R&D in Concrete Block Masonry

Manufactured concrete block represents a great success story of the 20^th century.  An entire global industry has developed and evolved into a high state of efficiency and economy, all based on manufactured concrete block.  This technology thrives in virtually every country on earth: the traditional, rectangular concrete masonry unit (CMU) is produced inexpensively and with an engineering knowledge which is well understood and successfully put into practice by block producers globally.  The result is something we all tend to take for granted: high-strength, consistently dimensioned, inexpensive, rapidly produced CMU’s which are suitable for vertical walls in virtually any type of building, including residential, commercial, public buildings and infrastructure.  With such a successful model of production, distribution, assembly and availability already well established and in place, what –if any- new developments can research and development (R&D) add to this existing industry and practice?

My own work as a masonry designer has addressed this question for 25 years now.  I will attempt to summarize the areas of potential future growth, development and design which this robust industry has left essentially unfulfilled.  A look at current areas of research conducted by various segments of the scientific and engineering world indicate areas which stand to benefit and develop rapidly from the existing engineering practices of the concrete block industry.  The research and development proposed here hold the potential to transform the concrete block industry’s offerings into an entirely new realm of products which will provide better building systems at a lower cost on a global basis.  A modest effort in research and development will reap huge benefits for humanity; it will grow the concrete block industry and make superior, affordable, beautiful and holistic construction available for all.

One specific area of current research which has garnered significant attention from scientists, engineers, designers and practitioners is the idea of topological interlocking structures.  “Topological” refers to “Topology (from the Greek τόπος, "place", and λόγος, "study") [which] is the mathematical study of shapes and topological spaces. It is an area of mathematics concerned with the properties of space that are preserved under continuous deformations including stretching and bending, but not tearing or gluing. This includes such properties as connectedness continuity and boundary.  Topology developed as a field of study out of geometry and set theory, through analysis of such concepts as space, dimension, and transformation. Such ideas go back to Leibniz, who in the 17th century envisioned the geometria situs (Greek-Latin for "geometry of place") and analysis situs (Greek-Latin for "picking apart of place"). The term topology was introduced by Johann Benedict Listing in the 19th century, although it was not until the first decades of the 20th century that the idea of a topological Space was developed. By the middle of the 20th century, topology had become a major branch of mathematics” (taken from Wikipedia).

Currently, concrete block design and practice do not provide for topological construction.  The standard rectangular concrete block designs (with which we are so familiar) can only be used to create straight vertical walls and square corners.  A few designs allow for a slightly curving wall, which have found use mainly in retaining walls and landscaping applications.  Other novel designs allow for slight variations to the basic idea of a vertical wall, including corners which occur at 45 degrees and so on.  Current concrete block designs are far from providing a full expression of topology.  Curving walls –such as those provided by landscaping applications- only curve in one dimension, like a cylindrical surface, and do not allow curvature in two dimensions, like a spherical surface.  A form of concrete block known as “articulated block” (shown above and below) does some interesting work as an erosion-arresting embankment material.  Articulated block do not interlock in the plane being assembled; blocks can slide in and out of the assembly.   There are some great articulated block designs being developed though.

The design of CMU’s which allow for full topological expression provides the ability to use block to make roofs and complete curved structures (e.g. complete spheres, ovals, elliptical, catenary and other designs).  The design ability which can create a full expression of topology allows the use of high strength, affordable, rapidly produced building components which provide all the benefits of concrete block, including: fire resistance, termite resistance, rot resistance, building longevity, resale value, solidity, appearance, and the ability to withstand extreme weather events (hurricanes, tornadoes, typhoons, storm surges, tsunamis, etc.).    The creation of CMU designs which allow for full topological expression will create an entirely new architectural vocabulary for building with concrete block, and will create entirely new markets for concrete block.

If an interlocking aspect is included in the masonry unit then the topology in masonry is made particularly more effective.  One striking example (which has fueled much of the current research) is the failure of thermal tiles on the space shuttle Columbia.  Because they did not interlock, these topological tiles (designed to wrap around the shuttle: topologically) were free to move and dislodge themselves from their protective positions since they were held in place only by adhesive, leaving the shuttle vulnerable to catastrophic reentry into the earth’s atmosphere.  Researchers were quick to realize that if an interlocking aspect of each masonry unit (or tile) were incorporated, then the geometry of the individual masonry units would have helped keep them in their proper location (anchored by adjacent masonry units) and prevented them from being removed.  Furthermore, researchers have realized that topological interlocking masonry units (or tiles) would not suffer complete, systemic failure if one of these masonry units were damaged: the other adjacent and surrounding tiles would stay in place, even if one tile broke or was removed.  By including the interlocking feature into the masonry unit itself, a separate independent connector is not required.

While this idea of the beneficial nature of interlocking masonry units is illustrated by the Columbia tragedy, it holds great significance for the less exotic application of buildings here on terra firma.  To fully understand this, we will look at the current state-of-the-art for masonry engineering analysis.  Examining a masonry arch, the current engineering model makes 3 assumptions: 1. Masonry units have infinite compressive strength; 2. Masonry units have no tensile strength; 3. Masonry units never slide against each other (they remain in their fixed position).  We will concern ourselves here with the third assumption, the idea that masonry units in an arch (known as voussoirs) never move relative to one another.

In reality and in practice, voussoirs are known to move against each other in a masonry arch.  When this occurs, the arch can be significantly weakened and this movement of voussoirs can result in failure and collapse of the arch.  A catenary thrust line is an imaginary line of force which exists in the wall thickness of the arch.  Catenary (from Latin “catena” or chain) is the shape of a hanging chain or cable under gravity; if this shape of a hanging chain is inverted, then a catenary thrust line is generated.  As long as this imaginary thrust line does not touch or exit the arch wall thickness, the arch will remain standing and stable.  If the imaginary catenary thrust line touches or exits either the inner surface (intrados) or the outer surface (extrados) of the arch, then a hinge will form at that location.  Several hinges allow a mechanism for movement of the arch, resulting in a buckling or folding of the arch about these hinge locations, leading to failure and collapse of the arch.  However, if voussoirs possess an interlocking feature such that they are not free to move relative to any adjacent (interconnected) voussoirs, then the catenary thrust line will not touch or exit either the intrados or extrados of the arch due to movement.  Thus interlocking masonry units in an arch are fundamentally much stronger, more robust and more stable than masonry units which do not interlock.

The creation of an effective interlocking feature on a topological masonry unit produced on a standard conventional block machine is a very real challenge for the masonry designer.  Interlocking features are actually commonplace in standard (non-topological) blocks: the ‘top’ and ‘bottom’ of the concrete masonry unit can readily incorporate interlocking features.  A wide variety of designs is possible if the interlocking feature does not include topological arrangements, but the designer is still limited to building straight vertical walls.  In order to provide an interlocking feature for a topological masonry unit, the sides of the block must be used (not just the ‘top’ and ‘bottom’ of the block) as sites of interlock.  The difficulty here is that a block mold must be readily stripped from the block without any undercut, or draft, or negative angle.  In other words, an interlocking feature on a topological block will create undercuts: an interlocking topological block simply will not release from a mold.  This contradiction can be overcome by symmetry and design.

Another difficulty in creating an interlocking topological block on a block machine is the ability of the mold cavity to be filled completely, evenly and homogeneously.  If a section of the mold near the ‘bottom’ of the block has an overhanging feature (steel mold above it) then it will not fill as readily as an open cavity which allows the concrete mix to flow into it, unimpeded.  A section of mold cavity which has an overhanging feature will impede the flow of concrete into the cavity, resulting in segregation of aggregate.  This segregation of aggregate will typically result in a weakened section of the block where larger aggregate is prevented from filling as easily as in an open mold cavity.  Lack of larger aggregate in a filled mold section creates a weaker section of concrete as a result.

In addition to sections of mold being less than ideally filled due to overhanging mold parts, there is another problem where a section of mold cavity at the ‘top’ of the mold has an open space below it (at the ‘bottom’).  This will create an overhanging projection of block, which is unsupported from underneath (at the ‘bottom’).  These cantilevered features of block are prone to cracking and breaking, especially upon handling as the un-cured block leaves the block-making machine. 

How can a topological interlocking masonry unit be created in a manner that provides adequately filled mold cavities at the ‘bottom’ of the mold, while also not creating weak cantilevered sections at the ‘top’ of the mold?  This is a very interesting design challenge; one which I hope will attract the efforts and solutions of other designers.

Catenary thrust line analysis of masonry domes is another area of current research.  Computer models which digitally process the applied stress and the resulting strain as hinge mechanisms are used to develop visual models.  Catenary thrust line analysis is also used to digitally analyze a computer 3D model as a tool for designing buildings.

Biomimicry/Biological Design as a source of masonry design is ripe with potential.  “Nature’s masons” include single-celled radiolarian and foraminifera, coral, sea anemones, sea horses, turtles and tortoises, Thor’shero shrew, and an endless array of life’s other innovative design solutions.

Anisotropy in manufactured concrete block has not been fully utilized with current block designs.  Vertical block walls are made with the weaker axis of the block facing horizontally, to the outside.  It is possible to orient the block so that the high strength axis faces outside, resulting in a significantly stronger building.

Robotic assembly is still in its early stages regarding masonry, but real progress continues in this field.  Robots may play an important role in the future of masonry.  Robotic assembly may have an early adaptation for situations that might endanger a human mason, such as radiation or other hazardous materials.  Construction Robotics is one company that is currently successfully developing robotic masonry.

3D Printing is also in its early stages, but is expected to develop with time.  3D printing should find early use in masonry applications which require a unique masonry piece, such as at the intersection of two arches, or to allow conduit or openings, etc.   In this role it will be cost effective fairly soon.

Thor's Hero Shrew and masonry design

I have written a few times on this blog about masonry in nature, as evidenced by several species of animals, including seahorses.  A couple years ago a new species of shrew was discovered in the Democratic Republic of Congo, whose spine exhibits incredible strength and toughness.  “Thor’s Hero Shrew” is worth taking a look at from the perspective of interlocking masonry design.

As discussed in this article, “Scientists at Chicago's Field Museum and international collaborators have described a new species of Hero Shrew – the mammal with the most bizarre lower spine on Earth. The interlocking vertebrae of the Hero Shrew render the spine four to five times more robust relative to body mass, a condition not found in any other mammal. The spine has been an enigma to evolutionary biologists, with no known adaptive significance.

This new species of Hero Shrew, named Scutisorex thori, possesses features that may represent intermediate character states between the only other known Hero Shrew species (Scutisorex somereni), and other shrews. In addition, a novel hypothesis for the function of the animal's expanded lower spine has been proposed. The study will be published July 24, 2013 edition of Biology Letters.

First discovered in 1910, the Hero Shrew's most notable feature was not revealed for another seven years, when a specimen was dissected to reveal the most peculiar backbone of any mammal. The remarkable spine of the Hero Shrew is unique among mammals, in that the lower vertebrae have multiple lateral processes that interlock with the processes of neighboring vertebra. The arrangement, along with surrounding musculature, affords the animal extraordinary strength, so much so that the Hero Shrew has traditionally been worn as a talisman.

"This shrew first came to light when explorers came to the eastern part of the Democratic Republic of Congo," said Bill Stanley, Director of Collections and zoologist at the Field Museum. "The explorers watched in amazement as a full-grown man stood on the back of the Hero Shrew, and the animal walked away, unharmed."

Until now, there have been no other species of this bizarre shrew. The new species described in this study represents a possible intermediate between the original Hero Shrew and other shrews, since is possesses an interlocking spine, but with fewer lower vertebrae and lateral processes than the first Hero Shrew species.

"You and I have five lumbar vertebrae," said Stanley. "And so do most other mammals, but the Hero Shrew at least 10. Scutisorex thori has eight vertebrae, and fewer lateral processes than the original species."

The specimen of the new Hero Shrew species was collected in the lowland forest near the Tshuapa River in the Democratic Republic of Congo. Based on the observations of one of the co-authors on the study, the authors present a novel hypothesis for the functional significance of the spine of Scutisorex thori; they suggest that these shrews position themselves between the trunk and leaf bases of Palms, and use their unique spine to exert force and gain access to concentrated sources of beetle larvae that are otherwise protected from predation. The same adaptation may allow these animals to lift logs or rocks to access invertebrates – a food resource that remains unavailable to many other mammals.

The specimen of Scutisorex thori now residing at The Field Museum is a holotype, meaning that it will be the standard for identifying other members of the species. The new species is named in honor of Thorvald "Thor" Holmes, Jr. of the Humboldt State University Vertebrate Museum, at the suggestion of Bill Stanley, who did his graduate work there. The suggested common name is "Thor's Hero Shrew", appropriately invoking Thor, the god of strength in Norse mythology.

"The Age of Discovery is not over," said Stanley. "In fact, discoveries such as these happen in natural history collections, like the ones that we have at The Field Museum. In addition, hypotheses such as the one that we've generated concerning the functional significance of the Hero Shrew's spine fuel the scientific machine. We can't wait to see the results of further scientific studies that test the ideas presented in this article."

As Wikipedia states, “The structure of Thor's hero shrew's cranium and vertebrae suggest that it may be descended from an evolutionary intermediate between the hero shrew and other shrews. Its existence may help explain the evolution of the hero shrew which, Stanley explains, has historically been cited as an excellent example of punctuated equilibrium, a theory that holds that species sometimes evolve very rapidly in short periods of time after long periods of stability. The existence of an intermediate species hints at a more gradual or incremental evolution for the hero shrew's extreme specialization.”

It appears to me that Thor’s hero shrew utilizes an interlocking masonry-like arrangement to achieve the incredibly high spinal strength it possesses.  The ability to sagitally flex its spine would seem to indicate conjugate shearing between lumbar vertebrae, similar to the seahorse tail strength mechanism.

Nature is the Grand Master of design.  Thor’s hero shrew is an exemplar of masonry technique used to achieve high strength and toughness.  Its discovery is perhaps an omen of punctuated equilibrium in the evolution of masonry as used by man.

It's lonely up here, but that's OK

While this blog is my personal record of some of my musings, thoughts, designs and ideas, I am generally not keen to make it about “me.”  Who cares about me?  Why should they?  It is not my intent to speak about myself, but sometimes it is unavoidable.  I have slowly realized that nobody else is doing what I am doing, and so today I write briefly about this as a personal experience and how it affects my work.

For over 25 years now I have been focusing my entire work on designing manufactured concrete block which are used to build roofs, including domes and spheres.  When I began this, I had no idea that nobody was doing this, it seemed so obvious: surely others must be engaged in this sort of work?  But no, I am alone in this odd pursuit.  Over the decades, in my extensive dealings with industry, manufacturers, contractors, block producers, working masons and others that inhabit this masonry realm, nobody else is working on this particular problem.   I have asked virtually everyone I’ve met in my journey through this technological development if they are aware of others working on this problem?  The answer has always been “no” (if anyone is aware of others working on manufactured block as I am, please let me know!).   

My unique vocation is made more curious because –since its early inception- I have chosen to focus on triangular concrete masonry units.  Again, nobody is remotely close to pursuing this sort of thing, yet it seems so obvious to me.  To make it even more weird, I have decided to pursue interlocking triangular manufactured concrete block.  The reasons for this are plainly evident (even self-evident) as I’ve attempted to describe repeatedly over the years that I’ve written this blog.  Yet nobody else is doing anything like this.

My ‘home base’ in upstate western NY is property populated with numerous models, prototypes, structures, finished buildings and so forth.  I have been visited by numerous friends and acquaintances over the years who have observed this work, entered these buildings, and inspected these structures with varying amounts of interest and curiosity.  The common response is “but it’s all so obvious!” which it is.  Yet nobody else has pursued this type of masonry.

The apparently obvious, simple, and clear reasons for these masonry designs and configurations become somewhat obscured as my designs have developed into articulated, detailed and specialized forms which have evolved to meet the very specific constraints and limits imposed by the method of manufacture (concrete block machines) and the demanding specifications of assembly and –finally- the performance requirements of the finished building itself (strength, toughness, low cost, design flexibility, etc ).  Upon close inspection this ‘obvious’ masonry unit design has features and properties which pique the curiosity of an interested observer.

Although this work has appeared as an obvious and simple solution, it is very different from the standardized practices and existing methods used by the masonry industry.  Standardized practices generally involve only straight walls, square corners and rectangular block or brick.  These parameters have defined the scope of research and investigation within the masonry industry and academic community.  Because my designs are not rectangular (they’re triangular), they make much more than straight walls, and they behave differently than regular manufactured concrete block and the structures assembled from rectangular block.

My experience with academia has been quite humbling.  My work is typically referred to (or rather dismissed) as “concrete igloos” by those academicians who encounter it.  These individuals usually fail to grasp the inherent benefits of these designs; I am usually embarrassed for them, and smile meekly or write stupid poems in which I join them and mock myself along with my critics.

I have scoured academia for anyone doing work within the field of masonry science which might pertain to my own work.  I have encountered some great minds doing wonderful work, but nobody really does any work which is akin to my own particular designs.  It has been a source of frustration for me.  All assumptions, equations, engineering models, failure mechanisms, and in general all ways of viewing masonry structures are not adequate or appropriate to describe my own work.  This frustration at the unique nature of my particular focus has also served as source of inspiration and motivation for me to continue in my development of ideas and practices.

When I am able to demonstrate my ideas by making them, some people look twice.  Slowly, deliberately and knowingly I have built a small yet growing and important number of believers in my pursuit.  In our current age of instant gratification seemingly personified by the internet, I realize that I am a weirdo.  I don’t know how many other people could pursue an idea without compensation or acknowledgement or other justification for over 25 years, alone and with the tenacity and perseverance I have come to know so intimately.  It’s a lonely place I occupy, yet I find solace in this solitude.  Yes, I am a weirdo.

Change is afoot in masonry design.  I shall continue this pursuit with the same passion that was sparked in me as a seven year-old boy entering the great cathedrals of Europe for the first time.   There is much more to come, just watch what’s next.  I am as eager as ever.

"Don't wait for the trends to develop. Instead, watch for people messing with the rules, that is the earliest sign of significant change." - Joel Arthur Barker,  'Paradigms, the Business of Discovering the Future'