Cómo reparar el desprendimiento de agregados en concreto en pisos industriales

In my more than 20 years of experience leading civil engineering and maintenance projects in plants in the metropolitan area of Monterrey, Saltillo, Torreón, and Piedras Negras, I have encountered all types of pavement failures. However, few pathologies are as destructive to the daily operation of a distribution center or a heavy manufacturing plant as aggregate pop-outs in concrete. This failure, which begins almost imperceptibly with small detachments of sand and fine gravel, can quickly ruin the polyurethane wheels of your narrow-aisle forklifts and halt your production line.

When coarse and fine aggregates begin to separate from the cementitious matrix, the floor loses its flatness and is exposed to accelerated wear. In this technical article, I will explain in detail why this pathology occurs, how to diagnose it correctly in your plant, and what are the most effective engineering methods to repair this problem at its root using cutting-edge technology, ensuring that your investment in polished concrete pays off for decades.

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Table of Contents

• What are aggregate pop-outs in concrete?
• Main causes of aggregate pop-outs and spalling in Mexico
• Pathology diagnosis: Superficial detachment or structural damage?
• Materials needed for industrial repair (Epoxy mortars and resins)
• Step-by-step guide to fix aggregate pop-outs in concrete
• Contraction joint treatment to prevent future crumbling
• Quality and prevention standards in concrete mix (NMX-ONNCCE)
• Preventive maintenance and sealing of industrial concrete floors
• Advantages and disadvantages of repair systems
• Common errors in the Mexican industry when repairing floors
• Real case: Auto parts plant in Ramos Arizpe, Coahuila
• Professional checklist for repair supervision
• Frequently Asked Questions
• Conclusion
• Sources and References

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What are aggregate pop-outs in concrete?

Industrial aggregate pop-outs in concrete (known in English technical literature as aggregate pop-outs o delamination) is a physical and mechanical pathology of concrete where fragments of the floor surface detach, leaving small conical cavities or craters. This condition should not be confused with uniform abrasive wear; it is a localized or generalized failure of the interface between the cement paste and the aggregate (interfacial transition zone).

In an industrial floor with a standard mix design, the compressive strength $f'c$ (which typically ranges between $250 \text{ kg/cm}^2$ and $350 \text{ kg/cm}^2$ to withstand heavy traffic) depends on the cohesion of the cement paste and the quality of the stone aggregates. When this cohesion fails, it results in spalling, exposing the coarse and fine aggregates to the direct action of dynamic loads.

If not addressed in time, the constant passage of forklifts generates an impact effect that accelerates the crumbling of the cavity edges, transforming a small 2-centimeter pothole into an industrial safety problem that violates the NOM-001-STPS-2008 (which requires keeping work area floors clean and free of obstacles to ensure safe transit).

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Main causes of aggregate pop-outs and spalling in Mexico

In the context of industrial construction in Mexico, aggregate pop-outs in industrial floors are often the result of a combination of climatic factors, poor placement practices, and deficiencies in local raw materials. The main causes we detect in the field are:

1. Excess mixing water (High water/cement ratio): To facilitate concrete placement (increase slump), many crews add water on-site without authorization from the structural engineer. This severely weakens the surface layer of the floor, drastically reducing its compressive strength $f'c$.
2. Excessive bleeding and premature finishing: If mechanical troweling (helicopter) is performed while the concrete is still bleeding, water and fines become trapped just below the hardened surface, creating a thin crust prone to spalling.
3. Contaminated or reactive aggregates: In certain regions of northern Mexico, stone aggregates may contain clay particles, silts, or expansive minerals (such as reactive chert). Upon contact with moisture, these particles expand and burst the concrete surface.
4. Deficient curing: In areas with extreme climates like Torreón or Saltillo, rapid evaporation of curing water prevents complete hydration of the cement on the surface, leaving an extremely fragile layer prone to repairing concrete spalling prematurely.

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Pathology diagnosis: Superficial detachment or structural damage?

Before opening the toolbox or buying materials, an accurate diagnosis is mandatory. Not all superficial failures require the same intervention technique.

To assess the severity of concrete pathologies like spalling, we apply three fundamental field tests:

• Percussion Test (Metallic Sound): We strike the perimeter of the damaged area with a ball-peen hammer or drag a steel chain. A clear, sharp sound indicates healthy, dense concrete; a hollow or dull sound reveals internal delamination (voids beneath the surface).
• Scratch Test (Relative Hardness): Using a hardened steel punch, we attempt to scratch the healthy surface and the affected area. If the concrete crumbles easily like chalk, we are facing a severe problem of cement deficiency or carbonation.
• Core Drilling: In large-scale projects, we extract 2 or 3-inch diameter concrete cores for laboratory analysis to determine the depth of the failure and verify if the actual $f'c$ strength meets design specifications.

Damage Level	Failure Depth	Typical Diagnosis	Recommended Solution
Mild	Less than 5 mm	Dusting and micro-spalling of the surface.	Diamond grinding and application of lithium densifier.
Moderate	From 5 mm to 20 mm	Localized spalling of medium aggregates (pop-outs).	Perimeter cutting, cleaning, and patching with high-strength epoxy mortar.
Severe	Greater than 20 mm	Structural damage, deep delamination, failure in contraction joints.	Total reconstruction of the section with an epoxy bonding agent and structural mortar.

Engineer's Tip: Never attempt to repair a structural problem by applying a thin layer of common mortar over the damaged surface. The lack of mechanical adhesion and the difference in elastic moduli will cause the repair to detach in less than a month under forklift traffic.

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Materials needed for industrial repair (Epoxy mortars and resins)

To ensure a repair that withstands continuous mechanical abuse, we must forget about traditional sand and gray cement mixes from construction sites. The key to a successful restoration lies in the use of high-performance polymers.

Epoxy mortar for concrete repair

This three-component system (Resin Part A, Hardener Part B, and Selected Silica Aggregate Part C) is the gold standard in the industry. It possesses a compressive strength exceeding $700 \text{ kg/cm}^2$ (more than double that of conventional concrete) and adhesion to old concrete that surpasses the tensile strength of the substrate itself.

Epoxy resin for damaged concrete floors (Bonding agent)

It is used as a primer or primer low-viscosity liquid. Its function is to penetrate the open pores of old concrete to ensure perfect chemical anchoring with the new repair mortar. High-performance generic brands like SikaDur 32 Primer or equivalents from Fester are excellent options for this purpose.

Graded quartz aggregates

For the reconstruction of floors that will subsequently receive a finish of polished concrete with lithium densifier, it is crucial that the aggregate of the repair mortar is of controlled granulometry and free of moisture, thus preventing the formation of bubbles (blistering) during the chemical reaction of the resin.

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Step-by-step guide to fix aggregate pop-outs in concrete

Below, I detail the engineering procedure we execute at SINE Mexico to ensure a polished concrete floor repair with automotive plant quality.

[Zona Dañada] ──> [Corte Perimetral con Disco de Diamante (90°)] ──> [Remoción y Limpieza] ──> [Imprimación Epóxica] ──> [Colocación de Mortero Epóxico] ──> [Nivelación y Desbaste]

Step 1: Demarcation and perimeter cutting of the affected area

Delimit the damaged area by drawing a rectangle that extends at least 5 cm beyond the limit of the deteriorated concrete. Using a diamond disc cutter, make a vertical perimeter cut to a minimum depth of 10 mm (never finish the repair with a "feather edge" or "zero" edge, as this guarantees future detachment).

Step 2: Removal of weak concrete and deep cleaning

Using a light rotary hammer or manual chisel, remove all crumbled concrete within the delimited area until a sound and firm concrete substrate is reached. Subsequently, perform a deep cleaning using an industrial pressure washer or high-power vacuum cleaner to eliminate all traces of dust, oils, greases, and release agents. The surface