# 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 |

Words: | 6383 |

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