ISO 21690:2021

INTERNATIONAL ISO
STANDARD 21690
Second edition
2021-11
Glass in building — Glass blocks —
Specification and test methods
Verre dans la construction — Briques de verre — Spécification et
méthodes d'essai
Reference number
© ISO 2021
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Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols . 2
5 Types of glass block . .2
5.1 Categories. 2
5.2 Shapes of glass block . 3
5.3 Surface aspect and treatment . 3
6 Dimensional tolerances . 4
6.1 Methods . 4
6.2 Hollow glass block face thickness . 4
6.3 External dimensions . 4
7 Irregularities inherent to the production of hollow glass block .4
7.1 Dimensional irregularities measurement method . 4
7.1.1 Welded seam protrusion . 4
7.1.2 Twisting or misalignment . 5
7.1.3 Face depressions or bulge . 5
7.2 Dimensional irregularities limitation . 5
8 Appearance for hollow glass blocks .6
8.1 Method . 6
8.2 Appearance requirements . 6
9 Mechanical properties .7
9.1 Compressive strength of hollow glass blocks . 7
9.2 Applied load test . 7
10 Thermal shock resistance for hollow glass blocks . 7
Annex A (normative) Mechanical resistance test procedures . 8
Annex B (informative) Mechanical resistance test procedures — Thermal shock test
procedures .11
Bibliography .12
iii
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
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expressions related to conformity assessment, as well as information about ISO's adherence to
the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see
www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 160, Glass in building, Subcommittee SC 1,
Product considerations.
This second edition cancels and replaces the first edition (ISO 21690:2006), which has been technically
revised.
The main changes compared to the previous edition are as follows:
— Clause 5 in the previous edition on materials has been deleted;
— the external dimensions has been changed to one value ±1,5 mm in 6.3;
— the dimensional irregularities twisting Δt or misalignment Δm have been changed to not exceed
1,5 mm in 7.2;
— subclause 6.2.2 in the previous edition on visual irregularities has been changed to Clause 8 on the
appearance for hollow glass blocks, including its test method and requirement;
— the compressive strength minimum value in the previous edition subclause 6.3.1 has been changed
2 2
from 6,0 N/mm to 4,4 N/mm in 9.1;
— Clause 10 on thermal shock resistance for hollow glass blocks, with a 40 °C temperature falling, has
been added;
— subclause 6.3.3 in the previous edition on thermal properties has been deleted;
— subclause 6.3.4 in the previous edition on radiation properties has been deleted.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
Light transmitting glass blocks are used for the construction of building elements both in non-load
bearing walls and load bearing horizontally spanning panels.
Glass blocks for non-load bearing walls carry only their own weight and withstand horizontal forces
such as those generated by the wind. Glass block walls and horizontally spanning panels do not carry
any forces generated by the building.
Glass blocks used for the construction of horizontally spanning panels (e.g. floors, vaults and domes)
carry their own weight and any other imposed loads (e.g. pedestrian or vehicular traffic).
v
INTERNATIONAL STANDARD ISO 21690:2021(E)
Glass in building — Glass blocks — Specification and test
methods
1 Scope
This document specifies requirements for the properties of glass blocks used for the construction of
non-load-bearing walls and horizontally spanning panels. This document also specifies test methods
used to verify these properties for square, rectangular and circular glass blocks.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 48-2, Rubber, vulcanized or thermoplastic — Determination of hardness — Part 2: Hardness between
10 IRHD and 100 IRHD
EN 998-2, Specification for mortar for masonry — Part 2: Masonry mortar
ISO 7500-1, Metallic materials — Calibration and verification of static uniaxial testing machines — Part 1:
Tension/compression testing machines — Calibration and verification of the force-measuring system
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
hollow glass block
two pressed glass bodies fused together to form an airtight seal enclosing a cavity
3.2
dished glass block
pressed glass body having a concave face
3.3
solid glass block
one-piece cast or pressed glass body without a concave face
3.4
gap
visible interspaces between two half glass parts caused by welding during the hollow glass block (3.1)
production
3.5
glass dreg
glass fragments left inside of the hollow glass block (3.1)
3.6
scissors track
marks caused by shearing molten glass
3.7
drip mark
mark on the glass block surface caused by a glass drip in the mould
3.8
press head mark
inner surface appearance blemish during the stamping forming process caused by a press head
3.9
mould mark
outer surface appearance blemish caused by mould during the stamping forming process
4 Symbols
For the purpose of this document, the symbols and designations given in Table 1 apply.
Table 1 — Symbols and designations
Symbols Designation Unit References
T Face thickness of the hollow glass block mm Figure 3
f
L Length mm Figure 3
W Width mm Figure 3
D Diameter mm Figure 3
T Thickness mm Figure 3
Δt Twisting difference value mm Figure 5
Δm Misalignment difference value mm Figure 5
Δb Bulge difference value mm Figure 5
Δd Depression difference value mm Figure 5
Δs Seam protrusion Figure 5
5 Types of glass block
5.1 Categories
The three categories of glass block shown in Figure 1 can be used for construction of non-load bearing
walls and horizontally spanning panels.
Key
1 hollow glass block
2 dished glass block
3 solid glass block
Figure 1 — Categories of glass block
5.2 Shapes of glass block
Glass blocks belonging to any of the categories mentioned in 5.2 can be manufactured in different
shapes (e.g. see Figure 2).
NOTE Other shapes can be manufactured but test procedures for those shapes are not covered by this
document.
Key
1 square
2 rectangular
3 circular
Figure 2 — Shapes of glass block
5.3 Surface aspect and treatment
The inner and or outer surfaces of the glass blocks may be smooth, sandblasted, coloured, coated,
etched or embossed with a pattern.
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