GB/T 17671-2021 English PDF (GB/T17671-2021)

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GB/T 17671-2021: Test method of cement mortar strength (ISO method)
GB/T 17671-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 91.100.10
CCS Q 11
Replacing GB/T 17671-1999
Test method of cement mortar strength (ISO method)
(ISO 679:2009, Cement - Test methods - Determination of strength,
MOD)
ISSUED ON: DECEMBER 31, 2021
IMPLEMENTED ON: JULY 01, 2022
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of China.
Table of Contents
Foreword ... 4
1 Scope ... 8
2 Normative references ... 8
3 Terms and definitions ... 9
4 Method summary ... 9
5 Laboratory and equipment ... 9
5.1 Laboratory ... 9
5.2 Curing box ... 9
5.3 Maintenance pool ... 10
5.4 Test cement, Chinese ISO standard sand and water ... 10
5.5 Wire mesh test sieve ... 10
5.6 Equipment ... 10
6 Composition of mortar ... 18
6.1 Sand ... 18
6.2 Cement ... 19
6.3 Water ... 19
7 Preparation of mortar ... 19
7.1 Mix ratio ... 19
7.2 Stirring ... 19
8 Preparation of specimen ... 20
8.1 Size and shape ... 20
8.2 Molding ... 20
9 Maintenance of specimen ... 21
9.1 Treatment and maintenance before demolding ... 21
9.2 Demolding ... 21
9.3 Curing in water ... 21
9.4 Age of strength test specimen ... 22
10 Test procedure ... 22
10.1 Determination of flexural strength ... 22
10.2 Determination of compressive strength ... 23
11 Test results ... 24
11.1 Flexural strength ... 24
11.2 Compressive strength ... 24
12 Acceptance inspection of Chinese ISO standard sand and substitute equipment .. 25
12.1 General ... 26
12.2 Acceptance test of Chinese ISO standard sand ... 26
12.3 Acceptance test of alternative molding equipment ... 30
Test method of cement mortar strength (ISO method)
1 Scope
This document specifies the summary of the method for testing the strength of cement
mortar (ISO method), laboratory and equipment, mortar composition, mortar
preparation, specimen preparation, specimen maintenance, test procedures, test results,
acceptance inspection of Chinese ISO standard sand and substitute equipment.
This document is applicable to the flexural and compressive strength testing of general
Portland cement and limestone Portland cement mortar. Other cements and materials
may refer to this document. This document may not be applicable to strength testing of
some types of cement mortar, such as cement with a very short initial setting time.
2 Normative references
The following referenced documents are indispensable for the application 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.
GB/T 6003.1, Test sieves - Technical requirements and testing - Part 1: Test sieves
of metal wire cloth (GB/T 6003.1-2012, ISO 3310-1:2000, MOD)
GB/T 6682, Water for analytical laboratory use -- Specification and test methods
(GB/T 6682-2008, ISO 3696:1987, MOD)
JC/T 681, Planetary cement mortar mixer
JC/T 682, Cement mortar specimen forming vibrator
JC/T 683, 40mm x 40mm Jig for cement compressive strength test machine
JC/T 723, Cement mortar vibration compaction equipment
JC/T 724, Electrically driven flexure testing device for strength of cement mortar
JC/T 726, Mould for cement mortars
JC/T 959, Curing box for cement mortar specimens
JC/T 960, Cement mortar strength automatic pressure testing machine
3 Terms and definitions
There are no terms or definitions to be defined in this document.
4 Method summary
This method is for the determination of the compressive strength and flexural strength
of cement mortar of 40mm×40mm×160mm prism.
The specimen is made of a set of plastic mortar mixed with one part of cement, three
parts of Chinese ISO standard sand and half of water (water-cement ratio w/c is 0.50)
by mass. It has been demonstrated that the cement strength results obtained using the
Chinese ISO standard sand are not significantly different from those obtained using the
ISO reference sand (Chapter 12).
In the benchmark test step, the mortar is mixed with a planetary mixer and formed on a
vibrator. Alternative equipment and procedures may be used, provided it is
demonstrated that the cement strength test results obtained using them are not
significantly different from those obtained using the reference vibrator and procedures
(Chapter 12).
When in dispute, only reference equipment and operating procedures may be used.
The specimen together with the test mold are cured in moisture for 24 h. After
demolding, cure in water until strength test.
When the test age is reached, the specimens are taken out of the water. First use an anti-
folding machine to conduct a flexural strength test. After breaking, conduct a
compressive strength test on each section.
5 Laboratory and equipment
5.1 Laboratory
The temperature of the laboratory shall be maintained at 20℃±2℃. Relative humidity
shall not be less than 50%.
Laboratory temperature and relative humidity are recorded at least once a day during
work.
5.2 Curing box
The temperature of the mold curing specimen curing box shall be maintained at
8 Preparation of specimen
8.1 Size and shape
The specimen is a prism of 40mm×40mm×160mm.
8.2 Molding
8.2.1 Molding by vibrator
Molding is carried out immediately after the mortar is prepared. Fix the empty test mold
and mold sleeve on the vibrator. Use a spoon to clean the mortar on the wall of the pot
into the pot and turn it over to stir the mortar to make it more even. During molding,
put the mortar into the test mold in two layers. When installing the first layer,
approximately 300 g of mortar is placed in each slot. First use a spoon to draw the sand
along the length of the trial mold to cover the mold grooves. Then use a large distributor
(see Figure 3) to stand vertically on the top of the mold sleeve and move it back and
forth along each mold slot to spread the material layer evenly. Then tap 60 times. Then
add the second layer of mortar. Use a spoon to draw the rubber sand along the length of
the test mold to cover the mold groove, but do not touch the vibrated rubber sand. Then
use a small cloth maker (see Figure 3) to smooth the cloth. Tap 60 times. During each
vibration, a piece of cotton gauze that has been wetted with water and wrung out and
slightly larger than the size of the mold cover can be covered on the mold cover to
prevent the mortar from splashing during vibration.
Remove the mold sleeve. Remove the test mold from the vibrator. Use a metal straight-
edge ruler (see Figure 3) to rest on one end of the top of the test mold at an angle of
approximately 90° (but slightly inclined toward the scraping direction). Then slowly
move to the other end in a transverse sawing motion along the length of the test mold
(see Figure 2). Scrape off the mortar that exceeds the part of the test mold. The amount
of sawing action and the angle of the ruler depend on the consistency of the mortar.
Thicker mortar requires multiple sawing operations. The sawing action shall be slow to
prevent pulling of the vibrated mortar. Use a wrung wet towel to wipe clean the mortar
on the top of the test mold end plate. Then use the same straight edge to smooth the
surface of the specimen at a nearly horizontal angle. The number of times of smoothing
shall be minimized. The total number of times shall not exceed 3 times. Finally, wipe
off the mortar around t...