Anchoring and anchor grouting: grouts and anchor resins

Two ways to fix an anchor in concrete

A foundation bolt, stud or starter bar can be fixed in concrete in two fundamentally different ways. The first is to set the anchor in a pocket (recess or sleeve) left during concreting, or in an oversized hole, and fill the space around it with flowable grout. The second is to drill a hole slightly larger than the bar diameter in the hardened concrete and bond the anchor in with injection resin from a cartridge. Both methods are reliable, but they are intended for different tasks and require different preparation.

Grouting into pockets and sleeves

This is the traditional method for equipment and column foundations: the anchor bolts are positioned on site in a template, aligned and grouted in. The same non-shrink cementitious or epoxy grouts are used as under baseplates — many technical data sheets explicitly list anchoring among the applications (for example, SikaGrout-212, Mapefill R, Conbextra GP, Five Star Grout, Chockfast Gray). European products for this purpose are often tested to EN 1504-6 “Anchoring of reinforcing steel bar”, where one of the performance criteria is the displacement of the bar under pull-out load.

Points to watch

Pocket cleanliness. Debris, water, ice and laitance on the walls reduce the bond. In its Sikadur-42 data sheet, Sika specifically requires anchor pockets and sleeves to be free of water before the epoxy grout is poured.
Pocket size. The gap around the bolt must be no smaller than the minimum layer thickness permitted for the selected grout; otherwise the material will not fill the cavity.
Free length of the bolt. If the design calls for the anchor to be tensioned, part of its length is debonded with a sleeve or wrapping, so that the bolt stretches over its design length and not just above the grout.
Pouring sequence. The pockets are filled before the grout under the baseplate or at the same time, as specified in the design. The grout is poured from one side to displace the air.
Substrate moisture. For cementitious grout, the pocket walls are pre-soaked and the excess water is removed; for epoxy grout, they are dried unless the technical data sheet permits a damp substrate.

Injection anchor resins

Anchor resins are used when an anchor is installed in an existing structure: fixing equipment to an existing floor, adding bolts, or installing starter bars to extend a structure. The main chemistries are pure epoxy (slow curing, high load capacity, long working time), and vinyl ester and epoxy acrylate (fast curing, convenient for installation in cold weather). The resin is dispensed from a cartridge through a static mixer.

Regulatory framework

In Europe, chemical anchors are covered by European Technical Assessments (ETAs). Anchors in concrete are assessed to EAD 330499 (formerly ETAG 001), and post-installed rebar to EAD 330087. An ETA states the permitted diameters and embedment depths, the installation conditions (dry concrete, damp concrete, water-filled hole), the temperature ranges and, separately, the suitability for cracked concrete and seismic actions. For example, Hilti HIT-RE 500 V4 holds ETAs to EAD 330499 and EAD 330087; Sika AnchorFix-3+ and MasterFlow 920 AN hold ETAs to ETAG 001.

Hole cleaning

The most common cause of low load capacity in a chemical anchor is a poorly cleaned hole. Hilti puts it bluntly in its documentation: improper cleaning means low load values. The standard procedure described in manufacturers’ data sheets is blowing out with oil-free compressed air and brushing, repeated several times, starting from the bottom of the hole. For AnchorFix-3+, Sika requires at least two blow-outs and two passes with the brush.

Some restrictions concern the drilling method: Mapei, for example, does not permit Mapefix VE SF to be used in holes drilled with a diamond core bit, as the smooth walls impair the bond.

Damp and water-filled holes

Damp concrete and a water-filled hole are different conditions, and an ETA assesses them separately. Many resins tolerate a damp substrate, but with a longer curing time: according to Sika, the curing time of AnchorFix-3+ doubles in damp concrete. According to its technical data sheet, MasterFlow 920 AN tolerates a damp but not a wet substrate. For water-filled holes and underwater installation, manufacturers specify a special procedure: flushing with water instead of blowing out, injecting from the bottom of the hole through an extension tube and a piston plug, and applying reduction factors in the design.

Temperature and curing time

The time before an anchor can be loaded depends on the substrate temperature and increases several-fold in cold weather. Technical data sheets give tables of “working time / time to loading” for different temperature ranges. Until curing is complete, the anchor must not be disturbed, tightened or loaded. The first portions of resin from a new cartridge or a new mixer nozzle are discarded until the colour is uniform. In summer, cartridges are stored somewhere cool: in a hot cartridge, the resin hardens faster than the anchor can be installed.

Service temperature and creep

Anchor resins are polymers, and their load capacity under sustained load decreases as they heat up. That is why ETAs and technical data sheets specify temperature ranges with two values: the maximum short-term and the maximum long-term temperature. Each range has its own characteristic bond strength values, and a reduction factor is given for sustained loading. This matters in Central Asia: concrete in the sun or next to furnaces, boilers and hot pipework gets hotter than the air. The designer carries out the anchor design for the relevant temperature range, using the ETA for the specific product.

What to choose

New foundations with anchor bolts in pockets — non-shrink cementitious grout; with vibration and dynamic loads — epoxy grout.
Fixing to existing concrete — injection resin with an ETA covering the required diameter and conditions.
Winter work — products approved for low temperatures (for example, epoxy acrylate resins) and strict adherence to the curing tables.
High service temperature — a resin with a suitable temperature range in its ETA.

Materials from leading manufacturers

Sika AnchorFix-3+ — Sika — epoxy anchoring adhesive for rebar, studs and bolts.
Hilti HIT-RE 500 V4 — Hilti — epoxy injection mortar for anchors and post-installed rebar, including in water-filled holes.
Mapefix VE SF — Mapei — styrene-free vinyl ester chemical anchor, also suitable for fixing rails and supports.
MasterFlow 920 AN — Master Builders Solutions — epoxy acrylate anchor resin for rebar and foundation bolts.
SikaGrout-212, SikaGrout-314 — Sika — cementitious grouts for anchoring reinforcing steel to EN 1504-6.
Mapefill R — Mapei — rapid-hardening expansive mortar for anchor bolts.
Conbextra GP — Fosroc — non-shrink grout for anchor bolts and column baseplates.
Chockfast Gray — ITW Performance Polymers — epoxy compound, also used for setting anchor bolts in concrete.
MasterFlow 9200, MasterFlow 9400 — Master Builders Solutions (now Sika) — ultra-high-strength grouts for the anchorages of wind turbine towers.
Five Star Special Grout 400 — Five Star Products — fluid cementitious grout for post-tensioning tendon ducts and cables.
Five Star Fluid Epoxy — Five Star Products — fluid epoxy for anchor bolts and low-clearance grouting from 3 mm.
Euco Cable Grout PTX — Euclid Chemical — thixotropic cementitious grout for post-tensioning cable ducts.
Hilti HIT-HY 200-A V3 — Hilti — fast-curing injection mortar for anchors and post-installed rebar in concrete.
Euco Rapid Grout — Euclid Chemical — rapid-setting non-shrink grout for anchoring and structural grouting, placed from 2 °C.
Hilti HIT-HY 170 — Hilti — injection mortar for anchor rods, sleeves and rebar in concrete, installed from −5 °C.
PAGEL E1, E1-P — Pagel — flowable and plastic anchor mortars for rock, soil, concrete and masonry.
Planigrout AR — Mapei — unsanded thixotropic cementitious grout for injecting anchors and cables into rock and soil.
Hilti HIT-RE 10 — Hilti — epoxy injection mortar for threaded rods and rebar in non-cracked concrete.
Hilti HIT-RE 100-HC — Hilti — epoxy mortar for post-installed rebar φ8–φ40 up to 1500 mm deep.
Hilti HIT-HY 270 — Hilti — hybrid injection mortar for anchoring in solid and hollow masonry.
Hilti HIT-MM PLUS — Hilti — hybrid injection mortar for anchors in non-cracked concrete and masonry.
Hilti HIT-FP 700 R — Hilti — mineral injection mortar for rebar φ8–φ40, service up to 160 °C.
Hilti HIT-CT 100 — Hilti — hazard-label-free injection mortar for anchor rods and rebar, installed from −5 °C.
SikaGrout-110 AN — Sika — rapid-setting anchoring cement for bolts, posts, railings and base grouting.
Sika AnchorFix-1 — Sika — fast-curing polyester anchoring adhesive for concrete and masonry, installed from −10 °C.
Sika AnchorFix-3001 — Sika — epoxy anchoring adhesive for threaded rods and rebar in cracked concrete.
Fosroc Lokfix E77 — Fosroc — 3:1 epoxy anchoring system for rebar and threaded rods in cracked concrete.
Mapefix PE SF — Mapei — styrene-free polyester chemical anchor for non-cracked concrete and hollow masonry.
Planigrout PT — Mapei — non-shrink cementitious grout for injecting post-tensioning tendon ducts.
Sikadur-42 Grout-Pak PT — Sika — pre-proportioned epoxy system protecting post-tensioning tendon anchorages.
Sika AnchorFix-2 — Sika — fast-curing epoxy acrylate anchoring adhesive for threaded rods and rebar.
Sika AnchorFix-500 — Sika — 1:1 adhesive anchoring system for threaded rods and rebar in uncracked concrete.
Sika AnchorFix-2020 — Sika — anchoring adhesive for cracked and uncracked concrete, installed from −10 °C.
Fosroc Lokfix E45T — Fosroc — vinyl ester anchoring resin in cartridges for hot climates.
Fosroc Lokfix E35S — Fosroc — polyester anchoring resin in cartridges for uncracked concrete and masonry.
Fosroc Lokfix RA — Fosroc — pourable polyester resin grout for anchoring bolts and bars into rock.
Fosroc Conbextra LC — Fosroc — non-shrink cementitious slurry for injection, cable anchoring and micropiles.
Fosroc Conbextra Cable Grout HS — Fosroc — high-strength non-shrink grout for post-tensioning cable ducts.
Fosroc Lokfix EP — Fosroc — thixotropic epoxy anchoring grout for threaded rods and rebar in concrete.
Fosroc Lokfix E55 — Fosroc — styrene-free vinyl ester anchoring resin for rebar and rods, installed from −20 °C.
Fosroc Lokfix DUR — Fosroc — epoxy acrylate cartridge anchoring resin for M8–M24 rods in concrete and stone.
Fosroc Lokfix — Fosroc — pourable polyester anchoring resin for bolts and rebar in concrete, masonry and rock.
Fosroc Conbextra Cable Grout — Fosroc — non-shrink cementitious grout for post-tensioning tendon ducts, 60 MPa at 28 days.
SikaGrout Cable PT — Sika — sand-free non-shrink cementitious grout for post-tensioning ducts.
SikaGrout-190 — Sika — shrinkage-compensated fluid grout for post-tensioning ducts and anchors.
Sika AnchorFix-3030 — Sika — epoxy anchoring adhesive for cracked and uncracked concrete, seismic C1/C2.
Sika AnchorFix S — Sika — fast-curing polyester anchoring adhesive for concrete, masonry and stone.
SikaGrout-960 — Sika — rapid-setting cementitious anchoring compound for threaded rods and rebar, installed from −5 °C.
Hilti HVU2 — Hilti — foil adhesive capsule anchor for M8–M30 rods in cracked and uncracked concrete.
Mapegrout HF W — Mapei — non-shrink anchoring and grouting mortar for −10…+15 °C, layers up to 50 mm.

Frequently asked questions

Can an anchor be bonded into a hole that has not been blown out?

No. Drilling dust acts as a release layer, and the load capacity drops sharply. Cleaning is a mandatory step described in the instructions for every resin.

Which is better for foundation bolts: grout or resin?

If the bolts are set in pockets left during construction of the foundation — grout. If a bolt has to be added to an existing foundation — resin in a drilled hole, with an ETA covering the relevant diameter and depth.

Can a chemical anchor be installed in a wet hole?

Only if the ETA and the technical data sheet for that particular resin allow it, and only by following a special procedure. Normally the water is removed, and the curing time in damp concrete is extended in line with the manufacturer’s table.

Why do anchors “run out of time” in hot weather?

At high temperatures, the working time of the resin drops to a matter of minutes. Store cartridges somewhere cool, work during the cooler part of the day and do not prepare resin in advance.