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  • Overview
  • Specs
  • Application

Wacker HDK H18 Fumed Silica Thickening Agent

Wacker HDK H18 Fumed Silica Thickener is used in concrete repairs with epoxy systems and polyester resins as a thickening and thixotropic agent to create a smooth, non-sagging, high-strength mixture for structural bonding, filleting, and filling. It’s best to use Fumed Silica when high-strength and easy to to apply low-density are required. Fumed Silica is a hydrophobic grade and is great to mix with composites, coatings, adhesives and sealants, especially epoxy and polyurethane systems for bulking up for various uses including use in crack and joint repairs.

For DIY homeowner and smaller repair projects, see our ready-to-use HyperCURE Concrete Repair Kit.  HyperCURE is easy to use and offers minimal waste.

Wacker H18 Fumed Silica comes in a (10kg) 22 lb container (we only sell in minimum quantity of  5 bags shipped LTL Freight) and is meant for larger concrete repairs.  A 5 quart quantity of Fumed Silica Thickener when combined with 1 gallon of mixed epoxy/hardener, will produce about 1.75 gallons of smooth, thixotropic epoxy joint and crack filler.  You can use more or less Fumed Silica depending on how thick you want the gel to become.  Suggest using mask when mixing Fumed Silica as it is composed of very fine particles.

Recommend mixing the Fumed Silica with HyperFLEX Epoxy which offers an exceptionally quick 15-30 minute recoat time.  Apply coatings over your repair up to 24 hours after your repair without any special preparation.  After 24 hours requires sanding 100 grit sander then wipe down with acetone solvent and when flash dry, can apply new coating over the repaired area.

 Where is Wacker HDK H18 Fumed Silica Used in Concrete Repair Projects?

  • Concrete Cracks, holes, spalls and control joints
  • Concrete Thresholds
  • Flooring Installation
  • Uneven Concrete Slabs
  • Garage floors
  • Warehouse floors
  • Freezer floor projects
  • Other applications include:
  • • Adhesives
    • Anti-Corrosive Coatings
    • Antifriction Agents & Lubricants
    • Do It Yourself
    • Hair Care
    • Industrial Coatings
    • Make-up
    • Marine & Protective Coatings
    • Rheology Control
    • Sealants
    • Silane Modified Polymers (GENIOSIL)
    • Skin Care
    • Structural Bonding of Wind Turbines
    • Wind Energy

Why Wacker HDK H18 Fumed Silica?

  • Great thickening agent to wide range of coatings including epoxy and polyurethane coatings
  • Allows coatings to be used as great concrete crack, hole, joint and spall repairs
  • When mixed into fast cure epoxy, makes for very quick repairs


Specific Surface Are (BET) 170-230 m²/g   DIN ISO 9277 DIN 66132
pH Value in 4% dispersion 4.0-6.8   DIN EN ISO 787-9
SiO₂-Content (based on ignited material) > 99.8 %   DIN EN ISO 3262-19
Loss on drying (2 hours at 105C) < 0.6 %   DIN EN ISO 787-2
Appearance Fluffy white powder
Tamped density approx. 50 g/l   DIN EN ISO 787-11
Carbon content 4.0 – 5.2 %    DIN ISO 10694



The ‘Best use before end’ date of each batch is shown on the shipping label and the certificate of analysis. HDK® H18 should be stored in the original packaging in dry storage areas. Storage beyond the date specified on the label does not necessarily mean that the product is no longer usable. In this case however, the properties required for the intended use must be checked for quality assurance reasons


HDK H18 is applied as a thickening and thixotropic agent in composites, coatings, adhesives and sealants, especially in vinylester, epoxy and polyurethane systems.  HDK® H18 is not suitable for pharmaceuticals, food and feed.  A good dispersion of HDK® H18 is a must to assure optimum performance


NOTICE TO BUYER: DISCLAIMER OF WARRANTIES AND LIMITATIONS ON OUR LIABILITY We warrant that our products are manufactured to strict quality assurance specifications and that the information supplied by us is accurate to the best of our knowledge. Such information supplied about our products is not a representation or a warranty. It is supplied on the condition that you shall make your own tests to determine the suitability of our product for your particular purpose. Any use or application other than recommended herein is the sole responsibility of the user. Listed physical properties are typical and should not be construed as specifications. NO WARRANTY IS MADE, EXPRESSED OR IMPLIED, REGARDING SUCH OTHER INFORMATION, THE DATA ON WHICH IT IS BASED, OR THE RESULTS YOU WILL OBTAIN FROM ITS USE. N0 WARRANTY IS MADE, EXPRESSED OR IMPLIED, THAT OUR PRODUCT SHALL BE MERCHANTABLE OR THAT OUR PRODUCT SHALL BE FIT FOR ANY PARTICULAR PURPOSE. NO WARRANTY IS MADE THAT THE USE OF SUCH INFORMATION OR OUR PRODUCT WILL NOT INFRINGE UPON ANY PATENT. We shall have no liability for incidental or consequential damages, direct or indirect. Our liability is limited to the net selling price of our product or the replacement of our product, at our option. Acceptance of delivery of our product means that you have accepted the terms of this warranty whether or not purchase orders or other documents state terms that vary from this warranty. No representative is authorized to make any representation or warranty or assume any other liability on our behalf with any sale of our products. Our products contain chemicals that may CAUSE SERIOUS PHYSICAL INJURY. BEFORE USING, READ THE MATERIAL SAFETY DATA SHEET AND FOLLOW ALL PRECAUTIONS TO PREVENT BODILY HARM.