ASTM C928: Rapid-Hardening Cementitious Materials for Concrete Repairs
Standard specification for packaged, dry, rapid-hardening materials used in bridge deck, highway, and structural concrete repairs
Last updated: April 19, 2026
Overview
ASTM C928 is the standard that governs packaged, dry, rapid-hardening cementitious materials for concrete repairs. If you've ever patched a bridge deck overnight, filled a highway spall during a weekend closure, or repaired a parking garage floor with a bag mix that hardens in hours instead of days, you've probably used a C928-compliant product.
The standard covers two material forms: concrete (contains aggregate retained on a 3/8-inch sieve) and mortar (finer aggregate). Both are packaged dry and mixed with water or manufacturer-supplied liquid on site. The standard explicitly excludes materials with organic binders like epoxy or polyester. C928 is hydraulic cement only.
Current edition is ASTM C928/C928M-25, published June 2025. The 2025 revision was primarily editorial (aligning language with ASTM's style manual). The technical requirements are largely unchanged from the C928-20 edition. The standard is 5 pages and costs $72 from ASTM.
Scope
What C928 covers: packaged, dry, rapid-hardening cementitious mortar or concrete materials for repair of hardened hydraulic-cement concrete pavements and structures. Must be mechanically mixed with water or aqueous solutions provided by the manufacturer.
What C928 does NOT cover:
- Epoxy-based repair materials
- Polyester polymer concrete
- Latex-modified concrete overlays (those have their own standards)
- Site-batched concrete mixes
R1, R2, R3 Classifications
Three classifications based on rate of hardening:
| Classification | Description | Flow Test Timing |
|---|---|---|
| R1 | Rapid Hardening | 15 +/- 1.5 minutes after mixing |
| R2 | Rapid Hardening | 5 +/- 1.5 minutes after mixing |
| R3 | Very Rapid Hardening | 5 +/- 1.5 minutes after mixing |
R3 is the fastest-setting category. R2 and R3 share the same flow test timing but have different strength requirements. R1 allows longer working time. Many products meet all three classifications (the manufacturer tests at each timing window).
Tip: When a DOT spec calls for "ASTM C928, Classification R3," they want the fastest-setting material. If the spec just says "ASTM C928" without a classification, check with the engineer. The working time difference between R1 and R3 is significant on a hot day.
Performance Requirements
Four key test properties define whether a product meets C928. The numbers below come from product data sheets of compliant materials, not the ASTM minimums themselves (which are behind the paywall).
Compressive Strength (ASTM C109, modified)
| Test Age | R3 Products Typically Achieve | R1/R2 Products Typically Achieve |
|---|---|---|
| 1 hour | 2,000-3,300 psi | N/A |
| 3 hours | 3,500-5,000 psi | 3,500 psi |
| 1 day | 5,000-7,000 psi | 5,200 psi |
| 28 days | 7,500-9,500 psi | 7,500-8,500 psi |
Bond Strength (ASTM C882, modified per C928)
| Test Age | Typical Range |
|---|---|
| 1 day | 1,100-2,370 psi |
| 28 days | 1,500-3,910 psi |
Length Change (ASTM C157)
Reported as drying shrinkage (-0.06% to -0.12% typical) and wet expansion (+0.02% to +0.10% typical).
Scaling Resistance (ASTM C672, 25 cycles)
Visual rating 0 (no scaling), mass loss under 0.05 lb/ft².
Freeze-Thaw (ASTM C666, Procedure A, 300 cycles)
Relative dynamic modulus 80-100%.
Note: The strength numbers above are from product data sheets, not the ASTM minimum requirements. Most products exceed the ASTM minimums by a comfortable margin. If you need the exact minimum thresholds for a specification, purchase the standard from ASTM ($72).
Referenced Test Methods
C928 references a set of ASTM test methods that define how each property is measured:
| Method | What It Tests |
|---|---|
| C39 | Compressive strength (cylinders) |
| C109 | Compressive strength (2-in. mortar cubes) - primary test for C928 |
| C157 | Length change (shrinkage/expansion) |
| C191 | Setting time (Vicat needle) |
| C266 | Setting time (Gillmore needles) |
| C666 | Freeze-thaw resistance (Procedure A, 300 cycles) |
| C672 | Scaling resistance (deicing chemicals, 25 cycles) |
| C882 | Bond strength (slant shear) - modified per C928 |
| AASHTO T260 | Chloride content |
State DOT Usage
Most state DOTs do not adopt C928 verbatim. They reference it as a baseline and layer on their own requirements for approved product lists, minimum strengths, and testing protocols.
Caltrans
References C928 in Section 90-4.02. Maintains an Authorized Materials List. Adds requirements: min 7-day compressive 4,000 psi, min 28-day bond 1,500 psi, max shrinkage -0.15%, max chlorides 0.05%. Authorization valid 5 years.
TxDOT
Uses DMS 4655 classification (Type B Ultra-Rapid 2-4hr, Type A Rapid 6-8hr, Class K under 12hr, Class S standard). Min opening strength 3,600 psi. Does not directly reference C928 but accepts C928-compliant products.
NYSDOT
Material code 701-09, maintains approved list of roughly 17 products. Requires initial set of at least 10 minutes at 70 degrees F.
AASHTO/NTPEP
Runs a Rapid Set Concrete Patch Materials evaluation program testing products against C928. Multiple DOTs accept NTPEP results instead of independent testing.
Tip: Before specifying a C928 product, check your state DOT's approved product list. Most DOTs maintain a QPL (Qualified Products List) and will only accept products on that list, even if the product meets C928.
Product Types
Products meeting C928 are grouped by the underlying cement chemistry. Each type has different working characteristics, and the chemistry matters when you're choosing a product for specific site conditions.
Calcium Sulfoaluminate (CSA)
CTS Rapid Set product line (DOT Repair Mix, DOT Concrete Mix, Cement All). Fastest-setting category. Good chloride and sulfate resistance. Most common on DOT projects.
Magnesium Phosphate Cement (MPC)
SikaQuick Set-45. The cold-weather champion. Works down to 0 degrees F without heating. Short working time (10-20 min at room temp). Highest cost.
Portland Cement-Based Rapid Set
SikaQuick-2500, W.R. Meadows FUTURA-15 and FUTURA-45, SpecChem RepCon 928 FS. Familiar chemistry with accelerators.
| Product | Manufacturer | Chemistry | 1-Hour Strength | 28-Day Strength |
|---|---|---|---|---|
| DOT Repair Mix | CTS Rapid Set | CSA | 3,000 psi | 8,500 psi |
| Cement All | CTS Rapid Set | CSA | 2,400 psi | 8,500 psi |
| SikaQuick Set-45 | Sika | MPC | 3,300 psi | 7,500 psi |
| SikaQuick-2500 | Sika | Portland | 2,500 psi | 7,500 psi |
| FUTURA-15 | W.R. Meadows | Portland | 2,000 psi | 7,500 psi |
| RepCon 928 FS | SpecChem | Portland | 2,200 psi | 8,000 psi |
Application Context
Lane closure constraints drive the decision between C928 materials and regular concrete. Regular concrete needs 2-7 days to reach opening strength. C928 R3 products open to traffic in 1-3 hours.
Typical Scenarios
- Overnight bridge deck repairs
- Weekend highway patching
- Emergency spall repair
- Airport runway repairs (between flight windows)
- Parking garage repairs with tenant access constraints
Depth Guidance
Partial-depth repairs (top 1/3 of slab), minimum 3/4" below top rebar. For depths over 3", extend with coarse aggregate per manufacturer instructions.
Temperature Constraints
| Condition | Guidance |
|---|---|
| Below 40 degrees F | Most products prohibited. Exception: MPC works to 0 degrees F |
| 40-70 degrees F | Normal range |
| 70-85 degrees F | Accelerated set, use chilled water |
| Above 85 degrees F | Use high-temp formulations or switch to conventional concrete |
BABA Connection
Cement and cementitious materials are currently exempt from BABA as construction materials. But packaged C928 repair mixes (cement + polymers + aggregates combined into a product with different properties) could be classified as manufactured products under FHWA guidance. The classification depends on whether the product arrives at the work site in "final form."
Most major C928 products are manufactured in the US already, so BABA compliance is likely satisfied either way. But the legal distinction matters for documentation purposes on federally funded projects.
For more on BABA requirements and how they apply to construction materials, see the Build America, Buy America deep reference and the Buy America Compliance Guide.
Frequently Asked Questions
What's the difference between R1, R2, and R3?
Rate of hardening. R3 is fastest. R1 gives you the most working time. R2 and R3 share the same flow test timing (5 minutes after mixing) but R3 has higher strength requirements. Many products meet all three classifications.
Can I use C928 material for full-depth repairs?
Yes, but extend with coarse aggregate for depths over 3 inches. For full-depth structural repairs, some DOTs prefer conventional concrete for long-term durability.
What opening strength do I need before traffic?
Most DOTs require 3,000 psi. TxDOT defaults to 3,600 psi. Check your project specs, as the required opening strength varies by agency and repair type.
Can I use C928 products in cold weather?
Most portland and CSA products require 40 degrees F minimum ambient and substrate temperature. MPC products like SikaQuick Set-45 work down to 0 degrees F. Always check the manufacturer's temperature range for the specific product.
Do I need a bonding agent with C928 materials?
Depends on substrate preparation. Hydrodemolition surfaces often don't need one. Jackhammer-prepared surfaces usually benefit from an epoxy or slurry coat. Check the manufacturer's instructions and your project spec.
How long do C928 repairs last?
TxDOT notes that "faster return to service correlates with shorter anticipated service life." Expect 5-15 years for rapid-set vs. 20-30+ years for conventional concrete. Proper surface prep and depth below rebar are the biggest factors in service life.
Is C928 the same as "rapid set concrete"?
C928 covers packaged, dry, rapid-hardening materials. Not all rapid-set concrete meets C928. Site-batched high-early concrete and UHPC (Ultra-High Performance Concrete) are separate categories with their own standards.
Which C928 product should I use?
Check your DOT's approved product list first. If you have flexibility: CSA for general use, MPC for cold weather, portland-based for longer working time. All three chemistries produce compliant products.
This page is for informational purposes only and does not constitute engineering, procurement, or specification advice. ASTM standards are revised periodically, and state DOT approved product lists change frequently. Consult the current edition of ASTM C928 and your project engineer for specification-level decisions.
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