How Do You Repair Spalled Concrete and Damaged Control Joints in a Plant Floor?

Repair a spalled plant floor joint in four steps: sound the floor to find the limit of unsound concrete, saw-cut a square-edged perimeter and remove to sound concrete, rebuild the edge with an epoxy mortar, and fill the joint full depth (2 in minimum in formed joints) with a semi-rigid filler at Shore A 80 to 95 that takes forklifts in 1 to 12 hours depending on chemistry. The timing rule matters as much as the material: filler manufacturers set 30 days as the minimum slab age and ACI recommends 60 to 90 days or longer, with an extra 7 to 14 days in cold storage. DTI's crews follow the two SOPs linked below; this article explains the decisions behind them.

By Alexi Cortez · November 4, 2026 · 10 min read

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Why do plant floor joints spall in the first place?

Four causes, and the fix depends on which one you have.

  • Joint edge impact from hard wheels. An unfilled or under-filled saw-cut joint leaves two unsupported concrete edges. Each hard polyurethane or steel wheel that crosses them loads one edge at a time and chips it. Semi-rigid fillers exist to protect those edges: the ASCC position statement says they must be stiff compared with a joint sealant and have minimal lateral expansion capability.
  • Filler separation. The filler pulls away from the joint wall or tears inside itself because the slab kept shrinking after the joint was filled. ACI 302.1R-15, 310R-13 and 360R-10 agree that separation should be expected when joints are filled early and does not indicate a failure of the filler or the installation; most shrinkage happens in the first year, especially the first 90 days.
  • Freeze-thaw and wet-dry cycling. Dock doors, cold storage thresholds and wash-down areas see water in the joint that freezes or dries repeatedly and breaks down the edge. Look for spalling only near doors and drains.
  • Rebar corrosion and delamination. Rust expands and lifts the concrete above it, so a spall that sounds hollow with brown staining is a corrosion repair, not a joint repair. ACI's spall repair bulletin says to chip until uncorroded bar is found and to consult a structural engineer if the bar has lost cross section.

How do you find the real extent of the damage?

Sound the floor. Drag a chain or tap with a hammer across the suspect area; delaminated concrete rings hollow, and ASTM D4580 is the standard method for mapping it. Mark the boundary of hollow-sounding concrete, not the visible crack, because the visible spall is usually the smaller area. For joints, run a thin blade along the filler to find where it has separated from the wall, and check whether the concrete edge on either side is still intact; separated filler with sound edges is a refill, chipped edges are a re-nosing.

How do you remove the damaged concrete and prepare the edges?

Follow ACI RAP-7. Lay out the repair in simple geometric shapes with few re-entrant corners, saw-cut the perimeter so the repair has square vertical edges (a feathered edge is the next spall), and keep the saw cut no deeper than the cover over the reinforcement. Remove to sound concrete with a 15 lb or 30 lb breaker; anything larger than 30 lb can damage reinforcement. Where bar is exposed and corroded, clear about 3/4 in all the way around it. Clean the cavity with high-pressure water at 3,000 psi minimum or abrasive blasting, then bring the substrate to the moisture condition the repair material requires: saturated surface dry for cementitious, dry for epoxy.

For a joint edge spall, the saw cuts run parallel to the joint on each side to a width that captures all of the broken edge, and the joint itself is re-cut to its original width and cleaned to full depth before refilling.

Which repair material fits which case?

Values are from manufacturer data sheets at 70°F unless noted.

Joint and spall repair materials by case
CaseMaterialKey propertyReturn to forklift traffic
Control joint, heavy hard-wheel duty, ambient floorSemi-rigid epoxy joint fillerShore A 90 to 95; full joint depth in saw cuts, 2 in minimum in formed jointsLight traffic 6 to 8 hours; full traffic 8 to 12 hours
Control joint, retail or moderate duty, polished floorSemi-rigid polyureaShore A 80 to 81 (moderate duty) or 86 to 90 (heavy duty); better long-term color stability than epoxy on polished floorsLight traffic 30 minutes; full traffic 60 minutes (heavy duty); traffic ready 1 hour (moderate duty)
Control joint, cooler or freezerLow-temperature polyureaRated for final temperatures to -20°F (moderate duty) or -30°F (heavy duty); Shore A 92 to 94 at 0°FAbout 3 hours at 0°F for construction traffic
Joint edge spall under 1 in wideSemi-rigid filler, or a higher Shore A filler modified with sand or aggregateFill full depth; shallow installation is the leading cause of joint filler failurePer filler above
Joint edge spall over 1 in wide, or deep spallStructural re-nosing with early-set epoxy mortar; polymer-modified or ready-mixed concrete for larger patchesEpoxy mortar: hard-wheeled traffic in 8 hours or less; repair concrete per ACI: 4,000 psi minimum, w/cm 0.40 or less, 7-day wet cure8 hours (epoxy mortar); days (cementitious)
Spall in a shutdown windowQuick-set epoxy mortar; DTI Concrete Repair Kit for small spalls and cracksQuick-set mortar: foot traffic 1 hour, normal traffic 2 hours; DTI kit: trim at 15 minutes, 30-minute foot-traffic block at 70°F or higher, colder temperatures extend cure2 hours (quick-set mortar); DTI kit: forklift time per the crew lead on site
Random cracksPolyurea or semi-rigid epoxy, routed and filledSame materials as joints; cementitious fillers are generally not recommended for long-term durabilityPer filler

Epoxy versus polyurea in one sentence: epoxy for long-term durability in high-volume distribution and heavy manufacturing, polyurea for fast access, color stability on polished floors, and cooler or freezer work. DTI's own SH-85/86 joint filler is a two-component, 100% solids, rapid-cure semi-rigid polyurea at Shore A 85 to 86, the semi-rigid class ACI 302.1R describes for hard-wheeled forklift traffic. It is moisture tolerant, displacing water during placement to hold wall adhesion without foaming, trims with a razor scraper 15 to 45 minutes after dispensing, and takes forklift traffic in 60 to 90 minutes at about 70°F, or 90 to 120 minutes on a cold slab. DTI's field SOP applies a more conservative rule on every job: no foot traffic for 3 hours.

When should joints in a new slab be filled?

Later than the schedule wants. Filler manufacturers set 30 days as the minimum, and ACI 302.1R-15 recommends deferring joint filling as long as possible, with 60 to 90 days or longer the common recommendation, because most shrinkage happens in the first year and especially the first 90 days. HVAC start-up speeds slab shortening, so a slab filled before the building is conditioned will open its joints.

Cold storage waits longer. Filler data sheets ask that refrigerated and frozen rooms be pulled down to operating temperature and held stable for an additional 7 to 14 days or longer before filling, because the slab shrinks again as it cools. Write into the contract who comes back to refill joints that separate, and when; ASCC recommends that the construction documents name that party and set a return date or reserved funds.

When does a joint need re-cutting instead of refilling?

Refill when the filler has separated but the concrete edges are intact and the joint width is unchanged: remove the old filler, clean to full depth, and refill. Re-cut when the edges are spalled wider than the original saw cut, when old filler cannot be removed cleanly, or when the joint was never filled to full depth; filler manufacturers call shallow installation the leading cause of joint failure and say the shallow filler usually has to come out. Re-cutting widens the joint to clean concrete on both sides, so it pairs with edge re-nosing when the spall is more than 1 in wide. A true expansion or isolation joint is never filled with a semi-rigid material; it gets a flexible sealant because it is designed to move.

How fast can forklifts come back?

From the table: heavy-duty polyurea opens to light traffic in 30 minutes and full traffic in 60 minutes at 70°F, and DTI's SH-85/86 polyurea takes forklifts in 60 to 90 minutes; semi-rigid epoxy takes 8 to 12 hours; quick-set epoxy mortar takes about 2 hours; early-set epoxy mortar 8 hours or less; cementitious repairs cure for days. Cold rooms slow everything, and polyurea for cooler work should be kept at a minimum of 75°F before placing. DTI schedules joint work by aisle so no lane is closed longer than its filler's traffic time; see /blog/warehouse-floor-repair-without-shutting-down for how that phasing works.

DTI's repair SOPs

See the DTI repair procedures in the resources box below.

Frequently asked questions

How do you repair a spalled control joint in a warehouse floor?

Sound the area to find hollow concrete, saw-cut a square-edged perimeter no deeper than the rebar cover, break out to sound concrete, clean with 3,000 psi water, rebuild the edge with epoxy mortar if the spall is over 1 in wide, then fill the joint full depth with semi-rigid filler at Shore A 80 to 95.

Semi-rigid epoxy or polyurea for control joints?

Epoxy (Shore A 90 to 95) for heavy hard-wheel traffic and long-term durability; it takes full traffic in 8 to 12 hours. Polyurea (Shore A 80 to 90) for fast access, polished floors and freezers; it opens to full traffic in 60 minutes and low-temperature grades work to -30°F. DTI's SH-85/86 is a Shore A 85 to 86 polyurea.

How long after a new slab is poured can you fill the joints?

Not before 30 days, and ACI 302.1R recommends deferring as long as possible, commonly 60 to 90 days or longer, because most shrinkage happens in the first 90 days. Cold storage rooms should be at operating temperature for another 7 to 14 days first. Joints filled early will separate and need refilling.

How soon can forklifts drive on a repaired joint?

Heavy-duty polyurea filler: light traffic in 30 minutes, full traffic in 60 minutes at 70°F. Semi-rigid epoxy filler: 8 to 12 hours. Quick-set epoxy mortar for spalls: about 2 hours. Early-set epoxy mortar: 8 hours or less. Cementitious repairs need days of cure. Cold rooms extend every figure.

When does a joint need to be re-cut rather than refilled?

When the edges are spalled wider than the saw cut, when old filler cannot be removed cleanly, or when the joint was filled shallow instead of full depth. Refill alone is enough when the filler separated but the concrete edges are intact. Expansion and isolation joints are never filled with semi-rigid material.

Related reading

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