GROUT
ACI defines grout as “ a mixture of cementitious material and water , with or without aggregate , proportioned to produce a pourable consistency without segregation of the constituents .” The terms “ grout ” and “ mortar ” are frequently used interchangeably but are not the same . Grout need not contain aggregate ( mortar contains fine aggregate ), is supplied in a pourable consistency ( mortar is not ), and fills voids ( mortar only bonds elements together ).
In summary , grout is used to fill spaces or cavities and provide continuity between building elements . In some applications , grout will act in a structural capacity , such as in unreinforced masonry construction .
Grout , with respect to post-installed anchorages , is specified by the design official . When post-installed anchors are tested for the development of design values , the grout is specified according to applicable ASTM standards . Design engineers are encouraged to become familiar with the characteristics of the grout used in performance testing to better understand the applicability of the design loads published in this guide .
3.0 ANCHOR DESIGN IN MASONRY
The Strength Design method for anchor design in concrete has been incorporated into several model codes such as IBC and ACI 318 . The method assigns specific strength reduction factors to each of several possible failure modes , provides predictions for the strength associated with each failure mode , and compares the controlling design strength with factored loads . The Strength Design method is a more accurate estimate of anchor resistance as compared to the Allowable Stress Design ( ASD ) method . The Strength Design method is state-of-the-art , and Hilti recommends its use where applicable .
Anchor design in masonry base materials is adopting the framework of the Strength Design method from ACI 318 Chapter 17 with only a few modifications specific to masonry base materials . For full discussion on the mechanical anchor design provisions for masonry , please reference ICC-ES AC01 Section 3.0 . For full discussion on the adhesive anchor design provisions for masonry , please reference ICC-ES AC58 Section 3.0 . The similarities and differences between anchor design in masonry and anchoring design in concrete will be discussed in the following sections .
FULLY GROUTED CMU CONSTRUCTION
Based on Section 3.3 of ICC-ES AC01 and AC58 , the tension failure modes for post-installed anchors in fully grouted CMU construction are steel failure , masonry breakout failure , pullout failure ( mechanical anchors only ), and bond failure ( adhesive anchors only ). The shear failure modes for postinstalled anchors in fully grouted CMU construction are steel failure , masonry breakout failure , pryout failure , and masonry crushing failure .
The corresponding equations and variables are provided below . For further discussion and commentary , please refer to ACI 318-19 section / equation references provided below parenthetically ( e . g ., 17.6.1.2 ). Additionally , some design values will be provided in the technical data of this guide or can be located in the applicable third-party evaluation report ( i . e ., ICC-ES ESR or IAPMO UES ER ).
Tension — Nominal Strengths
Steel Strength
N sa
= A se , N ƒ uta ( 17 . 6 . 1 . 2 ) where :
A se , N
= Effective cross-sectional area of an anchor in tension , in . 2 ƒ uta
= Minimum ultimate tensile strength of anchor , psi
Masonry Breakout
N mbg
= A Nm
A Nmo ψ ec , N , m ψ ed , N , m ψ c , N , m
N b , m where :
A Nm
= Projected masonry failure area of a single anchor or group of anchors in tension , in . 2 ( 17.6.2.1.1 )
A Nmo
= Projected masonry failure area of a single anchor in tension if not limited by edge distance or spacing , in . 2 ( 17.6.2.1.4 )
= 9h ef
2 where : h ef
= Effective embedment depth of the anchor element , in . ψ ec , N , m
= Breakout eccentricity factor ( 17.6.2.3 ) =
1 +
1 e ́N
1.5h ef
≤1.0 ψ ed , N , m
= Breakout edge effect factor ( 17.6.2.4 ) = 1.0 if c a , min
≥ 1.5h ef
= 0.7 + 0.3 c a , min
1.5h ef if ca
, min < 1 . 5h ef
4 Masonry Fastening Technical Guide Edition 24 Hilti , Inc . 1-800-879-8000 | en español 1-800-879-5000 | www . hilti . com | Hilti ( Canada ) Corporation | www . hilti . ca | 1-800-363-4458