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Concrete mix design optimized approach.

Catatan Redaksi:

Perencanaan campuran beton (mix design) adalah suatu langkah yang sangat penting dalam pengendalian mutu beton. Campuran yang salah akan mempengaruhi kemudahan pelaksanaan maupun performa beton dalam pemakaian. Makalah yang menarik ini mengungkapkan pengalaman dan praktek yang dilakukan di Romania dalam merencanakan campuran beton untuk berbagai kepentingan.

INTRODUCTION

In its simplest form, concrete is a mixture of paste and aggregates. The paste, composed of Portland cement and water, coats the surface of the fine and coarse aggregates. Through a chemical reaction called hydration, the paste hardens and gains strength to form the rock-like mass known as concrete. Within this process lies the key to a remarkable characteristic of concrete: it is plastic and malleable when freshly mixed, strong and durable when hardened. The key to achieving a strong, durable concrete rests in the careful selection and proportioning of its constituent ingredients.

DESIGNING THE CONCRETE MIX

The necessary first step to be taken to design a concrete mix is to establish clearly the requirements that the mix design must meet. These generally include one or more of the followings: mechanical strength, durability, characteristics of concrete member, and special requirements specified by the project design.

MIX DESIGN PROCEDURE

The mix design can not be resolved totally analytically, it requires, after the determination of job parameters (e.g. quantities of water, cement, aggregate, w/c ratio), calculation of weights, experimental adjutants (trial) tests on concrete for ensuring that it meets the design specifications.

With this information and the aid of tables or simple calculations, the quantities (in kg) of cement, coarse aggregate, water, and entrained air required per cubic meter can be determined. The absolute volumes of the ingredients can be calculated and totaled. Based on a 1 m3 of mix, subtracting the total of the four ingredients from 1 will provide the absolute volume of the fine aggregate required. From the absolute volume, the mass of the fine aggregate can then be calculated.

Thus, the quantities of materials required for 1 m3 of concrete have been estimated and a trial batch based on these quantities can be made. If adjustments are necessary, further batches should be adjusted by keeping the water: cement ratio constant and adjusting the aggregates and entrained air to produce the desired slump and air content.

QUALITY REQUIREMENTS AND FACTORS AFFECTING DESIGNED CONCRETE

The physical characteristics, chemical composition, and the proportions of the ingredients from mix affect the properties of concrete, in its fresh and hardened state. When designing, we must consider the following quality requirements of concrete:

--Fresh concrete: air content, flow behavior (workability/consistency), bleeding, cement type, setting time, hydration heat limitation.

--Hardened concrete: strength at specified age--short term (e.g. initial pre stress force and long term), durability-environment/ exposure (e.g. carbonation, chloride penetration, acid resistance, sulfate resistance), frost-thaw resistance, permeability (fluids, gas), resistance against early age cracking.

Factors to be considered regarding durability:

--Choice of slump.

--Environment conditions (dry, humid, humid with frost, marine and chemical aggressiveness).

--Exposure conditions (constructions protected against rain and humidity, frost-thaw saturated (no saturated) with water, exposure to water under pressure, exposed to marine or chemical environment etc.).

--Maximum size of aggregate.

--w/c ratio.

--Type of additive / admixture used.

--Minimum cement content:

Factors to be considered:.

* watertightness (grades: [P.sup.10.sub.4], [P.sup.10.sub.8], [P.sup.10.sub.12], [P.sup.20.sub.4], [P.sup.20.sub.8], [P.sup.20.sub.12] (1) it may be tested by measuring the flow through a saturated specimen, of 100 mm respectively 200 mm, subjected to pressure; a penetration test is more appropriate in cases where moisture is drawn in by capillary action.

* freeze-thaw resistance G50, G100, G1502.

Proportioning relates to the following aspects:

--Workability (regarding fresh concrete).

--Durability, strength (regarding hardened concrete).

--Economy by:

* Minimizing the amount of cement and w/c ratio.

* Minimizing the amount of water, to reduce cement content, and to increase strength durability.

--Batch weights calculations.

--Adjustments.

Factors to be considered when choosing aggregates:

--Economical consideration:

* Minimize water and cement, stiffest possible mix;

* Largest particle max size of aggregate, shape, surface texture;

* Optimize ratio of fine to coarse;

* Grading and its significance: consistency, strength, finisability.

--Size and shape of members: maximum size aggregate;

--Physical properties: strength;

--Exposure condition: Air entraining or not, sulfate attack;

--Maximum aggregate size: The largest maximum aggregate size that will conform to limitations given below:

* Nominal maximum size aggregate should not be larger than:

[phi]max [less than or equal to] 1/4 of narrowest dimension of structural member;

[less than or equal to] 1/3 thickness of slab

[less than or equal to] 1/6 reservoir wall thickness

[less than or equal to] spacing between re-bars - 5 mm

[less than or equal to] 1,3 x concrete cover of re-bars

[less than or equal to] 1/3 concrete pump piping

Factors to consider when choosing water to cement ratio:

--Compressive strength is inversely proportional to w/c:

--Economical consideration: Minimize water and cement, stiffest possible mix.

DETERMINATION OF JOB PARAMETERS

Step 1: Durability conditioning of concrete

Environment conditions, obtained for table 2 [right arrow] class of exposure

Requirements of grade and durability, obtained form table 3 and 4.

1. W/C ratio:

Table 3 [right arrow] suggested w/c ratio.

2. Cement content:

Table 4 [right arrow] suggested minimum cement content C (kg/[m.sup.3]).

Step 2: Preliminary procedures for determining the quality mix proportions of concrete constituents

1. Slump:

Table 1 [right arrow] suggested slump T (mm).

2. Minimum cement content:

Table 5 [right arrow] suggested minimum cement content C (kg/[m.sup.3]).

3. Aggregates:

a) Selection of aggregates by type (table 14).

b) Nominal maximum size of aggregates: Computed according to the following restrictions:

[phi] max [less than or equal to] minimum dimension of bearing member/4;

[phi] max [less than or equal to] thickness of slab/3;

[phi] max [less than or equal to] thickness of reservoir wall/6;

[phi] max [less than or equal to] minimum distance between re-bars --5 mm;

[phi] max [less than or equal to] 1,3 x reinforcement concrete cover;

[phi] max [less than or equal to] diameter of pump hose/3

4. Gradation of aggregate particles:

Table 6 [right arrow] suggested grading curve [right arrow] table 7 [right arrow] upper and lower gradation limits.

5. Cement:

Table 10, 11, 12 [right arrow] Recommended cement type and grade.

6. Water-cement maximum ratio:

Table 5 [right arrow] recommended water-cement maximum ratio.

Step 3: Procedures for determining the batch weights for mix proportions of constituents

1. Estimate mixing water and air content:

Table 13 [right arrow] W (kg/[m.sup.3]) Correction of water quantity according to maximum nominal size aggregate [right arrow] W' = W x c (kg/[m.sup.3]).

Table 11 [right arrow] suggested volume of air-entrainment

2. Water-cement ratio:

Table 16 [right arrow] suggested w/c ratio. Final adopted value of w/c = minimum value between (step 2.6. and step 3.2)

3. Cement:

C' = A' / A/C [kg/[m.sup.3]

Final adopted value of C = maximum value between (step 2.5. and step 3.3)

4. Estimate coarse aggregate: (First estimate of aggregate weight)

The total amount of dry aggregates will be calculated as follows:

Knowing that

V = m/x [rho]:

V ag = V total - V water = V cement - V air

Ag = [rho]ag x (1000 - C/[rho]c - A'/[rho]a - p) [kg/[m.sup.3]]

Where:

[rho]ag = relative density of aggregates (2,7 kg/[dm.sup.3]);

[rho]c = relative density of cement (3,0 kg/[dm.sup.3]);

p = void parameter (table 11), when not using additives, (when using additives the parameter will be computed according to laboratory tests).

5. Gradation of aggregate:

Table 7 [right arrow] percentage limits of aggregate passing.

The amount of aggregate for each grade is found as follows:

[A.sub.gi] = [A.sub.g] x [P.sub.i] - [P.sub.i-1] / 100 (kg/[m.sup.3])

Where:

Ag = amount of aggregates (kg);

pi = percent passing by mass through sieve "i";

pi-1= percent passing by mass through sieve "i-1";

6. Adjustment for moisture in the aggregate:

The following moisture adjustment should be made to the aggregate so that the water content of the concrete will not be affected by the natural moisture content of the aggregate.

[DELTA]A = [summation][A.sub.gi] x [u.sub.i] / 100 (1/[m.sup.3])

Where:

Agi = amount of aggregate form sieve "i' (kg);

ui = free moisture of sieve "i" (%);

n = total numbers of sieves.

[A.sup.*] = A' - [DELTA]A (l/[m.sup.3])

The free amount of moisture form fine aggregates ([U.sub.FA]%), is calculated as follows:

[DELTA][A.sub.FA] = [summation][A.sub.gi]x [u.sub.i] / 100 kg/[m.sup3]

The free amount of moisture form coarse aggregates (UCA%), is calculated as follows:

[DELTA][A.sub.CA] = [summation][A.sub.gi]x [u.sub.i] / 100 kg/[m.sup.3]

The total amount of free moisture is calculated as follows:

[DELTA]A = [DELTA][A.sub.FA] + [DELTA][A.sub.CA] kg/[m.sup.3]

Adjusted amount of water: [A.sup.*] = A' - [DELTA]A (kg/[m.sup.3])

7. Adjustment of total amount of the aggregates by sieve sizes:

The total amount of aggregates by sieve sizes, is found as follows:

[A.sup.*.sub.gi] = [A.sub.gi]x (1 + [u.sub.i]/100) (kg/[m.sup.3])

Where:

Agi--amount of aggregate form sieve "i' (kg);

ui = free moisture of sieve "i" (%).

8. Final adjustment of aggregate weight:

The total amount of aggregates, is found as follows:

[Ag.sup.*] = [DELTA]Agi * (kg/[m.sup.3])

Where:

[Ag.sup.*] = adjusted amount of aggregate form sieve "i' (kg);

n = number of sieves sizes.

[Ag.sup.*] = [summation] [A.sup.*]gi kg/[m.sup.3]

9. Total mass of concrete produced:

The total mass of concrete produced will be calculated as follows:

[G.sub.c] = [A.sup.*] + C' + [Ag.sup.*]

[G.sub.c] will be compared with the value of normal weight concrete that ranges between 2160 to 2560 kg/[m.sup.3]

10.Trial batch: Using the proportions developed in the above steps, a 30-liter concrete trial batch is made using only as much water as needed to reach the desired slump.

Three separate concrete batches should be prepared, as:

* a primary batch with ingredients as calculated;

* a second batch with a cement content increased with 7% but minimum 20 kg/[m.sup.3] in comparison with the primary batch, maintaining constant the water and aggregate quantities (according to the primary batch calculations);

* a third batch with a cement content reduced with 7% but minimum 20 kg/[m.sup.3] in comparison with the primary batch, maintaining constant the water and aggregate quantities (according to the primary batch calculations);

From all three batches din minimum 12 concrete samples should be tested for compressive strength (according to STAS 1275-88);

Six samples should from every batch should be tested after 7 days (according to STAS 1275-88), the adopted preliminary concrete mix design will be the one for which the determined strength are equal to the ones indicated by the Concrete Practice Code NE 012-1999;

The remaining six specimens shall be testes after 28 days, the results being analyzed for defining the final mix proportioning. The mean strength value for each mix [f.sub.bm] will be adjusted according to the real cement strength value, using the following equation:

[f.sub.cori] = 1,15 class_ciment / strength_of_cement x [f.sub.bmi]

The final mix proportion will be adopted for the batch of which the adjusted recorded strength value ([f.sub.cori]) is equal to the one determined after 28 days indicated by the Concrete Practice Code NE 012-1999 (table 1);

11. Summary of mix design:
Enter batch percentage:                         %
Compressive strength at 28 days:              MPa
Slump: Maximum                                 mm
       Minimum                                 mm
Nominal maximum size of aggregate:             mm
Water-cement ratio:
Concrete type
Air content:                                    %
Permeability:
Freeze-thaw:
Unit weight of aggregates: F.A.       kg/[m.sup.3]
                           C.A.       kg/[m.sup.3]
Mass of batched concrete: [rho]c =    kg/[m.sup.3]


Technical notes:

1. During winter conditions it is recommended to use, for members that have thickness over 1,5 m, cements with rapid setting time noted with R.

2. The setting of cement types II B, II H, H II/BS (that have a maximum amount of mixture of 35%), for reinforced concrete members will be made only with the approval of a specialist institute.

Technical notes: The values concerning the quantities of water required for mix specified in annex 13. are valid only if used with natural aggregates size 0 ... 31 mm. They will be increasing or decreasing as follows:

--decrees with 10% when using aggregates size 0 ... 71 mm;

--decrees with 5% when using aggregates size 0 ... 40 mm;

--decrees with 10-20% when using additives;

--increase with 10% when using crushed stone;

--increase with 20% when using aggregates size 0 ... 7 mm;

--increase with 10% when using aggregates size 0 ... 16 mm;

--increase with 5% when using aggregates size 0 ... 20 mm.

Technical notes:

1. The values for the table are valid for grade II homogeneity. For grade I, the values rise with 0,05 and for grade III they decrease with 0,05.

2. When using crushed stone the values form the table rise with 10%.

3. According to the environment conditions and exposure the A/C ratio, resulted form annex 2, should not be exceeded.

4. When the concrete is cured in steam rooms, according to the final decrease of strength, the A/C ration values will be adopted as follows:

--for grade I of homogeneity see table;

--for grade II of homogeneity, the proposed values for the table decreased by 0,05 (corresponding to grade III).

Technical notes: For grade I, respectively grade III of homogeneity, of the values required in the table, a certain value will be subtracted or added.

Values that will be subtracted or added to the recommended in the table for grade II, for grade I respectively II of homogeneity

CONCLUSIONS

The recommendations and proposals for improving the existing concrete mix design are different, according to the factors (human in regard of efficiency of personnel/ labor discipline and technological in regard of production process) that intervene in the achievement of the considered concrete mix at a minimum cost.

REFERENCES

[1.] Ilinoiu G. Quality of Concrete. Study on Code NE 012-1999. Nr. 3, Bulletin AICPS (2001), pp. 114-120. Journal of the Structural Design Engineers Association--Romania.

[2.] Ilinoiu G. Concrete durability. Journal Civil and Industrial Constructions. 2001, No. 24, pp. 36-37.

[3.] Ilinoiu G. Construction Engineering. Conspress Publishing House, 2003. pp. 49-64.

[4.] ENV 206, 1990. Concrete Performance, Production, Placing and Compliance Criteria. European Committee for Standardization.

[5.] STAS 1275-1988. Tests of concrete. Tests of hardened concrete. Determination of mechanical strengths;

[6.] STAS 9602-90. Reference Concrete. Specifications for manufacturing and testing.

[7.] NE 012-1999. Practice code for the execution of concrete, reinforced concrete and prestressed concrete works, Part 1--Concrete and reinforced concrete.

Note: Discussion is expected before June, 1 st 2004. The proper discussion will be published in "Dimensi Teknik Sipil" volume 6 number 2 September 2004

(1) Permeability, according to Romanian specification STAS 3519-76--Tests on concretes. Inspection of waterproofness and ISO 7031--Tests on concrete watertightness, is defined as the flow property of concrete which quantitatively characterizes the ease by which a fluid or gas will pass through it, under the action of a pressure differential. It may be tested by measuring the flow, measured in Bar (1 Bar = 10 MPa), through a saturated specimen, of 100 mm respectively 200 mm height, subjected to pressure (4, 8 or 12 Bar); (Permeability grades: [P.sup.10]4, [P.sup.10]8, [P.sup.10]12, [P.sup.4]20, [P.sup.8]20, [P.sup.12]20).

(2) Freeze -thaw strength, according to STAS 3518-89--Tests on concretes. Strength determination at frost-thawing, represents the maximum number of freeze-thaw successive cycles that the concrete specimens can go through without decreasing their strength by 25 % in comparison with the laboratory reference specimens. Freeze-thaw grades: G50, G100, G150 (approximately 50 cycles per year, average max. 150-200 cycles per year).

George Ilinoiu

Faculty of Civil, Industrial and Agricultural Constructions

Technical University of Civil Engineering of Bucharest

Bd. Lacul Tei, no. 124, sector 2, Bucharest, Romania

Telephone: 4021-242.12.08 / 157; Fax: 4021-242.07.81; e-mail: ilinoiug@hidro.utcb.ro
Table a. Characteristic strength of concrete
(MPa)

Concrete                  C        C       C        C        C
grades                   2,8       4       6        8       12
                          /        /       /        /        /
                         3,5       5      7,5      10       15
                         Characteristic strength of concrete
[f.sub.c,28] cylinder    2,8       4       6        8       12
[f.sub.c,28] cube        3,5       5      7,5      10       15

Concrete                  C        C       C        C        C
grades                    16      18       20      25       28
                          /        /       /        /        /
                          20     22,5      25      30       35
                         Characteristic strength of concrete
[f.sub.c,28] cylinder     16      18       20      25       28
[f.sub.c,28] cube         20     22,5      25      30       35

Concrete                  C        C       C        C
grades                    30      32       35      40
                                   /       /        /
                          37      40       45      50
                         Characteristic strength of concrete
[f.sub.c,28] cylinder     30      32       35      40
[f.sub.c,28] cube         37      40       45      50

Concrete                  C        C
grades                    45      50
                          /        /
                          55      60
                         Characteristic strength of concrete
[f.sub.c,28] cylinder     45      50
[f.sub.c,28] cube         55      60

Table 1. Recommended concrete consistencies
for different types of construction

Item    Type of concrete member          Type of Transport
no.

   1    Plain or reinforced footings,    Truck, bucket, belt
        massive elements                 conveyor

   2    Plain or reinforced footings,    Transit mix truck,
        massive elements, slabs,         bucket
        columns, beams, walls.

   3    Plain or reinforced footings,    Transit mix truck,
        massive elements, slabs,         pump
        columns, beams, walls,
        reservoirs placed by concrete
        pump

   4    Members and small reinforced     Transit mix truck,
        monolithic sections with         bucket
        difficulties while compacting

   5    Concrete prepared with           Transit mix truck,
        plasticizers or superplasticizersbucket
        additives

   6    Concrete prepared with           Transit mix truck,
        superplasticizers additives      bucket

Type of concrete member                  Consistency
                                         Grade       Slump (mm)

Plain or reinforced footings,            T2          30 [+ or -] 10
massive elements

Plain or reinforced footings,            T3          70 [+ or -] 20
massive elements, slabs,
columns, beams, walls.

Plain or reinforced footings,            T3/         100 [+ or -] 20
massive elements, slabs,                 T4
columns, beams, walls,
reservoirs placed by concrete
pump

Members and small reinforced             T4          120 [+ or -] 20
monolithic sections with
difficulties while compacting

Concrete prepared with                   T4/         150 [+ or -] 30
plasticizers or superplasticizers        T5
additives

Concrete prepared with                   T5          180 [+ or -] 30
superplasticizers additives

Table 2. Concrete Exposure class in different environmental Conditions

Type of environment                  Type or location of structure
0                     1                     2

1. Dry                a). Moderate   Concrete surfaces protected
environment                          against weather or aggressive
                                     conditions

                      b). Severe     Concrete surfaces exposed
                                     permanent to temperatures
                                     grater that 30 [degrees]C

2 Hummed              a). Moderate   Concrete surfaces exposed to
environment                          freezing whilst sheltered form
                                     severe rain or freezing whilst
                                     wet

                      b). Severe     Concrete surfaces exposed to
                                     freezing whilst continuously
                                     submerged under water;
                                     Concrete surfaces exposed to
                                     condensation or alternant
                                     wetting and drying;
                                     Concrete surfaces exposed to
                                     continuous water
                                     pressure on one side

3. Hummed environment subjected      Concrete interior or exterior
to freezing and deicing salts        surfaces exposed to freezing
                                     and de-icing salts

4. Marine             a).No          1).Weak    Concrete surfaces
environment           freezing       aggres-    exposed permanent
                                     sive       to sea water;
                                     condi-
                                     tions

                                     2).Inten-  Concrete surfaces
                                     sive       situated over the
                                     aggres-    variation level of
                                     sive       the sea
                                     condi-
                                     tions

                      b).With        1).Weak    Concrete surfaces
                      freezing       aggres-    situated over the
                                     sive       variation level of
                                     condi-     the sea indirectly
                                     tions      to marine
                                                environment

                                                Concrete surfaces
                                                exposed to freezing
                                                sheltered from
                                                wetting

                                                Concrete surfaces
                                                protected against
                                                weather without
                                                heating

                                     2).Inten-  Concrete surfaces
                                     sive       exposed to marine
                                     aggres-    environment by
                                     sive       alternant wetting,
                                     condi-     drying and salts.
                                     tions      Concrete surfaces
                                                exposed industrial
                                                technological
                                                condensation

5. Chemical           a).            Mild chemical aggressive
aggressive                           environment
environment
                      b).            Moderate chemical aggressive
                                     environment

                      c).            Severe chemical aggressive
                                     environment

                      d).            Very severe chemical aggressive
                                     environment

Table 3. Requirements for concrete durability
         assurance according to type of
         environment conditions

Item       Concrete mix    Environment conditions for concrete table 2
no.         components          1a      1b            2a

0               1               2       3             4

1                                  Water: Cement Ratio

       Plain concrete           -      0,65          0,55
       Reinforced concrete     0,65    0,60          0,55
       Prestressed concrete    0,60    0,55          0,55

2                            Minimum cement content (kg/[m.sup.2]).

       Plain concrete          150     300           250
       Reinforced concrete     300     300           350
       Prestressed concrete    350     350           350

3                            Percent of air entrained (%), min.

       Max. size aggregate      -       -             4
       31mm
       Size aggregate 16 mm     -       -             5
       Max. size aggregate      -       -             6
       7mm

4      Frost resisting          -       -            Yes
       aggregates

5                            Watertightness grade, min.

       Plain concrete           -              [P4.sup.10]
       Reinforced concrete      -              [P.sub.4.sup.10]
       Prestressed concrete     -              [P.sub.4.sup.10]

6                              Frost resistance

       Plain concrete                  G50           G100
       Reinforced concrete             G100          G150
       Prestressed concrete            G100          G150

    Concrete mix      Environment conditions for concrete table 2
     components                2b                  3

         1                     5                   6

                                 Water: Cement Ratio

Plain concrete                0,55                0,50
Reinforced concrete           0,50                0,50
Prestressed concrete          0,50                0,50

                        Minimum cement content (kg/[m.sup.2]).

Plain concrete                300                 350
Reinforced concrete           350                 350
Prestressed concrete          350                 350

                        Percent of air entrained (%), min.

Max. size aggregate            4                   4
31mm
Size aggregate 16 mm           5                   5
Max. size aggregate            6                   6
7mm

Frost resisting               Yes                 Yes
aggregates

                           Watertightness grade, min.

Plain concrete          [P4.sup.10]         [P8.sup.10]
Reinforced concrete     [P.sub.8.sup.10]    [P.sub.8.sup.10]
Prestressed concrete    [P.sub.8.sup.10]    [P.sub.8.sup.10]

                                 Frost resistance

Plain concrete                G150                 -
Reinforced concrete           G150                 -
Prestressed concrete          G150                 -

    Concrete mix      Environment conditions for concrete table 2
     components               4a1                 4a2

         1                     7                   8

                                 Water: Cement Ratio

Plain concrete                0,55                0,55
Reinforced concrete           0,50                0,50
Prestressed concrete          0,50                0,50

                        Minimum cement content (kg/[m.sup.2]).

Plain concrete                350                 350
Reinforced concrete           350                 400
Prestressed concrete          350                 400

                        Percent of air entrained (%), min.

Max. size aggregate            -                   -
31mm
Size aggregate 16 mm           -                   -
Max. size aggregate            -                   -
7mm

Frost resisting                -                   -
aggregates

                           Watertightness grade, min.

Plain concrete          [P4.sup.10]         [P4.sup.10]
Reinforced concrete     [P.sub.8.sup.10]    [P.sub.8.sup.10]
Prestressed concrete    [P.sub.8.sup.10]    [P.sub.8.sup.10]

                                 Frost resistance

Plain concrete                 -                  G150
Reinforced concrete            -                  G150
Prestressed concrete           -                  G150

    Concrete mix      Environment conditions for concrete table 2
     components               4b1                 4b2

         1                     9                   10

                                Water: Cement Ratio

Plain concrete                0,50                0,50
Reinforced concrete           0,45                0,45
Prestressed concrete          0,45                0,40

                        Minimum cement content (kg/[m.sup.2]).

Plain concrete                350                 350
Reinforced concrete           400                 400
Prestressed concrete          400                 450

                        Percent of air entrained (%), min.

Max. size aggregate            4                   4
31mm
Size aggregate 16 mm           5                   5
Max. size aggregate            6                   6
7mm

Frost resisting               Yes                 Yes
aggregates

                             Watertightness grade, min.

Plain concrete          [P8.sup.10]         [P8.sup.10]
Reinforced concrete     [P.sub.12.sup.10]   [P.sub.12.sup.10]
Prestressed concrete    [P.sub.12.sup.10]   [P.sub.12.sup.10]

                                  Frost resistance

Plain concrete                G150                 -
Reinforced concrete           G150                 -
Prestressed concrete          G150                 -

    Concrete mix      Environment conditions for concrete table 2
     components                5a                  5b

         1                     11                  12

                                 Water: Cement Ratio

Plain concrete                0,55                0,50
Reinforced concrete           0,55                0,50
Prestressed concrete          0,55                0,50

                        Minimum cement content (kg/[m.sup.2]).

Plain concrete                350                 350
Reinforced concrete           350                 350
Prestressed concrete          350                 350

                        Percent of air entrained (%), min.

Max. size aggregate            -                   -
31mm
Size aggregate 16 mm           -                   -
Max. size aggregate            -                   -
7mm

Frost resisting                -                   -
aggregates

                            Watertightness grade, min.

Plain concrete          [P4.sup.10]         [P8.sup.10]
Reinforced concrete     [P.sub.4.sup.10]    [P.sub.8.sup.10]
Prestressed concrete    [P.sub.4.sup.10]    [P.sub.8.sup.10]

                                  Frost resistance

Plain concrete                 -                   -
Reinforced concrete            -                   -
Prestressed concrete           -                   -

    Concrete mix      Environment conditions for concrete table 2
     components                5c                  5d

         1                     13                  14

                                 Water: Cement Ratio

Plain concrete                0,45                0,40
Reinforced concrete           0,45                0,40
Prestressed concrete          0,45                0,40

                        Minimum cement content (kg/[m.sup.2]).

Plain concrete                400                 450
Reinforced concrete           400                 450
Prestressed concrete          400                 450

                        Percent of air entrained (%), min.

Max. size aggregate            -                   -
31mm
Size aggregate 16 mm           -                   -
Max. size aggregate            -                   -
7mm

Frost resisting                -                   -
aggregates

                             Watertightness grade, min.

Plain concrete          [P12.sup.10]        [P12.sup.10]
Reinforced concrete     [P.sub.12.sup.10]   [P.sub.12.sup.10]
Prestressed concrete    [P.sub.12.sup.10]   [P.sub.12.sup.10]

                                  Frost resistance

Plain concrete                 -                   -
Reinforced concrete            -                   -
Prestressed concrete           -                   -

Table 4. Grading classes

                  Grading class in accordance to the cement
Consistency               content (Kg/[m.sup.3])

                  [less than or      300-450        > 450
                  equal to] 300

T2                      I              II            III
T3 and T3/T4            I           I (II) *     II (III) *
T4, T4/T5, T5           -               I            II

* Recommended when the concrete does not
  have tendency of honeycombing

** Upper and lower limit of gradation are as
   follows (annex 5): Table 5.1. to 5.6 for
   aggregate size 0 ... 7 mm; 0 ... 16 mm; 0 ... 20
   mm; 0 ... 31 mm; 0 ... 40 mm; 0 ... 71 mm.

Table 5. Upper an lower Limits of gradation

Table 5.1 Aggregates between 0 ... 7 mm

          Cumulative percent passing by mass (%)
Limits       0,2       1        3        7

Max.         12       40       70       100
Min.          3       25       54        95

Table 5.2 Aggregates between 0 ... 16 mm

Grading    Limits   Cumulative percent passing by mass (%)
 class               0,2     $1      $3      $7     $16

   I       Max.      15      45      65      85      100
           Min.      10      35      55      75       95

   II      Max.      10      35      55      75      100
           Min.       5      25      45      65       95

  III      Max.       5      25      45      65      100
           Min.       1      15      35      55       95

Table 5.3. Aggregates between 0 ... 20 mm

Grading    Limits   Cumulative percent passing by mass (%)
 Class               0,2      1     3 (9)   7 (10)   20

   I       Max.      15      40      60      80      100
           Min.      10      30      50      70       95

   II      Max.      10      30      50      70      100
           Min.       5      20      40      60       95

  III      Max.       5      20      40      60      100
           Min.       1      10      30      50       95

Table 5.4. Aggregates between 0 ... 31 mm

Grading    Limits   Cumulative percent passing by mass (%)
 Class               0,2      1       3       7      16       31

   I       Max.      15      40      50      70      90      100
           Min.      10      30      40      60      80       95

   II      Max.      10      30      40      60      80      100
           Min.       5      20      30      50      70       95

  III      Max.       5      20      30      50      70      100
           Min.       1      10      20      40      60       95

Table 5.5. Aggregates between 0 ... 40 mm

Grading    Limits   Cumulative percent passing by mass (%)
 Class               0,2      1     3 (5)   7 (10)   20       40

   I       Max.      15      30      45      60      80      100
           Min.      10      20      35      50      70       95

   II      Max.      10      25      35      50      70      100
           Min.       5      15      25      40      60       95

  III      Max.       5      15      25      40      60      100
           Min.       1       5      15      30      50       95

Table 5.6. Aggregates between 0 ... 71 mm

Limits     Cumulative percent passing by mass (%)
            0,2       1       3       7      16

Max.         8       18      32      45      61
Min.         1        6      13      22      38

Limits     Cumulative percent passing by mass (%)
             25      31      40      71

Max.         70      77      84     100
Min.         50      57      68      95

Table 5.7. Aggregates between 0 ... 71 mm

Limits     Cumulative percent passing by mass (%)
            0,2       1       3       7      16

Max.         8       18      32      45      61
Min.         1        6      13      22      38

Limits     Cumulative percent passing by mass (%)
             25      31      40      71

Max.         70      77      84     100
Min.         50      57      68      95

Table 6. Types of cement according to romani-an standards (SR)

  Type                      Sort          SR

    1        2                            3

          Portland Cement (without admixtures)

    I        Normal Portland            SR 388
             cement (without
             admixtures)

           Composite Cements (with admixtures)

 II A-M      Portland cement           SR 1500
             composite

 II A-S      Portland cement
             with slag

 II A-V      Portland cement
             with ash

 II A-P      Portland cement
             with natural
             pozzolan

 II A-L      Portland cement
             with lime

 II B-M      Portland cement           SR 1500
             composite

 II B-S      Portland cement
             with slag

 II B-P      Portland cement
             with natural
             pozzolan

 II B-L      Portland cement
             with lime

  III A      Blast furnace             SR 1500
             cement

  IV A       Pozzolan cement           SR 1500

   V A       Composite cement          SR 1500

                 Limited hydration Cements

   H I       Cement without
             mixture

 HII/A-S                               SR 3011
 HII/B-S     Cement with slag
 HIII/A

                 Sulfate resistant cements

   SRI       Cement without            SR 3011
             admixture

SRII/A-S     Cement with slag          SR 3011

SRII/A-P     Pozzolan cement           SR 3011

SRII/B-S     Cement with slag          SR 3011

 SRIII/A     Cement with slag          SR 3011

  Type                Admixture
                %                Type                   Grade

    1           4                  5                      6

                    Portland Cement (without admixtures)

    I           -                  -              32,5; 42.5; 52.5
                                                    32.5R; 42.5R;
                                                        52.5R

                   Composite Cements (with admixtures)

 II A-M        6-20      Mixture of slag,         32,5; 42.5; 52.5
                         ash, lime, pozzolan        32.5R; 42.5R;
                                                        52.5R

 II A-S                  Granulated blast
                         furnace slag

 II A-V                  Pulverized fuel ash

 II A-P

 II A-L                  Lime

 II B-M                  Mixture of slag,            32,5; 42.5
                         ash, lime, pozzolan        32.5R; 42.5R

 II B-S       21-35      Granulated blast
                         furnace slag

 II B-P

 II B-L                  Lime

  III A       36-65      Granulated blast            32,5; 32,5R
                         furnace slag

  IV A        11-35      Pozzolan and ash         32,5; 42.5; 32.5R

   V A        18-30      Granulated blast            32.5; 32.5R
                         furnace slag + ash
                         pozzolans

                      Limited hydration Cements

   H I          -                  -

 HII/A-S       6-20                               32,5; 42,5; 52,5
 HII/B-S      21-35      Granulated blast
 HIII/A       36-65      furnace slag

                     Sulfate resistant cements

   SRI          -                  -              32,5; 42,5; 52,5

SRII/A-S       6-20      Granulated blast
                         furnace slag

SRII/A-P       6-20      Natural pozzolan

SRII/B-S      21-35      Granulated blast
                         furnace slag
 SRIII/A      36-65      Pulverized fuel ash

Table 7. Approximate equivalency between
manufactured cement according to SR
and STAS
                                         Approximate equivalency
Item no.    Cements according to S.R.          with STAS

                  Type          S.R.        Type        STAS
0                  1              2          3           4
1           II B- S 32.5        1500     M 30           1500
2           II A-S 32.5                  Pa 35
3           I 32.5               388     P 40           388
4           I 42.5                       P 50 (P45)
5           H I 32.5            3011     H 35           3011
6           H II / A-S 32.5              Hz 35
7           SR I 32.5           3011     SR 35          3011
8           SR II / A-S 32.5             SRA 35

Table 8. Recommended cement types used for
         concrete work in normal conditions of
         exposure

Item       Work conditions         Concrete         Type of
no.         and/or member            grade         concrete
           characteristics

0                 1                    2               3

1       Members or                   C 5/4       Plain
        constructions with            ...
        thickness smaller           C 10/8
        than 1,5m produced
        in periods other that       C 15/20      Reinforced
        winter                        ...
                                    C 20/16

                                    C 25/12      Reinforced
                                    C 30/25
                                     C 35/

                                    C 37/30      Reinforced
                                     C 40/       (prestressed)
                                    C 45/35
                                    C 50/40

                                    C 55/45      High strength
                                    C 60/50      reinforcement
                                    C 70/60      (prestressed)
                                    C 80/70

2       Massive members or         < C 15/12     Plain
        constructions with          C 15/12
        thickness equal or
        larger than 1,5m
                                    C 20/16      Reinforced

                                    C 25/20      Reinforced
                                    C 30/25
                                    C 35/-

                                    C 37/30      Reinforced
                                    C 40/-       (prestressed)
                                    C 45/35
                                    C 50/40

                                    C 60/50      Reinforced
                                    C 70/60      (prestressed)
                                    C 85/70

  Concrete          Recommended         Usable types of
   grade          types of cement            cement

     2                   4                     5

   C 5/4        (IIIA,IVA,VA) 32,5     (IIIA,IVA,VA)32,5
    ...             IIB - 32,5              IIA 32,5
   C 10/8

  C 15/20           IIA - 32,5           IIB- 32,5 (1);
    ...                                  IIB- 42,5 (1);
  C 20/16                                    I 32,5
                                           IIA- 42,5

  C 25/12            I - 32,5             IIA - 32,5R;
  C 30/25                                 IIA - 42,5;
   C 35/                                    I - 42,5

  C 37/30            I - 42,5             I- 32,5 (2);
   C 40/             I -42,5A               I- 52,5;
  C 45/35                                   I 52,5A
  C 50/40

  C 55/45         I 52,5/ 52,5R;
  C 60/50        I 52,5A/ 52,5A-R
  C 70/60
  C 80/70

 < C 15/12        H III/A - 32,5           H II/B-S;
  C 15/12                                 II B-S 32,5;
                                           I A-S 32,5

  C 20/16          H II/A - 32,5           H I-32,5;
                                        HII/B-S32,5 (1);
                                          II A-S 32,5

  C 25/20           H I - 32,5            II A-S 32,5;
  C 30/25                                H II/A-S32,5;
   C 35/-                                    I 32,5

  C 37/30           H I - 42,5           H I-32,5 (2);
   C 40/-                                   I 42,5;
  C 45/35                                HII/A-S 42,5;
  C 50/40                                H42,5/42,5 RA;
                                          II A-S 42,5

  C 60/50           H I - 52,5           H II/A-S 52,5;
  C 70/60                                Hz52,5/52,5-A
  C 85/70

Table 9 Recommended cements types for plain
and reinforced concrete works that
are exposed to sea water and severe
freezing

Item      Work conditions
 no.       and/or Member           Concrete          Type of
          characteristics            grade          concrete

  0              1                     2                3

  1     Members or              < C 20/16          Plain
        constructions with
        thickness smaller       C20/16-C35/ -      Reinforced
        than 1,5m

                                C37/30-C50/40      Reinforced

                                C 55/45-C85/70     Reinforced

  2     Massive members         < C 20/16          Plain
        or constructions
        with thickness
        equal or larger that    C 20/16-C 35/      Reinforced
        1,5m
                                C 37/30-C50/40     Reinforced

                                C 55/45-C85/70     Reinforced

                     Recommend
   Concrete         ed types of         Usable types
    grade              cement            of cement

      2                  4                   5

< C 20/16         IIA-32,5/32,5R      I-32,5/32,5R

C20/16-C35/ -     I-32,5/32,5R        IIA-32,5/32,5R
                                      I-42,5A;
                                      I - 42,5/42,5R

C37/30-C50/40     I-42,5              I-32,5/32,5R;
                  I-42,5/42,5R        I-52,5/52,5R

C 55/45-C85/70    I-52,5A
                  I-52,5/52,5R

< C 20/16         H II/A-S32,5        H I-32,5;
                                      II A-S32,5

C 20/16-C 35/     III-32,5            III-42,5

C 37/30-C50/40    H I-42,5            H I-52,5;
                                      I-52,5

C 55/45-C85/70    H I-52,5

Table 10. Recommended types of cements for
plain and reinforced concrete works
that are in contact with aggressive
waters

           Nature of
Item       aggressive         Grade of
 no.        environ-         aggressive
              ment

  0            1                  2

  1     Alkalis             Mild

  2     Carbon              Mild

                            Severe
                            very severe

  3     Sulfate             Mild
                            Moderate
                            Moderate

                            Severe or
                            very sever
                            (for all
                            cases)

  4     Magnesium           Mild

                            Severe or
                            very sever

  5     Nitrogen            Mild
        salts

                            Severe or
                            very sever

  6     Base                Mild

                            Severe

                      Recommended types of
                             cement
  Grade of
 aggressive         Plain         Reinforced
                   concrete        concrete

      2               3                4

Mild             II A            II A-S

Mild             II A            II A-S

Severe
very severe      I 32,5;         I 32,5;

Mild             III A; IV A;    II A-S
Moderate         V A; II B;
Moderate         II A

Severe or        SR II/B-S       SR I SR II/A-S
very sever       SR III/A
(for all
cases)

Mild             H III/A         H II/A-S
                 H II/B-S

Severe or        SR II/B-S       SR II/A-S
very sever       SR III/A

Mild             H III A         H II/A-S
                 H II/B-S

Severe or        SR II/B-S       SR II/A-S
very sever       SR III/A

Mild             H II/A-S        H I

Severe           SR II/A-S       SR I

                     Usable types of cement
  Grade of
 aggressive         Plain         Reinforced
                   concrete        concrete

      2               5                6

Mild                I 32,5          I 32,5;
                     H I             H I;
                   H II/A-S        H II/A-S

Mild               I 32,5;          I 32,5;
                     H I;            H I;
                   H II/A-S        H II/A-S

Severe               H I;            H I;
very severe          SR I            SR I

Mild               H II A-S        H II/A- S
Moderate
Moderate

Severe or          H II/B-S          H I;
very sever         H III/A         H II/A-S;
(for all                            II A-S
cases)

Mild                H A-S           H A-S;
                                  H I; Sr I;
                                   SR II/A-S

Severe or           H A-S           H A-S;
very sever         H II/A-S        H II/A-S;
                                   H I; SR I

Mild                H A-S           H A-S;
                                  H I; SR I;
                                   SR II/A-S

Severe or          H II/A-S       SR I; H I;
very sever                         H II/A-S

Mild                H A-S          H II/A-S;
                                    II/A-S;
                                     SR I

Severe             H II/A-S          H I;
                                   H II/A-S

Table 11. Estimated mixing water requirement for various slumps

                       Water (l/[m.sup.3]) of concrete indicated
Concrete grade                       by consistency
                         T2         T3        T3/T4       T4

C 5/4                    160        170         -          -
C 10/8 ... C 25/20       170        185        200        220
> C 30/25                185        200        215        230

Relative Density

     Type of material          Density ( Kg/[dm.sup.3] )

Siliceous (stream deposits)               2,7
Calcareous                            2,3 ... 2,7
Ceramic                                   2,7
Basalt                                    2,9
Cement                                    3,0

Approximate volume of air-entrainment according
to maximum size aggregates

Maximum size of aggregates     10    16    20    31    40    70
           (mm)
     Air-entrainment %          7     6     5    4,5    4     3

Table 12. Maximum values for water: cement ratio after preliminary
tests (grade II concrete homogeneity)

Concrete grade             Cement grade
                   32,5        42,5        52,5

  C 10/8           0,75
  C 15/12          0,70
  C 20/16          0,60
  C 25/20          0,55
  C 30/25          0,50        0,55
  C 35/            0,45        0,50
  C 37/30          0,40        0,47
  C 40/            0,35        0,45        0,50
  C 45/35                      0,40        0,45
  C 50/40                      0,35        0,40
  C 55/45                      0,33        0,38
  C 60/50                      0,30        0,35
  C 70/

Table 13. Strength of concrete at 28 days after preliminary tests
for grade II homogeneity

               Characteristic strength
Concrete    fc preliminary (N/[mm.sup.2])     Concrete
 grade                                          grade
                Cube          Cylinder

 C 10/8          18             14,5           C 40/-
C 15/12         23,5             19            C 45/35
C 20/16          29              23            C 50/40
C 25/20          36              29            C 55/45
C 30/25          42             33,5           C 60/50
 C 35/-          47             37,5           C 70/60
C 37/30          48             38,5           C 87/70

               Characteristic strength
Concrete    fc preliminary (N/[mm.sup.2])
 grade
                Cube          Cylinder

 C 10/8         51,5             41
C 15/12         56,5             45
C 20/16         62,5             50
C 25/20          68             54,5
C 30/25          73             58,5
 C 35/-         84,5            67,5
C 37/30         101              81

 Concrete grade      (N/[mm.sup.2]) (Cube)    (N/[mm.sup.2]) (Cube)

C 10/8 - C 20/16               3                       2,5
C 25/20 - C 37/30              4                        3
C 40/- - C 55/45               5                        4
C 60/50 - C 85/70              6                        5
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Title Annotation:Technical Note
Author:Ilinoiu, George
Publication:Civil Engineering Dimension
Article Type:Report
Geographic Code:4EXRO
Date:Mar 1, 2004
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