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Lightweight Pumice Aggregate
MATERIAL SPECIFICATION
Grades
Pumice aggregates are processed in Lipari, S. Italy, by Pumex SpA and distributed in UK and Ireland by Pumex (UK) Ltd. The standard grades for the construction industry are: 0-10 (3/8”) , 0-16 (combined aggregate) and 4/16 (coarse aggregate).
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Grade |
% Passing at 4.00mm |
Unit Weight (damp and loose) |
Applications |
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0/4 |
96 |
850 (+/- 7%)kg/m3 |
Fair Faced Lightweight Blocks |
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0/10 |
75 |
800 (+/- 7%)kg/m3 |
Cast Stone, Chimney Flue Liners |
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0/16 |
52 |
750 (+/- 7%)kg/m3 |
Lightweight Concrete Blocks |
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4/16 |
11 |
660 (+/- 7%)kg/m3 |
Lightweight Concrete Blocks |
Legislation
Lipari pumice aggregates comply with EN 13055-1:2003 (Lightweight aggregates for concrete, mortar and grout). For chimney flues: The combination of high alumina cement, pumice and kiln burn aggregates meet European standards prEN 1857 “Chimneys – Components – Concrete Flue Liners”. For geotechnical projects: Italian lightweight pumice aggregate may be used in accordance with DoT Specification for Highway works provided it is described in the contract.
Applications
Lightweight concrete blocks – solid, hollow, fair –faced.
Lightweight concrete – ready mix for bridge, trench, flooring
Chimney flue liners – pumice and alumina cement blend.
Lightweight precast structures – lintels, beams and staircases.
Spray concrete – tunnelling and roofing systems.
Road pavements – lightweight sub-base for special projects.
Green Roof systems - lightweight substrate used for sedum planting.
Pumice VS other Lightweight Materials
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Materials |
Italian Pumice |
Sintered pfa |
Expanded Clay |
Comments |
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Properties |
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Compressive Strength (N/mm2) |
3.5 - 22 |
3.5-20 |
3.5 - 10 |
Pumice reduces dead weight whilst maintaining required structural integrity. |
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Average Density |
650 – 800 |
1060-1180 |
280-290 |
Pumice offers even distribution allowing structures to be produced using only pumice and reduced cement loadings. |
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Shape/colour |
Irregular/ |
Spherical/ |
Spherical/ |
The shape of pumice granules enables a higher friction angle (600) with reduction in cost of delivery and storage. The sphericity of the other materials exhibits tendency to bottom out. The lighter colour assists with finish. |
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Thermal Conductivity |
0.09 |
0.35 |
0.10 |
The absence of crystalline parts in pumice results in lower thermal transmittance coefficient. Improved insulating properties. |
Physical Properties
Granular Morphology
Lipari pumice grains were formed in a polyhedron-like shape that indicates they were formed in the volcano prior to being erupted.
Granular Compressive Strength
Contrary to normal concrete the compressive strength of lightweight concrete is essentially that of the aggregate. Due to the unique chemical composition (approximately 72% silica and 12% alumina) and morphology, pumice has a high granular compressive strength (>22N/mm2 or 220kg/cm2). This allows structures to be formed using reduced quantities of base materials, notably cement.
The compressive strength of the concrete increases with time (usually after the standard 28 days) due to the pozzolanic nature of pumice.
A solid block in lightweight pumice concrete (440mm x 215mm x 100mm) can achieve loadbearing strengths of 3.5N, 7N and 10.5N per mm2. Higher loadbearing strengths are attainable by increasing block thickness (up to 215mm).
Lightweight Properties
The apparent density of pumice granules depends upon the volume of the voids within the particles and voids between the particles. The apparent density of Lipari pumice ranges from 650 and 850kg/m3. The true density of Lipari pumice is approximately 2350kg/m3.
Shrinkage
Lightweight concrete blocks produced with Lipari pumice aggregate exhibit a very low drying shrinkage factor of 0.2mm/m (0.02%). Many other lightweight blocks produced using p.f.a or expanded clay tend to retain increased levels of water.
Thermal Insulation
The U values of standard pumice blocks for cavity walling comfortably meet industry requirements of 0.45W/m2K or better. For Lipari pumice the coefficient of thermal conductivity is λ = 0.09 kcal/mh0C.
Acoustic Insulation
Weighted Sound Reduction Index, Rw (db) of blocks produced with Lipari pumice aggregate have db values ranging from 40 to 50. These values can be improved with the addition of lightweight or dense plaster.
Fire Resistance
The melting point for pumice is 12000 C. The fire resistance of solid pumice blocks is obviously greater than for cellular or hollow. For 100mm thickness, unfinished solid blocks have a resistance between 90 and 120 minutes.
Resistance to Freezing
There is no visible sign of deterioration even after 20 cycles of 48 hours in water, 9 hours in a –10°C freezer and 15 hours in 35°C water.
Dosage of Cement
The pozzolanic/cementitious properties of pumice products permit exceptionally low cement ratios. Also the even distribution of pumice aggregate favours the block mix. Typical loadings are 15 parts pumice to 1 part cement.