne Extenive teting ha etablihed a relationhip between fi re reitance and the equivalent olid thickne of concrete maonry wall, a hown in Table. Equivalent thickne i eentially the olid thickne that would be obtained if the volume of concrete contained in a hollow unit were recat without core hole (ee Figure ). The equivalent thickne i determined in accordance with Standard Method of Sampling and Teting Concrete Maonry Unit, STM C40 (ref. 5), and i reported on the C40 tet report. If the equivalent thickne i unknown, but the percent olid of the unit i, the equivalent thickne of a hollow unit can be determined by multiplying the percent olid by the unit' actual thickne. The equivalent thickne of a 00% olid unit or a olid grouted unit i equal to the actual thickne. For partially grouted wall where the unfi lled cell are left empty, the equivalent thickne for fi re reitance rating purpoe i equal to that of an ungrouted unit. For partially grouted wall with fi lled cell, ee the following ection. Loadbearing unit conforming to STM C90 (ref. 6) that are commonly available include 00% olid unit, 75% olid unit, and hollow unit meeting minimum required face hell and web dimenion. Typical equivalent thickne value for thee unit are lited in Table. Filling Cell with Looe Fill Material If all cell of hollow unit maonry are fi lled with an approved material, the equivalent thickne of the aembly i the actual thickne. Thi alo applie to partially grouted concrete maonry wall where all ungrouted cell are fi lled with an approved material. pplicable fill material are: grout, and, pea gravel, cruhed tone, or lag that comply with STM C (ref. 7) requirement; pumice, coria, expanded hale, expanded clay, expanded late, expanded lag, expanded fly ah, or cinder that comply with STM C (ref. 8), perlite meeting the requirement of STM C549 (ref. 9), or vermiculite complying with C56 (ref. 0). Wall embly Fire Rating The fire reitance rating i determined in accordance with Table utilizing the appropriate aggregate type ued in the maonry unit and the equivalent thickne. Unit manufactured with a combination of aggregate type are addreed by footnote C, which may be expreed by the following equation (ee alo the blended aggregate example, below): T r = (T x V ) + (T x V ) (T x V ), where: n n T r = required equivalent thickne for a pecifi c fi re reitance rating of an aembly contructed of unit with combined aggregate, in. (mm) T, T,...T n = required equivalent thickne from Table for a pecifi c fi re reitance rating of a wall contructed of unit with aggregate type,,... n, repectively, in. (mm) V, V,... V n = fractional volume of aggregate type,,... n, repectively, ued in the manufacture of the unit (note that the clarifi cation "dry-rodded volume" wa added to the 007 edition of the Standard, although thi verbiage not included in the IBC) Blended aggregate example: The required equivalent thickne of an aembly contructed of unit made with expanded hale (80% by volume), and calcareou and (0% by volume), to meet a -hour fi re reitance rating i determined a follow. From Table : T for expanded hale ( hr rating) = 4.4 in. ( mm) T for calcareou and ( hr rating) = 5. in. (5 mm) T r = (T x V ) + (T x V ) T r = (4.4 x 0.80) + (5. x 0.0) = 4.6 in. (6 mm) Multi-Wythe Wall emblie The fire reitance rating of multi-wythe wall (Figure ) i baed on the fi re reitance of each wythe and the air pace between each wythe uing the following equation: R = (R R R n n ).7 where: R, R,...R n = fi re reitance rating of wythe,,...n, repectively (hr).,,... n = 0.0; factor for each air pace,,,...n, repectively, having a width of / in. ( mm) or more between wythe. Note that it doe not matter which ide i expoed to the fi re. For multi-wythe wall of clay and concrete maonry, ue the value in Table for the brick wythe in the above equation. Reinforced Concrete Maonry Column Concrete maonry column fi re teting evaluate the ability of the column to carry deign load under tandard fi re tet condition. Baed on a compendium of fi re tet, the fi re reitance rating of reinforced concrete maonry column i baed on the leat plan dimenion of the column a indicated in Table 4. The minimum required cover over the vertical reinforcement i in. (5 mm). NCM TEK 7-C

4 Concrete Maonry Lintel Fire teting of concrete maonry beam and lintel evaluate the ability of the member to utain deign load under tandard fi re tet condition. Thi i accomplihed by enuring that the temperature of the tenile reinforcement doe not exceed,00 o F (59 o C) during the rating period. The calculated fire reitance rating of concrete maonry lintel i baed on the nominal thickne of the lintel and the minimum cover of longitudinal reinforcement (ee Table 5). The cover requirement protect the reinforcement from trength degradation due to exceive temperature during the fire expoure period. Cover requirement may be provided by maonry unit, grout, or mortar. Note that for and 4 hour requirement, not enough cover i available for 6-in. (5 mm) maonry. However, if a pecial analyi indicate that the reinforcement i not neceary or not needed, uch a when condition for arching action are preent, the cover requirement may be waived. See TEK 7-C (ref. ) for lintel deign and condition for arching action. Control Joint Figure how control joint detail in fi re-rated wall aemblie in which opening are not permitted or where opening are required to be protected. Maximum joint width i / in. ( mm). lthough thee detail are not directly in the IBC, they are included by reference of the Standard. In addition to thee precriptive fire reitance rated control joint, other control joint may be permitted in fire rated maonry wall. For example, the IBC and the Standard include proviion for ceramic fiber joint protection for precat panel, which are imilar to concrete maonry wall in that both rely on concrete for fire protection, and both are governed by the STM E9 heat tranmiion criteria (ee Figure 4). The firt two categorie of aggre- Wythe (R ) ir pace factor ( ) for width in. ( mm) or greater Wythe (R ) R = Fire reitance rating of wythe R = Fire reitance rating of wythe = ir pace factor = 0. Figure Variable for Determining the Fire Reitance Rating of a Multi-Wythe Maonry Wall gate type in Table would correpond to the carbonate or iliceou aggregate concrete curve and the lat two aggregate categorie of Table would correpond to the emi-lightweight or lightweight concrete curve. For example, for an 8-in. (0-mm) limetone aggregate concrete maonry wall with a maximum control joint width of / in. ( mm), a in. (5 mm) thickne (meaured perpendicular to the face of the wall) of ceramic fiber in the joint can be ued in wall with fire reitance rating up to hour, while a in. (5 mm) thickne can be ued in the joint of a 4-hour wall. Steel Column Protected by Concrete Maonry Fire teting of a teel column protected by concrete maonry evaluate the tructural integrity of the teel column under fire tet condition, by meauring the temperature rie of the teel. The calculated fi re reitance Table Fire Reitance of Brick or Tile of Clay or Shale (ref.,, ) Minimum equivalent thickne for fi re reitance rating, in. (mm) Material type 4 hr hr hr hr > 75% olid 6.0 (5) 4.9 (4).8 (97).7 (69) Hollow unit B 5.0 (7) 4. (09).4 (86). (58) Hollow unit C 6.6 (68) 5.5 (40) 4.4 ().0 (76) See Equivalent Thickne ection for calculation. B Unfi lled hollow unit. C Grouted or fi lled according to the Filling Cell with Looe Fill Material ection. Table 4 Reinforced Concrete Maonry Column (ref.,, ) Minimum column dimenion, in. (mm), for fi re reitance rating of: hour hour hour 4 hour 8 (0) 0 (54) (05) 4 (56) Table 5 Reinforced Concrete Maonry Lintel Minimum Longitudinal Reinforcing Cover, in. (mm) (ref.,, ) Nominal lintel width, Fire reitance rating in., (mm) hour hour hour 4 hour 6 (5) / (8) (5) 8 (0) / (8) / (8) / 4 (44) (76) 0 (54) or more / (8) / (8) / (8) / (44) 4 May be permitted with a more detailed analyi per the Standard i.e. condition for arching action. 4 NCM TEK 7-C

5 rating of teel column protected by concrete maonry, a illutrated in Figure 5, i determined by: W T e R = D + K 0.8 dt m e (Englih unit) ( 0.5p T + e ) W T e R = D K dt m e ( 0.5p+ T ) e 0.8 (SI) where: d m = denity of concrete maonry protection, pcf (kg/m ) D = heated perimeter of teel, in. (mm) (Figure 5) K = thermal conductivity of concrete maonry, Table 6, Btu/hr. ft.o F (W/m. C) p = inner perimeter of concrete maonry protection, in. (mm) R = fire reitance rating of column aembly, hr. T e = equivalent thickne of maonry protection, in. (mm) W = average weight of teel column in lb/ft (kg/m) Note: The Standard (ref. ) ha a lightly different form of the equation but yield identical anwer. For more information on teel column protected by concrete maonry, ee TEK 7-6, Steel Column Fire Protection (ref. ). Effect of Finih Material on Fire Reitance Rating In many cae, drywall, plater or tucco finihe are ued on concrete maonry wall. While finihe are normally applied for architectural reaon, they can alo provide additional fire reitance. The IBC and the Standard make proviion for calculating the additional fire reitance provided by thee finihe. Note that when fi nihe are ued to achieve the required fi re rating, the maonry alone mut provide at leat one-half of the total required rating and the contribution of the finih on the non-fi re-expoed ide can not be more than one-half of the contribution of the maonry alone. Thi i to aure tructural integrity during a fi re. The fi nih material mut alo be continuou Joint reinforcement, Stop joint reinforcement at control joint Sealant Backer rod Vertical reinforcement, Preformed gaket Concrete maonry ah unit -Hour Fire Reitance Rating Joint reinforcement, Stop joint reinforcement at control joint Stop joint reinforcement at control joint Building paper or other bond break Sealant Joint reinforcement, Sealant Joint reinforcement, Stop joint reinforcement at control joint Sealant Backer rod Backer rod Backer rod Vertical reinforcement, Ceramic fiber felt (aluminailica fiber) Raked mortar joint Vertical reinforcement, Female concrete maonry unit Male concrete maonry unit Raked mortar joint, in. ( mm) min. depth Three Option for 4-Hour Fire Reitance Rating Figure Control Joint for Fire Reitant Concrete Maonry emblie (ref. ) NCM TEK 7-C 5

6 4 C, ceramic blanket thickne, in Panel thickne, in. C, ceramic blanket thickne, in. hr hr in. (5.4 mm) joint width hr Panel thickne in Figure 4 Ceramic Fiber Joint Protection w hr 8 in. (9.5 mm) joint width hr hr hr hr hr hr 4 hr 4 hr hr hr 4 hr d 4 hr in. (5.4 mm) maximum regardle of opening rating Ceramic fiber blanket C Joint width Panel thickne Carbonate or iliceou aggregate concrete Semi-lightweight or lightweight concrete over the entire wall. Certain fi nihe deteriorate more rapidly when expoed to fi re than when they are on the non-fi re ide of the wall. Therefore, two eparate table are required. Table 7 applie to fi nihe on the non-fi re-expoed ide of the wall, and Table 8 applie to fi nihe on the fi re-expoed ide. For fi nihe on the nonfi re-expoed ide of the wall, the fi nih i converted to an equivalent thickne of concrete maonry by multiplying the fi nih thickne by the factor given in Table 7. The reult, T ef, i then added to the concrete maonry wall equivalent thickne, T e, and ued in Table to determine the wall' fi re reitance rating (i.e., the equivalent thickne of concrete maonry aemblie, T ea = T e + T ef ). For finihe on the fire-expoed ide of the wall, a time (from Table 8) i aigned to the fi nih. Thi time i added to the fi re reitance rating determined for the bae wall and non-fire-expoed ide fi nih, if any. The time lited in Table 8 are eentially the length of time the variou fi nihe will remain intact d 0.5p t web p = (w + d) + (w - t ) web d 0.5p p = 4d p = πd Figure 5 Detail of Concrete Maonry Column Protection for Commonly Ued Shape Table 6 Concrete Maonry Conductivity (ref., ) Denity, d m Thermal conductivity, K pcf (kg/m ) Btu/hr. ft.o F (W/m. C) 80 (,8) 0.07 (0.58) 85 (,6) 0.8 (0.94) 90 (,44) 0.5 (0.46) 95 (,5) 0.78 (0.48) 00 (,60) 0.08 (0.5) 05 (,68) 0.40 (0.588) 0 (,76) 0.76 (0.650) 5 (,84) 0.46 (0.70) 0 (,9) (0.749) 5 (,00) (0.879) 0 (,08) 0.56 (0.97) 5 (,6) 0.60 (.07) 40 (,4) (.86) 45 (,) (.) 50 (,40) 0.87 (.449) Thermal conductivity at 70 o F. o C = ( o F-)( 5 / 9 ) 6 NCM TEK 7-C

7 when expoed to fi re (i.e., on the fi re-expoed ide of the wall). When calculating the fi re reitance rating of a wall with fi nihe, two calculation are performed, auming each ide of the wall i the fi re-expoed ide. The fi re rating of the wall aembly i the lower of the two. Typically, for an exterior wall with a fi re eparation ditance greater than 5 ft (,54 mm), fi re need be conidered on the interior ide only. Intallation of Finihe Finihe that contribute to the total fi re reitance rating of a wall mut meet certain minimum intallation requirement. Plater and tucco are applied in accordance with the proviion of the building code without further modifi cation. Gypum wallboard and gypum lath are to be attached to wood or metal furring trip paced a maximum of 6 in. (406 mm) o.c., and mut be intalled with the long Table 7 Multiplying Factor for Finihe on Non-Fire-Expoed Side of Wall (ref., ) ggregate type in concrete maonry: Siliceou, 80% or more by calcareou, volume of Type of fi nih limetone, expanded hale, applied to cinder, air- late, or clay, wall cooled blat- expanded lag furnace lag or pumice Portland cementand plater B, D Gypum-and plater.5.00 Gypumvermiculite or.75.5 C perlite plater Gypum wallboard.00.5 Value hown are 009 IBC & CI 6./TMS Note that in the 006 IBC, gypum wallboard wa included in the ame category and had the ame value a for gypum-and plater. However, the 006 IBC alo indicated that CI 6./TMS 6-97 could be ued, which i a hown here. B For portland cement-and plater 5 / 8 in. (6 mm) or le in thickne and applied directly to concrete maonry on the non-fi re-expoed ide, the multiplying factor i.0. C For expanded hale with le than 0% and, a multiplying factor of.50 may be ued per 009 IBC. D For 00% expanded lag, expanded clay or pumice, and portland cement-and plater not meeting the tipulation of footnote B, the multiplying factor hall be 0.50 per 009 IBC. dimenion parallel to the furring member. ll horizontal and vertical joint mut be upported and finihed. UNCONVENTIONL GGREGTES In recent year, manufacturer of concrete maonry product have been exploring the ue of alternative material in the production of concrete maonry unit. Some of thee material have not been evaluated uing tandardized fi re reitance tet method or have been evaluated only to a limited degree. Such unconventional material, which are typically ued a a replacement for conventional aggregate, may not be covered within exiting code and tandard due to their novelty or proprietary nature. While tet method uch a STM E9 defi ne procedure for evaluating the fi re reitance propertie of concrete maonry aemblie, including thoe Table 8 Time igned to Finih Material on Fire-Expoed Side of Wall (ref.,, ) Finih decription: Time, min. Gypum wallboard / 8 in. (0 mm) 0 / in. ( mm) 5 5 / 8 in. (6 mm) 0 Two layer of / 8 in. (0 mm) 5 One layer / 8 in. (0 mm) and one layer / in. ( mm) 5 Two layer of / in. ( mm) 40 Type "X" gypum wallboard / in. ( mm) 5 5 / 8 in. (6 mm) 40 Direct-applied portland cement-and plater Portland cement-and plater on metal lath / 4 in. (9 mm) 0 7 / 8 in. ( mm) 5 in. (5 mm) 0 Gypum-and plater on / 8 in. (0 mm) gypum lath / in. ( mm) 5 5 / 8 in. (6 mm) 40 / 4 in. (9 mm) 50 Gypum-and plater on metal lath / 4 in. (9 mm) 50 7 / 8 in. ( mm) 60 in. (5 mm) 80 For the purpoe of determining the contribution of portland cement-and plater to the equivalent thickne of concrete maonry for ue in Table, ue either the actual plater thickne or 5 / 8 in. (6 mm), whichever i maller. NCM TEK 7-C 7

8 contructed uing unconventional contituent material, there ha hitorically been no defi ned procedure for applying the reult of STM E9 teting to tandardized calculation procedure available through the Standard. To provide conitency in applying the reult of full-cale STM E9 teting to etablihed calculation procedure, NCM ha developed a guideline for thi purpoe, available for download through the technical FQ portion of the NCM webite ( Thi guideline tipulate that when applying the fire reitance calculation procedure of the Standard to product manufactured uing aggregate type that are not lited in the Standard, at leat two full-cale STM E9 tet mut be conducted on aemblie containing the unconventional material. Baed on the reult of thi teting, an expreion can be developed in accordance with thi indutry practice that permit the fire reitance of unit produced with uch aggregate to be calculated for interpolated value of equivalent thickne and proportion of non-lited aggregate. REFERENCES. Code Requirement for Determining Fire Reitance of Concrete and Maonry Contruction emblie, CI 6.-07/TMS merican Concrete Intitute and The Maonry Society, International Building Code 009. International Code Council, 009. International Building Code 006. International Code Council, Standard Tet Method for Fire Tet of Building Contruction and Material, STM E9-08a. STM International, Inc., Standard Method for Sampling and Teting Concrete Maonry Unit, STM C40-08a. STM International, Inc., Standard Specifi cation for Loadbearing Concrete Maonry Unit, STM C STM International, Inc., Standard Specifi cation for Concrete ggregate, STM C-08. STM International, Inc., Standard Specification for Lightweight ggregate for Concrete Maonry Unit, STM C-05. STM International, Inc., Standard Specifi cation for Perlite Looe Fill Inulation, STM C STM International, Inc., Standard Specifi cation for Vermiculite Looe Fill Thermal Inulation, STM C STM International, Inc., Steel Column Fire Protection, TEK 7-6. National Concrete Maonry ociation, llowable Stre Deign of Concrete Maonry Lintel, TEK 7-C. National Concrete Maonry ociation, Standard Specifi cation for Concrete Building Brick, STM C55-06e. STM International, Inc., Standard Specifi cation for Calcium Silicate Brick (Sand-Lime Brick), STM C7-05. STM International, Inc., Standard Specifi cation for Prefaced Concrete and Calcium Silicate Maonry Unit, STM C STM International, Inc., 008. NCM and the companie dieminating thi technical information diclaim any and all reponibility and liability for the accuracy and the application of the information contained in thi publication. NTIONL CONCRETE MSONRY SSOCITION 750 Sunrie Valley Drive, Herndon, Virginia 07 To order a complete TEK Manual or TEK Index, contact NCM Publication (70) NCM TEK 7-C