51.0

Adhesive Anchors

51.0 Adhesive Anchors







51.1 Introduction
Adhesive anchoring systems offer many advantages for applications
requiring high load capacities. Capsule type systems first appeared in
the market in the late 1970's followed by the early co-axial type
injection systems. Originally,these products were used in highway
and bridge construction as a substitute for grouted anchors because
of speed of installation. As industry realised the benefits of adhesive
systems, their use in other building applications became popular.
Major features applicable to adhesive systems include:
o High Strength
o Ability To Be Used With A Variety Of Rod Materials
o Stress Free (No mechanical forces)
o Sealed Anchor Hole For Weather Resistance
o Good Dynamic And Shock Load Performance
o Small Hole Diameter Compared To Grout
Typical applications for which adhesive systems may be used
are shown below.
Threaded Anchor Rods


Pipe Support	Machine Base


Median Barriers	Light Poles
Reinforcing Bars and Smooth Dowels

Deformed Bars	Smooth Bars

Hooked Bars	Block Reinforcing
Threaded Rod to Hollow Masonary

Timber to Block	Facade Pinning

Clip Angles to Brick	Seismic Upgrade

Powers Fasteners is the industry leader in adhesive anchoring systems

providing the broadest range of products to meet the needs of the

small, medium, and large user. The systems include both ester and

epoxy based systems which are selected based on the application

requirements. Refer to the specific product sections for details.

51.2 Adhesive Anchor Functioning

Adhesive anchors achieve their load capacities based on the ability of the

adhesive used to bond to the base material. This ability to bond, often

referred to as "wetting action" will vary depending upon the adhesive

type and formulation. While the adhesive bonds to the base material, it

also forms a mechanical interlock around the threaded rod. In order to

form this interlock, it is important to use anchor rods which have some

type of deformation. Examples would be threaded rod or deformed

reinforcing bars. Smooth dowel bars coated with epoxy can be used

with some types of adhesive systems.

In addition to the ability to bond to the base material, the strength of the

anchor rod used can be a critical factor. Many adhesive types can achieve

the load capacity of a standard Grade 2 or A 307 threaded rod. In order to

achieve the strength of the adhesive, it is often important to specify the

use of a high strength anchor rod.

51.3 Performance Data

The load capacities for adhesives published in this manual are based

on extensive testing conducted according to the requirements of ASTM

Standards E 488 and E 1512. To determine the bond strength of an

adhesive, a high strength anchor rod was used. From the initial testing

conducted, the adhesive bond strength for an anchor rod installed in

three concrete compressive strengths was developed allowing for the

calculation of various combinations of anchor rod and embedment. When

designing with an adhesive anchoring system, both the strength of the

adhesive resin arid the steel anchor rod must be considered. The

adhesive may often have an allowable or working load capacity that

is higher than that for the anchor rod. In order to account for this,the

capacities listed in this manual are published in two ways.

The ultimate or failure load for the adhesive resin is published first. Then

the allowable bond strength for the adhesive based on a safety factor of

four is tabulated along with the allowable load capacities for various

threaded steel anchor rod or reinforcing bars. The designer may wish to

use higher safety factors than the minirnurn safety factor of four. Steel

strength capacities for threaded rod are based on the design criteria

listed in the Ninth Edition of the AISC Manual of Steel Construction. For

reinforcing arid dowel bars, the capacities are based on the requirernents

of ASTM A 615. The designer should select the lesser of the published

allowable loads, either the bond strength or the steel strength to

determine the capacities of the anchorage.

The spacing and edge distance factors as listed in the following sections

should be considered. As in all applications, the actual safety factors

used and allowable load capacities should be reviewed and verified by

a design profersional familiar with the actual product installation.

51.4 Job Site Test Programs

In order to verify that the base material or structural member is able to

withstand the anticipated loading, a pre-installation job site test

program is recommencled. Test anchors simulating actual conditions

should be loaded to failure to verify site specific anchor performance.

During installation, it is good practice to conduct proof load testing on

10 to 15% of the installed anchors to verify proper installation.

51.5 Design Recommendations
	Adhesive Anchor Spacing and Edge Distance
	Spacing Between Adhesive Anchors
51.5.1 Base Material Thickness	Edge Distance for Adhesive Anchors
	Effect Of Elevated Temperature
	Maximum Torque Values
The minimum recommencled thickness of solid concrete or masonry base.
material, BMT, when using an adhesive anchor is 125% of the embedment
to be used, For example, when installing an anchor to a depth of 4", the
base material should be at least 5" thick. Conversely, the maximum
embedment should be 80% of the base material thickness. If a concrete
slab is 10" thick, an 8" depth would be the maximurn recommended anchor
embedment. This does not apply to products designed for installation in
hollow base rnaterials

51.5.2 Adhesive Anchor Spacing and Edge Distance

Adhesive type anchors can be installed closer to the edge of a concrete slab

than mechanical anchors with no cracking of the base material. The published

ultimate and allowable working loads are based on testing conducted at the

spacing and edge distance required to obtain maximum load and should be

reduced to account for decreased spacing and edge distance. The reduction

load factors listed are cumulative. For example, the allowable working load for

an anchor which is installed at a spacing and an edge distance less than that

required for maximum load capacity would be multiplied by the appropriate

factor from both the spacing and edge distance tables. The factors are

normally applied to the allowable working load of the adhesive resin and

then compared to the allowable strengths of the steel anchor rods used.

See Section 2.9.8 for a design example.

51.5.3 Spacing Between Adhesive Anchors

The following table lists the load reduction factor, Rs, for each anchor

diameter,d, based on the center to center anchor spacing. To obtain the

maximum working load in tension or shear, a spacing of 8 anchor diameters

(8d) should be used. The minimum recommended anchor spacing is 4 anchor

diameters (4d) at which point the allowable working load for the adhesive

resin should be reduced by 30%.

Anchor Size	Anchor Spacing, S (inches) Tension and Shear
d	8d	7d	6d	5d	4d
1/4	2	1-3/4	1-1/2	1-1/4	1
3/8	3	2-5/8	2-1/4	1-7/8	1-1/2
1/2	4	3-1/2	3	2-1/2	2
5/8	5	4-3/8	3-3/4	3-1/8	2-1/2
3/4	5	5-1/4	4-1/2	3-3/4	3
7/8	7	6-1/8	5-1/4	4-3/8	3-1/2
1	8	7	6	5	4
1-1/4	10	8-3/4	7-1/2	6-1/4	5
1-3/8	11	9-5/8	8-1/4	6-7/8	5-1/2
1-1/2	12	10-1/2	9	7-1/2	6
Rs	1.00	0.93	0.85	0.78	0.70

51.5.4 Edge Distance for Adhesive Anchors

Edge Distance - Tension

For adhesive anchors loaded in tension, the following table lists the load

reduction factor, Re, for each anchor diameter, d, based on the anchor

center to edge distance. To obtain the maximum tension load, an edge

distance of 6 anchor diameters (6d) should be used. The minimum

recommended edge distance is 4 anchor diameters (4d) at which point

the allowable working load for the adhesive resin should be

reduced by 40%.

Anchor Size	Anchor Spacing, S (inches) Tension Only
d	6d	5d	4d
1/4	1-1/2	1-1/4	1
3/8	2-1/4	1-7/8	1-1/2
1/2	3	2-1/2	2
5/8	3-3/4	3-1/8	2-1/2
3/4	4-1/2	3-3/4	3
7/8	5-1/4	4-3/8	3-1/2
1	6	5	4
1-1/4	7-1/2	6-1/4	5
1-3/8	8-1/4	6-7/8	5-1/2
1-1/2	9	7-1/2	6
Re	1.00	0.80	0.60

Edge Distance - Shear

The following table lists the load reduction factor, Re, for each anchor

diameter d, based on the anchor center to edge distance. To obtain the

maximum shear load, an edge distance of 12 anchor diameters (12d)

should be used. The minimum recommended edge distance is 4 anchor

diameters (4d) at which point the allowable working load for the

adhesive resin should be reduced by 50%.

Anchor Size	Anchor Spacing, S (inches) Shear Only
d	12d	11d	10d	9d	8d	7d	6d	5d	4d
1/4	3	2-3/4	2-1/2	2-1/4	2	1-3/4	1-1/2	1-1/4	1
3/8	4-1/2	4-1/8	3-3/4	3-3/8	3	2-5/8	2-1/4	1-7/8	1-1/2
1/2	6	5-1/2	5	4-1/2	4	3-1/2	3	2-1/2	2
5/8	7-1/2	6-7/8	6-1/4	5-5/8	5	4-3/8	3-3/4	3-1/8	2-1/2
3/4	8	8-1/4	7-1/2	6-3/4	5	5-1/4	4-1/2	3-3/4	3
7/8	10-1/2	9-5/8	8-3/4	7-7/8	7	6-1/8	5-1/4	4-3/8	3-1/2
1	12	11	10	9	8	7	6	5	4
1-1/4	15	13-3/4	12-1/2	11-1/4	10	8-3/4	7-1/2	6-1/4	5
1-3/8	16-1/2	15-1/8	13-3/4	12-3/8	11	9-5/8	8-1/4	6-7/8	5-1/2
1-1/2	18	16-1/2	12-1/2	13-1/2	12	10-1/2	9	7-1/2	6
Re	1.00	0.94	0.88	0.81	0.75	0.69	0.63	0.56	0.50

51.5.5 Effect Of Elevated Temperature

The bond strength of the all adhesive type anchors is effected by

elevated temperatures in the base material. As the temperature of the

base material increases, the bond strength of the cured adhesive will

decrease. Typically, the reduction in bond streng is based on testing

conducted in concrete test samples maintained at a given temperature

for a minimum of 24 hours before applying a test load. If the base

material will be maintained at a constant elevated temperature, the

allowable loads for the adhesive should be reduced accordingly.

During a fire, the actual behavior of an adhesive depends upon the heat

dissipation inside the concrete. The rate of dissipation will vary depending

upon the mix design along with the size and shape of the structural

member. Normally, at depths beyond 3", the concrete heats up

relatively slowly since only one face of a slab is

actually exposed to a fire.

In addition to the heat dissipation within the base material, the transfer of

heat into the adhesive by the anchor rod should be considered. One method

of reducing the transfer of heat energy is to protect the fixture and the

head of the anchor with a suitable coating. Stainless steel anchor rods

typically have a low degree of heat transfer and may be used with some

adhesives to provide an anchor which has a degree of fire resistance.

Testing conducted with Type 316 stainless steel rods installed in normal

weight concrete has shown that some adhesives can sustain a design

load for at least 30 minutes when exposed to a temperature of 1500° F.

Contact Powers Fasteners for details.

51.5.6 Maximum Torque Values

A maximum torque value is listed for applications in which an adhesive

anchor will be used to install a threaded rod. Although the application of

torque is not necessary to achieve the published loads, in some cases it

may be desirable to apply a clamping force to a fixture. The purpose of a

maximum torque is to prevent over stressing of the adhesive bond. These

values are based on testing in normal weight concrete at the standard

embedment for capsule type adhesives and nine diameters of embedment

for injection type adhesives. For specific applications, job site tests are

recommended. As with mechanical anchors, preload relaxation should be

expected due to creep within the concreteand in the adhesive. Refer to

the section on Anchor Selection Guidelines for details.

51.6 Adhesive Anchor Installation Guidelines	Use Of Adhesives In Cold Weather
As with any building component, proper installation is the key to a
successful application once the anchor has been properly selected. While
each individual adhesive product section provides specific installation
instructions, the following summary highlights general areas
of importance.

51.6.1 Anchor Holes

A properly drilled hole is a critical factor both for ease of installation

and optimum anchor performance. The anchors selected and the drill

bits to be used should be specified as part of the total anchoring

system. Powers Fasteners adhesive anchors are designed to be

installed in holes drilled with carbide tipped bits meeting the

requirements of the American National Standards Institute (ANSI)

Standard B212.15 unless otherwise specified. If alternate bit types

such as diamond tipped core bits are used, the tip tolerance should be

within the ANSI range. A diamond tipped bit drills a hole which has very

smooth walls. Although adhesive anchors tend to work acceptably in

diamond cored holes, testing should be conducted to verify performance.

When using adhesives, anchor holes should be thoroughly cleaned prior

to installation of the adhesive. During the drilling process, dust is often

pressed into the walls of the hole. Blowing the hole with compressed air

or vacuuming alone will not properly clean the hole. In order to insure

that the proper bond is developedwith the base material, the holes

should also be brushed using a nylon brush to remove dust and other

debris which may have been pressed into the walls of the hole.

51.6.2 Use Of Adhesives In Cold Weather

One of the differences between epoxy and ester based resins is the type of

chemical reaction. When the individual components of an epoxy are

combined or mixed, the reaction which occurs is called an addition

reaction. The reaction is described in this manner because it involves

the addition of an epoxy molecule with an amine molecule which are

then cross linked three dimensionally to form a polymer. When the

temperature is warmer, the molecules are freer and able to cross link

faster. As the temperature lowers, the cross linking becomes more

difficult and will stop at a certain point. In house test have shown that

the fast set version of the Power-Fast epoxy can gel and set in materials

as cold as 25º F., however, special installation procedures

should be followed.

Ester based resins react differently. In an ester based resin, the hardening

catalyst causes the ester molecules or monomers to link together forming

long chain polymers. In this type of reaction, the mix ratio is not as critical.

While colder temperatures do not effect the reaction of these resins as

severely, proper conditioning is still required.

As the temperature of the unmixed components of an adhesive material

decreases, they thicken which make dispensing or installation difficult in

cold weather. To prevent difficulty during installation, Powers Fasteners

recommends that adhesives be conditioned to a minimum temperature of

60ºF. prior to installation unless otherwise recommended in the individual

product sections. When an adhesive is conditioned, it should be maintained

at the required minimum temperature for a sufficient amount of time to

insure that the entire cross section of the container is brought to

temperature, Some systems such as Power-Fast Epoxy Injection

Gel have tool heaters available to keep the adhesive warm.

Some products, especially epoxies, are not recommended for use in base

materials having a temperature of 40º F. or less unless job site performance

tests are conducted. Although these materials may gel and cure at lower

temperatures, 40º F. was selected as a safe minimum temperature because

experience has shown that no special installation procedures are required

beyond our published instructions.

When adhesive anchors are installed in concrete which is in the freezing range,

frost or ice can form on the walls of the anchor hole. If this occurs, injection

type adhesives may not properly bond to the walls of the anchor hole. Spin-in

a type capsule systems which scrape the walls of the anchor hole during

installation are less sensitive to this. Since concrete is porous and acts like

sponge, even the pour water can freeze and prevent the adhesive from

properly wetting the surface of the hole. This can be prevented by heating

the anchor hole with a heat gun prior to installation of the adhesive. A torch

should never be used because it carbonates the concrete on the walls of the

anchor hole creating a residual dust.

Since variations in the concrete mix design may effect the formation of

frost or ice on the walls of an anchor hole, job site performance tests are

recommended for installations of epoxies in base materials having a

temperature of less than 40º F. to verify gel and cure times.