What is papercrete?

Papercrete - a portmanteau of paper and concrete - is essentially an industrial-strength papier mâché drawing on paper/cardboard, sand and Portland cement or clay. It can be fashioned in blocks, sheets or other moulded forms and used as a building material.

What are papercrete's origins?

Papercrete was first patented in 1928 by Eric Patterson and Mike McCain, who 'invented' it independently  as 'padobe' and 'fibrous cement' respectively. The pair have both contributed to the debate on potential applications and best practice for its production.

While there is a perception that the material is environmentally-friendly given its use of paper that would otherwise end up in landfill, the use of cement means it's not quite as 'green' as would be ideal.

As a building material it's enjoyed new-found popularity since the 1980s, particularly among DIY builders, with a burgeoning community online sharing applications and innovations.

What is used in the papercrete mix?

• Waste paper - Cardboard, newspapers, magazines, books and even junk mail are commonly used and may be added dry or pre-soaked depending on the mixing equipment being used.
• Aggregate - Either course or fine, typically sand, is used depending on the required strength.
• Cement or clay - This binds the mix together, providing strength and rigidity.
• Water

How is the papercrete mixed?

Mixing the material is fairly straightforward and sees water (which makes up around two thirds of the mix) combined with the waste paper and cement or clay which binds the mixture together.

The device used to mix the materials will need some form of sharp blade to chop the paper and combine the components and an online search brings up many examples of people devising their own machinery to best produce the mixture.

Once the materials have been successfully combined the slurry can be pumped into slip forms or added to moulds, with mixture levelled off and smoothed, to form building blocks. The blocks should remain in mould for a short time (around 30 minutes) to allow excess water to drain. It should take three to four days for the resulting blocks to cure allowing them to be used in construction.

How does papercrete fair in the rain?

Cured papercrete readily absorbs water unless it is specifically treated to prevent ingress. Indeed, its ability to absorb water means that in many applications the papercrete layer, even moistened, can be enough to retain structural integrity and prevent leaks, with captured moisture then released back to the atmosphere through evaporation.

What are the potential applications and limitations?

Papercrete has application in the delivery of small buildings and even houses. It can be used as a sound and heat insulator or to provide decorative coverings or built structures. Papercrete's papery origins mean it's not ideally suited to excessively wet conditions or for multi-storey buildings.

What are the pros and cons?

Pros

• The raw materials needed to make papercrete are abundant and inexpensive.
• You don't need specialist equipment needed to produce the mix and form blocks and can easily make or adapt your own.
• Papercrete has excellent heat and sound insulating properties.
• It's very lightweight - far lighter than concrete
• It has high compressive strength.
• Fasteners such as screws are generally able to be used without the risk of cracking the structure.
• The material is very malleable and can easily be formed to make blocks, sheets or panels.
• Papercrete does not catch fire easily and when it does it tends to smoulder for hours. When compared to say, wood, the spread of papercrete fires tends to be confined to a smaller area and less damaging as a result. Adding more cement and mineral material increases fire resistance.

Cons

• As you might expect from a paper-based material, papercrete offers poor moisture resistance. If exposed to water for prolonged periods it can begin to break down. Indeed, it can easily act as a wick to extract moisture from the ground across the built structure
• Mould can develop if the material remains warm and moist for too long.
• It can easily expand and contract leading to cracks and buckling.
• It offers poor tensile strength. Over doors and windows additional and more traditional support (in the form of wood or concrete) is often required.

What does the future hold for papercrete construction?

Experimenting with mixes to improve eco-efficiency has the potential to make papercrete a building material that's not only quick to make, can be flexibly applied and is relatively cheap, but also one that's eco-friendly.

There's a big potential market for papercrete construction across India, China and Africa, where there is particular need for constructions that can be made quickly and cheaply, and a growing army of papercrete builders are continuing to champion the cause worldwide.

Image: Appropedia Foundation, CC-BY-SA 2.0

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