Lightweight Concrete Made
From Natural (pόmez) and
Professor Emeritus & Honorary Research Professor
University of New Brunswick, Fredericton, NB, Canada
Ecuador January 2012
Natural Vesicular Aggregates
• Vesicular aggregates such as pumice and
scoria have been used since about
273 B.C. to make durable marine
• On the west coast of Italy, at Cosa, the
Romans went 40 km inland to get a
volcanic lightweight rock, even though
normalweight sand and gravel were
readily available on the beach.
Port of Cosa on the West Coast of Italy
Location of Volcanic Aggregates
Manufactured Vesicular Aggregates
• In 1918 Steven Hayde patented a process
of expanding shale, clay or slate in a
• This product was used to make the
U.S. Selma – a lightweight concrete ship
used in World War I.
• The method of manufacture and
microstructure of the aggregate produced
then is essentially unchanged to this day.
So good long-term durability is assured.
Bank of America,
47th Floor – 50 MPa
• In 1967, using expanded clay RHOBACK
Technologies of Germany succeeded in
achieving full control over grain size,
density, compressive strength and
spherical shape with bulk densities
ranging from 325 to 800 kg/m3.
CANMET Specimens at Treat Island
Marine Exposure Site
Non Structural Uses For Vesicular
Aggregates With Particular
Applications For Pumice
1) Low Density Granular Fill
Used to repair slope failures on highways.
Lightweight aggregates have a high angle
of internal friction.
Fill over low load bearing soil – load
2) Filter Beds
For treatment of municipal waste.
Used where bacterial film has to anchor
3) Arrester Beds
At end of airport runways, automobile
raceways, and high-speed highways in
4) Backfilling around Pipes, Tunnels and
High insulating aggregates reduce depth
needed to bury pipes in cold climates.
Reduces lateral and vertical stresses on
embedments by 50%.
5) Horticultural Growing Medium
Ideal material for “green roofs”.
Highly absorbent aggregates provide a
slow release of moisture and fertilizer.
6) Refractor Use
Can be used to reline furnaces when
combined with stainless steel fibres and
plastic fibres. The latter allows steam to
escape without explosive spalling.
• NOTE: All Six Non Structural Uses can
more effectively be accomplished with
the lighter pumic aggregates on the
Pacific Rim of South America.