GB/T 21236-2007 English PDF (GBT21236-2007)

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GB/T 21236-2007: Silica fume from electric-furnace
GB/T 21236-2007
GB
ICS 73.080
H 31
National Standard
of the People’s Republic of China
Silica fume from electric-furnace
ISSUED ON. OCTOBER 25, 2007
IMPLEMENTED ON. APRIL 1, 2008
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine of the People's Republic of China;
Standardization Administration Committee.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Designations ... 5 
4 Technical requirements ... 5 
5 Test methods ... 6 
6 Inspection rules ... 7 
7 Packaging, Marking, Transport, Storage, and Quality Certificates ... 8 
Foreword
This Standard was proposed by China Iron and Steel Association.
This Standard shall be under the jurisdiction of National Standardization Technical
Committee on Iron and Steel.
Drafting organizations of this Standard. Tianjin University, Tianjin Chaonai Building
Material Co., Ltd., Tianjin Geological Mineral Research Institute, and China
Metallurgical Information and Standardization Institute.
Main drafters of this Standard. Xu Daxiong, Liang Hui, Xu Tiemin, Gao Jianping, and
Feng Chao.
Silica fume from electric-furnace
1 Scope 
This Standard specifies the designations, technical requirements, test methods,
inspection rules, packaging, marking, storage, transport, and quality certificates of
silica fume products.
This Standard applies to the silica fume that is collected by dry dust collectors from
oxidized and agglomerated silica-bearing fume that is gathered by the fume hood of
electric-furnace in ferrosilicon or industrial silicon production. This product, in this
standard, is called “silica fume from electric furnace”, abbreviated as “silica fume”
(commonly known as “silicon ash”).
2 Normative references 
The provisions in following documents become the provisions of this Standard through
reference in this Standard. For 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 3007 Refractories - Determination of moisture content
GB/T 6901.1 Chemical analysis of silica refractories - Part 1. Determination of
loss on ignition - Gravmetric method
GB/T 6901.2 Chemical analysis of silica refractories - Part 2. Determination of
silicon dioxide - Gravimetric-molybdenum blue photometric method
GB/T 6901.3 Chemical analysis of silica refractories - Part 3. Determination of
silicon dioxide - Hydrofluoric acid gravimetric method
GB/T 6901.5 Chemical analysis of silica refractories - Part 5. Determination of
aluminium oxide - Chromazurol S photometric method
GB/T 6901.6 Chemical analysis of silica refractories - Part 6. Determination of
aluminium oxide - EDTA volumetric method
GB/T 6901.8 Chemical analysis of silica refractories - Part 8. Determination of
calciuim oxide and magnesium oxide - Atomic absorption spectrophotometric
5.7 Determination of chloride ion shall be conducted according to the specifications of
JC/T 420.
5.8 Determination of pH value. WEIGH 5.00g of silica fume. PUT it into a
150mL-beaker. ADD 50mL of distilled water which has been boiled and cooled down
to room temperature into the beaker. Continuously STIR the mixture for 5min until it
becomes homogeneous slurry. The following steps are proceeded according to GB/T
9724.
5.9 Determination of loss on ignition shall be conducted according to the
specifications of GB/T 6901.1.
5.10 Determination of moisture shall be conducted according to the specifications of
GB/T 3007.
5.11 Determination of specific surface area shall be conducted according to the
specifications of GB/T 19587.
5.12 Determination of 45μm-sieve residue shall be conducted according to the
specifications of YB/T 5164.
5.13 Determination of water requirement and pozzolanic activity index shall be
conducted according to the methods specified in Annex C of GB/T 18736-2002.
6 Inspection rules 
6.1 Group-batch and sampling
6.1.1 Group-batch
20t of silica fume that is continuously manufactured is deemed as a batch. Less-than
20t when it is insufficient is also deemed as a batch.
6.1.2 Sampling
Randomly take 10 bags from the bagged silica fume. Draw a portion of sample from
every bag; weight of each portion is 200~500; form the bulk sample. Mix evenly;
reduce the amount according to quartering method to be a sample that is twice as
much as the test needs.
6.1.3 The factory-exit inspection items specified in this Standards are. silica, loss on
ignition, moisture, 45μm-sieve residue, and pH value. If the production process or
customers are changed, all the items shall be tested according to Table 1. If there are
special requirements, it can be determined through negotiation between the supplier
and purchaser.
6.2 Decision rules
The technical indexes of the drawn samples shall meet the requirements in Table 1. If
one item is found unsatisfactory, double amount of samples shall be drawn from the
same batch to re-inspect the item. If it is still unsatisfactory, the product is determined
as non-conforming.
7 Packaging, Marking, Transport, Storage, and Quality Certificates 
The packaging, marking, transport, storage, and certificate of quality of the product
shall be conducted according to the specifications of YB/T 5142.