scholarly journals Silica Fume and Nanosilica Effects on Mechanical and Shrinkage Properties of Foam Concrete for Structural Application

2020 ◽  
Vol 2020 ◽  
pp. 1-10 ◽  
Author(s):  
Jianqing Gong ◽  
Lilin Zhu ◽  
Jiusu Li ◽  
Da Shi
Keyword(s):  
Electron Microscopy ◽  
Flexural Strength ◽  
Silica Fume ◽  
Autogenous Shrinkage ◽  
Foam Concrete ◽  
Ultrasonic Detection ◽  
Structural Application ◽  
Opposite Trend ◽  
Dry Shrinkage ◽  
Scanning Electron

Adding the appropriate amount of silica fume (SF) or nanosilica (NS) can improve the strength and reduce the shrinkage of foam concrete (FC), thereby widening its application. This paper reports on a study of FC mechanical and shrinkage properties when varying SF and NS proportions were used to replace cement. Scanning electron microscopy (SEM) and nonmetallic ultrasonic detection were employed to investigate the mechanism of strength changes. The result showed that when the SF and NS content was 15% and 4%, in the 28 days, the compressive strength of FC peaked at 32.8 MPa and 35.8 MPa, and the flexural strength maximized at 7.9 MPa and 9.1 MPa, respectively. The autogenous shrinkage reached the minimum value, separately, i.e., 741.2 × 10−6 and 797.1 × 10−6. The dry shrinkage value was the highest (862.5 × 10−6 and 1387.5 × 10−6). The results indicated that the compressive and flexural strength of FC first increased and then decreased as SF and NS content increased. Autogenous shrinkage first decreased and then increased with the increase of SF or NS content. An opposite trend of dry shrinkage could be observed. FC made with NS had higher shrinkage than it did with SF. The results also indicated that there was a correlation between microstructure and sound velocity in the presence of SF or NS.

Effect of Sintering Temperature on Microstructure and Mechanical Properties of Al2O3-TiC-ZrO2 Ceramic Composites

2012 ◽  
Vol 476-478 ◽  
pp. 1031-1035
Author(s):  
Wei Min Liu ◽  
Xing Ai ◽  
Jun Zhao ◽  
Yong Hui Zhou
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Fracture Toughness ◽  
Flexural Strength ◽  
Relative Density ◽  
Sintering Temperature ◽  
Ceramic Composites ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Electron

Al2O3-TiC-ZrO2ceramic composites (ATZ) were fabricated by hot-pressed sintering. The phases and microstructure of the composites were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The relative density and mechanical properties (flexural strength, fracture toughness and Vicker’s hardness) of the composites were tested. The results show that the microstructure of the composites was the gray core-white rim. With the increase of sintering temperature, the relative density and mechanical properties of the composites increased first and then decreased. The composite sintered at 1705°C has the highest synthetical properties, and its relative density, flexural strength, fracture toughness and Vickers hardness are 98.3%,970MPa,6.0 MPa•m1/2and 20.5GPa, respectively.

Effect of BN Short Fiber Content on Mechanical Properties of ZrB2-SiC UHTCs

2012 ◽  
Vol 512-515 ◽  
pp. 706-709 ◽  
Author(s):  
Chang Ling Zhou ◽  
Yan Yan Wang ◽  
Zhi Qiang Cheng ◽  
Chong Hai Wang ◽  
Rui Xiang Liu
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Fracture Toughness ◽  
Scanning Electron Microscopy ◽  
Flexural Strength ◽  
Hot Pressing ◽  
Ceramic Composites ◽  
Short Fiber ◽  
Hot Pressing Sintering ◽  
Scanning Electron

ZrB2-20%volSiC ceramic composites with different volume of BN short fiber were fabricated by the hot-pressing sintering under 2000°C. The content of BN short fiber changed from 0 to 15vol%. The density, flexural strength, fracture toughness and thermal expansions coefficient were studied. The microstructures of the samples were observed by scanning electron microscopy. The results show that the introducing of BN short fiber into the ZrB2-20%volSiC lead to a serious of change to the mechanical properties of the ceramic. When the content of the BN short fiber is 10vol%, the flexural strength and fracture toughness reach 422.1MPa and 6.15 MPa•m 1/2 respectively. And the mechanism of the increasing toughness was studied.

scholarly journals Synthesis of Pectiniform Polyurethane-Modified Polycarboxylate and Its Preliminary Application in Ultrahigh-Performance Concrete

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Shuncheng Xiang ◽  
Yingli Gao
Keyword(s):  
Silica Fume ◽  
Negative Impact ◽  
Raw Materials ◽  
Synthesis Method ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Isophorone Diisocyanate ◽  
Initiation System ◽  
Dry Shrinkage ◽  
Preliminary Application

In this paper, modified polyurethane prepolymer was synthesized by the segmental synthesis method using isophorone diisocyanate (IPDI), hydroxyl-terminated silicone, and polyether glycol dimethylolpropionic acid as raw materials. After that, pectiniform polycarboxylate, of which side chains were in roughly the same polymerization degree and main chains were in different lengths, was synthesized at normal temperature in the complex initiation system of H2O2, APS, sodium bisulfite, and Vc. Then, compared with commercial Sika polycarboxylate, their applications in ultrahigh-performance concrete (HUPC), including flowability, strength, drying shrinkage, and autogenous shrinkage, were investigated. The results showed that, due to the molecular structure of polyorganosiloxane, the synthesized polycarboxylate could be better dispersed. Dosage of silica fume could effectively improve the compressive strength of UHPC, while slag had a certain negative impact on its strength. Incorporation of slag and silica fume could effectively reduce the dry shrinkage of UHPC.

scholarly journals Influence of Coarse Aggregates and Silica Fume on the Mechanical Properties, Durability, and Microstructure of Concrete

Materials ◽  
2019 ◽  
Vol 12 (20) ◽  
pp. 3324 ◽  
Author(s):  
Seong Soo Kim ◽  
Abdul Qudoos ◽  
Sadam Hussain Jakhrani ◽  
Jeong Bae Lee ◽  
Hong Gi Kim
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Silica Fume ◽  
Mercury Intrusion Porosimetry ◽  
Construction Material ◽  
Chloride Penetration ◽  
Mercury Intrusion ◽  
Coarse Aggregates ◽  
Overall Performance ◽  
Scanning Electron

Globally, concrete is the most widely used construction material. The composition of concrete plays an important role in controlling its overall performance. Concrete is composed of approximately 70%–80% aggregates, by volume. Therefore, it is mandatory to investigate the effect of aggregates on the performance of concrete. For this purpose, this study investigated the effect of three different coarse aggregates on the mechanical properties, durability, and microstructure of concrete. Concrete specimens were made using aggregates obtained from three regions with different mineralogies. The specimens were also made by replacing cement with silica fume. The specimens were analyzed in terms of compressive, flexural, and splitting tensile strengths, chloride penetration, carbonation, mercury intrusion porosimetry, and scanning electron microscopy. The results demonstrate that the specimens made with rougher coarse aggregates and silica fume had enhanced performance in comparison to those made with smoother aggregates.

scholarly journals Properties of Luffa Fiber Reinforced PHBV Biodegradable Composites

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1765 ◽  
Author(s):  
Yong Guo ◽  
Li Wang ◽  
Yuxia Chen ◽  
Panpan Luo ◽  
Tong Chen
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Flexural Strength ◽  
Room Temperature ◽  
Moisture Resistance ◽  
Hot Press ◽  
Biodegradable Composites ◽  
Hot Press Forming ◽  
Pre Treatment ◽  
Scanning Electron

In this study, composites of poly (hydroxybutyrate-co-valerate) (PHBV) with untreated luffa fibers (ULF) and NaOH-H2O2 treated luffa fibers (TLF) were prepared by hot press forming. The properties of luffa fibers (LFs) and composites were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and other analysis methods. Results showed that pre-treatment effectively removed pectin, hemicellulose, and lignin, thus reducing the moisture absorptivity of LFs. The flexural strength of TLF/PHBV was higher than that of ULF/PHBV. With 60% LF content, the flexural strengths of ULF/PHBV and TLF/PHBV reached 75.23 MPa and 90.73 MPa, respectively, 219.7% and 285.6% more than that of pure PHBV. Water absorptivities of composites increased with increase in LF content. Water absorptivity of TLF/PHBV was lower than that of ULF/PHBV. The flexural strengths of composites decreased after immersion in water at room temperature. Meanwhile, flexural strength of TLF/PHBV was lower than that of ULF/PHBV. Pretreatment of LFs effectively improved the bonding between fibers and PHBV, resulting in enhanced and thus improved the moisture resistance of composites.

Pore Structure and Microstructure of Foam Concrete

2010 ◽  
Vol 177 ◽  
pp. 530-532 ◽  
Author(s):  
Xin Gang Yu ◽  
Shi Song Luo ◽  
Yan Na Gao ◽  
Hong Fei Wang ◽  
Yue Xiang Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Image Analysis ◽  
Light Microscopy ◽  
Pore Structure ◽  
Digital Image ◽  
Digital Image Analysis ◽  
Foam Concrete ◽  
Structure And Microstructure ◽  
Scanning Electron

The pore structure and microstructure of the foam concrete was analyzed by scanning electron microscopy and light microscopy combined with digital image analysis. The results show that: (1) even-distributed fine and close pores resulting in high strength and low permeability; (2) uneven-distributed large size pores and open pores lead to low strength and high permeability; (3) light microscopy combined with digital image analysis is a cheap and convenient tool fitting for the pore structure analysis of the foam concrete; (4) scanning electron microscopy is very appropriate for the pore structure and microstructure analysis of the foam concrete.

Synthesis of Ca(OH)2 Nanoparticles Aqueous Suspensions and Interaction with Silica Fume

2012 ◽  
Vol 629 ◽  
pp. 482-487 ◽  
Author(s):  
V. Daniele ◽  
G. Taglieri ◽  
A. Gregori
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Silica Fume ◽  
Calcium Silicate Hydrate ◽  
Thermal Analyses ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrate Phase ◽  
Work Interaction ◽  
Scanning Electron

In this work, interaction at ambient temperature between silica fume and artificially produced Ca(OH)2 nanoparticles by two different methods was analyzed. Initial products and formed hydrated phases were characterized by several investigations including X-ray diffraction, thermal analyses, transmission and scanning electron microscopy. Synthesized Ca(OH)2 nanoparticles appeared regularly shaped and hexagonally plated, with side dimensions from 200nm to less than 20nm. Characterization analyses showed that, by reducing particles dimensions, calcium silicate hydrate phase formation was evident already after 7 day of hydration and a nearly complete consuming of free Ca(OH)2 after 28 days was observed. Besides, formed hydrate phases showed a highly wrinkled layer with marked crumple and rough-edge surfaces.

Influence of Foaming Agent on Properties of Red Mud Lightweight Baking-Free Brick

2014 ◽  
Vol 541-542 ◽  
pp. 388-391
Author(s):  
Long Ma ◽  
Guo Zhong Li
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Compressive Strength ◽  
Fly Ash ◽  
Flexural Strength ◽  
Red Mud ◽  
Micro Structure ◽  
Foaming Agent ◽  
Scanning Electron

Red mud lightweight baking-free brick was prepared by red mud, fly ash and cement, mixed with a certain amount of activator agent and foaming agent. The influence of foaming agent on properties of red mud lightweight baking-free brick was studied. The micro-structure of red mud lightweight baking-free brick was characterized by scanning electron microscopy (SEM). The results show that when the foaming agent content is 10ml, the sample with better performance obtained and the density is 423kg/m3, flexural strength is 0.49MPa and compressive strength is 1.87MPa.

Influence of Sodium Hydroxide on the Properties of FGD Gypsum-Slag Composite Materials

2014 ◽  
Vol 675-677 ◽  
pp. 750-755
Author(s):  
Fang Huang ◽  
Bao Long Jiao ◽  
Dong Dong Wang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Composite Materials ◽  
Flexural Strength ◽  
Sodium Hydroxide ◽  
Setting Time ◽  
Maximal Strength ◽  
Action Mechanism ◽  
Fgd Gypsum ◽  
Scanning Electron

By examining the compressive and flexural strength of composite and using scanning electron microscopy (SEM), we analyzed the influence of sodium hydroxide on the properties of FGD gypsum and slag composite materials and discussed the influence of sodium hydroxide on the setting time and mechanical strength of the composite materials and presented the action mechanism of sodium hydroxide as a stimulator. The results show that when the content of sodium hydroxide was percent of 0.25, the maximal strength of FGD gypsum-slag composite materials was reached.

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