Crack path and fracture surface modifications in cement composites

2015 ◽  
Author(s):  
Sajjad Ahmad ◽  
Jean Marc Tulliani ◽  
Giuseppe Andrea Ferro ◽  
Rao Arsalan Khushnood ◽  
Luciana Restuccia ◽  
...  
Keyword(s):  
Tensile Strength ◽  
High Performance ◽  
Cement Composite ◽  
Absorption Capacity ◽  
Cementitious Composites ◽  
Cement Composites ◽  
Stress Concentrations ◽  
Strength Capacity ◽  
Macro Scale ◽  
Applied Stresses

There is a tremendous increase in the use of high strength and high performance self-consolidating cementitious composites due to their superior workability and mechanical strengths. Cement composites are quasi-brittle in nature and possess extremely low tensile strength as compared to their compressive strength. Due to the low tensile strength capacity, cracks develop in cementitious composites due to the drying shrinkage, plastic settlements and/or stress concentrations (due to external restrains and/or applied stresses) etc. These cracks developed at the nanoscale may grow rapidly due to the applied stresses and join together to form micro and macro cracks. The growth of cracks from nanoscale to micro and macro scale is very rapid and may lead to sudden failure of the cement composites. The present paper reports the modifications in the crack growth pattern of the high performance cement composites to achieve enhanced ductility and toughness. The objective was accomplished by the incorporation of the micro sized inert particulates in the cement composite matrix. The results indicate that the incorporation of micro sized inert particles acted as the obstacles in the growth of the cracks thus improving the ductility and the energy absorption capacity of the self-consolidating cementitious composites.

scholarly journals EXPERIENCE OF APPLICATION HIGH PERFORMANCE CEMENT COMPOSITES FOR CREATING DURABLE SCULPTURAL ELEMENTS

2017 ◽  
Vol 3 ◽  
pp. 286
Author(s):  
Genadijs Sahmenko ◽  
Sandis Aispurs ◽  
Aleksandrs Korjakins
Keyword(s):  
Water Absorption ◽  
High Performance ◽  
Cement Composite ◽  
Cement Composites ◽  
Freezing And Thawing ◽  
Initial Water ◽  
Good Potential ◽  
Freezing And Thawing Cycles ◽  
Material Ductility ◽  
And Control

Traditionally, sculptural and decorative elements of building facades are created from mortar mixes based on lime, gypsum or Portland cement. Generally these materials have porous and permeable structure, which determines their accelerated degradation, especially in the aggressive environment of modern cities. High performance cement composites (HPCC) have been considered for production and restoration of sculptural elements in historical buildings. For this purpose, fine-graded, multi-component and highly workable mixes were elaborated. Mix compositions were modified with micro-fillers, plasticizing and stabilizing admixtures, as well as fibers to improve material ductility and control shrinkage cracking. Basic mechanical properties and durability (such as water absorption, frost resistance) were determined and two types of HPCC were compared (>50 MPa: HPCC and >120 MPa: UHPCC). It has been confirmed that cement composite mixes are characterized by self-consolidating effect, high compressive strength, extremely high resistance versus freezing and thawing cycles and low water absorption. Surface quality was evaluated and initial water absorption (tube tests) were performed for laboratory samples and real sculptural elements after 5 years of exploitation. The results confirmed good potential for using HPCC for creating more attractive and durable architectural shapes and façade elements compared to elements made using traditional cement and lime mortar.

UHPC and FRC in Severe Environmental Conditions

2016 ◽  
Vol 711 ◽  
pp. 412-419 ◽  
Author(s):  
Stanislav Rehacek ◽  
Ivo Simunek ◽  
David Citek ◽  
Jiří Kolísko
Keyword(s):  
Environmental Conditions ◽  
Cement Composite ◽  
Joint Effect ◽  
Experimental Program ◽  
Cement Composites ◽  
Structure And Properties ◽  
Physical Chemical ◽  
Chemical Agents ◽  
Macro Scale ◽  
Scale Properties

Structure and properties of cement composite are time-varying characteristics, depending among others on environmental conditions. The key idea is a struggle for complex research of joint effect of physical, chemical and dynamic loads on the internal structure [1] of cement composite and understanding the correlation between changes in microstructure and macro-scale properties [2, 3]. During the experimental program, specimens will be exposed to combined influence of freeze-thaw cycles [4,5,6], aggressive chemical agents [7] and dynamic loading [8]. The aim is to create a theoretical basis for design of effective cement composites meant to be used in severe environmental conditions.

EFFECT OF RECYCLED MATERIALS ON THE TENSILE BEHAVIOR OF STEEL FIBER-REINFORCED CEMENT COMPOSITE

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Sun-Woo Kim ◽  
Wan-Shin Park ◽  
Young-Il Jang ◽  
Yi-Hyun Nam ◽  
Sun-Woong Kim ◽  
...  
Keyword(s):  
Tensile Strength ◽  
Fly Ash ◽  
Steel Fiber ◽  
Cement Composite ◽  
Fine Aggregate ◽  
Cement Composites ◽  
Fiber Reinforced ◽  
Direct Tension ◽  
Recycled Materials ◽  
Reinforced Cement

Conventional cement composite is generally produced with ordinary Portland cement (OPC) as a binder. However, during manufacturing the cement composite, large amount of carbon dioxide (CO2) are emitted. Therefore, fly ash is proposed to be replaced to OPC in order to reduce CO2 emission of cement composites. For reinforcing fibers, micro steel fibers were used. For investigating mechanical properties of steel fiber-reinforced cement composites (SFRCCs), direct tension tests were conducted. The test results showed that fly ash improves tensile strength and ductility of SFRCCs. However, tensile strength of the SFRCC decreased as replacement ratio of recycled fine aggregate increased. The use of recycled materials in FRCC helps to save natural resources and promote sustainability in civil engineering materials.

Cementitious Composites in Severe Environmental Conditions - Dynamic Loading

2015 ◽  
Vol 1124 ◽  
pp. 69-75
Author(s):  
Stanislav Rehacek ◽  
Ivo Simunek ◽  
David Citek ◽  
Jiri Kolisko
Keyword(s):  
Dynamic Loading ◽  
Environmental Conditions ◽  
Cement Composite ◽  
Joint Effect ◽  
Experimental Program ◽  
Cement Composites ◽  
Chemical Agents ◽  
Macro Scale ◽  
Load Tests ◽  
Scale Properties

Structure and properties of cement composite are time-varying characteristics, depending among others on environmental conditions. The key idea of the project is a struggle for complex research of joint effect of physical, chemical and dynamic loads on the internal structure [8] of cement composite and understanding the correlation between changes in microstructure and macro-scale properties [5]. During the experimental program, specimens will be exposed to combined influence of freeze-thaw cycles [9], aggressive chemical agents and dynamic loading [7]. The aim is to create a theoretical basis for design of effective cement composites meant to be used in severe environmental conditions. Results of first dynamic load tests carried out on prismatic specimens (100x100x400 mm) are presented in this paper. The results are supplemented by ultrasonic measurement.

scholarly journals Effect of Carbon Nanotube Size on Compressive Strengths of Nanotube Reinforced Cementitious Composites

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Tanvir Manzur ◽  
Nur Yazdani ◽  
Md. Abul Bashar Emon
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotube ◽  
High Performance ◽  
Construction Material ◽  
High Potential ◽  
Cement Matrix ◽  
Cementitious Composites ◽  
Cement Composites ◽  
Nanoscale Science ◽  
20 Nm

Application of nanoscale science to construction material has already begun. In recent times, various nanofibers have raised the interest of researchers due to their exceptional mechanical properties and high potential to be used as reinforcement within cement matrix. Carbon nanotube (CNT) is one of the most important areas of research in the field of nanotechnology. The size and exceptional mechanical properties of CNT show their high potential to be used to produce high performance next generation cementitious composites. In this study, an attempt has been made to investigate the effect of size of CNTs on compressive strengths of CNT reinforced cement composites. Seven different sizes of multiwalled nanotubes (MWNTs) were used to produce MWNT-cement composites. A trend was observed regarding the effect of nanotube size on compressive strength of composites in most cases. MWNT with outside diameter (OD) of 20 nm or less exhibited relatively better performance. Smaller MWNT can be distributed at much finer scale and consequently filling the nanopore space within the cement matrix more efficiently. This in turn resulted in stronger composites.

Experimental Study of Uniaxial Tensile of High Performance Ductile Engineered Cementitious Composites

2011 ◽  
Vol 255-260 ◽  
pp. 2444-2448
Author(s):  
Jia Liang Kou ◽  
Ming Ke Deng ◽  
Xing Wen Liang
Keyword(s):  
Tensile Strength ◽  
High Performance ◽  
Tensile Strain ◽  
Elasticity Modulus ◽  
Plain Concrete ◽  
Uniaxial Tensile ◽  
Cementitious Composites ◽  
Peak Strain ◽  
Stress Strain ◽  
Engineered Cementitious Composites

The tensile properties of high performance ductile engineered cementitious composites are tested through 60 specimens divided into 5 groups according to adding 5 various PVA fibres, the tensile strength, tensile elasticity modulus and the tensile pseudostrain-hardening stress-strain curves are obtained, the corresponding matrices are also tested for tension, the tensile strength relationships between different PVA fibres, and between tensile elasticity modulus and tensile strength are proposed according to the test results. In addition, multicracking can be see, and the ultimate tensile strain of partial high performance ductile engineered cementitious composites with filling different PVA fibres can reach to 3% which is 1000 times of the plain concrete. The influences of matrix and the different PVA fibres on ultimate tensile strain, peak stress and peak strain are analyzed by experimental data. At last, the tensile pseudostrain-hardening stress-strain curves are discussed, the experimental conclusions can provide a lot of experimental and theoretical bases for making the composites hold the high ductility consumption ability.

Experimental Analysis of Hydrothermal Curing Influence on Properties of Fiber-Cement Composite

2015 ◽  
Vol 732 ◽  
pp. 55-58 ◽  
Author(s):  
Ondřej Holčapek ◽  
Pavel Reiterman ◽  
Petr Konvalinka
Keyword(s):  
Tensile Strength ◽  
High Temperature ◽  
Cement Composite ◽  
Cement Composites ◽  
Research Activity ◽  
Temperature Resistance ◽  
Hydrothermal Curing ◽  
Aluminous Cement ◽  
Curing Condition ◽  
Strength In Bending

Special industrial application of fiber-cement composites is currently one important issue of concrete industry and research activity. The field of refractory and high-temperature resistance materials is very large and contains the cement composites too. Hydrothermal curing together with using aluminous cement with refractory basalt aggregates and fibers shows high potential for its applications in high temperature. These composite is characterized by compressive strength over 140 MPa and tensile strength in bending 12 MPa (investigated on specimens 40 x 40 x 160 mm). After exposure to temperature 1000 °C these parameters are 60 MPa in compression respective 6 MPa in bending. Achieved values are significantly higher than in the case of laboratory curing condition and there are suitable especially for prefabricated fire resistance cladding or other special application in the industry.

scholarly journals Flexural Behavior of High-Volume Steel Fiber Cementitious Composite Externally Reinforced with Basalt FRP Sheet

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Seungwon Kim ◽  
Cheolwoo Park
Keyword(s):  
High Performance ◽  
Volume Fraction ◽  
High Volume ◽  
Cement Composite ◽  
High Energy ◽  
Absorption Capacity ◽  
Flexural Behavior ◽  
Fiber Reinforced ◽  
Externally Bonded ◽  
Energy Absorbing

High-performance fiber-reinforced cementitious composites (HPFRCCs) are characterized by unique tensile strain hardening and multiple microcracking behaviors. The HPFRCC, which demonstrates remarkable properties such as strength, ductility, toughness, durability, stiffness, and thermal resistance, is a class of fiber cement composite with fine aggregates. It can withstand tensile stresses by forming distributed microcracks owing to the embedded fibers in the concrete, which improve the energy absorption capacity and apparent ductility. This high energy absorbing capacity can be enhanced further by an external stiff fiber-reinforced polymer (FRP). Basalt fabric is externally bonded as a sheet on concrete materials to enhance the durability and resistance to fire and other environmental attacks. This study investigates the flexural performance of an HPFRCC that is externally reinforced with multiple layers of basalt FRP. The HPFRCC considered in the study contains steel fibers at a volume fraction of 8%.

scholarly journals Effects of Supplementary Cementitious Materials and Curing Condition on Mechanical Properties of Ultra-High-Performance, Strain-Hardening Cementitious Composites

2021 ◽  
Vol 11 (5) ◽  
pp. 2394
Author(s):  
Min-Jae Kim ◽  
Booki Chun ◽  
Hong-Joon Choi ◽  
Wonsik Shin ◽  
Doo-Yeol Yoo
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Strain Hardening ◽  
High Performance ◽  
Tensile Behavior ◽  
Supplementary Cementitious Materials ◽  
Cementitious Composites ◽  
Cement Kiln ◽  
Strain Capacity ◽  
Test Result

This study investigated the influence of ordinary Portland cement (OPC) and reactive and non-reactive mineral additives on the characteristic microstructure and mechanical performance of ultra-high-performance, strain-hardening cementitious composites (UHP–SHCCs). Nine mixes of cementitious composites were considered composed of reactive and non-reactive materials, such as ground granulated blast furnace slag (GGBS), silica fume (SF), cement kiln dust (CKD), and silica flour. Compressive strength and direct tensile tests were performed on the nine mixes cured for 7 d and 28 d. The test result was analyzed based on microstructural inspections, including thermogravimetry and scanning electron microscopy. The test result and analysis showed that the microstructural property of the UHP–SHCC impacted the compressive strength and the tensile behavior and also influenced the fiber-matrix interaction. Although most of the 7 d cured specimens did not exhibit notable strain-hardening behaviors, the specimen containing the CKD exhibited a tensile strength of 11.6 MPa and a very high strain capacity of 7.5%. All the specimens with OPC, silica flour, GGBS, or SF exhibited considerably improved tensile behavior at 28 d. The specimen with only OPC as a binder could achieve the tensile strength of 11.6 MPa and strain capacity of 6.2%.

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