ICS 91.100.

30 NTON 12 – 008 - 09 September / 09 1/11

NICARAGUAN MANDATORY TECHNICAL STANDARD.

MANUFACTURE OF CONCRETE BLOCKS
NTON
12 008 - 09

Nicaraguan Mandatory Technical Standard

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The Nicaraguan Technical Standard called NTON 12 008 - 09 Manufacturing of

Concrete Blocks has been prepared by the Technical Transportation Committee.
Construction and Infrastructure and the following participated in its elaboration.
people:

Evangelina López CEMEX

Evelyn Fuentes HOLCIM
Juan Marcos Aráuz Arenas S.A
Diogenes Rios Arenas S.A
Vladimir Tercero Total Concrete
Anaverónica Pérez Nicaraguan Chamber of Construction CNC
Rodrigo Pereira Reyes Nicaraguan Chamber of Construction CNC
Juergens Lacayo Ministry of Transport and Infrastructure MTI
Oscar Dávila Ministry of Transport and Infrastructure MTI
Helman Taleno Ministry of Transport and Infrastructure MTI
Evert Antonio Rivera Ministry of Transport and Infrastructure MTI
Alvaro Corea Nicaraguan Institute of Cement and Concrete
Denis Saavedra Ministry of Development, Industry and Commerce MIFIC
Oscar López Ministry of Development, Industry and Commerce MIFIC

This standard was approved by the Technical Committee at its latest working session on the day
September 1, 2009.

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1. OBJECT

Establish the physical and mechanical requirements of the concrete blocks that are
they are used in civil construction, as well as the procedures for control
of the quality of the same.

2. FIELD OF APPLICATION

It applies to the blocks used in the construction of civil works, both as

structural element for the construction of walls, as non-structural.

3. DEFINITIONS

3.1 Gross Area. The gross area of the blocks will be the total area including
the cells, measured in the plane perpendicular to the direction of the charges
gravitational

3.2 Net Area. The net area of the blocks will be the gross area excluding
the area of the cells, measured in the plane perpendicular to the direction of the
gravitational charges.

3.3 Concrete Block. It is a solid or hollow prismatic body.

used to shape the masonry, made of Portland cement or
Modified, water and mineral aggregates with or without the inclusion of other materials.

3.4 Confined Masonry. It is a construction system that resists

lateral loads in which the masonry is confined by concrete frames
reinforced; the masonry blocks constitute the soul of a diaphragm and the
brackets constitute the skates.

3.5 Reinforced masonry. Construction system in which are used

walls made of solid or hollow concrete blocks, in which is arranged
of reinforcing steel both in the vertical and horizontal direction, in such a way
that steel and masonry work together.

3.6 Hollow Blocks. They are those that present in their section more
unfavorable a net area of at least 50% of the gross area and the thickness of
its walls should at least be equal to 2.5 cm.

3.7 Solid blocks. They are the ones that present in their section more
unfavorable a net area of at least 75% of the gross area and the thickness of
its walls should be at least 2.5 cm.

4. CLASSIFICATION OF CONCRETE BLOCKS

4.1 Structural Block 1 (BE - 1). Hollow or solid block with

characteristics that allow their use for construction systems of

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confined and reinforced masonry, with a minimum compressive strength of

12.19 MPa (1,765 psi) with respect to the net area and to be used in seismic zone C
of the National Construction Regulations of Nicaragua.

Note. For L and T type blocks to be used in the reinforced masonry system,
the procedure for determining the compressive strength will be of the
In the following manner, the specimens must be cut to remove any projection.
from the external walls. The resulting specimen must be a cell or cells that
contain four sides that ensure one hundred percent of the application surface of
load. When the cut with the saw does not result in a closed unit on four sides.
walls, the specimen must be a cut fraction of the outer wall of each unit.

In the case of open blocks, such as U-shaped blocks, blocks for pilasters or others
type in which the block does not have its walls connected in such a way that the test of
compression resistance does not represent its real capacity to withstand loads, the
compression resistance will be carried out using a section obtained from one of the
external walls of the block with a thickness, height, and length ratio of 1:2:4,
the application of the load must be in the direction of the specimen's height, which must
match the same direction of the height dimension of the complete unit.

4.2 Structural Block 2 (BE - 2). Hollow or solid block with

characteristics such that allow their use for the construction systems of
confined and reinforced masonry, with a minimum compressive strength of
7.51 MPa (1 090 psi) with respect to the net area and to be used in the areas
seismic A and B of the National Construction Regulations of Nicaragua

4.3 Non-Structural Block (BNE). Hollow or solid block used in

the construction of non-structural elements with a compressive strength
minimum of 5.04 MPa (732 psi) with respect to the net area.

4.4 Special Block. Solid or hollow structural block that is used for
special conditions and must meet dimensional requirements,
resistance and absorption approved by the MTI.

5. PHYSICAL AND MECHANICAL PROPERTIES OF MATERIALS

CONSTITUENTS

5.1 Cement. Portland Cement or Modified Portland, which must

comply with the ASTM C150 or ASTM C1157 specifications, respectively.

5.2 Aggregates. Coarse Aggregate (Natural stone or crushed gravel): The

Coarse aggregate must comply with ASTM C 33.

Fine Aggregate (Natural or manufactured sand). The fine aggregate must meet the requirements.
ASTM C 33 standard

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5.3 Water. The water used for the manufacture of blocks

concrete must be potable or meet the requirements of ASTM C 1602.

5.4 Other Minerals. Concrete blocks can have other

additives such as hydrated lime, color pigments, repellents, silica
natural, among others, as long as they do not diminish the resistance and durability of the
same.

6. PHYSICAL AND MECHANICAL REQUIREMENTS OF THE BLOCKS OF

CONCRETE

6.1 Physical Requirements.

6.1.1 Dimensions of the Blocks. The nominal and actual dimensions of

the blocks are those established in table 1

Table 1 Nominal and real dimensions of the blocks

Type of block Long Long Wide Width Height High
Nominal Real Nominal Real Nominal Real
cm cm cm cm cm cm
BE-1 of 10 cm 40 39 10 10 20 19
BE-1 of 15 cm 40 39 15 15 20 19
BE-1 of 20 cm 40 39 20 20 20 19
BE-1 of 25 cm 40 39 25 25 20 19
BE-1 of 30 cm 40 39 30 30 20 19
BE-2 of 10 cm 40 39 10 10 20 19
BE-2 of 15 cm 40 39 15 15 20 19
BE-2 of 20 cm 40 39 20 20 20 19
BE-2 of 25 cm 40 39 25 20 20 19
BE-2 of 30 cm 40 39 30 20 20 19
BNE of 10 cm 40 39 10 10 20 19
BNE of 15 cm 40 39 15 15 20 19

None of the actual dimensions (width, height, and length) may differ by more than
less than 3 mm of the specified actual dimensions.

The minimum thicknesses of the external and internal walls of the blocks will be
the following:

Table 2. Minimum thicknesses of the external and internal walls of the blocks
Type of block Minimum thickness of the Minimum thickness of the
external wall ( mm ) inner wall ( mm )
BE-1 of 10 cm 25 25
BE-1 of 15 cm 25 25
BE-1 of 20 cm 30 25
BE-1 of 25 cm 35 30

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BE-1 of 30 cm 40 30
BE-2 of 10 cm 25 25
BE-2 of 15 cm 25 25
BE-2 of 20 cm 30 25
BE-2 of 25 cm 35 30
BE-2 of 30 cm 40 30
BNE of 10 cm 25 25
BNE of 15 cm 25 25

6.1.2 Absorption: Absorption is the property of the block to absorb

water until reaching the saturation point.

To determine the absorption percentage, a test must be conducted according to ASTM.

C-140.

Concrete blocks must meet the maximum absorption requirements.

according to the following table:

Table 3 Maximum absorption values by type of block

Block type Maximum value in a
block (%)

Block BE-1 10
Block BE-2 12
BNE Block 15

6.1.3 Density: It is the relationship between the gross volume and the mass of the block.

To determine the density, a test must be conducted according to ASTM C-140.

The blocks will be classified according to their density according to table 4.

Table 4 Classification of blocks according to their density

Block type Weight block Weight block Weight block
light ( kg/m3) medium (kg/m)3) normal ( kg/m3)
Block BE-1 Until 1682 From 1682 to more than 2000
less than 2000
Block BE-2 Until 1682 From 1682 to more than 2000
less than 2000
BNE Block Until 1680 From 1680 to over 2000
less than 2000

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6.2 Mechanical Requirements.

6.2.1 Compression Resistance. The blocks must comply with the

next requirement for compressive strength at 28 days of manufacture

Table 5 Minimum compressive strength values of the blocks

concrete
Type Minimum average of minimum resistance to the
three units compression for a
individual piece
Block BE-1 13.65 MPa (1980 psi) 12.19 MPa (1765 psi)
Block BE-2 8.41MPa (1220 psi) 7.51 MPa (1090 psi)
BNE Block 5.65 MPa (820 psi) 5.04 MPa (732 psi)
The resistance calculation is based on the net area.

Note: 1 MPa equals 10.19 kg/cm2

7. QUALITY CONTROL

7.1 Sampling, Number of Units. For the determination of the

compressive strength, absorption and unit weight (density) of the specimens
They must be selected according to the following table.

Table 6 Determination of the sample according to batch size

Minimum sample size for
Batch Size Dimensions and resistance to Absorption, net area and
understanding unit price
0 - 2 000 3 3
2,001 - 10,000 6 3
>10,000 < 100,000 12 6
6 units for every 50,000 6
>100,000
units or fraction of a lot

7.2 Visual Inspection. All the blocks must be in good condition.

free of cracks, breaks, and other defects that could interfere with the
proper placement of the unit or goods that influence resistance and durability
of the units.

Blocks with small cracks will not be eligible for return.

minor damages of 25 mm inherent to its production or its transport and delivery,
as long as the damaged amount does not exceed 5% of the order.

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7.3 Method for the Compression Resistance Test.

7.3.1 Identification. Each sample must be marked in such a way that in

any moment can be identified.

7.3.2 Devices to Use. Testing machine: must be equipped with two

steel pressure plates of which the top is circular and transmits
pressure on the specimen surface.

The other is a rigid plate on which the specimen will rest. If the area of
the pressure of the steel plates is not sufficient to cover the area of the sample,
Steel plates will be placed between these and the sample.

The pressure steel plates and dishes: the surface of these plates and dishes
they must be flat with variations of no more than 0.02 mm for every 150 mm in
any dimension of the plane.

The center of the circular steel plate of the dish or steel sheet if used,
it must align with the center of the pressure surface of the specimen.

The circular steel plate must be held firmly in one place but will be free
to turn in any direction. The diameter of the faces of these plates
the steel must be more than 15 cm and if plates are used, their thickness must be
it will be at least equal to one third of the distance between the
edge of the circular steel plate and the farthest corner of the sample. In
No case will be less than 12.5 mm.

7.3.3 Test Sample. It must be examined within 72 hours.

following their delivery to the laboratory. During this time, it will be kept at
normal laboratory temperature and air.

A plaster-cement paste with special resistance conditions is prepared now.

that must withstand a compressive force of 2.45 MPa (355.70 psi) when
test its resistance in 5 cm cubes two hours after its preparation
mix of 1:1 or 1:2 gypsum-cement, plus enough water for consistency
desired).

This paste spreads evenly over a non-absorbent surface,

generally a steel plate, which has been lightly coated with oil; it is
you can omit the use of oil if the surface of the plate and that of the sample are
they can separate without damaging the plaster cover to form.

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The sample is placed on this paste and pressed down manually.

Once the paste is dry and the covering is formed over the surface edges of the
unit, it is lifted and checked that the cover is well made. If not
it is completely removed from the surface of the block and the process is repeated.
Both sides of the sample must be covered, forming two smooth surfaces.
and parallel. The average thickness of this cover must not exceed 0.5 cm,
You must wait at least 24 hours before checking the stress tests.
corresponding.

7.3.4 Procedure.

Position: The samples must be tested with the centroid of their surface.
pressure aligned vertically with the center of the thrust bearing under pressure
from the testing machine.

100% solid units and special hollow units for use with the cavities
in horizontal position, they can be tested in the same direction of use.

Test speed: The load of the first half of the expected maximum load
it is done at a convenient speed. Next, the machine controls
must be adjusted to perform a uniform movement, so that the load
the remainder should be applied in no less than 1 and no more than 2 minutes.

7.4 Net area calculation The net area must be calculated according to ASTM
C140.

7.5 Calculations. The compressive strength of the blocks will be taken as

maximum load in Newton divided by the net area of the unit.

7.6 Results report. The results report must contain as

at a minimum, the following information:

1. Laboratory Name
2. Factory of origin of the sample
3. Sample Identification
4. Reference of the standard under which the test is carried out
5. Results
6. Responsible for the execution of the essay
7. Date of execution

8. LABELING

The structural blocks BE-1 and BE-2 must be labeled in such a way that they
easily identify the type of block

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The structural blocks BE-1 will be labeled with a high or low relief that
consists of two vertical lines with a radius of 2 mm and that covers at least the
half of the height of the block located at one of its ends.

The structural blocks BE-2 will be labeled with high or low relief that
consists of a vertical line with a radius of 2 mm that covers at least half
from the top of the block located at one of its ends.

Non-structural BNE blocks will not require labeling.

9. ACCEPTANCE OR REJECTION CRITERIA

If the average and the individual result of compressive strength are

less than specified in section 6.2.1 will be redone as
established in section 7.1, this must be carried out in duly accredited laboratories
accredited or in laboratories approved by the competent authority. In the case of
If the result is lower than required, the batch will be reclassified according to the results.
obtained in a smaller type of block, that is to say if the sampled lot is of
structural blocks type BE-1, and the average resistance obtained corresponds to
Structural blocks type BE-2 must be reclassified and remarked.

In the case of non-structural blocks BNE, if the resistance is lower than the
specified in section 6.2.1 of this standard, the batch will be rejected.

10. SANCTIONS

The non-compliance with this Nicaraguan Mandatory Technical Standard

will sanction in accordance with the provisions of Law 219 Technical Standardization Law
and Quality.

11. COMPLIANCE WITH THE REGULATION

The verification and application of this standard will be the responsibility of the Ministry of
Transport and Infrastructure.

12. ENTRY INTO FORCE

This Nicaraguan Mandatory Technical Standard will come into effect with
mandatory from its publication in the Official Gazette La Gaceta.

13. NORMATIVE REFERENCES

a) National Construction Regulation of Nicaragua RNC.

b) ASTM C 90-08 'Standard Specification for Loadbearing Concrete Masonry'

Units.

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c) ASTM C 140-08a "Standard Methods of Sampling and Testing Masonry Units".

d) ASTM C 33-07, “Standard Specification for Concrete Aggregates”

e) ASTM C150-07, "Standard Specification for Portland Cement."

f) ASTM C 1157-03, 'Standard Performance Specification for Hydraulic Cement'.

g) ASTM C 1602-06 "Standard Specification for Mixing Water Used in the "
Production of Hydraulic Cement Concrete.

h) INTE 06-0213-07, "Sampling and testing of masonry units"

concrete (concrete blocks)

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