# Research on Fracture Toughness of C120 Ultra-High-Performance Concrete in Kingkey Financial Center Project

Authors: Hao-Wen Ye; Nai-Qian Feng; Zhi-Wei Ran; Li-Xun Lin; Yan Ling-Hu; Shi-Kun Qi; Yi Dong
Journal: Advances in Materials Science and Engineering
 (2012)

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## Abstract

By adding polypropylene fiber, fracture toughness of C120 ultra-high-performance concrete in Kingkey Financial Center project has been enhanced. The tests conducted by the Building Material Lab of the Civil and Water Conservancy Institute of Tsinghua University provided satisfactory results of mechanical property and fracture toughness of C120 ultra-high-performance concrete.


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## Body

## 1. Preface

In order to understand the mechanical property of C120 ultra-high-performance concrete under static modulus of elasticity and anticracking properties, including fracture toughness, the research group of C120 ultra-high-performance concrete conducted a series of tests in the Building Material Lab of the Civil Water Conservancy Institute of Tsinghua University.


## 2. Experimental Details

### 2.1. Raw Materials

Following raw materials are used in this research: (1) cement (Nanjing Xiaoyetian PII52.5), (2) microballoon (Made in Kunming), (3) ganister sand (from Zhunyi, Guizhou), (4) Fine aggregate (sea sand, desalted, FM2.6~2.8), (5) coarse aggregate (macadam, 5–10, 10–20 mm in diameter), (6)   Water reducer (BASF poly carboxylic acid, solid content: 40%, made in Guangdong), (7) water (Shenzhen tap water), and (8) polypropylene fiber (Grace 19 mm long fiber and short fiber provided by Shenzhen Lijian Concrete Company).


### 2.2. Mix Proportions

Please refer to Figure1. This test aims to see what the difference is in concrete with long fibers and short fibers, so the compositions of every group of test pieces are the same, except fiber types and quantities.Figure 1
Damaged C120 concrete.


### 2.3. Mixing Process

Get certain amount of raw materials ready. At first, put gelatinizer and sand into a mixer and run for 1 minute; then add water and additive, mix for 2 minutes; lastly, put in coarse aggregate, mix for 1 minute. For materials that are too sticky, mix 1 more minute after adding coarse aggregate. Find Mix Proportions in Table1.Table 1
Mix proportions.
No.W/BCSF+FA+BFSSG1G2Polycarboxylic acid additiveFibers10.175501507502856652.5%No fiber20.175501507502856652.5%Long fiber, 1 kg/m330.175501507502856652.5%Long fiber, 2 kg/m340.175501507502856652.5%Short fiber, 2 kg/m3


### 2.4. Specimens

Below specimens are used in the research:100 mm × 100 mm × 400 mm prisms (3),100 mm × 100 mm × 300 mm prisms (6),100 mm × 100 mm × 100 mm cubes (3).


### 2.5. Curing

Upon being demoulded, specimens were transferred to the caring unit and soaked into calcarea hydrica solution (lime water) for 28 days. Finished specimens were immediately sent to the Building Material Lab of the Civil Water Conservancy Institute of Tsinghua University.


## 2.1. Raw Materials

Following raw materials are used in this research: (1) cement (Nanjing Xiaoyetian PII52.5), (2) microballoon (Made in Kunming), (3) ganister sand (from Zhunyi, Guizhou), (4) Fine aggregate (sea sand, desalted, FM2.6~2.8), (5) coarse aggregate (macadam, 5–10, 10–20 mm in diameter), (6)   Water reducer (BASF poly carboxylic acid, solid content: 40%, made in Guangdong), (7) water (Shenzhen tap water), and (8) polypropylene fiber (Grace 19 mm long fiber and short fiber provided by Shenzhen Lijian Concrete Company).


## 2.2. Mix Proportions

Please refer to Figure1. This test aims to see what the difference is in concrete with long fibers and short fibers, so the compositions of every group of test pieces are the same, except fiber types and quantities.Figure 1
Damaged C120 concrete.


## 2.3. Mixing Process

Get certain amount of raw materials ready. At first, put gelatinizer and sand into a mixer and run for 1 minute; then add water and additive, mix for 2 minutes; lastly, put in coarse aggregate, mix for 1 minute. For materials that are too sticky, mix 1 more minute after adding coarse aggregate. Find Mix Proportions in Table1.Table 1
Mix proportions.
No.W/BCSF+FA+BFSSG1G2Polycarboxylic acid additiveFibers10.175501507502856652.5%No fiber20.175501507502856652.5%Long fiber, 1 kg/m330.175501507502856652.5%Long fiber, 2 kg/m340.175501507502856652.5%Short fiber, 2 kg/m3


## 2.4. Specimens

Below specimens are used in the research:100 mm × 100 mm × 400 mm prisms (3),100 mm × 100 mm × 300 mm prisms (6),100 mm × 100 mm × 100 mm cubes (3).


## 2.5. Curing

Upon being demoulded, specimens were transferred to the caring unit and soaked into calcarea hydrica solution (lime water) for 28 days. Finished specimens were immediately sent to the Building Material Lab of the Civil Water Conservancy Institute of Tsinghua University.


## 3. Main Mechanical Property Tests

Results of cube compression test, prismoid compression test, and static modulus of elasticity test have been listed in Figures1 and 2. Equipment used in the tests included YE-200A hydraulic pressure test machine, YJR-5 static digital strain gauging unit, and YEW-200A dropping electrode compression-testing machine (Tables 2 and 3).Table 2
Compressive strength test results of cube specimens.
No.AgeSizeIndividual valueCompression strength1: Initial28 days100 × 100 × 100 mm127.0 MPa124.0 MPa121.0 MPa124.0 MPa2: 1 kg long fiber28 days100 × 100×100 mm129.0 MPa124.7 MPa126.0 MPa119.0 MPa3: 2 kg long fiber28 days100 × 100 × 100 mm140.0 MPa135.3 MPa123.0 MPa141.0 MPa4: 2 kg short fiber28 days100 × 100 × 100 mm120.0 MPa118.0 MPa115.0 MPaTable 3
Results of compressive strength and static modulus of elasticity of prism specimens.
No.AgeSizeCompression strengthStatic modulus of elasticityIndividualAverageIndividualAverage1: Initial28天100 × 100 × 300115.2 MPa138.0 MPa5.20 × 104 MPa5.20 × 104 MPa138.0 MPa5.18 × 104 MPa138.8 MPa5.22 × 104 MPa2: 1 kg long fiber28天100 × 100 × 300127.2 MPa128.7 MPa5.10 × 104 MPa5.23 × 104 MPa126.8 MPa5.21 × 104 MPa132.0 MPa5.37 × 104 MPa3: 2 kg long fiber28天100 × 100 × 300137.2 MPa136.6 MPa5.22 × 104 MPa5.30 × 104 MPa139.0 MPa5.22 × 104 MPa133.6 MPa5.45 × 104 MPa4: 2 kg short fiber28天100 × 100 × 300104.8 MPa116.7 MPa5.18 × 104 MPa5.25 × 104 MPa116.4 MPa5.23 × 104 MPa128.8 MPa5.33 × 104 MPaFigure 2
C120 high-performance concrete fracture parameter test.


## 4. C120 Concrete Fracture Toughness Test

### 4.1. Equipment

Toni2071 Pressure Flexure Compression Testing Machine was made in Germany, Maximum Capacity 200 KN, for flexure and crack opening displacement tests under constant rate of loading or rate of displacement.


### 4.2. C120 Concrete Fracture Parameter Test

See Figures2 and 3.Figure 3
Crack opening displacement test.


### 4.3. P-CMOD andσ-w Curve Charts for 4 Types of Concrete

Through tests, we got the P-CMOD (loading—crack opening displacement) curve charts for basic concrete, concrete with 1 kg long fiber, concrete with 2 kg long fiber, and concrete with 2 kg short fiber, on which we came up with the O-W (softening relation) curve charts (Table4).Table 4
Concrete fracture parameter test results.
TypeNo.E(GPa)Pfc (N)Pmax (N)σc (MPa)σfc (MPa)σt (MPa)σf (MPa)Gf (J/m2)lch (cm)Basic151.9500014000127.06.826.869.07213.823.52460014500121.06.27—9.39——3470013800124.06.41—9.59——Avg.476714100124.06.506.869.35213.823.51 kg long fiber152.2480013800129.06.556.678.94291.833.82500015500126.06.827.0810.04302.927.93500015300119.26.82—9.91——Avg.493314867124.76.736.889.63297.3530.92 kg long fiber152.2480012000140.86.556.567.78322.839.22500015000123.66.82—9.73——3520014000141.47.097.229.08322.133.4Avg.500013667135.36.826.898.86322.536.32 Kg short fiber152.0510014000120.06.956.979.07300.330.02500014000115.06.826.849.07321.830.73520014000—7.09—9.07——Avg.510014000118.06.956.919.07311.130.4(Pfc = cracking load, Pmax = maximum load, E= modulus of elasticity, σc = compression strength, σfc = cracking strength, σt = tensile strength, σf = flexural strength, Gf = fracture energy, lch = brittleness; the smaller the lch is, the more brittle the concrete is)


## 4.1. Equipment

Toni2071 Pressure Flexure Compression Testing Machine was made in Germany, Maximum Capacity 200 KN, for flexure and crack opening displacement tests under constant rate of loading or rate of displacement.


## 4.2. C120 Concrete Fracture Parameter Test

See Figures2 and 3.Figure 3
Crack opening displacement test.


## 4.3. P-CMOD andσ-w Curve Charts for 4 Types of Concrete

Through tests, we got the P-CMOD (loading—crack opening displacement) curve charts for basic concrete, concrete with 1 kg long fiber, concrete with 2 kg long fiber, and concrete with 2 kg short fiber, on which we came up with the O-W (softening relation) curve charts (Table4).Table 4
Concrete fracture parameter test results.
TypeNo.E(GPa)Pfc (N)Pmax (N)σc (MPa)σfc (MPa)σt (MPa)σf (MPa)Gf (J/m2)lch (cm)Basic151.9500014000127.06.826.869.07213.823.52460014500121.06.27—9.39——3470013800124.06.41—9.59——Avg.476714100124.06.506.869.35213.823.51 kg long fiber152.2480013800129.06.556.678.94291.833.82500015500126.06.827.0810.04302.927.93500015300119.26.82—9.91——Avg.493314867124.76.736.889.63297.3530.92 kg long fiber152.2480012000140.86.556.567.78322.839.22500015000123.66.82—9.73——3520014000141.47.097.229.08322.133.4Avg.500013667135.36.826.898.86322.536.32 Kg short fiber152.0510014000120.06.956.979.07300.330.02500014000115.06.826.849.07321.830.73520014000—7.09—9.07——Avg.510014000118.06.956.919.07311.130.4(Pfc = cracking load, Pmax = maximum load, E= modulus of elasticity, σc = compression strength, σfc = cracking strength, σt = tensile strength, σf = flexural strength, Gf = fracture energy, lch = brittleness; the smaller the lch is, the more brittle the concrete is)


## 5. Analysis

(1)
From Figures4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15, we could tell that P-CMOD and O-W curves were similar for the same type of concrete, which meant test piece’s dispersion was not large.(2)
4 types of concrete were almost the same, except fiber content, which only presented difference after cracking. Therefore, the cracking load for all 4 types of concrete was similar.(3)
As fiber content increased, concrete’s tensile strength almost remained the same.(4)
As fiber content increased, concrete’s cracking energy mounted too. When the fiber content remained the same, fiber type played a role in cracking difference. Test results suggested that cracking energy rose in order of basic concrete < concrete with 1 kg long fiber < concrete with 2 kg long fiber < concrete with 2 kg short fiber.(5)
Characteristic length of brittleness “lch” notates the brittleness of concrete. The smaller the number is, the more brittle the concrete is. From the test results, we learnt that as fiber content increased, concrete’s toughness enhanced too. Characteristic length of brittleness varies in order: basic concrete < concrete with 1 kg long fiber < concrete with 2 kg short fiber < concrete with 2 kg long fiber, and toughness varies in order:basic concrete < concrete with 1 kg long fiber < concrete with 2 kg short fiber < concrete with 2 kg long fiber.Figure 4
P-CMOD for basic concrete.Figure 5
σ-w for basic concrete.Figure 6
P-CMOD for concrete with 1 kg long fiber.Figure 7
σ-w for concrete with 1 kg long fiber.Figure 8
P-CMOD for concrete with 2 kg long fiber.Figure 9
σ-w for concrete with 2 kg long fiber.Figure 10
P-CMOD for concrete with 2 kg short fiber.Figure 11
σ-w for concrete with 2 kg short fiber.Figure 12
Cracking strength comparison.Figure 13
Tensile strength comparison.Figure 14
Cracking energy comparison.Figure 15
Characteristic length comparison.


## 6. Conclusions

(1)
C120 ultra-high-performance concrete’s fracture toughness can be enhanced by adding fiber, and as fiber content increases, cracking energy mounts too. When fiber content stays the same, fiber type makes difference too.(2)
Characteristic length of brittleness notates the brittleness of concrete. The smaller the number is, the more brittle the concrete is. As fiber content increases, concrete’s toughness enhances too.



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*Source: 537432-2012-05-20.xml*