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TECHNICAL REQUIREMENTS OF SAND USED IN CONCRETE AND TILE ADHESIVE/MORTAR PRODUCTION

What is sand?

Sand is a mixture of small aggregate particles formed by the weathering process of natural sand and rock. The most common component in sand is silica (silicon dioxide or SIO2). Silica has significant hardness and good weathering resistance.

CLASSIFICATION OF SAND USED IN CONCRETE AND ADHESIVE/MORTAR PRODUCTION 

According to technical requirements in TCVN 7570:2006 on aggregates for concrete and mortar issued by the Ministry of Science and Technology, sand used for concrete and mortar is divided into 2 main groups including:

  • Coarse sand: Has a modulus of magnitude ranging from >2.0 to 3.3
  • Fine sand: Has a modulus of magnitude ranging from 0.7 to 2.0

GRAIN SIZE REGULATIONS

FLOOR HOLE SIZE (mm) CUMULATIVE RESIDUE ON FLOOR (% m) CUMULATIVE RESIDUE ON FLOOR (% m)
COARSE SAND FINE SAND
2,5 0 – 20 0
1,25 15 – 45 0 – 15
630 35 – 70 0 – 35
315 65 – 90 5 – 65
140 90 – 100 65 – 90
Amount passing through 140mm sieve, not more than 10 35

Fine sand used for making concrete and mortar is specified as follows:

  • For concrete:
    • Sand with a modulus of magnitude in the range of 0.7 – 1 (particle composition as in the table above) can be used to produce concrete of lower grade than B15.
    • Sand with a modulus of magnitude in the range of 1 – 2 (particle composition as in the table above) can be used to produce concrete grades from B15 to B25.
  • For mortar:
    • Sand with a modulus of magnitude in the range of 0.7 – 1.5 can be used to produce mortars of smaller grades and = M5.
    • Sand with a modulus of magnitude in the range of 1.5 – 2 can be used to produce mortar of grade M7.5.

SOME STANDARDS ON IMPURITIES CONTENT OF SAND USED IN CONSTRUCTION AND MORTAR PRODUCTION

When producing glue/mortar, sand is not allowed to contain more than 5% of the mass of particles larger than 5mm.

The content of impurities in sand is specified with the following parameters:

IMPURITIES TEMPORARY MATTER CONTENT (% m, not more than) TEMPORARY MATTER CONTENT (% m, not more than) TEMPORARY MATTER CONTENT (% m, not more than)
CONCRETE GRADE BETTER THAN B30 LOWER GRADE CONCRETE AND = B30 MORTAR
Clay/lumpy impurities must not have 0,25 0,50
Mud, dust, clay content 1,50 3,00 10,00

In addition, when determined by the color comparison method, the organic compounds in the sand must not be darker than the standard tone.

However, construction sand that does not satisfy the above criteria can also be used if the results of testing and verification in concrete show that the organic impurity content does not affect the physical properties required for this product.

Some construction sand standards for chloride content (icon Cl–) and alkali-silica

Chloride content (Cl- ion)

According to TCVN 7570:2006, the chloride content in sand (calculated by Cl- ions dissolved in acid) is specifically regulated as follows:

TYPES OF CONCRETE AND MORTAR Cl- ION CONTENT (% m, not more than)
Used in prestressed reinforced concrete structures 0,01
Used in concrete structures, reinforced concrete and conventional mortar 0,05

However, sand with Cl– ion content greater than the values ​​specified in the above table can also be used if it satisfies the following conditions:

  • The total Cl–ion content/1m3 from all manufacturing material sources shall not exceed 0.6kg.

Alkali-silicon content

  • Sand is put into use when its alkali-silica reactivity (tested by chemical method TCVN 7572-14:2006) must be in the harmless aggregate zone.
  • If the alkali-silica reactivity of the tested aggregate is in the potentially harmful range, additional testing by the mortar bar method (TCVN 7572-14:2006) should be conducted for further assurance.
  • Sand is considered to be unlikely to undergo alkali-silica reaction if the strain (e) at 6 months determined by the mortar bar method is less than 0.1%.

With more than 15 years of experience in the industry of providing manufacturing additives, THACH HIEN COMPANY LIMITED is committed to providing customers with products that meet standards with the best quality. Customers who need more detailed advice on parameters as well as black stone prices according to each size, please contact: Hotline 0986 306 052.