Dr. Owen Geiger has sent us drawings of an engineered wall using recycled plastic blocks.
The first drawing has elevation showing foundation, windows, and doorways. Click on the drawing to make it larger
Dr. Geiger shows using horizontal wall reinforcement. (click on drawing to make full size
- Purposes:To strengthen the wall against “bowing” in due to lateral pressure (earth, wind, seismic)
- To make the wall more ductile (i.e., less brittle) and hold it together in extreme events such as earthquake or hurricane.
b. Horizontal joint reinforcement consists of heavy wire welded together to take the shape of a ladder (or truss), and is usually selected as follows:
- 10 Gage wire – for light duty interior or exterior applications
- 9 Gage wire – standard duty
- 8 Gage – heavy duty for use in seismic or other high-stress applications
- 3/16″ diameter wire – extra heavy duty for extreme conditions
c. Horizontal joint reinforcement placed in horizontal mortar joints as follows:
- Placed in every CMU course if used for foundation wall
- Placed every 2 or 3 courses for above-ground walls (or more if necessary)
The Recycled Plastic Block doesn’t have cavities for vertial supports like CMU blocks have.
Vertical CMU Wall Reinforcement: (link to source of information below)
- Purpose – Greatly strengthen the wall to accommodate larger vertical loads as well as resist lateral loads.
- Vertical CMU wall reinforcement consists of inserting steel rebar (usually #4 or #5 rebar) into open cores of the wall, then filling those cores solid with a concrete-like grout.
We get the same vertical support by placing the rebar outside of the Recycled Plastic Blocks in our walls. (see Dr. Geiger’s drawing at the top of the page) The rebar is tied to the blocks it contacts and to the opposite rebar with wire ties.
We are working to get a local engineering school involved in the Recycled Plastic Blocks. One of the facets of the Recycled Plastic Block wall that we want to study is the R value provided by the plastic blocks inside a plastered wall. Intutition suggests that it will provide a greater R value than CMU block construction.
3. Possible disadvantages of CMU buildings: (link to information below)
- Expensive labor – CMU construction is labor-intensive. Depending on localities, labor CAN be very expensive.
- Heavy – Masonry buildings weigh more than comparable steel-framed and wood-framed buildings.
- Absorbent – CMU, like any other cementitious material is absorbent to water penetration and must be weather-proofed.
- Modular – Typical CMU has modular 8″ x 8″ x 16″ nominal dimensions, and is a bit difficult to have walls that have odd dimensions or smooth curves.
- Difficult to insulate – Block has a very low “R” value and generally, walls must be insulated by adding width to them – decreasing available floor square footage.
Most of the disadvantages of the CMU block construction don’t apply to the Recycled Plastic Block concept.