FAQ's

1 What is the Minimum Asphalt Thickness?

The BoltHold anchors are tested in asphalt with 2" thickness. Asphalt is usually laid in 3 layers -- the bitumen (blacktop) layer on top, a layer of compacted gravel, and the soil underneath. The blacktop layer is the one that determines the pull resistance of the anchors.

The pull resistance of the anchors increases at a rate that is proportional to the thickness. The SP10 anchor is rated at 1,500 lb. pull in 2" asphalt. At 4" (which is double the thickness of 2"), the pull resistance is about 3,000 lbs.

Asphalt thinner than 2" has not been tested and, if the application is in such asphalt, we discourage the use of our anchors.

2 Why did my Anchor Fail a Pull Test?

One reason can be that it was installed too close to the edge of the asphalt. We recommended keeping 12" away from the edge of the asphalt.

Another reason is if the grout was not poured to the very top of the hole. The asphalt is usually only 2-3 inches deep, and if the grout reached only 2" below the surface, there will be hardly any area of bonding between the anchor and the asphalt.

The picture on the right shows an anchor that was improperly grouted. There is no grout in the top 2" of the anchor, and it was in essence only attached to the gravel and sand.

A full analysis of possibilities can be found in AN44 in our Library.

3 How Critical is the Size of the Hole?

The size of the hole that needs to be drilled to accommodate the anchor is determined by 3 factors:

The widest diameter of the anchor

The diameter of the head of the anchor

The length of the anchor

The widest diameter of the body of SP10 and SP12 is about 7/8" (22mm). The widest diameter of the SP18 is 1" (25mm). Thus the hole size needs to be equal or larger than these dimensions to that the anchor can be pushed into the ground without major hammering (which may otherwise damage it).

The hole can be larger in diameter than these minimum diameters, but it must be smaller by at least 10mm than the diameter of the head of the anchor. The reason is that the head needs o cover irregularities in the drilled hole to give the installation a finished look. Thus, for the SP10 and SP12, the hole can be between 7/8" and 1" (22-25mm). For the SP18, the hole can be between 1" and 1-1/16" (25-27mm).

The length of the SP10 is 6" (150 mm). The length of the SP12 and SP18 are 12" (300 mm).

4 Can I use existing holes?

If the existing holes are smaller than the diameter of the new holes you need to drill for installing our asphalt anchors, the answer is YES -- you can use the existing holes.

HOWEVER, if the asphalt was torn and damaged around the old holes, it is not recommended. Just move the item 6 inches away and drill new holes.

5 How important is the selection of the grout?

The type of grout used will materially affect the strength and longevity of the anchor installation. The recommended grout should be a cement-based expanding cement. These are sometimes referred to as anchor cements. We offer a tested and proven grout, in the EPX2.

Do not use regular concrete -- it will crack over time. Do not use gypsum-based expanding cements -- they will deteriorate over time in wet conditions. Do not use Kwixset or Rockite products -- they are not suitable for applications in asphalt due to their vulnerability to water.

You may use 2-part epoxies specifically formulated for holding anchors in concrete. They are excellent, but be ready to pay significantly more than for cement grout. The pull performance will be the same as when using our EPX2, because in both the epoxies and the EPX2, the bond to the asphalt is stronger than the asphalt itself.

6 Can the anchors be used without grout?

NO NO NO

Theoretically you can force-drive the anchors into a smaller hole. The problem is that the anchor will be force wedged into the asphalt, and within a short time, the asphalt will yield to the pressure and flow away, leaving the anchor loose in the hole.

The tubular construction of the anchors is designed to resist pull forces, but it will be damaged if the anchors are hammered into a small hole. In addition to the thread and the tube of the anchor, the welded spiral that is designed to grab the grout is relatively delicate and will not survive the force of hammering the anchor into the ground.

The SP 10, SP12, SP18 and DP58 were all designed for an oversize hole so that they can be easily dropped in. The adhesion to the asphalt is performed by the grout.

7 Can Anchors be installed in Cold Weather?

Yes, the anchors can be installed in rain and in colder weather, with certain limitations. The issues are related to the curing of the grout. For a guide how to install at temperatures lower than 45F, see AN36 in out Library.

1. RAIN -- Water can affect the uncured cement-based grout, primarily by diluting it before it cures. If the area is covered to prevent rain from mixing with the grout as it is poured and in the 15 minutes it takes for it to cure, the cement grout can be used. Once cured, our grout is water resistant.

Our EPX3 epoxy grout is not sensitive to rain and can be applied to holes full of water.

2. TEMPERATURE -- Cement based grout uses water in the mix. If the ambient temperature is below 50oF, used warm water in the mix, then quickly dispense the mix into the hole. As the ambient temperatures approach freezing, the curing process of the grout will slow down. The manufacturer does not recommend using the grout at ambient temperatures below 40F.

For epoxy grout, the curing time will rise dramatically when the material is colder. We recommend warming the cartridge of the EPX3 immediately prior to its application. That will allow you to work up to 14F.

3. ICE -- Do not apply the grout when the grout is frozen. The process of bonding between the grout and the crevices in the asphalt will fail if the hole in the asphalt is frozen.

8 How to Remove Installed Anchors?

Our BoltHold asphalt anchors are designed to be installed flush with the asphalt surface and be as tenacious as possible. If the installed objects need to be permanently removed, the anchors stay inconspicuously in the asphalt without protruding so that they do not present a risk to pedestrians or cars. For applications where the anchors will need to be reused in the future, we offer ThreadGuards which are plastic inserts that snap into the thread-hole in the anchor, to protect it from dirt.

The anchors themselves can not be removed without seriously damaging the asphalt. You will need to jackhammer the area around each anchor to a radius of about 2" and to a depth of 6" or 12" depending on the model of the anchor, to remove the anchor with minimum damage to the asphalt. If you try to pull out the anchors, the asphalt will crack in a area defined by circle about 6" in diameter. The repair will be costly -- you will need to cut the asphalt cleanly with a saw all the way to the gravel level, then apply new asphalt and compact it. A method suggested by a customer was to over-tighten the bolt until the entire anchor breaks away from the grout cocoon. We have not tested this solution.

9 Can BoltHold Anchors be used on Porous Asphalt?

Porous asphalt is a special mix of conventional asphalt with certain plastics that allow rainwater to filter through the asphalt.

Our asphalt anchors can be used with porous asphalt as long as the specified 4" thickness of asphalt is maintained (as is required in the specifications for porous asphalt).

10 Does the asphalt Have to be flat?

The key issue is to prevent a gap between the head of the anchor and the bottom of the plate that is being atatched. Such a gap will allow the anchor to be pulled out while tightening the bolt that attaches the plate to the anchor.

Use a suitable washer to fill in the gap.

11 Can Hydraulic Cement be used as Grout?

Hydraulic cement is designed specifically to cure FAST under water. We have not run torque and pull tests on that material, and thus we can not recommend it nor will our specifications be valid if it is used.

12 How much force can the anchors resist?

We are often asked about the engineering ratings for the BoltHold asphalt anchors. What pull forces, sideways forces, and torque can the installed anchors withstand?

We have run tests in a 30 year old, 2.25" asphalt parking lot with 4" compacted fine gravel underneath. With the criteria being that the anchor fails if the asphalt starts rising (crowning), we found that the SP12 (installed in a 7/8" hole with EPX2 grout) can resist 2,000 lbs. The SP10 can resist 1,500 lb. and the SP18 can resist 2,500 lb. of pull. Details of the tests can be found here. We have tested our SP58 in 3" asphalt and found that the pull resistance exceeded 6,000 lb.

The resistance of asphalt to pull increases approximately with the asphalt thickness. A 4" thick asphalt will resist 3-4 times the forces that a 2" asphalt does. In the case of the SP12, rated at 2,000 lb. at 2.25" asphalt, the asphalt may withstand 8,000 lbs. of momentary pull forces if the asphalt is 5.5" thick.

Note that such forces will exceed the strength of the 3/8" bolts that are threaded into the anchor. The anchors are supplied with Grade 5 bolts; the 3/8" bolts (used in the SP10-38 and SP12-38) are rated for 4,250 lb. of pull. Also note that the anchor itself is not capable of withstanding forces that are that much higher than its ratings, even if it adhesion to the asphalt exceeds these values.

(The SP18 is rated for 2,500 lb. of pull. The SP18-716 uses a 7/16" grade 5 bolt which may withstand 6,500 lb.)

When installing anchors close together, derate the pull strength of the additional anchors by 6% for every 25mm less than 300mm. Thus an arrangement of 4 anchors at 100mm apart will resist a total pull force of 2,304 Kg (900 + (3 x (52% x 900)).

About competition...An overseas asphalt anchor manufacturer specifies the pull resistance only for 5" hi-grade asphalt, used exclusively for highways. The results for a typical non-highway surface will be radically lower.

If in doubt, ask your asphalt supplier about the strength or thickness of the type of asphalt you will be installing your equipment on.

13 Can Your Anchors be used on Concrete?

The short answer is yes. Customers encountered concrete as a layer below the asphalt, and want to know if they can still use our BoltHold anchors. The only change from normal installation procedure is that the holes to be drilled for the anchors need to be 1/8" larger than the hole when installing in asphalt.

SP10 and SP12 need 1" holes. SP18 needs 1 1/8" hole.

What about pull strength? If anything, the pull capacity will be materially improved if there is a layer of concrete that the anchors have to go through. However, this requires careful cleaning of the hole with compressed air or a blower. The dust on the concrete section needs to be removed to assure bonding between the grout and the concrete.

14 Can BoltHold anchors be used to hold up Tents?

The BoltHold anchors can be used to hold up tents under the restrictions listed below:

1. The tent must have a skeleton that will hold it upright without the anchors

2. If the anchors are used for tie-downs of cables, the pull force on the cables must be limited to 25% of the rating of the anchors. For example, for the SP12 (2,000 lb. rated) the continuous tension on the cables should not exceed 500 lb.

3. The recommended method of limiting and controlling the pull force is to use bungee cords. In general, one needs a predictable yielding element in the cable otherwise the pull force can change from loose to excessive with a small amount of movement of the cable.