Non-shrink cementitious grouts: types, selection, mistakes

What is a non-shrink cementitious grout?

A cementitious grout is a factory-made dry mix of cement, graded sand and a package of admixtures, which is mixed with water on site in a strictly specified ratio. What sets it apart from site-mixed mortar is volume control. Ordinary cement mortar loses some of its volume as it hardens, and a gap opens up under the baseplate. A grout contains components that compensate for shrinkage: in the plastic phase it expands slightly, and once it has gained strength it stays in tight contact with the steel and the concrete.

Manufacturers use different compensation mechanisms: gas-generating admixtures that act in the first few hours, and expansive mineral components that work during hardening. Many modern grouts combine both mechanisms. Technical data sheets usually cover this in the section on expansion, stating the test method (for example, ASTM C827 for the plastic phase and ASTM C1090 for the hardened state).

Flowable and thixotropic grouts

Flowable (pourable) grouts

This is the main type used for grouting under machinery and baseplates. The mix is highly flowable and fills the gap on its own, displacing the air. Many grades allow the consistency to be adjusted within a narrow range by varying the water content: from plastic (for short flow paths and large gaps) to fluid (for long flow paths under a wide baseplate). The upper water limit must never be exceeded, as this leads to segregation, bleeding and loss of strength.

Thixotropic (plastic) grouts

Thixotropic grouts do not flow and are placed by trowel or by packing. They are used where formwork is difficult to install: for packing under shims, filling holes in walls, vertical and overhead details, and as repair mortars. They are not suitable for conventional grouting under a pump baseframe, as they will not fill the gap completely.

Special grades

  • Rapid-hardening — for repairs with a short shutdown window.
  • For large volumes — containing coarse aggregate or approved for extension with crushed stone, to reduce heat generation and dry-mix consumption.
  • High-strength grades for wind energy — for the “foundation — tower” connection, which is subject to cyclic fatigue loading.
  • For underwater placing — with admixtures that prevent the cement from being washed out.
  • For prestressing tendons — duct injection grouts, a separate group with its own requirements.

Strength classes

Technical data sheets give the compressive strength of a grout at several ages — typically 1, 3, 7 and 28 days. Grades can only be compared fairly under identical conditions: the same consistency (plastic or fluid), the same specimen size (40, 50, 70 or 100 mm cubes and 40×40×160 mm prisms give different results) and the same temperature. A data sheet often gives two rows of strength values — for the minimum and the maximum water content; for design purposes, use the one that matches the consistency actually used on site.

European manufacturers often declare compliance with EN 1504-3 class R4 (structural repair mortar) and EN 1504-6 (anchoring of reinforcing steel). American products declare compliance with ASTM C1107, which classifies grades by their shrinkage-compensation mechanism.

Where cementitious grouts are used

  • steel column baseplates, precast concrete columns in pocket foundations;
  • pumps, fans, electric motors, gearboxes, tanks and vessels under static load;
  • grouting in anchor bolts in pockets and sleeves;
  • grouting under crane girders and rails where the design does not call for an epoxy grout;
  • bridge bearings, joints between precast elements;
  • wind turbine foundations (special high-strength grades).

Common grouting mistakes

Formwork

Formwork must be grout-tight: cement paste leaks out through any gaps, leaving honeycombing at the edge of the grout. On the pouring side, the formwork is set back from the baseplate and raised above its underside to create a head; on the opposite side, a small gap is left for air to escape. A head box or chute helps to keep the head of grout constant.

Dry substrate

Dry concrete draws water out of the grout, producing a weak layer at the interface and sometimes debonding. The substrate is pre-soaked as specified in the technical data sheet (usually several hours in advance), and standing water is removed before pouring — ponded water is just as harmful as over-dry concrete.

Unprepared concrete

Laitance on the foundation surface, oil, dirt and any loose layer must be removed down to sound concrete with exposed aggregate. Anchor pockets are cleared of debris and water.

Excess water and “retempering”

Do not add water beyond the maximum to improve flow, and do not retemper grout that has already started to set. Mix with a low-speed mixer for the time specified by the manufacturer, and prepare only as much as can be placed in time.

Interrupted pouring

Pour continuously from one side (or from two adjacent sides) until the grout emerges on the opposite side. Pouring from all sides at once traps air under the baseplate.

Curing

Exposed grout surfaces are covered immediately with wet hessian, polythene sheeting or a curing compound. In a Central Asian summer, grout left without curing dries out quickly and cracks along the edges; in winter it is protected from freezing and never placed on a frozen substrate. Where possible, the grout projecting beyond the baseplate is kept to a minimum and chamfered.

Material temperature

In hot weather, keep the bags and water in the shade, use cold water and work in the morning or evening. In cold weather, warm the water and the substrate within the limits specified by the manufacturer.

See also: grouts — overview, epoxy grouts, equipment grouting, anchoring.

Materials from leading manufacturers

  • SikaGrout-980 (MasterFlow 980) — Sika — shrinkage-compensated cementitious micro-concrete for precision machine grouting, aggregate up to 8 mm.
  • MasterFlow 928 — Master Builders Solutions (now SikaGrout-928) — non-shrink grout with extended working time.
  • SikaGrout-212 — Sika — general-purpose shrinkage-compensated flowable grout, class R4 to EN 1504-3.
  • SikaGrout-214 — Sika — non-shrink grout with two-stage expansion for turbines, compressors and pumps.
  • SikaGrout-314, SikaGrout-318 — Sika — fluid grouts for machinery and precast concrete joints (318 — for thicker layers).
  • SikaGrout-300 PT — Sika — sand-free injection grout for narrow gaps and voids.
  • SikaGrout-3200 — Sika — rapid-hardening grout for wind turbine tower joints.
  • Mapefill — Mapei — high-flow expansive mortar for grouting under machine tools and steel structures.
  • Mapefill R — Mapei — rapid-hardening version for anchoring and for repairs with short downtime.
  • Mapefill GP — Mapei — general-purpose non-shrink grout.
  • Conbextra GP, Conbextra HF — Fosroc — general-purpose non-shrink grout and high-flow precision grout.
  • Conbextra HS — Fosroc — ultra-high-strength grout for machinery and crane rails.
  • MasterFlow 4316 — Master Builders Solutions (now SikaGrout-4316) — ultra-high-strength grout suitable for cold-weather placing.
  • MasterFlow 9200, MasterFlow 9400 — Master Builders Solutions (now SikaGrout-9200/9400) — ultra-high-strength grouts for wind turbine foundations.
  • Five Star Grout, Five Star Fluid Grout 100 — Five Star Products — non-shrink grouts to ASTM C1107 without gas-generating admixtures.
  • PAGEL V1/10, V1/50 — Pagel Spezial-Beton — pourable grouts for thin and medium gaps.
  • PAGEL V1/50HF — Pagel Spezial-Beton — ultra-high-strength grout for wind turbines.
  • PAGEL V14/10, V14/40, V14/80 — Pagel Spezial-Beton — plastic mortars for packing under baseplates.
  • Five Star Hybrid Grout — Five Star Products — sulfate-resistant high-flow cementitious grout, placed from 2 to 38 °C.
  • Five Star Instant Grout — Five Star Products — rapid-strength cementitious grout reaching 27.6 MPa in 4 hours.
  • Five Star High Strength 130 Grout — Five Star Products — flowable high-strength cementitious grout, 90 MPa, pumpable over long distances.
  • Euclid Hi-Flow Grout — Euclid Chemical — high-flow non-shrink cementitious grout for machinery, columns and crane rails.
  • PAGEL V2 (V2/20, V2/50, V2/160) — Pagel — quick-setting grout reaching at least 15 MPa in 2 hours.
  • PAGEL V1/80 — Pagel — 0–8 mm aggregate grout for machinery and columns, 30–200 mm gaps.
  • Five Star NSG Grout — Five Star Products — general-purpose non-shrink cementitious grout, from dry pack to flowable consistency.
  • Five Star Cementitious Underwater High-Strength Grout — Five Star Products — non-shrink cementitious grout for underwater placement and pile jackets.
  • Euclid Dry Pack Grout — Euclid Chemical — non-shrink dry-pack cementitious grout placed by ramming.
  • Euclid NC Grout — Euclid Chemical — non-corrosive non-shrink cementitious grout, from plastic to fluid consistency.
  • Euco Pre-Cast Grout — Euclid Chemical — fast-setting non-shrink grout for precast concrete panels and structural supports.
  • PAGEL V80C45, V160C45 — Pagel — concrete grout for large volumes and deep pours up to 400 mm.
  • PAGEL VB (VB20, VB50, VB160) — Pagel — rapid-setting grout loadable after 30 minutes, at least 15 MPa in 2 hours.
  • PAGEL HF10 — Pagel — ultra-high-strength fine grout, class C100/115, for joints and cavities.
  • Mapefill SP — Mapei — super-flow non-shrink grout for precision anchoring of machinery in 10–100 mm layers.
  • Mapefill HES — Mapei — rapid-setting structural grout reaching 25 MPa in 2 hours, 10–200 mm layers.
  • Planigrout 712 — Mapei — non-shrink non-metallic silica-fume cementitious grout for structural grouting and anchoring.
  • Planigrout 740 — Mapei — non-shrink underwater tremie grout for bridge piers, piles and harbour walls.
  • Planigrout 755 — Mapei — general-purpose cementitious grout for base plates, anchors and precast members.
  • Euco Tremie Grout — Euclid Chemical — non-shrink cementitious grout for underwater placement with an anti-washout additive.
  • SikaGrout-328 — Sika — non-shrink cementitious grout with extended working time, from dry pack to fluid.
  • Fosroc Conbextra GP2 — Fosroc — non-shrink cementitious grout for turbines, compressors and pumps.
  • Fosroc Conbextra HES — Fosroc — rapid-setting non-shrink grout for urgent works and railing fixing.
  • Mapefill 318 — Mapei — pumpable multi-purpose non-shrink grout for anchoring and machine baseplates.
  • SikaGrout-428 FS — Sika — fast-setting non-shrink ViscoCrete cementitious precision grout.
  • SikaGrout-500 Aqua — Sika — non-shrink cementitious grout for underwater and tidal-zone placement.
  • SikaGrout-528 SF — Sika — flowable non-shrink silica-fume grout for tight clearances and voids.
  • Fosroc Conbextra GP1 — Fosroc — general-purpose non-shrink free-flow cementitious grout for static loads.
  • Fosroc Conbextra GP3 — Fosroc — high-strength non-shrink precision grout with dual shrinkage compensation.
  • Fosroc Conbextra AT — Fosroc — high-strength non-shrink grout for bridge bearings and parapet posts.
  • Fosroc Conbextra UHS — Fosroc — ultra-high-strength flowable grout with dual shrinkage compensation, 10–150 mm.
  • Fosroc Conbextra AT+ — Fosroc — high-strength non-shrink grout for bridge bearings and machine baseplates.
  • Fosroc Conbextra GPXtra — Fosroc — high-strength non-shrink grout for column baseplates and anchoring.
  • Fosroc Conbextra Sureflow 120 — Fosroc — free-flow non-shrink R4 class grout for layers up to 120 mm.
  • Fosroc Conbextra SS — Fosroc — multi-purpose non-shrink grout for precast bedding and void filling.
  • Fosroc Conbextra GV08 — Fosroc — non-shrink grout with 8 mm aggregate for pours thicker than 150 mm.
  • Fosroc Conbextra MF — Fosroc — fine-aggregate non-shrink precision grout for gaps up to 70 mm.
  • Fosroc Conbextra UW — Fosroc — washout-resistant non-shrink grout for underwater and tidal-zone placement.
  • Fosroc Conbextra TS — Fosroc — non-shrink aggregate-filled grout for thick sections, voids and anchor pockets.
  • Fosroc Conbextra Sureflow 100 — Fosroc — high-flow cementitious grout with dual shrinkage compensation for 10–100 mm gaps.
  • Fosroc Conbextra STD — Fosroc — general-purpose non-shrink cementitious grout for 10–100 mm gaps under baseplates.
  • Fosroc Conbextra PM — Fosroc — thixotropic pumpable cementitious mortar for gaps in precast units and tunnel anchors.
  • Fosroc Conbextra P — Fosroc — pumpable non-shrink cementitious grout for narrow 5–40 mm gaps.
  • Fosroc Conbextra GPA — Fosroc — non-shrink aggregate-filled cementitious grout for thick 50–200 mm gaps.
  • Fosroc Conbextra BB80 — Fosroc — high-strength non-shrink grout for bridge bearings and heavy column bases, 85 MPa.
  • Fosroc Conbextra BB — Fosroc — non-shrink cementitious grout for bridge bearings, parapet posts and lighting columns.
  • SikaGrout-105 — Sika — economical general-purpose non-shrink grout for 10–75 mm layers.
  • SikaGrout-4 UW — Sika — shrinkage-compensated grout for underwater and tidal-zone placement.
  • SikaGrout-520 — Sika — general-purpose free-flow non-shrink grout for layers up to 80 mm.
  • SikaGrout-4800 — Sika — ultra-high-strength metallic-aggregate grout for machinery under impact loads.
  • SikaGrout-828 — Sika — non-shrink cementitious grout for ballastless slab track and equipment, 10–80 mm layers.
  • SikaGrout-340 TR — Sika — high-strength non-shrink grout for equipment, baseplates and anchoring, 10–300 mm layers.
  • SikaGrout-215 — Sika — pumpable non-shrink grout with two-stage expansion for machine foundations and anchors.
  • SikaEmaco T 1200 PG — Sika — non-shrink flowable concrete for rapid repair and grouting down to −10 °C.
  • SikaGrout-4 N — Sika — self-levelling expanding cementitious mortar for equipment grouting and anchoring.
  • SikaGrout-311 — Sika — expanding cementitious grout for thin 3–10 mm gaps under equipment and in joints.
  • SikaGrout-212 RU — Sika — high-flow expanding cementitious mortar for grouting and repair, 10–60 mm layers.
  • SikaGrout-825 MF — Sika — cementitious installation grout for embedding supports, connections and precast joints, 15–160 mm.
  • SikaGrout-316 — Sika — rapid-hardening pourable grout for equipment, columns and concrete repair, 20–120 mm layers.
  • SikaGrout-214 IN — Sika — non-shrink grout with two-stage expansion for turbines, compressors and pumps.

Frequently asked questions

How much water should be added to a grout?

Exactly as much as the technical data sheet specifies for the required consistency. Most manufacturers give a range per bag; the upper limit must not be exceeded, or the grout will segregate and lose strength.

Does cementitious grout need to be vibrated?

As a rule, no. Flowable grouts are designed to self-compact under head; a number of technical data sheets expressly prohibit vibration. To keep the grout moving, use a head box and pour continuously from one side.

Can cementitious grout be placed in winter?

Only within the temperature limits given in the technical data sheet, and with protection against freezing until the grout has gained strength. There are special grades for cold weather — for example, according to the manufacturer, MasterFlow 4316 can be placed at temperatures from +2 °C. Never pour onto a frozen substrate without heating it first.

What if the gap is larger than the grade allows?

Choose a grade designed for greater thicknesses, or extend the grout with crushed stone in the proportion permitted by the manufacturer. For example, Mapei permits 6–10 mm pea gravel to be added to Mapefill for layers thicker than 100 mm.

How does a flowable grout differ from a repair mortar?

Repair mortars are designed to be applied to a surface and are often thixotropic; grouts are designed to fill an enclosed gap with guaranteed contact with the baseplate. Some products are certified both as repair mortars (EN 1504-3) and as anchoring products (EN 1504-6), but always confirm the intended use in the technical data sheet.