The blocks are better than they were

The blocks are better than they were the snow is getting brown 

The mason's waist is plumper the ice is out of town.

The tender wears one less sweater the scaffold less forlorn 

Lest I sh'd be more chastened I’ll put a tool belt on. 

i carry your trowel with me

i carry your trowel with me(i carry it in
my hand)i am never without it(anywhere
i go you go,my block; and whatever is laid
by only me is your doing,my block)
i fear
no wall(for you are my wall,my block)i want
no wood(for rickety you are my wood,my rot)
and it's you are whatever a lunar base always cement
and whatever a solar wind will always fire this block

here is the deepest mortar nobody sees
(deep in the wall of the mall and the wall of Wal-mart
and the rows of the Lowe's of an aisle called block;which builds
higher than the code can hope or mine can hod)
and this is the mortar that's keeping the blocks apart

i carry your trowel(i carry it in my hand)

 

Alone in my pursuit

It is hard for me to believe, I still don't quite get it
I work in a field thousands years old, you can bet it.
Masonry arches have been made by man forever
and the ubiquitous concrete block is found wherever.

But somehow, some way, nobody has ever attempted:
to make an arch with concrete block, mortar all cemented.
It is so obvious! I'm not just a parroting fool!
An arch made of concrete block is so strong, and cheap and cool.

I have scoured the country and searched this whole planet,
looked into concrete from cinders, limestone and granite.
But nobody, no one, no single person anywhere,
has dared use concrete block to build arches in the air.

It's a conservative industry, and works well enough
there is no need to contemplate your newfangled stuff
We've done well without any arches, without any art
without any soul, without beauty too, without your part.

And still I pursue it, I can't help but do it, arch block
an unfulfilled, undiscovered unknown way with rock
Yet known too well, for millenia, masonry arch roof:
that I should be the first (and only!) is a humbling truth.

Anisotropy

Concrete is made of rocks and sand
glued together with cement
the aggregate you understand
is irregular, with intent.

The intention of irregular shape
is tip-to-face contact all throughout
aggregate packed to reduce the gape
of free space between the grout.

Concrete made into block
has aggregate pressed and jostled
irregular aggregate interlock
frozen into position, fossiled.

The axis of this huge compaction
is the one of greatest strength
energy of vibrating action
aligns the rocks along their length.

When measured strength is the same
in all the measured block directions
"Isotropic" is the name
for equally strong strength detections.

When manufactured block's the topic
It's not so strong in sideways view.
It's known to be anisotropic
and highest strength is vertical too.

New Blocks on the Kid

Five years ago today, my friend Jennifer L. Knox double-dog-dared me to write a poem every day for the month of April about masonry, for National Poetry Writing Month, or NaPoWriMo.  This will be my fifth year of participating in NaPoWriMo.  It's tricky to come up with poems every day for a month, and especially so when they are all about a specific topic: masonry.  I beg the reader's indulgence while I try this again.

New Blocks on the Kid
March has left like a lion
April is on the lam
But soon I will be tryin'
To make the best blocks I can

I will because I must
I must because it's there
It's there because I trust
in warming of the air.

With warmth I'll mount the mold
upon the block machine
In with new, out with old
new block never seen.

With contempt we leave you, March
and hope for a new beginning
A new block to make an arch
and April will be winning

All the cold dark winter long
patents filed, mold was made
nothing should really go wrong
as winter too soon shall fade.

As the earth will soon awaken
and I make this new design
the doubts of winter are forsaken
This new block will align

And stack upon itself with ease
into an arch with lovely lines
with facility sure to please
questions in the mason's minds.

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.

3D Printing and Masonry: a Brave New World of Construction

Three dimensional printing, or 3D printing, has come a long way over the past decade or so.  This technology is growing rapidly, and holds the possibility of disrupting many conventional technologies and entire industries.  One of the conventional construction technologies facing competition from 3D printing is masonry.  Will 3D printing eventually phase out traditional masonry construction?  What are the relative benefits of each technology: masonry versus 3D printing?  How soon will the masonry industry be impacted by 3D printing?

Recent developments in the field of 3D printing include the use of concrete and concrete-like material to create objects.  These objects include both masonry-like units which are subsequently assembled into an integrated structure and also the monolithic entire structure itself, “assembled” as a whole 3D printed object.  At the forefront of this technological breakthrough are 3D printing methods such as those under development by BehrokhKhoshnevis, professor of Industrial & Systems Engineering and Civil & Environmental Engineering and Director of the Center for Rapid Automated Fabrication Technologies (CRAFT) at the University of Southern California.  Khoshnevis refers to this technology being applied to print entire buildings as “Contour Crafting.”  He and others in the field speak of very high-strength 3D printed concrete materials as being just on the horizon; material with a compressive strength of around 10,000 psi.  Currently manufactured concrete block has a minimal compressive strength of around 3,000 psi, although high-performance concretes (HPC’s) are currently available with strengths up to around 20,000 psi and higher.

The advantages of 3D printed concrete –as compared to conventional concrete- include: fairly rapid construction, the ability to make complex shapes and forms, freedom from the constraints of molding, and potentially very high strength.  These benefits may also eventually include the ability to 3D print very detailed and intricate structural features integrated into the building; including ventilation, plumbing, wiring, etc.  Other developers in the 3D printed structures include the principals of “Emerging Objects”, Ronald Rael (at University of California Berkeley) and Virginia SanFratello (at San Jose State).  Their work includes hollow, interlocking masonry like units which assemble in a manner similar to topological interlocking structures (as discussed earlier on this blog).  It holds the promise of potentially creating structural configurations suitable for seismic areas and the ability to withstand major earthquakes.

Still others are 3D printing entire homes, and appear to be close to commercialization.  Among these is a Chinese company, whose equipment is said to be capable of producing ten houses in one day.  It should be noted that these houses are not printed as a whole; they are printed in panels and these panels are then assembled.  There is also a Dutch company, Dus Architects, whose equipment is also capable of printing ‘chunks’ of house, which then must be assembled into a home.

The advantages of 3D printing should appear as obvious, namely: the ability to create virtually any shape, without the limitations imposed by a block machine, or undercuts, or draft angles; the relatively rapid pace of fabrication; a choice of materials (including plastics, concrete, and composites); and the ease of producing an object from a 3D computer file.  It would seem that the 3D printing of homes is inevitable, and that masonry will soon become a lost art - and go the way of film photography, which has been replaced by digital photography.

A few critical factors appear as though masonry will remain in the construction industry for the foreseeable future.   First of all, buildings must begin with a foundation.  In climates with freezing winters the foundation must be placed 3 or four feet below grade, or below the extent of the frost line on the coldest days.  This is simply not possible with the state-of-the-art in 3D printing technology available now.  3D printing technology cannot create a foundation below grade, although it is likely to overcome this obstacle in the future.  Secondly, most 3D printing technologies simply produce panels, or pieces or chunks of a structure which must then be assembled; this basically describes masonry, and is not an improvement over masonry per se.   Those 3D printers which are capable of producing an entire integrated, complete finished structure require an extensive working platform on which to operate.  This platform requires extensive, expensive, detailed site preparation for the 3D printer; this negates many of the so-called benefits of 3D printing an entire structure (more expensive, difficult, and time consuming).  Another major impediment to 3D printing is the fact that the construction industry is an extremely conservative industry and is very slow to accept new technologies.  This fact is made more relevant by the fickle nature of the construction consumer: people want houses, homes and buildings to look like they’ve always looked.  The 3D printing approach to providing homes still has a very long way to go before it produces houses that look very much like every house produced everywhere.  This is not an arena for brave new ideas: homeowners want their homes to look like their neighbors’.  “Fitting in” in the aesthetic sense is probably much more important than efficiency, strength, environmental concerns, longevity, or any other factor about construction.  The appearance of the finished product cannot be overemphasized, and 3D printing has a long way to go here.  Finally, and perhaps most importantly, is the factor of cost.  While 3D printer advocates say that they are faster and less expensive than masonry, it is instructive to note that the concrete block manufacturing industry has developed to a state of high efficiency and economy.  An 8 inch x 8 inch x 16 inch rectangular concrete block is produced in around 2 seconds, and typically costs around $1.00 or so.  This is the benchmark to beat, and 3D printing is not anywhere close to this, despite the claims being made.  It appears as though concrete block will probably be around for a while yet.

3D printing holds great promise for the future of construction.  Those who assume that it will never affect their industry (designers, builders, blockmakers, masons, etc.) do so at their own extreme risk; they are likely to go the way of film photography, i.e., extinction.  Instead, it appears inevitable that 3D printing will have a huge transformative effect on construction in general and on masonry in particular.  It seems that masonry will –in all likelihood- always exist, but that it will be fundamentally transformed by 3D printing.  Masons can design their work and have custom blocks produced on-site, instantly and inexpensively.  Brunelleschi would have put 3D printing of masonry to spectacular use; he wouldn’t have had to carve shapes from turnips to show his masons how he wanted block made.  They would be made instantly, exactly as he envisioned them.  It seems that 3D printing could well add to the art, science and craft of masonry in the relatively near future.