Block Filler

Reviewed by Raghvendra GopalCheckmark
Last updated: August 13, 2021

What Does Block Filler Mean?

Block filler is a filler material used under epoxy, alkyd and latex top coats for interior and exterior concrete finishes. It is used in masonry preparation on concrete block and cinder block (poured and precast). It is used before top coats so that the surface assumes a flat, smooth and uniform profile. It is required for professional quality finishes since it seals void, porous, cracked and pin-holed surfaces.

Concrete blocks used in the construction of block foundations are hollow. After these concrete blocks are laid in place, these voids can then be filled with poured concrete that contains small pea gravel or a cement-based mortar. When this is done in the building process, the filled concrete block walls become almost identical to poured concrete walls.

Holes in concrete block walls are filled by mixing together one-part cement, three parts sand and adding only enough water to make the mixture into a stiff patching compound. Block fillers greatly slow down the corrosion process of materials that may be embedded in concrete, such as steel rods and other materials used in the construction process. The high alkalinity of concrete gives a form of protection to the reinforcing steel rods, which prevents rapid corrosion.


Corrosionpedia Explains Block Filler

The substances commonly used in making block fillers are called low volatile organic compounds (VOCs), and contain vinyl-acrylic resin, extender pigments and titanium dioxide. Most of the block fillers have a volatile organic compounds (VOC) ratio of below 50 g/L.

Surface preparation is required before using this filler since moisture, dust, rust, oil and other foreign particles might tamper with the adhesion efficiency of the block filler. The mode of application is determined based on the preference of the users; it can be brushed, squeegeed, rolled and sprayed (conventional or airless). However, each mode of application has its requirements of use.

To obtain a quality surface modification, the instructions are based on the right temperature, humidity and film thickness; these factors are proportional to the dry time to be used. When used, it produces a good concrete finish with desirable uniform texture.
Block filler is a good choice for masonry like bricks, stucco and concrete as it seals the porous surfaces of such material. It fills and covers smaller cracks on a surface easily, including fuzz from drywall.

This product also provides a base for the application of latex, enamel or epoxy paints on different types of surfaces.
There are many advantages of concrete block filler use. It provides resistance to moisture, and can be used in deteriorated ceilings and walls without any issues. It is due to its many uses that it is favored for a wide range of purposes.


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