Building The Ultimate Stress Test

Words: Peter Roberts
Photos: Spherical Block, LLC

Check out the full video here: FALLOUT | Stress Test

Seven years ago, we had a conversation with Jeff Buczkiewicz, president of the Mason Contractors Association of America (MCAA). We were introducing our company and its technology to him: Spherical Block, LLC. We use specialty concrete blocks to make roofs, such as arches and domes. He asked if we could build a structure that could withstand having a car dropped onto the roof. “Sure! We can do that.” So began an interesting and dramatic experiment.

This experiment had some logistical challenges. The main one was simply geography and distance. Our company is in western New York State; the proposed test site was in central Texas, near Waco. Communication took place with phone calls, emails, and the occasional live video conference.

The Planning
First, we had to agree on a structure: what would it be? We suggested a one-car garage, for reasons that seemed obvious. A one-car garage is an appropriate size on which to drop a car. We have also built a few garages, and had some experience in the design and construction of such a structure. We agreed on a building with a footprint of 13 feet 4 inches wide by 22 feet 4 inches long. We suggested a wall height of 8 feet; this was later changed to 11 feet 4 inches, or to 13 feet 4 inches to the top center of the arch.

Next, we had to configure the arch itself. Our arch designs include a few different arrangements. Over a live video meeting, we described the corrugated arrangement, where arch blocks are laid in a herringbone-type configuration, creating a series of furrows across the arch. These corrugations provide greater structural rigidity to the assembled structure, just like corrugated cardboard is stronger than flat cardboard. Our comments were met with skeptical silence. Or we could lay the block in a simple running bond, without corrugations. It would not be as strong, but it was an option. The Texas masons seemed to relax and fell into the familiar idea of concrete block laid in a running bond, like a comfortable pair of old cowboy boots. We decided to build a smooth (non-corrugated) arch, using a simple running bond.

Initially, we wanted the test to include semi-automated equipment to be used during assembly. This was intended to show how rapidly assembly can occur. This equipment was to include 3-dimensional concrete printing (3DCP) as a MaxiPrinter provided by Constructions 3D, a French company. This unit uses a robotic arm, rather than a gantry system, allowing rapid set-up and deployment. The MaxiPrinter would be used to deposit beds of mortar rapidly and efficiently. The other piece of equipment was to be a MULE (Material Unit Lift Enhancement) provided by Construction Robotics of Victor, New York. The MULE allows blocks to be placed rapidly and effortlessly by human masons. The timing, distances, and logistics prevented deploying both the MaxiPrinter and MULE on this test: we had enough on our plate. Instead, the test relied on the excellent, skilled masons from Brazos Masonry of Waco.

The test also required an observation building to house people and cameras safely during testing and keep everyone safe from flying debris during testing. We suggested a simple square building, with a small dome roof on top. This was agreed on, as we decided to make a building with a square footprint, 8 feet on each edge and 8 feet in height, with one door facing away from the test site. The dome was to be around 7 feet in diameter, made from our “Dome” block. The dome was to be constructed as a truncated icosahedron, which is a polyhedron shaped like a soccer ball (where the white patches are hexagons made from 6 “hex” blocks and the black patches are pentagons made from 5 “pent” blocks).

The team attempted to find a concrete block producer in Texas to make our block and prevent having to ship blocks all the way from New York. During this time, we were at the end of the COVID crisis, and pent-up demand for concrete block was being met by producers; their production time was at a premium. We had to ship from our inventory in New York, using block produced at Southern Tier Concrete Products in Alfred, NY. Blocks were palletized and loaded onto trucks and shipped to Texas. We also required non-metallic fiber-reinforced polymer (FRP) rebar. We used basaltic FRP, which is stronger than fiberglass rebar and provides substantially better corrosion resistance than fiberglass rebar. We used #3 FRP basaltic rebar (3/8-inch diameter), which comes in 300-foot lengths, as coils. This rebar is lightweight, easy to bend (important for curved arches), is around 3 times stronger than steel in tension, and does not rust. The rebar is provided by Smarter Building Systems in Newport, Rhode Island. We shipped this rebar to Texas.

Design Flexibility of Spherical Block’s Masonry System
Here is a photo of a test structure being built at our New York business location, showing a smooth arch in the foreground and a corrugated arch in the background (these are both catenary arches). The catenary form is the strongest possible arrangement for an arch under gravity. ‘Catenary’ comes from the Latin ‘catena,’ meaning chain: if a chain is allowed to hang suspended from both ends with some slack, and turned upside down (inverted), one has a catenary arch. Because we were dropping a car on the roof, we figured a simple round form would be stronger than a catenary and would be easier to assemble. Thus, a round arch was used for the roof.

Making the Test Building
Construction began at the ranch of Mackie Bounds, CEO of Brazos Masonry. Mackie’s property is in Axtell, Texas, around 20 minutes from Waco. Mackie and his son Kent were excellent partners in this endeavor. Once Mackie decided where he wanted to place these structures, he had the footprint excavated for both the garage and the observation building. Concrete footers were poured for both buildings, with #7 steel rebar reinforcement. The footer was 12 inches thick and 16 inches wide.

We decided to build the vertical walls from 8-inch-wide CMUs with a running bond. This design used common CMUs, which are found everywhere in construction. We figured that this would be strong enough to handle the impact of having a car dropped on the roof, with proper detailing. This detailing included #3 basaltic FRP rebar vertically placed in the core holes of all blocks, 8 inches OC, running into the footer with an elbow, grouted into place. We also used horizontal steel ladder-type reinforcement in the horizontal mortar beds. Finally, we placed a horizontal bond beam at the top of the wall, running around the entire perimeter of the wall and including a lintel halfway along the length of the building, tying the opposite walls together. This bond beam used 3 pieces of #7 steel rebar around its entire length and across the midway lintel. This bond beam and lintel were critically important to resolve any splaying thrusting forces which would result from dropping a load on the roof of the building and help resolve any tension forces resulting from impact. The vertical walls were assembled by the masons of Brazos Masonry while we remained in New York, with regular sharing of photographs during assembly. Brad Bailey of Brazos Masonry was very helpful in coordinating the vertical wall construction.

The vertical walls were built with the #3 basaltic rebar sticking out from the vertical core holes 4 feet at the top of the walls. This would allow the rebar to tie directly into the arch from the vertical wall, for continuous tensile reinforcement. To make a bend or elbow that would allow the rebar to go from the wall into the arch, we used a simple handheld propane torch to burn out the polymer in the FRP and bend the rebar. This was not ideal because the loss of strength in the rebar from doing this is estimated at around 30%. Nonetheless, the basaltic FRP rebar is around 3 times stronger (in tension) than steel rebar. We suggested we could use #3 steel rebar to lap at this joint from wall to roof, but ultimately, we decided to simply create elbows using the propane torch. We figured the stress would be kept largely in compression and rely on the high compressive strength of concrete block.

Design Flexibility of Arch Block
Here are patent illustrations of the “Arch” block. Note that the shape has a slight compound angle, which allows the block to form a curving arch. The wider edge of the block is oriented towards the outside, and the thinner edge is oriented towards the inside of the arch. Molds were made by Besser Company and are designed for a 3-at-a-time machine. These molds produce 8 blocks per cycle, in approximately an 8-second cycle time, or around 1 block per second. This provides the block producer with high production throughput and good profit margin. Molds include a divider plate to produce half-blocks. Full blocks may be combined with half-blocks to create independent arches, including 3 pieces of rebar per arch. These independent arches may be used to construct flying buttresses on the outside of buildings, to resolve outward thrusting forces which result from arched roofs. Thus, the “Arch” block provides extensive design flexibility, including: corrugated arches, smooth arches, arched (cambered) lintels, flying buttresses, independent arches, and round windows or openings. The grooves in the Arch block are wide enough to accommodate up to #7 rebar. In the structure built in Texas, we used #3 rebar, but larger rebar may be used for larger spans or stronger reinforcement. Use of FRP rebar is highly recommended (as opposed to steel rebar) because FRP rebar bends much more easily to assemble arches.

Here are some photographs of the Arch block being used to create various structures, demonstrating the design flexibility offered by this masonry unit. First is the arched or cambered lintel:

The flying buttress is another example of what can be done with Arch block, using one full block and one half-block per course, with three pieces of rebar. An actual chain was used to establish the catenary curve for rebar; a plywood form was cut and used as a template for assembly of the inverted catenary flying buttress profile, to help support the masonry during assembly (note the use of 3 rebar per buttress):

Here is an example of the flying buttresses employed in a two-car garage, to help resolve the thrusting forces of the masonry arch roof:

Here is the masonry arch roof (30 feet span) which was reinforced by the flying buttresses. Note the corrugated arch arrangement:

Any mortar used in the assembly of an arch is subject to shrinkage as it cures. This is not problematic at all: the arch will use gravity to prevent any gaps from occurring. The masonry arch compensates for any shrinkage because it is in compression.

Practice has shown that it is generally best to lay full horizontal courses of block when assembling arches. There may be circumstances where it is beneficial to lay block in an ascending arrangement so that they touch at the top center of the arch and become self-supporting and reinforce the arch as assembly is completed.

Making the Test Garage
We arrived at Mackie’s ranch in early December 2026 to begin the roof assembly. It began with meeting the excellent masonry crew from Brazos Masonry and giving them some quick instructions about how our concrete block masonry roofing system works. One of the things we told them about was the concept of anisotropy in concrete block, and how this makes the roof stronger.

The Importance of Anisotropy
Isotropic material has the same strength in all directions: if you consider a wet-cast concrete cube, the strength is equal in the x, y, and z directions. Manufactured concrete block is not isotropic, it is anisotropic. It has a much higher strength in the vertical direction, which is the direction of compaction as blocks are made. This is due to the violent vibration of the concrete mix as blocks are produced; it arranges the aggregate with a preferential orientation so that the long axis of the aggregate tends to be oriented in the horizontal direction. As a result, the high-strength axis is around 70% stronger than the weaker axis. In our roofing masonry system, the high-strength axis is always oriented to the outside. For a curved roof, the high-strength axis is always radially oriented to the outside and better able to withstand shock or impact from flying debris, which may result from extreme weather events, such as tornadoes or hurricanes. Or having a car dropped on the roof.

Below are some images which show this anisotropy and its effects on strength. This was done by one of our ceramic engineering students, Stephen LiVoti, for his senior thesis at Alfred University’s NYS College of Ceramics (concrete is ceramic). He analyzed the same concrete we used in this Texas test. The micrograph shows the aggregate in the concrete from our block; note the horizontal alignment. This was analyzed with Python software. Our roof was around 70% stronger simply because of the orientation of the concrete block. The additional strength provided by utilizing the orientation of the block regarding anisotropy has big implications regarding storm surge performance, among other things.

One challenge posed by this test was determining the height from which the car would be dropped. Jeff Buczkiewicz of MCAA was not sure. The impact was critically influenced by how high the fall would be, and we wanted to be sure our roof was strong enough. As a result of this uncertainty, we decided to make the roof two wythes (layers) thick of our Arch block. Given the response of the structure from the test, this might have been over-designed, because it remained completely intact after multiple impacts. We now know that two wythes create an incredibly strong and robust roof.

Before the arch blocks were laid, we assembled wooden support structures to help support the blocks. We used simple wooden supports, placed on top of conventional steel scaffolding placed inside the building.

Once the wooden support was in place, the #3 basaltic FRP rebar was placed 8 inches OC running across the arch. Currently, we are planning tests using an inflatable bladder as support for laying block as arches and domes for roofs, instead of wooden support. An inflatable bladder (like inflatable tents for construction sites) can be rapidly set up and then deflated and taken down once the arch is assembled, for subsequent reuse. A good inflatable structure is typically made from Kevlar fabric; it is very strong and durable.

We were fortunate to work with excellent masons from Brazos Masonry, including Renato Ramirez Jr., Leonell Perez, Jose Pichardo, and crew. These men are skilled, experienced, great workers; it was a pleasure working with them. Together we laid Arch block, being careful to fill the grooves in the Arch block with mortar, so that rebar had proper cover and was well anchored. We did not place mortar in the head joints. This is because the arch blocks are designed to make the corrugated arrangement described earlier and have dimensions of full 8 inches x full 16 inches, so there is no allowance for a 3/8-inch head joint. Once the masons had a little practice and gained some familiarity, assembly proceeded quickly.

We used #7 metallic rebar (2 feet OC) run the entire horizontal length of the roof. This was done in both wythes to help provide tensile strength and help handle the impacts the building was subject to. There were 7 lengths of #7 metallic rebar placed in each wythe. This rebar was placed on top of the #3 basaltic FRP rebar, inside the mortar bed between the arch blocks.

After the first wythe was completed, the next day we assembled the second wythe. A thin skim coat of mortar was applied between wythes to avoid air gaps and provide a solid, continuous masonry assembly. We used 2” x 4” pieces of wood to provide the spacing and proper location of #3 basaltic FRP rebar. The same process used in the first wythe was repeated for the second wythe. With the gained experience and practice of assembling the first wythe, the second wythe went even faster.

There were some gaps at the corners of the roof, where the Arch block encountered the bond beam which ran around the top of the wall. These gaps were filled with concrete; a wooden form was attached to the wall with TapconTM screws and subsequently removed after adequate curing.

Making the Observation Building
The observation building roof was also assembled in December 2025. First, we assembled a wooden form to make a concrete slab on top of the vertical walls known as a pendentive. The pendentive allows a round dome to sit on top of a square (or hexagonal, octagonal, etc.) base. We made the form using plywood at the bottom and sides. The pendentive was made 8 inches thick. After the wooden form was made, #3 basaltic FRP rebar was placed inside the form to provide tensile strength. The form was then filled with concrete and allowed to cure. Once it had cured, the dome was assembled as shown.

The triangular dome blocks are arranged around the base perimeter, first with tips pointing up, then (between them) with tips pointing down. Once a complete course is assembled, another course is laid, using the same technique. The dome was assembled in around 2 hours.

During the testing that occurred following assembly, the film crew referred to the observation building as “the turret,” which we found amusing.

Design Flexibility of Dome Block
The dome used for the observation building roof was the smallest masonry dome that can practically be assembled using the Dome block. Much larger domes are possible by using the concept of the Sierpinski fractal. This fractal subdivides the triangles which comprise the truncated icosahedron into 4 triangles, and these may, in turn, be subdivided into 4 triangles, etc., to make larger and larger domes or sections of domes. Each larger dome is known as a “frequency.” The dome made for the observation building was a first frequency at around 7 feet in diameter. We utilize FRP rebar to create a supporting form to help in the assembly of structures, so that they are self-supporting as they are assembled. The best way to do this is to complete one course (which is then stable and self-supporting) and then to assemble another course on top of it. There are grooves on the inside face of the block which receive the rebar; blocks are placed over three sections of rebar so that they align with the three grooves on a block, and this rebar will help support the block. Mortar is applied to the abutting faces of the block before the next block is added. Here are some photographs showing this assembly method, as dry-stacked assembly (without mortar for the purposes of demonstration). Use of mortar is highly recommended. This dome shown below is a second frequency arrangement, twice as large as the observation dome at around 14 feet in diameter.

Here are some photographs of a fourth frequency truncated icosahedron dome, which is around 32 feet in diameter. Larger domes than this can be made. All use the same two blocks: “pent” (for making pentagons) and “hex” (for making hexagons).

The Dome block may also be used to assemble complete spheres. These complete spheres have been used to build both cisterns for storing water and septic tanks. These structures are assembled below ground and require excavation. The examples shown below are a first-frequency truncated icosahedron, with a diameter of around 7 feet and a volume of around 1,300 gallons.

Storm Shelter Design
In February 2026, we attended a course on Storm Shelter Certification arranged by MCAA in Euless, Texas, at Acme Brick. The presenter, Jerry Painter, stressed the importance of proper reinforcement and the necessity of grouting all reinforcement with proper cover. We were relieved by the recent work completed in December at Mackie Bounds’ ranch, which involved extensive reinforcement and high-slump grout, which helped provide proper cover for the reinforcement. The importance of this detailing was made clear by Mr. Painter during this course; it was informed by his decades of seeing the actual damage of extreme weather events on buildings and structures.

Final Preparation
We returned to Mackie’s ranch in March 2026. We spent a few days checking on the work we did in December and oversaw some finishing work. This included a parge coat of mortar to the inside ceiling of the garage, and application of a stucco covering to the exterior of both the test garage roof and the observation building roof.

Stucco was applied to the roofs of both structures, and a parge coat of mortar was applied to the ceiling of the garage. One advantage of an arched roof is that there is no possibility of standing water, which can eventually lead to leaking. We visited Puerto Rico in the wake of Hurricane Maria; many homes have flat concrete roofs and had suffered from leaking due to standing water.

The car for testing arrived on site.

It was great to meet Jeff Buczkiewicz and Mackie Bounds during the testing. Mackie’s hospitality set the stage for dramatic testing that exceeded all of our expectations.

The Educational Aspect
For over 20 years, we taught Masonry Science to engineering students at both Alfred University’s New York State College of Ceramics and at Alfred State College. Both schools are in Alfred, New York, home also to Spherical Block LLC. We give students practical exposure to everyday work involved in innovation, arch and dome design, new materials, and use of masonry technology at the cutting edge of industrial practice. Several classes of students have learned the intricacies of intellectual property by becoming involved in composing US patents and are listed as authors on patents filed by the Company. Over 30 students from both schools have had this educational experience of becoming authors of US patents, a credential which helps them as they seek meaningful employment upon graduation. One of our former students has moved from western New York to Dallas, Texas, and was able to visit during our testing in Axtell. Miss Cable was a student of ours 7 years ago; we stayed in contact and were very happy to see her at Mackie Bounds’ property. Miss Cable is an author of a US patent with the Company and remains actively interested in Masonry Science.

Fortunately, the weather cooperated on the main day of testing. We began early and went through a lot of testing to everyone’s satisfaction and even amazement. It was a very successful experiment that will help redefine the concept of resiliency for complete masonry building envelopes for years to come.

Currently, Spherical Block products (Arch and Dome block) are available at Southern Tier Concrete Products in Alfred, NY.

Check out the full video here: FALLOUT | Stress Test

Building The Ultimate Stress Test

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