scholarly journals Autogenous Shrinkage, Microstructure, and Strength of Ultra-High Performance Concrete Incorporating Carbon Nanofibers

Materials ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 320 ◽  
Author(s):  
Jacob Lim ◽  
Sudharshan Raman ◽  
Md. Safiuddin ◽  
Muhammad Zain ◽  
Roszilah Hamid
Keyword(s):  
Compressive Strength ◽  
Carbon Nanofibers ◽  
Packing Density ◽  
High Performance ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Mix Design ◽  
Ultra High Performance Concrete ◽  
Dense Microstructure ◽  
Entrapped Air

The mix design of ultra-high performance concrete (UHPC) is complicated by the presence of many “ingredients.” The fundamental packing density allows a simpler mix design with fewer ingredients to achieve optimum packing density and dense microstructure. The optimum particle grading increases the flowability of UHPC and eliminates entrapped air. This study presents a simplified particle grading design approach that positively influences the strength, autogenous shrinkage, and microstructure characteristics of UHPC. Carbon nanofibers (CNFs) of superior mechanical properties were added to enhance the strength of UHPC and to reduce its autogenous shrinkage. In addition, ground granulated blast-furnace slag (GGBS) was used as a cement replacement material to reduce the amount of cement in UHPC mixes. Test results showed that the presence of homogeneously dispersed CNF increased the compressive strength and compensated the autogenous shrinkage of UHPC. The findings indicated that an ideal particle distribution, which is close to the modified Andreasen and Andersen grading model, contributed to achieving high compressive strength and CNFs were capable of providing nano-bridges to compensate the shrinkage caused by GGBS.

Mechanical Properties and Durability of Ultra-High Performance Concrete Incorporating Coarse Aggregate

2014 ◽  
Vol 629-630 ◽  
pp. 96-103 ◽  
Author(s):  
Juan Yang ◽  
Gai Fei Peng ◽  
Yu Xin Gao ◽  
Hui Zhang
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Coarse Aggregate ◽  
High Performance Concrete ◽  
Fresh Concrete ◽  
Raw Materials ◽  
Autogenous Shrinkage ◽  
Mineral Admixtures ◽  
Ultra High Performance Concrete ◽  
Spalling Failure

Ultra-high performance concrete (UHPC) incorporating coarse aggregate was prepared with common raw materials. Fresh concrete had excellent good workability with slump of 265 mm and slump spread of 673 mm. Compressive strength of UHPC at 56 d reached 150 MPa. However, UHPC exhibited high brittleness in terms of spalling failure which occurred during compression loading.The ratio of splitting tensile strength to compressive strength of about 1/18 and the ratio of flexural strength to compressive strength of about 1/14 at 56 d were also associated with the brittleness of UHPC in this research. Mineral admixtures and fluidity of fresh concrete influenced compressive strength of UHPC significantly. Moreover, UHPC had excellent permeation-related durability but considerable shrinkage. Autogenous shrinkage of UHPC was less than half of free shrinkage, for which the reason is unknown and needs further research.

scholarly journals Mechanical Performance and Microstructure of Ultra-High-Performance Concrete Modified by Calcium Sulfoaluminate Cement

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Meimei Song ◽  
Chuanlin Wang ◽  
Ying Cui ◽  
Qiu Li ◽  
Zhiyang Gao
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Mechanical Performance ◽  
High Performance Concrete ◽  
Autogenous Shrinkage ◽  
Ultra High Performance Concrete ◽  
Maximum Heat ◽  
Degree Of Hydration ◽  
Calcium Sulfoaluminate ◽  
Shrinkage Property

High autogenous shrinkage property is one of the disadvantages of ultra-high-performance concrete (UHPC), which may induce early age cracking and threaten the safety of concrete structure. In the present study, different dosages of calcium sulfoaluminate (CSA) cement were added in UHPC as an effective expansive binder. Hydration mechanism, autogenous shrinkage property, and compressive strength of UHPC were carried out to investigate the effect of CSA addition on the mechanical properties of UHPC. Scanning electron microscopy was also employed to characterize the intrinsic microstructural reasons relating to the changes in macroproperties. Based on the XRD diagram, increasing formation of ettringite and Ca(OH)2 can be found with increasing CSA content up to 15%. In the heat flow results of UHPC with 10% CSA addition, the maximum heat release increases to 2.6 mW/g, which is 8.3% higher than the reference UHPC, suggesting a higher degree of hydration with CSA addition. The results in autogenous shrinkage show that CSA expansion agent plays a significantly beneficial role in improving the autogenous shrinkage of UHPC. The corresponding autogenous shrinkage of UHPC is −59.66 μ ε , −131.11 μ ε , and −182.31 μ ε , respectively, at 7 d with 5%, 10%, and 15% addition, which is 108%, 117%, and 123% reduction compared to the reference specimen without CSA. In terms of compressive strength, UHPC with 5%, 10%, 15%, and 20% CSA addition has 10.5%, 17.4%, 30.2%, and 22.1% higher compressive strength than that for the reference UHPC at 28 d. Microstructural study shows that there is an extremely dense microstructure in both the bulk matrix and interfacial transition zone of UHPC with 10% CSA addition, which can be attributed to the higher autogenous shrinkage property and can therefore result in higher mechanical performance.

scholarly journals Mix design of high-volume fly ash ultra high performance concrete

2021 ◽  
Vol 15 (4) ◽  
pp. 197-208
Author(s):  
Nguyen Van Tuan ◽  
Pham Sy Dong ◽  
Le Trung Thanh ◽  
Nguyen Cong Thang ◽  
Yang Keun Hyeok
Keyword(s):  
Heat Treatment ◽  
Compressive Strength ◽  
Fly Ash ◽  
Co2 Emissions ◽  
High Performance ◽  
High Performance Concrete ◽  
High Volume ◽  
Mix Design ◽  
Ultra High Performance Concrete ◽  
High Volume Fly Ash

The addition of supplementary cementitious materials (SCMs) to replace cement, especially with a high volume (> 50%), is an effective way to reduce the environmental impact due to the CO2 emissions generated in the production of ultra-high performance concrete (UHPC). Unfortunately, no official guidelines of UHPC using a high volume of SCMs have been published up to now. This paper proposes a new method of mix design for UHPC using high volume fly ash (HVFA), that is referred to the particle packing optimization of the Compressive Packing Model proposed by F. de Larrard. This proposed method also considers the heat treatment curing duration to maximize the compressive strength of HVFA UHPC. The experimental results using this proposed mix design method show that the optimum fly ash content of 50 wt.% of binder can be used to produce HVFA UHPC with a compressive strength of over 120 MPa and 150 MPa under standard curing and heat treatment, respectively. Moreover, the embodied CO2 emissions of UHPC reduces 56.4% with addition of 50% FA.

Study on compressive properties and chloride permeability of ultra-high-performance concrete

2021 ◽  
Vol 11 (6) ◽  
pp. 982-987
Author(s):  
Baolin Guo ◽  
Ruishuang Jiang ◽  
Baomin Wang ◽  
Shuai Liu ◽  
Yongzhi Guo
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
Steel Fiber ◽  
High Performance Concrete ◽  
Type A ◽  
Compressive Properties ◽  
Ultra High Performance Concrete ◽  
Chloride Permeability ◽  
Dense Microstructure ◽  
Heat Curing

In this work, two UHPC premixes were applied in investigating compressive strength and chloride permeability. Results indicated that the compressive strength of UHPC increased with content of steel fiber in standard curing. Compressive strength of type-A premix specimen with 2.0 vol% steel fiber was more than 150 MPa after heat curing. All UHPC in the experiment showed low chloride permeability under heat curing. Compared with type-B premix, the type-A premix had greater advantages in mechanical property and chloride permeability. In addition, the low porosity and dense microstructure of UHPC specimen were detected by mercury intrusion porosimetry (MIP) and scanning electron microscope (SEM), respectively. Furthermore, it was found that the introduction of fiber could refine the pore size distribution of specimen.

scholarly journals Effect of Pre-Wetted Zeolite Sands on the Autogenous Shrinkage and Strength of Ultra-High-Performance Concrete

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2356
Author(s):  
Guang-Zhu Zhang ◽  
Xiao-Yong Wang
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
Isothermal Calorimetry ◽  
Autogenous Shrinkage ◽  
Control Group ◽  
X Ray Diffraction ◽  
Ultra High Performance Concrete ◽  
Carrier Effect ◽  
Series Of Experiments

In this study, the carrier effect of zeolite sands in reducing the autogenous shrinkage and optimizing the microstructure of ultra-high-performance concrete (UHPC) is studied. Pre-wetted calcined zeolite sand (CZ), calcined at 500 °C for 30 min, and natural zeolite sand (NZ), with 15 wt.% and 30 wt.% in UHPC, are used to partially replace standard sands. On that basis, a series of experiments are executed on the developed UHPC, including compressive strength, autogenous shrinkage, X-ray diffraction (XRD), and isothermal calorimetry experiments. With the increase of the zeolite sand content, the autogenous shrinkage of UHPC decreases gradually. Moreover, when the added CZ content is 30 wt.% (CZ30 specimen), it is effective in reducing autogenous shrinkage. Meanwhile, at the age of 28 days, the compressive strength of CZ30 is 97% of the control group. In summary, it is possible to effectively reduce the autogenous shrinkage of UHPC containing 30 wt.% CZ, without sacrificing its mechanical properties.

scholarly journals Ultra-high-performance concrete with local high unburned carbon fly ash

DYNA ◽  
2021 ◽  
Vol 88 (216) ◽  
pp. 38-47
Author(s):  
Joaquín Abellán García ◽  
Nancy Torres Castellanos ◽  
Jaime Antonio Fernandez Gomez ◽  
Andres Mauricio Nuñez Lopez
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
High Performance ◽  
High Performance Concrete ◽  
Unburned Carbon ◽  
High Tech ◽  
Ultra High Performance Concrete ◽  
Conventional Concrete ◽  
The Cost

Ultra-high-performance concrete (UHPC) is a kind of high-tech cementitious material with superb mechanical and durability properties compared to other types of concrete. However, due to the high content of cement and silica fume used, the cost and environmental impact of UHPC is considerably higher than conventional concrete. For this reason, several efforts around the world have been made to develop UHPC with greener and less expensive local pozzolans. This study aimed to design and produce UHPC using local fly ash available in Colombia. A numerical optimization, based on Design of Experiments (DoE) and multi-objective criteria, was performed to obtain a mixture with the proper flow and highest compressive strength, while simultaneously having the minimum content of cement. The results showed that, despite the low quality of local fly ashes in Colombia, compressive strength values of 150 MPa without any heat treatment can be achieved.

scholarly journals Optimised Mix Design for Normal Strength and High Performance Concrete Using Particle Packing Method

2011 ◽  
Vol 57 (4) ◽  
pp. 357-371 ◽  
Author(s):  
S. Gopinath ◽  
A. Ramachandra Murthy ◽  
D. Ramya ◽  
Nagesh R. Iyer
Keyword(s):  
Compressive Strength ◽  
High Performance ◽  
High Performance Concrete ◽  
American Concrete Institute ◽  
Particle Packing ◽  
Mix Design ◽  
Concrete Compressive Strength ◽  
Normal Strength Concrete ◽  
Normal Strength ◽  
Packing Method

Abstract This paper presents the details of optimized mix design for normal strength and high performance concrete using particle packing method. A critical review of mix design methods have been carried out for normal strength concrete using American Concrete Institute (ACI) and Bureau of Indian Standards (BIS) methods highlighting the similarities and differences towards attaining a particular design compressive strength. Mix design for M30 and M40 grades of concrete have been carried out using ACI, BIS and particle packing methods. Optimization of concrete mix has been carried out by means of particle packing method using EMMA software, which employs modified Anderson curve to adjust the main proportions. Compressive strength is evaluated for the adjusted proportions and it is observed that the mixes designed by particle packing method estimates compressive strength closer to design compressive strength. Further, particle packing method has been employed to optimize the ingredients of high performance concrete and experiments have been carried out to check the design adequacy of the desired concrete compressive strength.

Optimized design of ultra-high performance concrete (UHPC) with a high wet packing density

2019 ◽  
Vol 126 ◽  
pp. 105921 ◽  
Author(s):  
Xinpeng Wang ◽  
Rui Yu ◽  
Qiulei Song ◽  
Zhonghe Shui ◽  
Zhen Liu ◽  
...  
Keyword(s):  
Packing Density ◽  
High Performance ◽  
High Performance Concrete ◽  
Optimized Design ◽  
Ultra High Performance Concrete

scholarly journals Mechanical Properties and Environmental Evaluation of Ultra-High-Performance Concrete with Aeolian Sand

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3148 ◽  
Author(s):  
Hongyan Chu ◽  
Fengjuan Wang ◽  
Liguo Wang ◽  
Taotao Feng ◽  
Danqian Wang
Keyword(s):  
Compressive Strength ◽  
Environmental Impact ◽  
Young’S Modulus ◽  
High Performance ◽  
High Performance Concrete ◽  
Young's Modulus ◽  
Ultra High Performance Concrete ◽  
Aeolian Sand ◽  
Binder Ratio ◽  
Water Binder Ratio

Ultra-high-performance concrete (UHPC) has received increasing attention in recent years due to its remarkable ductility, durability, and mechanical properties. However, the manufacture of UHPC can cause serious environmental issues. This work addresses the feasibility of using aeolian sand to produce UHPC, and the mix design, environmental impact, and mechanical characterization of UHPC are investigated. We designed the mix proportions of the UHPC according to the modified Andreasen and Andersen particle packing model. We studied the workability, microstructure, porosity, mechanical performance, and environmental impact of UHPC with three different water/binder ratios. The following findings were noted: (1) the compressive strength, flexural strength, and Young’s modulus of the designed UHPC samples were in the ranges of 163.9–207.0 MPa, 18.0–32.2 MPa, and 49.3–58.9 GPa, respectively; (2) the compressive strength, flexural strength, and Young’s modulus of the UHPC increased with a decrease in water/binder ratio and an increase in the steel fibre content; (3) the compressive strength–Young’s modulus correlation of the UHPC could be described by an exponential formula; (4) the environmental impact of UHPC can be improved by decreasing its water/binder ratio. These findings suggest that it is possible to use aeolian sand to manufacture UHPC, and this study promotes the application of aeolian sand for this purpose.

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