GB/T 17656-2008 English PDF (GBT17656-2008)

This standard specifies the requirements, test methods, inspection rules, marking, labeling, packaging, transportation, storage of plywood for concrete formwork.

GB/T 17656-2008
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 79.060.10
B 70
Replacing GB/T 17656-1999
Plywood for concrete form
ISSUED ON: SEPTEMBER 02, 2008
IMPLEMENTED ON: MARCH 01, 2009
Issued by: General Administration of Quality Supervision, Inspection and Quarantine of PRC;
Standardization Administration of PRC.
Replaced
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Normative references ... 5
3 Requirements ... 6
4 Test method ... 12
5 Inspection rules ... 13
6 Signs, labels, packaging, transportation, storage ... 15
Appendix A (Normative) Correction factor for flexural performance of plywood for concrete formwork under service conditions ... 16
Plywood for concrete form
1 Scope
This standard specifies the requirements, test methods, inspection rules, marking, labeling, packaging, transportation, storage of plywood for concrete formwork. This standard applies to plywood for concrete formwork, which is made of wood veneer, including:
a) Plywood for concrete formwork, without surface treatment (referred to as plain board);
b) Plywood for concrete formwork, after treated with resin veneer (referred to as resin-coated board);
c) Plywood for concrete formwork, that has been veneered with impregnated film paper (referred to as film-coated board).
2 Normative references
The provisions in following documents become the provisions of this Standard through reference in this Standard. For the dated references, the subsequent amendments (excluding corrections) or revisions do not apply to this Standard; however, parties who reach an agreement based on this Standard are encouraged to study if the latest versions of these documents are applicable. For undated references, the latest edition of the referenced document applies.
GB/T 9846.2-2004 Plywood - Part 2: Tolerances on dimensions
GB/T 9846.5-2004 Plywood - Part 5: Inspection codes of plywood for general use GB/T 9846.6-2004 Plywood - Part 6: Marking, tag, packaging of plywood for general use
GB/T 9846.7-2004 Plywood - Part 7: Cutting of test specimens
GB/T 17657-1999 Test methods of evaluating the properties of wood-based panels and surface decorated wood-based panels
GB/T 19367.1-2003 Wood-based panels-Determination of thickness, width and length of boards
GB/T 19367.2-2003 Wood-based panels - Determination of squareness and
3.2 Structure of plywood
3.2.1 The wood grains of two adjacent layers of veneer shall be perpendicular to each other. The veneers of the symmetrical layers, on both sides of the central layer, shall be of the same tree species or tree species with similar physical and mechanical properties AND the same thickness.
3.2.2 The uniformity of the finished product structure shall be considered. The total thickness of the surface panel AND the veneer with the same fiber direction as the surface panel, shall not be less than 40% and not more than 60% of the plywood blank thickness. The number of layers of the plywood shall not be less than 7. The thickness of the surface panel shall not be less than 1.2 mm. The thickness of the surface panel of the film-coated board shall not be less than 0.8 mm.
3.2.3 The same layer of surface panel shall be of the same tree species. The tight surface of the surface panel shall be facing outward. The surface panel and core board shall not be terminated without bevel glue or finger splicing.
3.2.4 Inclusions, that affect use, shall not be left in the plywood. Non-porous adhesive tape for seaming must not be used inside plywood. If it is used for splicing or repairing the panel, in addition to not decorating, the tape shall be removed; no obvious tape marks shall be left.
3.3 Tree species
3.3.1 The wood species, which are used for the plywood for concrete formwork, are masson pine, Yunnan pine, larch, radiata pine, poplar, birch, lotus, sweetgum, pseudo- alder, Liuan, Oakland, Clone, Alder Bidong, etc.
3.3.2 The tree species of the surface panel, which is used for plywood for concrete formwork, shall be the tree species of the plywood.
3.4 Adhesive
3.4.1 The adhesive of plywood for concrete formwork shall be phenolic resin or resin of equivalent performance.
3.4.2 Phenolic resin or resin of equivalent performance shall be used, for resin finish treatment.
3.4.3 The resin used for coating shall be phenolic resin or resin of equivalent performance.
3.5 Grades and allowable defects
3.5.1 Generally, the grade is judged by visual inspection of the allowable defects on the finished plywood. The grade depends on the allowable material defects, processing be 0.10 MPa or 0.20 MPa lower than the index value, which is specified in Table 6, respectively.
3.6.3 In the design of formwork engineering, see Appendix A for the correction factor, for the flexural performance of plywood used for concrete formwork.
4 Test method
4.1 Measurement of dimensions
4.1.1 The finished samples, which are used for dimension determination of plywood for concrete formwork, shall be randomly selected, from the batch submitted for inspection. 4.1.2 The thickness, length, width of plywood for concrete formwork shall be carried out, in accordance with the provisions of GB/T 19367.1-2003. The straightness and perpendicularity of the edge shall be carried out, in accordance with the provisions of GB/T 19367.2-2003. The measurement of warpage shall be carried out, in accordance with the provisions of GB/T 9846.2-2004.
4.2 Determination of physical and mechanical properties
4.2.1 For the specimen, for the determination of moisture content and bonding strength of plywood for concrete formwork, it shall be prepared according to the provisions of GB/T 9846.7-2004.
4.2.2 For the determination of moisture content of plywood for concrete formwork, it shall be carried out in accordance with the provisions in 4.3 of GB/T 17657-1999. 4.2.3 For the determination of the bonding strength of plywood for concrete formwork, it shall be carried out in accordance with the provisions in 4.15 of GB/T 17657-1999. The conditioning of the test piece shall be carried out, in accordance with the conditioning method a) Type-I plywood in 4.15.4.2.
4.2.4 For the determination of static bending strength and elastic modulus of plywood for concrete formwork, it shall be carried out according to the provisions in 4.9 of GB/T 17657-1999. According to the distribution of the bonding strength specimens from each sample, respectively cut 3 specimens, whose length is parallel to the fiber direction of the surface panel (rift grain) or perpendicular (cross grain). The length of the test piece is 20 times the nominal thickness of the board plus 50 mm; the width is 75 mm. 4.2.5 For the determination of dipping peel performance of plywood for coated concrete formwork, it shall be carried out in accordance with the provisions of 4.17 in GB/T 17657-1999. The method shall be carried out according to the conditioning a) in 4.17.4.1. From each sample plate, cut 3 pieces of 75 mm × 75 mm specimens, according to the distribution of the bonding strength specimens.
5.2.3.3.1 The results of testing the bonding strength are determined as follows: When the number of test pieces, that meet the requirements of the bonding strength index value, is equal to or greater than 90% of the total number of valid test pieces, the performance of this batch of plywood is judged to be qualified. When it is less than 70%, it is judged to be unqualified. If the number of test pieces, that meet the requirements of the bonding strength index value, is greater than or equal to 70% of the total number of valid test pieces, BUT less than 90%, re-sampling is allowed for re- inspection; when the number of test pieces, that meet the performance requirements of this index, is greater than or equal to 90% of the total number of valid test pieces, it is judged as qualified; when it is less than 90%, it is judged as unqualified. 5.2.3.3.2 The results of testing moisture content, static bending strength, elastic modulus are determined as follows:
When the arithmetic mean moisture content, arithmetic mean static bending strength, arithmetic mean elastic modulus of all test specimens meet the requirements of the index values, the moisture content, static bending strength, elastic modulus of the batch of plywood are judged to be qualified. If a certain item fails, it is allowed to re-sample it for re-inspection AND then determine whether it is qualified or not. 5.2.3.3.3 The results of the test dipping peel performance are determined as follows: When all the test specimens meet the requirements of the index value, it is judged to be qualified; otherwise, it is judged to be unqualified, AND it is allowed to re-sample them for re-inspection and then judge whether they are qualified or not.
5.3 When the three inspections of size, appearance grade, physical and mechanical properties are all qualified, the batch of products is judged as qualified; otherwise, it is judged as unqualified. For products with unqualified appearance grades, the manufacturer shall re-inspect them all.
5.4 The finished product is calculated in cubic meters; its allowable tolerance shall not be counted. When measuring a single board, it can be accurate to 0.00001 m3; when calculating a batch of boards, it can be accurate to 0.001 m3.
5.5 When the product leaves the factory, the manufacturer shall issue a product quality certificate, indicating the product grade, size, physical and mechanical properties, production batch number, etc.
5.6 Under the storage conditions that are stacked flat, free from high temperature and moisture, the time limit for the manufacturer to accept product quality disputes is within one year, from the date of delivery.