20 Lb 3/4 in Fiberglass for Concrete Mortar Mix - Reinforcement

Our review of the 20 Lb 3/4 in fiberglass for concrete mortar mix finds it most useful for DIYers and small contractors who need an affordable, easy-to-add reinforcement to reduce cracking and seepage in cement work. The bottom line: this two-piece 10 lb pack delivers a simple way to increase mortar toughness and permeability resistance, especially in wet areas like basements, ponds, and exterior walls. It is not a substitute for structural rebar, but as a fiber additive it strengthens impact resistance and helps inhibit small crack formation when mixed properly.

Key Features

• Package Includes: Two 10 lb bags provide a total of 20 lb of white fiberglass, enough for multiple small repair or finishing jobs around the home.
• Fiber Size: At 0.75 in length the fibers distribute irregularly through mortar to enhance toughness without dramatically changing mix workability.
• Anti Leakage: The fibers increase cement density and help reduce penetration and seepage in wet or damp areas when mixed evenly.
• Impact Resistance: High strength filaments form a dense network inside the cured cement to help resist impact and minor seismic forces for non-structural elements.
• Easy to Use: The fibers are added to sand and cement before water; expect to stir 30-60 seconds longer than normal to fully disperse the fibers.
• Wide Application: Suitable for basements, gardens, exterior walls, courtyards and other locations where improved crack resistance and impermeability are desired.

Who It's For

This product is aimed at homeowners, landscapers and small-scale masons who perform repair work, overlays or new non-structural concrete pours and want a simple additive to improve toughness and reduce hairline cracking. It fits projects such as garden slabs, floor patches, exterior wall rendering and pond repairs where improved impermeability matters.

It is not intended for primary structural reinforcement on load-bearing beams or columns; engineers and contractors should use engineered reinforcement like rebar or mesh where structural ratings are required. Professional projects requiring certified lab-tested admixtures might look elsewhere.

Pros & Cons

Pros

• Increases mortar toughness and helps inhibit small crack formation when dispersed evenly.
• Improves impermeability and reduces penetration in wet applications such as basements and ponds.
• High strength filaments interlock to enhance impact resistance for non-structural concrete works.
• Convenient two-piece packaging gives 20 lb total for multiple small jobs.

Cons

• Requires longer stirring time (30-60 seconds extra) and may affect workability if overdosed.
• Not a replacement for structural reinforcement like rebar for load-bearing elements.

Specifications

Brand	Marsui
Package Weight	20 lb (two 10 lb pieces)
Fiber Length	0.75 in (3/4 in)
Color	White
Primary Use	Reinforcement for concrete, cement and mortar
Key Benefits	Anti seepage, anti cracking, impact resistance
Typical Applications	Basements, ponds, exterior walls, garden floors, courtyards

Our Verdict

The 20 lb 3/4 in fiberglass for concrete is a practical, cost-effective additive for non-structural concrete and mortar work where reduced cracking and improved impermeability are priorities. For homeowners and small contractors it offers clear benefits in wet areas and repair jobs, but it should be used as a complement to, not a replacement for, engineered structural reinforcement.

Frequently Asked Questions

How is the fiber added to a mix?
Mix sand, cement and the fiberglass evenly before adding water, then stir 30-60 seconds longer than usual to disperse fibers.

Can this replace rebar?
No, these fibers improve toughness and crack resistance but are not a substitute for structural rebar or mesh in load-bearing elements.

Where is it best applied?
It is best for wet or damp areas and non-structural surfaces such as basements, ponds, exterior walls, garden floors and courtyards.