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Artificial stone. Cement conglomerates (terrazzo)Characteristics and requeriments of terrazzo tiles for internal and external floors

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CHARACTERISTICS AND REQUIREMENTS OF TERRAZZO TILES FOR INTERNAL AND

EXTERNAL FLOORS

The following table details the characteristics envisaged in the respective

standards:

Terrazzo tile characteristicsFor internal use

[EN 13748-1]

For external use

[EN 13748-2]

► Dimensional quality

●

Length and width

● Thickness

●

Straightness of fair face edge

● Flatness of the fair face

►

Surface characteristics and visual

appearance

► Bending strength/breaking load

►

Abrasion resistance

► Slip resistance

►

Water absorption

► Reaction to fire[1]

►

Thermal conductivity

► Climate resistance

● Water absorption

● Resistance to frost/thaw cycles

► External fire performance

-

-

NOTE: Standards EN 13748-1 and EN 13748-2 include test methods for evaluating these characteristics or explicitly refer to otherstandards. Tests are carried out on terrazzo tiles at least 28 days ol . d

[1] Terrazzo tiles need not be tested and are automatically classified as Alfl

Dimensional quality

Minimum thickness is only considered for double-layer terrazzo tile, two

classes being envisaged, depending on whether mechanical polishing processes are

applied after the tiles have been installed. The classes and their related codes are the

same, independently of the intended location:

Class I (Th I): Terrazzo facing layer thickness of 4 mm or more Class II (Th II): Terrazzo facing layer thickness of 8 mm or more, if the

product is going to be polished after it has been installed [*]

[*]In terrazzo tiles with relief, a minimum thickness of 2 mm is required of the facing layer at the bottomof the groove or bas-relief

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DIMENSIONAL TOLERANCES

Characteristic Internal or external use

Side length or widthThickness (thickness < 40 mm)

Thickness (thickness ≥ 40 mm)

Straightness of edges [1]

Flatness [2]

± 0.3%± 2 mm

± 3 mm

± 0.3 %

± 0.3 %

[1] Measured as maximum difference between the edge and a standard straightedge and expressed as a % in regard to the length

of that edge.

[2] Measurement of the maximum deviation at any point in regard to the diagonal of the tile. This is not considered in textured

tiles.

Surface quality

Defined as the absence of projections, depressions, exfoliations, and cracks in

the fair face, based on visual inspection at a distance of 2 m, with natural light and dry

environment. Smaller holes may be permanently filled, without it being necessary to

define these. In addition, it is stated that when colorations are applied, they shall be

contained in the terrazzo facing layer or throughout the tile.

Slight variations in colour consistency between different lots of tiles, assignable

to shade variations in cements and aggregates, changes in the manufacturing process,

and/or environmental conditions, are allowed. The manufacturer shall define what is

considered a lot.

Moisture variations can lead to small differences in colour, which is why

maximum protection is always recommended during storage before installation.

Bending strength/breaking load

There are different classes for these parameters, with their corresponding

marking, depending on whether the terrazzo tiles are intended for interiors or exteriors.

TERRAZZO TILES FOR INTERNAL USE

Bending strength (MPa)► The average strength of the four test pieces shall be 5 MPa or greater

► No individual test value shall be below 4 MPa

Breaking load (kN)

Class Marking Requirement

1(*) BL I No requirements

2 BL II Tile surface area ≤ 1100 cm2 No individual value < 2.5 kN

3 BL III Tile surface area > 1100 cm2 No individual value < 3 kN

(*)

For the use of this class it is required that the installation substrate or base shall be rigid, and that the tiles shall be installed on amortar bed.

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TERRAZZO TILES FOR EXTERNAL USE

Bending strength (MPa)

Class Marking Average strength Individual strength

1 ST 3.5 2.8

2 TT 4.0 3.2

3 UT 5.0 4.0

Breaking load (kN)

30(*) 3T 3.0 2.4

45 4T 4.5 3.6

70 7T 7.0 5.6

110 11T 11.0 8.8

140 14T 14.0 11.2

250 25T 25.0 20.0

300 30T 30.0 24.0

(*) For class 30, it is recommended to install the terrazzo tile on a rigid continuous deck.

Abrasion resistance

Just as with natural stone, resistance to impairment of appearance by abrasion,

here called abrasive wear , is evaluated by measuring the groove made by a disc on the

fair face (deep abrasion). In this case, the test method is included in European standard

EN 13748-1. An alternative method [Böhm test method] is also put forward, which

measures volume loss of the test piece caused by the action of a rotating disc that exerts

a constant force of 294 N on the tile surface while it rotates, with artificial corundum

being fed between the test piece and the disc. The volume loss is measured after 16

cycles of 22 revolutions per cycle.

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In terrazzo tiles for use in interiors, it is assumed that the abrasive wear

requirement is met if:

1-Test piece holder 2-Counterweight 3-Test piece 4-Test track 5-Load 6-Rotating disc

Böhm test method for the measurement of abrasion resistance

► No test piece provides a groove exceeding 25 mm, by the deep abrasion

method

► No test piece provides a volume loss per unit surface area exceeding 30

cm3/50 cm2 with the Böhm test

g 30

cm3/50 cm2 with the Böhm test

Terrazzo tiles for use in exteriors feature four classes with their corresponding

marking codes, as shown in the following table.

Terrazzo tiles for use in exteriors feature four classes with their corresponding

marking codes, as shown in the following table.

ABRASION RESISTANCE OF TERRAZZO TILES INTENDED FOR EXTERIORS

Class Marking Deep abrasion test

groove length in mm

Böhm test

volume loss per unit surface area

cm3/cm2

1 F Characteristic not measured

2 G ≤ 26 ≤ 26/50

3 H ≤ 23 ≤ 20/50

4 I ≤ 20 ≤ 18/50

Slip resistance

The standard states that unpolished, dry terrazzo tile exiting the factory has

satisfactory non-slip performance. As a result, this consideration should be taken into

account in customarily dry internal locations.

However, now that the Technical Building Code (CTE) has been approved in

Spain, the slip resistance shall be characterised of all tiles intended for floors for private

communal use and in publicly trafficked architecture, in dry and wet surface conditions,

based on the demands of the document on safety against risk of pedestrian slip-falls [SU

1 of the CTE], as already mentioned for both ceramic tiles and natural stone tiles.


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For the sake of safety, it is advisable to test this characteristic in all unpolished

terrazzo tiles, since they may be intended for interiors with risk (floors that are often

wet, floors that can be accessed from outside, etc.)

If the tiles display reliefs or a rough surface texture, it may be assumed that theyare slip resistant, though this statement cannot be generalised, since terrazzo tiles with

certain polished (or even unpolished) high reliefs exhibit poor wet anti-slip performance

(for example, in pavements and outdoor urban paving).

The test values and demands according to the above SU 1 document of the

Spanish CTE are given below.

1 Sample holder

2 Sample

3 Adjustable mass

4 Water inlet

5 Adjustable abrasive hopper and dispensers

6 Polishing wheel

7 Rubber ring

Flat-bed polishing machine

1 Scale C (126 mm slip length)

2 Scale F (76 mm slip length)3 Pointer

4 Pendulum arm

5 Rubber slider

6 Levelling screw

7 Test piece

8 Bubble level indicator

9 Vertical adjustment screw

Pendulum friction tester

FLOOR CLASSIFICATION ACCORDING TO SU 1

Slip resistance Rd Floor classes

R d ≤ 15 Class 0

15 < R d ≤ 35 Class 1

35 < R d ≤ 45 Class 2

R d > 45 Class 3


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FLOOR CLASS AS A FUNCTION OF SLIP RISK

Area Floor class

Dry internal areas- surfaces with a slope of less than 6% Class 1

- surfaces with a slope of 6% or higher and stairs Class 2

Wet internal areas, such as bathrooms, kitchens, indoor swimming pools, etc.(1)

- surfaces with a slope of less than 6% Class 2

- surfaces with a slope of 6% or higher and stairs Class 3

Internal areas in which, in addition to water, there may be agents that reduce slipresistance (grease, lubricants, etc.), such as industrial kitchens, slaughter houses,garages, areas of industrial use, etc.

Class 3

External areas. Swimming pools

(2)

Class 3(1) These include floor areas around building entrances from outside, except when direct accesses to dwellings or to areas of

restricted use, as well as covered terraces, are involved.(2) In areas intended for barefoot users and swimming pool floors, in areas not deeper than 1.50 m.

In addition to the characterisation of the slip risk of terrazzo tiles that have been

subjected to mechanical polishing and subsequent lapping treatment, terrazzo tiles

should also be characterised that are intended for public flooring under a wide spectrum

of risks, including the presence of grease and other substances that encourage slipping.

In short, it is very important to determine the USRV (unpolished skid resistance

value) of a terrazzo tile, and it is to be appreciated when the manufacturer supplies that

value for a polished surface.

Water absorption

In terrazzo tiles it is sought to combine water absorption of the rear (generally of

the tile mass), which allows installation with mortar according to the different variants

of the traditional technique, with limited fair surface suction that will not encourage dirt

to lodge. As a result, standard EN 13748-1 establishes two test results to measure

absorption:

► Per unit surface area, by capillarity at atmospheric pressure, expressed in

g/cm2, and measured after 24 h immersion

► Total water absorption of the terrazzo tile, expressed as a % in relation to the

dry mass of the test tile

For tiles intended for interiors, maximum values of water absorption through

the fair face are set of 0.4 g/cm2 (for no individual tested piece) and of 8% for total

absorption.

In terrazzo tiles intended for exteriors, standard EN 13748-2 establishes certain

classes, linking total water absorption (in %) to the climate resistance parameter, which

correlates that absorption with the results of the frost/thaw cycle test, using dissolvedde-icer salts and evaluating the results by the mass loss of the test pieces, expressed in

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kg/m2, after 28 cycles from +20 to -20ºC. The climate resistance classes are presented in

the following table.

CLASSES BY CLIMATE RESISTANCE (TERRAZZO TILES FOR EXTERNAL USE)

Class Marking Water absorption

(% by weight)

Mass loss after frost/thaw test

cycles (in kg/m2)

1 A Not evaluated Not evaluated

2 B #6 (as an average) Not evaluated

3 D Not evaluated≤ 1.0 as an average

No individual value > 1.5

Reaction to fire

Just as with ceramic tiles and natural stone tiles, terrazzo tiles need not be testedin order to be automatically classified as Alfl [Commission Decision 96/603/CE], unless

they contain 1% by weight or more of the tile in organic matter. This consideration

extends to in-factory surface treatments that involve the application of organic products

(sealants, primers, etc.).

Fire resistance is a key characteristic that shall be included in the CE marking.

External fire performance

This parameter is included in standard EN 13748 for terrazzo tiles intended for

exteriors, as deck elements, the same consideration being applied as for the reaction to

fire (automatic classification as Alfl).

Thermal conductivity

Parameter to be considered when terrazzo tiles are intended for a construction

element that is required to provide thermal efficiency. In that case, the manufacturer

shall state the thermal properties using the data given in Table L.2 of standard EN

13369.

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