Epoxy resin mortar for hydraulic abrasion and corrosion resistance

Repair Material Solutions for Scour and Abrasion Areas in Hydraulic Reservoirs: Comparative Application of Epoxy Mortar and Propylene Emulsion Mortar

I. Solution Overview

This solution aims to provide selection and application guidance for two high-performance repair materials—epoxy mortar and polymer cement mortar (propylene emulsion mortar)—for addressing common scour and abrasion damage areas in hydraulic and hydroelectric engineering. Due to their excellent physical and mechanical properties and durability, these materials are widely used to repair and enhance the abrasion and cavitation resistance of concrete structures, thereby extending the service life of projects. This solution will focus on the core characteristics of both materials and their respective optimal application areas.

II. Material Characteristics

1. Epoxy Mortar

Epoxy mortar is a high-performance polymer mortar composed primarily of epoxy resin, along with hardeners, toughening agents, and aggregates such as quartz sand.

• Ultra-High Strength and Bonding Force:

  • Compressive and Flexural Strength: Significantly higher than ordinary concrete and propylene emulsion mortar, with exceptional mechanical properties capable of withstanding strong impact and shear stresses.

  • Bonding Strength: Extremely strong adhesion to substrates such as concrete and steel, far exceeding the material's own tensile strength, enabling "substrate failure" rather than "interface debonding," ensuring excellent integrity of the repair.

• Outstanding Abrasion and Cavitation Resistance:

  • The material has a dense structure and high hardness, offering excellent resistance to media such as sediment and gravel carried by high-velocity water flow, making it the preferred material for addressing severe scour and cavitation issues.

• Low Permeability and Chemical Stability:

  • Forms a dense network structure after curing, making it nearly impermeable with a high anti-seepage grade.

  • Resistant to erosion by freshwater, seawater, oils, and various chemical media, with excellent anti-corrosion properties.

• Good Toughness:

  • Compared to brittle materials, epoxy mortar has certain deformation capacity, allowing it to better adapt to minor substrate deformations and vibrations, with good crack resistance.

• Limitations:

  • Temperature Resistance: Strength significantly decreases at high temperatures (typically above 65-80°C) and is not resistant to open flames.

  • UV Resistance: Prone to aging and yellowing under prolonged sunlight exposure, requiring protective measures.

  • Cost: Relatively high material cost.

  • Substrate Requirements: Extremely strict requirements for substrate dryness; damp substrates can affect curing and bonding effectiveness.

2. Propylene Emulsion Mortar (Acrylate Copolymer Emulsion Cement Mortar)

Propylene emulsion mortar is an organic-inorganic composite material formed by incorporating propylene emulsion polymer into cement mortar and curing.

• Excellent Impermeability and Density:

  • The polymer emulsion forms a film within the cement mortar, filling capillary pores and microcracks in the cement hydration products, significantly increasing density and improving impermeability by several times compared to ordinary mortar.

• High Bonding Strength and Crack Resistance:

  • High bonding strength with old concrete substrates, overcoming the shortcomings of poor adhesion and susceptibility to hollowing in ordinary mortar.

  • The polymer film imparts good flexibility to the material, with a lower elastic modulus, allowing it to adapt to certain deformations and exhibiting strong resistance to shrinkage cracking.

• Good Wear Resistance and Weather Resistance:

  • Abrasion resistance is superior to ordinary concrete, meeting the requirements of moderate-intensity water flow scour environments.

  • Better resistance to atmospheric aging and UV radiation compared to epoxy-based materials, making it suitable for outdoor applications and water level fluctuation zones.

• Corrosion Resistance and Toughness:

  • Good resistance to chemical media such as chloride ions and salts, with excellent carbonation resistance.

  • Exhibits certain toughness, improving the brittleness of cement-based materials.

• Environmental Friendliness and Construction Adaptability:

  • Water-based system, non-toxic and environmentally friendly.

  • Less stringent requirements for substrate dryness compared to epoxy mortar; can be applied on damp substrates but not on surfaces with standing water.

  • Cost: High cost-effectiveness, with material costs significantly lower than epoxy mortar.

III. Recommended Application Areas

Based on the above material characteristics and considering the operational environment and damage mechanisms of different parts of hydraulic reservoirs, the following recommendations are provided:

Preferred Application Areas for Epoxy Mortar (Suitable for Extremely Harsh Scour Environments)

1. High-Velocity Flood Discharge Structures:

   • Spillway Chute Sections, Flip Buckets, Stilling Basin Floors, and Sidewalls: These areas experience extremely high water velocities, often accompanied by cavitation. The ultra-high strength, cavitation resistance, and exceptional abrasion resistance of epoxy mortar make it irreplaceable here.

2. Sediment Discharge Bottom Outlets and Scouring Tunnels:

   • High sediment content and hard particles in the water flow cause severe abrasion to sidewalls and floors. Epoxy mortar is the preferred material for protecting these critical areas.

3. Turbine Scroll Cases and Draft Tubes:

   • Subject to high-velocity water flow and cavitation damage caused by impellers. Epoxy mortar is commonly used for repair and protection.

4. Steel Structure Surface Protection:

   • Such as gate slots and embedded parts, utilizing its ultra-strong bonding force for protection and repair.

Preferred Application Areas for Propylene Emulsion Mortar (Suitable for Moderate and Lower Scour Environments or as an Anti-Seepage Enhancement Layer)

1. Water Level Fluctuation Zones and Splash Zones:

   • Such as upstream faces of dams, pier columns, bridge piers, and docks. These areas are affected by wet-dry cycles, freeze-thaw cycles, and wave action. The high impermeability, strong bonding, and good weather resistance of propylene emulsion mortar make it highly suitable.

2. Water Conveyance Tunnels and Channel Linings:

   • For water conveyance structures with low flow velocities but requiring impermeability and wear resistance, propylene emulsion mortar is an economical and effective choice, improving abrasion resistance while effectively preventing leakage.

3. Anti-Carbonization and Anti-Corrosion Coatings for Concrete Structures:

   • Widely used on concrete surfaces of dams and powerhouses as protective layers to prevent reinforcement corrosion.

4. Auxiliary Repair for Moderate-Velocity Discharge Structures:

   • In areas with less severe scour or as transition and enhancement layers around epoxy mortar repair zones.

IV. Summary

• Epoxy mortar is the "special forces" for addressing high-intensity, high-velocity scour and cavitation damage, with exceptional performance but higher costs, making it suitable for the most severe conditions.

• Propylene emulsion mortar is the "main force" for addressing moderate scour, high impermeability, and durability requirements, offering a balance of performance and cost advantages, with a broader range of applications.

In practical engineering, a comprehensive technical and economic comparison should be made based on the water flow velocity, sediment content, cavitation risk, environmental conditions (wet-dry, freeze-thaw), and project budget of the damaged area. The most suitable material should be selected, or a composite repair solution combining both materials should be adopted to achieve optimal repair effectiveness and economic benefits.23