Mortarless Brick – Is it Feasible?

Mortarless Brick

Can This Invention be Put to Use?

Background

160209 Brick-rendered-wall-250mm

In 2004 the author had a patent awarded for a mortarless brick system –                           patent GB2394730  – which was conceived when playing Lego. In building a Lego wall it appeared to be a very strong structure albeit with tight fitting Lego blocks.

Taking the idea further a bolted brick construction was invented, eccentric perhaps, but not unlike numerous other inventions: interlocking blocks, bolted timber assemblies and so on. This invention involves two components – bricks (material not specific – moulded form – plastic, GRP, concrete most likely) and bolts with ‘female’ threaded sockets in their heads.

Bricks fit onto bricks below, kept in place with prismatic hollow protuberances through which bolts may be inserted. The size of brick envisaged for building is similar to stock bricks used today (75mm deep, 125mm wide and 250mm long). Modular bolt lengths based on a mutliple of courses; between 3 and 8 courses as a practical length.

The number of protruding heads on a prototype was eight per bolt but it was later thought to be too many and was cut down in the latest components (see image above).

Attempts were made to market the idea, but short of questionable investors online, keen for money from the inventor to set things up and dubious track records, the idea has to date been taken no further. It does have real potential in the construction industry, particularly as a strong form of construction with tight tolerances and hence standardisation, but would need some investment in material selection research and cost models. It would take limited skill for the application and could be dismantled and rebuilt as a form of wall. Sustainable no less!

Prototype

Prototype

To test the idea a garden workshop prototype was made with timber blocks and adhesively bonded nuts as the bricks and specially machined rods with tap welded nuts to make the bolts. This demonstrated that:

  • Bricks could be stacked and bolted together with ease
  • It held together well with preload from the bolts (as demonstrated by standing on a length of brick resting on books!)
  • It was not too difficult to find the hidden nuts below to screw the studs into and to engage in the threaded hole

Materials (Bricks)

Not a great deal of research was made into suitable (mouldable) material for the bricks. But two appeared to stand out:

Fibremesh reinforced concrete

This has high strength and good impact resistance with low ‘creep’ and may be moulded into small components with a fine aggregate. It may also be coloured to a variable tone/colour. Very fine fibres, smaller than commercial types for slabs are envisaged.

Recycled Polypropylene

A versatile DIY (Do it Yourself) application which may be tailor made to limit materials with internal stiffening. May be made in virtually any colour. Use for stands, internal shelves and so on.

Materials (Bolts)

Stainless or Galvanised Steel

For construction application – strong and cheap to obtain.

Nylon/Polypropylene

For DIY applications where high torque is not needed for tightening.

Stages of Construction

Briefly the stages of construction for the ‘construction application’ are outlined below:

Stage 1 – Lay first two courses. Fit and grout in anchor bolts

160405-brick3-squaretop-built-stage 1

Stage 2 – Lay next courses (3 in diagram). Fit and screw in bolts where anchors are fitted below

160405-brick3-squaretop-built-stage 1

Stage 3 – Repeat with upper courses

160405-brick3-squaretop-built-stage 2

A more thorough explanation may be found in the patent link patent GB2394730 .

Aspects to Consider in Construction

There are a number of pertinent matters to consider if designing a wall:

  • Manufactured curved blocks would be envisaged for cricular shapes
  • Number of bolts may be varied. The interlock of the bricks (if layered in an overlapping may) allows varying numbers of bolts depending on strength needed.
  • Bolt torque – a calculation shows what might be a limiting factor, but use of a torque wrench allows some control of the wall strength/stiffness.
  • Head shape – two are shown in the walls above – a square headed and conical headed variation. The square headed may give better grip and shear resistance
  • Thickness of wall – as with traditional brick wall may be doubled or more in thickness for greater strength

160209 Brick-rendered-wall-250mm

Is it Stronger than Traditional Masonry?

This brings us back to the approximation topic. Three calculations were made assuming unreinforced concrete.

The limiting factor in the calculations appears to be the punching shear in the brick from bolt ‘pull through’ but the shear stress allowed is believed to be on the conservative side; tests would be needed to prove the material.

Calculation Parameters

The brick checks were for Compression, Bending and Shear…

CCI05016_mortarless_brick_strength_parameters

Compression – 500kN/m line load capacity

CCI05016_mortarless_brick_shear_1

Shear – 10kN/m capacity

Part 1 (See above)

Part 2 (See below)

CCI05016_mortarless_brick_shear_2

Bending (parallel to joints critical) –

Capacity 1.10 kNm/m

Presumed Limiting Factor ‘bolt pull through’ – see below

CCI06016_shear_perimeter_failure

Bending Strength – See below…

CCI05016_mortarless_brick_bending

Summary (Fibremesh Concrete Brick)

Shear capacity (3 bolts per metre run) – similar to equivalent brick wall but better than block
Compression and Bending Capacity (3 bolts per metre run)- somewhat higher than traditional brickwork  – about 4 or more times
Racking (in plane shear walls) – not calculated but envisaged to be somewhat better than traditional masonry. Good for earthquake resistance?

Looks good? Will it Ever be a Good Proposition?

Any comments or suggestions welcome. 

Any investors out there interested?

……who knows!

 

Leave a Reply

Your email address will not be published. Required fields are marked *