Design method for mix proportion of hydraulic high performance concrete based on overall calculation

Civil Engineering and Technology June 2014, Volume 3, Issue 2, PP.34-37

Design Method for Mix Proportion of Hydraulic High Performance Concrete Based on Overall Calculation Jun Feng1, 2#, Shuyou Huang1, Bingfang Zhao 1, Liyu Sun 1 1. College of Water Conservancy and Environment Engineering, Changchun Institute of Technology, Changchun 130012, China 2. Laboratory of Applied Disaster Prevention in Water Conservation Engineering of Jilin Province, Changchun Institute of Technology, Changchun 130012, China #

Email: junefeng@yeah.net

Abstract High Performance Concrete (abbreviated as HPC) are becoming more and more important, however there is no uniform standard for mix proportion design method. In order to improve the frost resistance of concrete, this paper used the method of overall calculation for mix proportion design basis on achievements of previous research, and corrected the relevant parameters, so that avoided getting amount of binding materials and fine-to-coarse ratio comparatively bigger. The rationality of using overall calculation and correcting the relevant parameters was validated through the strength and frost resistance experiments of C25 hydraulic HPC. Keywords: Hydraulic HPC; Overall Calculation; Experiment

1 INTRODUCTION HPC is a new term emerged in the last two decades with such many advantages as energy-saving, materials-saving, and environmental protection, etc. that is a better "green concrete" created in the long-term process of research and practice. In addition to cement, water, aggregates, HPC must be mixed with a certain amount of fine mineral admixtures and efficient additives. So, the performance, quality and durability of the concrete are directly or indirectly related with the mix proportion. The old theory is based on the specific surface area method. As the continuous development of high-performance concrete, the work of HPC mix proportion, basing on the old theory and specification have brought a lot of errors [1].

So far, although people have put forward many methods of high performance concrete mix proportion, there have been no reliable codes and standards. Besides, different projects and industries of engineering with different requirements will come up with different performance and durability indicators. For instance important hydraulic structures including the mass concrete construction on the durability and volume’s stability with a high level of requirements, while, the strength’s requirements are not high. The hydraulic concrete makes the frost resistance and durability as main requirements, in accordance with the Technical Specifications for Concrete Construction of minimum strength grade, by guarantee rate 95% to determine the configuration’s strength. With a maximum water-cement ratio as the primary water-binder ratio, then, in turn, reduce 0.05~0.1 percentage points, take 3~5 water-cement ratio to try mixing. The next do obtain the linear relationship between water-cement ratio and strength, and do find the water-cement ratio which met preparation strength’s demand, and try mixing and adjust again. This text combined with the characteristics of HPC, aiming at preparing C25 hydraulic HPC, by means of whole calculation method for the preparation.

2 EXPERIMENTAL WORK - 34 http://www.ivypub.org/cet

2.1 Overall Calculation Overall calculation[2] is a half experience-half test method according to the theory of American scholar P.K. Mehta and P. C Aitcin, the recommended volume ratio of cement slurry and aggregates is 35:36 for HPC to reach the best concrete workability and strength at the same time. After calculate amount of materials, and as a result of constant adjustments, determine the final mix proportion.

2.2 Design Basis This experimentation is mainly basis on Test Code for Hydraulic Concrete (DL/T5150—2001), Test Code for Aggregates of Hydraulic Concrete (DL/T5151—2001) and Code for Mix Design of Hydraulic Concrete (DL/T5330—2005). Evaluation of experimentation results and selection of experimentation parameters are according to Specification for Hydraulic Concrete Construction (DL/T5144—2001) and Code for Utility Technical Concrete Admixture (GB 50119-2003).

2.3 Materials 1)

Cement

We used grade 42.5 Ordinary Portland cement with a specific gravity of 3.3 g/cm3. Initial and final setting times were 155 min and 215 min respectively. Its specific surface area was 3300 cm2/g.

2)

Aggregate

Dry and clean aggregate was used as coarse aggregate in this experiment. The gravel was 31.5mm maximum nominal size, and its apparent density in saturated surface dry condition was 2.85 g/cm3. River sand was used as fine aggregate with fineness modulus 3.05 and apparent density 2.62 g/cm3.

3)

Concrete Admixture

The concrete admixture used was entraining and water reducing admixture.

4)

Silica Fume

In this experiment, we used grade one silica fume with density 2.20 g/cm3 5)

Water

We used Normal running water.

2.4 Design of concrete Mix Proportion 1)

Calculation of strength of concrete

fcu ,0  fcu , k  1.645  2  1.645  4  31.58MPa in which

f cu ,0 is the trial-mix strength. f cu , k is the designed strength of the concrete.

 is the standard deviation of concrete strength.

2)

Calculation of Water-cement ratio（

W ） F C

W 1 1    0.53 31.58 F  C f cu ,0  0.52 B 0.48  48.0 Af ce

in which f ce is the actual measured compressive strength of cement after 28 days, if the value is not tested, it should be

calculated by this forma fce   c  f ce, g , where  c is the extra coefficient of cement, f ce , g is cement strength grade - 35 http://www.ivypub.org/cet

value (MPa);

A,B are the regression coefficients, when the aggregate is gravel taken as 0.48 and 0.52, when the aggregate is scree taken as 0.50 and 0.51.

As this experiment is for the cold regions, the maximum water-cement ratio should not exceed 0.50 (0.60 in concrete dam). To meet Specification for Hydraulic Concrete Construction (DL/T5144—2001), concrete water-cement ratio is taken 0.50 finally.

3)

the Amount of Water W

Ve  Va 350  20   202kg / m3 31.58 f      0.52  1  0.335  cu ,0  B  1  0.335  0.48  48.0   Af  ce 

in which Ve is the cement slurry volume, Va is the air volume of the cement mortar,they are generally taken350 and 20 in

HPC. Actual Water Content after Adding Concrete Admixture W '  W  (1  a%)  202  (1  17%)  167kg / m3

4)

the Amount of binding Material

1 C  F  mc  f  mw    334kg / m3   167  W 0.50   mf  mc  f  a%  334 10%  33.4kg / m3 5)

fine-to-coarse ratio sp 

Ves  Ve  Vw 450  350  167  100%   0.42 1000  Ve 1000  350

WenkeYang pointed out that in the modern concrete, fine-to-coarse ratio has no significant effect on the strength[1].

On this issue, academician Zhongwei Wu and professor Huizhen Lian co-authored high performance concrete[3] is considered that water-cement ratio of 0.53 to 0.55, the fine-to-coarse ratio from 34% to 46% have little effect on the strength, especially when the water-cement ratio is The maximum value. Accordingly, we adjust the fine-to-coarse ratio s p  0.36 .

6)

the Amount of Aggregate

ms  g  100  W  s  1000  Ves  Vw   g  100  167   2.62  1000  450  202   2.85  1791kg / m3

ms  SP  ms  g  0.36  1791  645kg / m3 mg  1  SP   ms  g  1  0.36 1791  1146kg / m3

in which

Ves is the cement mortar volume taken 450 in HPC, Vw is the water volume.

7)

adjusting

In terms of the durability adjusted the amount of cement. Keeping water cement ratio unchanged, reduced the amount of water and cement. Repeated trial mixing and measured the slump about180mm at the same time, because concrete in this state have excellent concrete workability. Therefore, the preliminary mixing proportion binding Material to Sand to Gravel to water is 334:645:1146:167.

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On the basis of 0.50 as preliminary water-cement ratio, using 0.45, 0.50, 0.55 three water-cement ratio, then following the same steps to calculate the preliminary mixing proportion, we can determine 0.50 as the water-cement ratio after strength test finally

2.5 Experiment Plan This experiment took design strength of C25 as ascertaining the basic mix proportion, and fixed water-binder ratio as 0.50 and total binding materials as 334 kg, respectively, then we made 5 percents, 10 percents of Silica Fume equal replacement of cement. Totally, we got 3 groups of mixture ratio. Two parts of specimens were individually carried to test cubic compressive strength and freeze-thaw cycle. Specimen shape size: 150mm*150mm*150mm (cubic compressive strength) and 400mm*100mm*100mm (freezing-thawing cycle). Step one: mixed coarse aggregate and fine aggregate with force mixer; Step two: vibrated specimens with platform vibrator until specimens are formed; Step three: 24 hours later, demould specimens and took specimens by the way of natural cure in the standard curing room 28 days age. Step four: test specimens followed relevant codes or standards. Mix proportion and cubic compressive strength values are shown in Table 1. Test result for resistance of concrete to rapid freezing-thawing cycle is shown in Table 2.

Tab.1 Consumption of various materials in every stere (kg) and test result for compressive strength group

cement

S1 S2 S3

330.7 314.0 297.3

silica fume percent amount 0 0 5% 16.7 10% 33.4

sand

gravel

water

admixture

645 645 645

1146 1146 1146

167 167 167

3.3 3.3 3.3

strength 28d 36.1 37.2 39.7

Tab.2 Test result for resistance of concrete to rapid freezing-thawing cycle 0 Cycle times S1 S2 S3

50

100

150

200

250

300

m损

P

m损

P

m损

P

m损

P

m损

P

m损

P

m损

P

0 0 0

100.0 100.0 100.0

0 0 0

98.0 98.7 98.6

0 0 0

96.0 97.3 97.6

0 0 0

95.0 95.8 96.5

0 0 0

92.6 93.1 95

0 0 0

91.3 92.2 93.5

0 0 0

87.6 88.3 91.2

3 CONCLUSIONS 1) Aiming at improving the frost resistance of concrete, the result showed that overall calculation for mix proportion design method is scientific, reasonable, accurate with the advantages of the more accurate amount of materials, the better workability of concrete, the denser construction, the more sufficient assurance of strength and durability, etc.

2) Overall calculation has the problem of amount of binding materials and fine-to-coarse ratio comparatively bigger, so we should correct the Water Content and fine-to-coarse ratio to reduce project cost.

3) Using optimal mix proportion to test C25 hydraulic HPC, its strength met the design requirement, and the frost resistance increased.

Acknowledgment This research was supported by Research and Application demonstration for Increasing Life Technology of Hydraulic Structure Concrete. Ministry of Water Resources Public Welfare Project, Project Number: 201201040.

REFERENCES [1]

Wenke Yang. Problems and Research of Modern Concrete Science. Beijing: Tsinghua University press, 2012

[2]

Jiankui Chen, DongMin Wang. “a New Method of High Performance Concrete Mix Proportion Design—Overall Calculation.”

Journal of the Chinese Ceramic Society. 2000, 28(2): 194-198

[3]

Zhongwei Wu, Huizhen Lian. High Performance Concrete. Beijing: China Railway Publishing House,1999

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