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.

Thickness of dome walls

Thrust force lines must be kept within wall thickness for a structure to remain standing; this makes wall thickness critically important.  The triangular interlocking masonry system described on this blog can provide different wall thicknesses through different techniques.
 

A spherical dome under gravity is subject to "hoop" stress (like lines of latitude, horizontal) which varies from the crown down to the bottom edge. This stress is completely under compression from the top center down to the haunch (51.82⁰ from vertical).  Below the haunch there are tensile forces pushing out, which grow stronger and tend to introduce cracks at the bottom of the masonry dome.  These tensile hoop forces at the bottom of a masonry dome are typically resolved by either a tension ring, or a massive abutment, or both.

Historically masonry analysis refers to “lunes” which are like the sliced sections of an orange peel.  Each lune is viewed as a discreet arch section for the purpose of stress analysis.  From the top of the lune down to the base of the dome, the stress increases as the weight increases.  The wall thickness increases accordingly to accommodate this increased stress. 

Although vertical cracks are known to develop at the bottom of large domes, this does not necessarily make these domes unsafe.  Many large domes with cracks at their bases are known to have stood for centuries, and are standing still; such as the Hagia Sophia, the Pantheon, and many others. 

A wall in a hemispherical dome is considered "thin shelled" if the wall thickness is 10% (or less) of the radius.  This 10% proportion is considered safe for a full hemisphere which goes 90 degrees from crest to base.  If a spherical dome is a segmental section which only goes 70 degrees from crest to base, then a wall thickness of 4% proportion (thickness to radius) is considered safe.  This shows how dramatically stress increases at the bottom of a spherical dome.

Wall thickness may be increased by simply making the bricks thicker.  That is, the dimension of the block from outside surface of the dome to the inside of the dome can be made larger for a thicker wall.  The center of the wall, at midway between outside and inside, is always an axis of symmetry for the interlocking features of the block.  This means that different thicknesses of block can be used together; they will still interlock and connect to each other.  Thinner blocks can be placed on top of thicker blocks.

Wall thickness can also be adjusted by using a core or depression or cavity within the block.  This technique does not change wall thickness from inside to outside the dome, but within the block itself.   A larger core (or hole) will produce thinner, lighter block.  (It is useful to note that standard rectangular concrete block is also typically hollow, and have cores).  Different core sizes can be used on a given mold.  This technique has been used historically by ancient master masons, including the Pantheon with its “coffers” on the dome interior.   (The first block which I had mass-produced on a block machine all had a hollow triangular core, they work well).

Thickness can also be adjusted by having multiple wythes, or layers of block, like layers of onion skin.  This arrangement is recommended for applications which require a high safety factor, including tornado shelters, hardened structures, blast resistant structures, etc.  This technique of multiple wythes can also be used at the base of very large domes to resolve thrusting forces.  The strength of a structure built with concentric wythes or layers of triangular block can be further increased by weaving the blocks together with a tensile element, like steel cable.

Sestina

As a child I became enthralled with masonry

and entered reverently great halls of stone

and marveled at structures made of block.

How was it made, this wonderful building?

Who were these people so skilled with mortar?

What had become of this lost art?



The cathedrals of Europe showed me this art.

I was lucky to see this bold masonry

and contemplate the skilled slingers of mortar.

How did they figure and know that a stone

could be cut such a way to construct this building?

All this amazement at stacks of block.



As I grew older the wonder of block

seemed to vanish with the lost art.

Daily surrounded by boring new building,

concrete blocks stacked in straight-walled masonry.

Gone from my sight were wonders of stone,

just boring-ass buildings, institutional mortar.



Gone from my mind were wonders of mortar,

gone too was thought of carved block;

when I looked on the ground an occasional stone.

Painting and drawing replaced my lost art.

Carpentry, plumbing, drywall and masonry

all seemed the same dreary task used in building.



As an adult I threw pots, and was soon building

giant architectural vases: assembly without mortar.

A house out of clay was my goal, without masonry,

still far removed from thought of block.

Twisted, turning and long was this art

for I would return to the skill of built stone.



How could it be done, to build wonders with stone?

Using modern methods and materials for building

to reclaim this lost and once lofty art?

To assemble a vaulted roof with mortar?

When all that was left was rectangular block:

a mass-produced world didn’t want good masonry.



I thought of art, casting concrete as stone,

realized masonry was still a key to good building.

Alas I found mortar, and secrets of triangular block.

Non-Fired brick and Block: for a Green Future

Bricks and blocks made from material which is not fired, or heat treated, have long been a goal of the masonry industry. Firing bricks creates pollution and contributes to greenhouse gasses.


China has long been the world’s major producer of fired clay bricks. They have recently begun to phase out the creation of fired clay bricks, and are now using cement-based bricks, which create less pollution and CO2 than fired bricks.

In this article, shared with me by my business partner Mike Wong, a recent effort to create non-fired brick in Viet Nam is discussed. This effort appears very promising, and may help the world find an adequate solution toward the creation of non-fired brick and block.

Here is another description of making non-fired brick. This technology uses bacteria and room temperature sand, and also appears very promising.

Interestingly, the Vietnamese approach relies on industrial waste, like slag from combustion and metal processing. This approach hearkens back to the cinder block, as developed and invented by Francis Straub, as discussed earlier in this blog. Sometimes it seems there is nothing new, only that which has been forgotten.

A few images

Here are some Images using the "dimp" blocks.  Just click on these images to see them better.

Here's a cylinder section:

Here's an outside dome section:

Here's a view of the interior of a dome:

Introduction

I'm a masonry designer developing novel masonry systems for new applications. This blog will describe what my ideas are, how I'm making them, various uses, and so on. I will share ideas and hope to get feedback from as many interested people as I can.

I'm especially interested in doing more with concrete block than is currently possible. I want to expand the architectural vocabulary of concrete block construction to include much more than straight vertical walls and square corners. This is pretty much the status quo with current block design and construction.

As a child I had the good fortune of seeing some of the great cathedrals of Europe. This experience left an indelible impression on me. It's probably why I do what I do; masonry architecture can be so much more than rectangular block and vertical walls. Arch, cylinder, dome and sphere should all be part of the masonry repertoire. This is possible with block manufacturing methods and materials, through innovative design.

This is an exciting realm that combines ages-old building techniques with current scientific  engineering knowledge and high-efficiency production methods.