6 Best High Strength Mortars For Bedding Heavy Duty Shims

Securing heavy-duty equipment or structural steel onto a concrete base requires more than just standard mortar. When shims are involved, the grout must support intense localized pressure without cracking or shrinking away from the contact point. Choosing the right material ensures that the load is distributed evenly, preventing structural failure or vibrating machinery issues down the line. Proper bedded contact is the difference between a long-term installation and a call-back that costs double to fix.

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QUIKRETE Precision Grout: Best for Availability

When a project hits a snag and an extra bag is needed immediately, QUIKRETE Precision Grout is the standard choice found at almost any major supply house. It is a non-shrink, high-strength formulation designed specifically for structural applications where support is critical.

This product handles high-compressive loads effectively, making it reliable for anchoring steel plates or heavy machinery bases. Because it is widely available, it remains the go-to for many contractors who cannot afford to wait on specialty shipping for smaller or mid-sized jobs.

While it lacks the extreme performance additives found in industrial-specific brands, it is consistently reliable for standard shim bedding. Always verify the batch date at the store, as older inventory in humid environments can compromise the chemical setting properties.

SikaGrout 212: Top Choice for General Grouting

SikaGrout 212 is a professional-grade hydraulic cement grout that offers excellent flow characteristics without sacrificing strength. It excels in applications where the grout needs to travel under a large base plate to ensure full, void-free coverage.

The non-shrink nature of this product is its standout feature, ensuring that the grout maintains contact with the shims even after curing. This prevents the “hollow” sound often heard when low-quality grout pulls away from the steel surface during the drying process.

It is highly versatile, usable in both fluid and plastic consistencies depending on the water ratio. For deep voids where the shim density is high, the fluid consistency is essential to prevent air pockets that create structural weak points.

MasterFlow 885: For Extreme Dynamic Load Support

MasterFlow 885 is engineered for the heavy hitters, specifically where machinery generates constant vibration or massive impact loads. In environments like industrial manufacturing or high-traffic structural support, this grout prevents the degradation that causes equipment to shift over time.

This product features a high-performance metallic aggregate that provides exceptional compressive strength and durability. It is designed to handle the thermal expansion and contraction cycles that would cause standard cementitious mortars to crumble under pressure.

Choosing this level of protection is an investment in the longevity of the installation. It is overkill for a residential deck post, but for a roof-mounted HVAC unit or heavy machinery platform, it is the safest bet against dynamic fatigue.

Euclid EUCO-SPEED MP: Fastest Set for Quick Jobs

Time is often the most expensive component on a construction site, and EUCO-SPEED MP addresses this by offering an incredibly fast set time. This allows crews to move to the next phase of construction—such as tightening anchor bolts—without waiting for a full 24-hour cure.

This grout maintains high early-strength, which is critical when working on tight schedules or in areas where equipment must be operational within a few hours. It minimizes the window of opportunity for accidental movement or disturbance of the shimmed base.

Keep in mind that rapid set times leave little room for error during placement. Once this mix hits the water, the clock is ticking; ensure the shims are perfectly aligned and the formwork is rock-solid before committing to the pour.

Rapid Set Cement All: The Ultimate All-In-One Fix

Rapid Set Cement All is a favorite for those who need a versatile repair material that holds up under pressure. While not a “grout” in the traditional heavy-industry sense, its high-strength, non-shrink properties make it perfect for smaller shim-bedding tasks where precision and speed are required.

Its main advantage is its ease of use; it reaches structural strength in just a few hours and bonds well to existing concrete. For a roofer or builder performing a localized repair on a concrete curb or base, this prevents the need to haul heavy bags of specialized industrial grout.

It should not be used for massive structural pours or wide-gap industrial bedding, as its chemistry is optimized for general repair. When used correctly for shim support on smaller projects, it provides a permanent, high-bond connection.

SAKRETE High Strength Mix: A Solid Budget Option

SAKRETE High Strength Mix is a baseline product that works well for basic structural support where extreme industrial specs are not required. It is an affordable option for DIYers or for non-critical bedding tasks where the load is well within standard thresholds.

This mix is generally coarser than precision grouts, meaning it may not flow into the tightest crevices under a base plate. If using this for shims, ensure the gaps are wide enough for the aggregate to pack effectively, or the grout might bridge over the space without making full contact.

It is best suited for scenarios where a simple, reliable base is needed for light-duty posts or secondary support structures. When in doubt about load requirements, always opt for a non-shrink precision grout instead of a general-purpose mix.

Non-Shrink vs. Epoxy Grout: Which Is Best?

The primary choice in the field is between standard non-shrink cementitious grout and epoxy-based systems. Non-shrink grout is the industry standard for most construction applications because it is cost-effective, easy to mix, and performs well under steady, compressive loads.

Epoxy grouts, however, provide superior chemical resistance and much higher tensile strength. They are essential when the shimmed base will be exposed to oils, acids, or constant, aggressive movement that would cause cement-based products to crack.

The trade-off is cost and ease of use; epoxy is significantly more expensive and requires a more controlled environment for curing. Use non-shrink grout for 90% of jobs, and save the epoxy for the specific 10% where the environment is hostile to standard concrete.

PSI Demystified: How Much Strength Do You Need?

Compressive strength, measured in PSI (pounds per square inch), is the most advertised metric for grout, but it is often misunderstood. For most residential and light commercial jobs, a grout with 6,000 to 8,000 PSI is more than sufficient.

Higher PSI does not automatically equate to a better installation if the preparation is poor. A 12,000 PSI grout will fail just as quickly as a 5,000 PSI grout if it is improperly mixed or poured into a void filled with loose debris or dust.

Focus less on finding the highest number on the bag and more on the consistency and the manufacturer’s instructions. Match the grout strength to the substrate and the expected load, ensuring that the grout is never the weakest link in the chain.

Mixing Grout for Perfect Base Plate Shim Contact

Achieving a perfect bond starts with the water-to-powder ratio, which is the most critical factor for strength. Too much water creates a “bleed” that weakens the structure, while too little makes it impossible to work the material into the gaps.

Always mix until the consistency is uniform, then “rodding” or “pumping” the grout into the shim space to ensure air is completely displaced. In roofing and structural applications, an air pocket under a shim is a ticking time bomb for vibration and load-bearing failure.

Never try to “stretch” the grout by adding extra sand or filler. Use the product exactly as specified, as the chemical additives inside are balanced for that specific mix ratio.

Surface Prep and Curing for Max Bond Strength

Surface preparation is the step that separates a pro job from a disaster. The concrete base must be saturated surface dry (SSD), meaning it is damp but has no standing water, before the grout is applied.

Dust, loose aggregate, and oil are the primary enemies of a good bond. Clean the area with a wire brush or compressed air, and ensure the base plate or shim has been thoroughly degreased to allow the grout to lock onto the material.

Curing is the final stage; protect the grout from drying out too fast in direct sun or high wind. If it dries too quickly, it will crack—defeating the purpose of using a non-shrink product in the first place.

When you invest the time to choose the correct material and execute the pour with attention to detail, you minimize risk and maximize the lifespan of the structure. Whether working on a simple post base or a complex industrial frame, the right grout applied correctly ensures the foundation stays solid for years to come.