Quick Answer: Cementitious or Epoxy?
If you are grouting an equipment foundation, filling anchor bolt pockets, or repairing a structural void, the choice between cementitious grout and epoxy grout comes down to three factors: load type (static vs. dynamic), chemical exposure, and budget. Cementitious grout handles most general foundation work at a fraction of the cost. Epoxy grout is the right call when you need zero shrinkage under heavy dynamic loads or chemical resistance in aggressive environments.
This guide covers structural and industrial grouting — not tile or flooring grout. If you are installing machinery, grouting bridge bearings, or filling structural voids, you are in the right place.
What Is Cementitious Grout?
Cementitious grout is a Portland cement-based material blended with graded aggregates, expansion agents, and performance admixtures. It cures through hydration — the same chemical reaction that hardens regular concrete — but is engineered for much higher early strength and controlled expansion.
Modern cementitious grouts for structural applications are classified as non-shrink grouts under ASTM C1107/C1107M. The standard requires:
- Compressive strength ≥ 7 MPa (1,000 psi) at 1 day
- Compressive strength ≥ 17 MPa (2,500 psi) at 3 days
- Compressive strength ≥ 24 MPa (3,500 psi) at 7 days
- Compressive strength ≥ 35 MPa (5,000 psi) at 28 days
- Zero shrinkage at 28 days (tested per ASTM C827 and CRD-C621)
Types of Cementitious Grout for Structural Use
Not all cementitious grouts are the same. The formulation changes dramatically based on what the grout needs to do:
General-purpose non-shrink grout is the workhorse. It achieves 50–60 MPa compressive strength at 28 days, flows into complex geometries under gravity alone, and costs significantly less than epoxy alternatives. You mix it with water on site — no specialized equipment or two-part metering. This is the right choice for equipment bases, column-to-foundation joints, and anchor bolt pockets where static loads dominate. Fast-setting cementitious grout reaches structural strength in hours, not days. Our Fast-Setting Grout XQ-GJ-FS hits 30 MPa in 4 hours and 60 MPa in 24 hours. This matters when downtime is expensive — think turbine bearing replacement, emergency bridge repair, or overnight equipment realignment. Underwater (anti-washout) grout is formulated with anti-washout admixtures that prevent the cement paste from dispersing when placed in water. Our Underwater Grout XQ-GJ-UW maintains cohesion in flowing water and achieves 40 MPa compressive strength even when fully submerged during curing. It is pumpable up to 50 meters, making it practical for dam repair, dock foundations, and submerged pile cap connections.What Is Epoxy Grout (for Structural Applications)?
Structural epoxy grout is a three-component system — epoxy resin, hardener, and graded aggregate — that cures through an exothermic polymerization reaction. Unlike cementitious grout, epoxy grout contains no Portland cement and does not require water.
The key advantages of epoxy grout over cementitious grout are:
- True zero shrinkage with slight expansion (0.02–0.05%), ensuring full contact with the baseplate
- Superior dynamic load resistance — critical for rotating equipment that generates vibration
- Chemical resistance to acids, alkalis, oils, and solvents
- Higher compressive and flexural strength — our Epoxy Grout XQ-GJ-E reaches 80 MPa compressive and 25 MPa flexural strength
Head-to-Head Comparison: Cementitious vs Epoxy Grout
| Property | Cementitious Grout (XQ-GJ-C60) | Epoxy Grout (XQ-GJ-E) |
|---|---|---|
| Compressive Strength (28d) | ≥ 60 MPa | ≥ 80 MPa |
| Flexural Strength | 8–10 MPa | ≥ 25 MPa |
| Bond Strength (to concrete) | ≥ 2 MPa | ≥ 3 MPa |
| Shrinkage | Non-shrink (0.02–0.05% expansion) | Zero shrinkage (0.02–0.05% expansion) |
| Chemical Resistance | Moderate — not suitable for acid/solvent exposure | Excellent — resists acid, alkali, oil, solvent |
| Dynamic Load Suitability | Static to light dynamic | Heavy dynamic and vibratory loads |
| Temperature Range (service) | −20°C to +80°C | −30°C to +120°C |
| Mixing | Just add water | Three-component metered mixing |
| Pot Life (at 25°C) | 30–40 minutes | 20–30 minutes |
| Cost per m³ (approximate) | $200–$400 | $800–$1,500 |
| Cure Mechanism | Hydration (water-based) | Polymerization (chemical reaction) |
| ASTM Standard | ASTM C1107/C1107M | ASTM C579 |
The strength numbers tell part of the story, but the real decision driver is usually the loading profile. A CNC machine bolted to a concrete pad generates very different forces than a gas turbine spinning at 3,600 RPM. The CNC machine only needs cementitious grout. The turbine needs epoxy.
When to Choose Cementitious Grout
Cementitious grout is the right answer for the majority of structural grouting applications. Here is where it works best:
Equipment foundations under static or light dynamic loads. Presses, storage tanks, compressors on isolation mounts, HVAC chillers, and similar equipment that generates minimal vibration. The 60 MPa compressive strength of a high-quality cementitious grout far exceeds the bearing pressure of most base plates. Column-to-foundation connections. The annular gap between a steel column base plate and its concrete pedestal is a textbook application for non-shrink cementitious grout. The micro-expansion ensures full bearing contact, and the material cost keeps the project budget in check. Anchor bolt pockets and crane rail grouting. After anchor bolts are positioned and torqued, the pocket is filled with cementitious grout to lock them in place and transfer loads into the foundation. Self-leveling flow (cone spread ≥ 270 mm for our C60 grade) fills the annular gap completely without vibration. Large-volume pours. When the grouting volume exceeds a few hundred liters, cementitious grout is significantly more practical. The lower exotherm compared to epoxy means less risk of thermal cracking, and the just-add-water mixing simplifies batch production on site.When to Choose Epoxy Grout
Epoxy grout earns its higher cost in specific situations where cementitious grout cannot perform:
High-speed rotating equipment. Turbines, generators, large pumps, and centrifugal compressors generate continuous dynamic loads that can fatigue cementitious grout over years of service. The higher flexural strength (25 MPa vs 8–10 MPa) and creep resistance of epoxy grout are critical here. This is not optional — most turbine manufacturers specify epoxy grout in their installation manuals. Chemical plant foundations. If the base plate will be exposed to acid spills, solvent splashes, or lubricant migration, cementitious grout will degrade. Epoxy grout resists a broad spectrum of chemicals that would attack Portland cement binder. Precision alignment applications. When equipment alignment tolerances are measured in thousandths of an inch (mils), the absolute zero-shrinkage guarantee of epoxy grout matters. Any dimensional change in the grout pad after alignment will throw the machine out of spec. High-temperature service. Foundations under furnaces, kilns, or exhaust systems that see sustained temperatures above 80°C should use epoxy grout rated for the expected service temperature. Our epoxy grout maintains structural integrity up to 120°C continuous service.Polymer Modified Cementitious Mortar: The Third Option
Between cementitious grout and epoxy, there is a middle ground: polymer modified cementitious mortar. This material starts with a cement base but incorporates polymer additives (typically acrylic or SBR latex) that form a co-matrix with the hydrated cement.
The result is a mortar that combines the ease of use of cementitious products (just add water, single component) with improved adhesion, reduced permeability, and better crack resistance. Our Polymer Modified Repair Mortar XQ-SJ-P achieves 45 MPa compressive strength at 28 days with bond strength of 2 MPa or higher.
Polymer modified mortar is not a substitute for grout in equipment foundations — it is designed for surface repair and restoration. Use it for:
- Concrete spall and patch repair (3–30 mm thickness per layer)
- Surface leveling before protective coatings
- Restoring cross-sections of deteriorated beams and columns
- Protective overlays on bridge decks and parking structures
Underwater Grouting: Can Cement Cure Underwater?
Yes — but only if the grout is specifically formulated for it. Standard cementitious grout will wash out and segregate when placed in water, resulting in a weak, porous mass. Anti-washout grout solves this by incorporating viscosity-modifying admixtures that keep the cement paste cohesive even in flowing water.
Our Underwater Grout XQ-GJ-UW achieves 40 MPa compressive strength when cured fully submerged — compared to 55 MPa when cured in dry conditions. The mass loss in water is held below 5% per the EN anti-washout test. It is pumpable, self-leveling, and requires no cofferdam or dewatering.
Common underwater grouting applications include dam toe and apron repair, dock and wharf foundation reinforcement, submerged pile cap connections, and bridge pier scour protection.
5-Step Selection Framework
Use this decision process to select the right grout type:
Step 1 — Define the load profile. Is the equipment static (tanks, presses, structures) or dynamic (turbines, generators, compressors)? Static loads almost always point to cementitious grout. Step 2 — Check chemical exposure. Will the grout pad be exposed to acids, solvents, oils, or other aggressive chemicals? If yes, choose epoxy grout. Step 3 — Assess the environment. Is the pour underwater? Use anti-washout cementitious grout. Is the service temperature above 80°C? Use epoxy grout rated for that range. Step 4 — Consider the volume. For pours exceeding 500 liters, cementitious grout is more practical due to lower cost and lower exothermic heat generation. For critical but small-volume pours (turbine sole plates, precision equipment), epoxy is justified. Step 5 — Check the specification. Many equipment manufacturers and engineering firms specify the grout type in their foundation design documents. Always follow the project specification — it takes precedence over general guidelines.Related Guides
- Epoxy Anchors for Concrete: Types, Load Capacity & Installation Guide
- Chemical Anchor Systems: Types, Selection & Step-by-Step Installation
- Epoxy Crack Injection for Concrete: Methods, Resin Types & Step-by-Step Guide
- Structural Bonding Adhesive: Epoxy for Steel, Concrete & CFRP Applications
Frequently Asked Questions
What is the compressive strength of non-shrink cementitious grout?
ASTM C1107/C1107M requires a minimum of 35 MPa (5,000 psi) at 28 days for non-shrink grout. High-performance formulations significantly exceed this — our XQ-GJ-C60 reaches 60 MPa (8,700 psi) at 28 days with early strength of 20 MPa (2,900 psi) at just 1 day.
Can you use cementitious grout underwater?
Standard cementitious grout will wash out in water. You need a grout specifically formulated with anti-washout admixtures. Our Underwater Grout XQ-GJ-UW maintains cohesion in flowing water and achieves 40 MPa compressive strength when cured fully submerged. It requires no cofferdam or dewatering.
How long does cementitious grout take to cure?
Standard cementitious grout reaches approximately 40 MPa at 3 days and 60 MPa at 28 days. Fast-setting cementitious grout can reach 30 MPa in just 4 hours and 60 MPa in 24 hours — critical for emergency repairs or equipment that cannot remain offline for extended periods.
Is epoxy grout stronger than cementitious grout?
In compressive strength, epoxy grout is moderately stronger (80 MPa vs 60 MPa). The more significant difference is flexural strength: epoxy grout typically achieves 25 MPa versus 8–10 MPa for cementitious. This higher flexural strength makes epoxy grout essential for dynamic loads from rotating equipment.
What is polymer modified cementitious mortar used for?
Polymer modified cementitious mortar is used for concrete surface repair, spall patching, and protective overlays — not for equipment foundation grouting. The polymer additives improve adhesion and crack resistance compared to plain cement mortar, making it ideal for restoring deteriorated concrete surfaces.
What is the difference between grout and mortar?
Grout is designed to flow and fill voids — it is poured or pumped into gaps under base plates, anchor bolt pockets, and structural joints. Mortar is designed to be troweled onto surfaces for repair, bonding, or rendering. Grout is self-leveling; mortar is thixotropic (stays where you put it). Both come in cementitious and epoxy formulations, but their rheology and application method are fundamentally different.
Need help selecting the right grout for your project? Contact XINCHOR with your project details — load requirements, environmental conditions, and pour volume — and our engineering team will recommend the optimal product.