A Study of Piezoresistivity of Graphite Cement Mortar Specimen Embedded Double Electrodes by a Series Connected AC Circuit

2010 ◽  
Vol 143-144 ◽  
pp. 733-737
Author(s):  
Wei Min Gan ◽  
Zhang Guo Li ◽  
Xin Huang
Keyword(s):  
Cyclic Loading ◽  
Cement Mortar ◽  
Mortar Specimen ◽  
Relative Resistivity ◽  
Loading Methods

Cement mortar shows piezoresistivity after being mixed with small amount of graphite, thus the resistivity of the material will changed with stress. In this study, specimens embedded double electrodes which made of cement based material with small amount of graphite (3 wt.% of cement) are used in the experiments of one-time loading and cyclic loading, and the relative resistivity are measured by a series connected AC circuit. The results show that the specimens’ piezoresistivity goes down while the stress increases, and different curves of piezoresistivity can be observed in experiments with different loading methods. The relative resistivities of the specimen show a similar change as strain.

Mechanical Strength and Resistance to Ultraviolet Radiation of Repairing Mortars Based on Epoxy Resin

2011 ◽  
Vol 391-392 ◽  
pp. 807-811
Author(s):  
Fang Liu ◽  
Zhi Bin Zhang ◽  
Ling Ling Xu ◽  
Ming Shu Tang
Keyword(s):  
Compressive Strength ◽  
Bond Strength ◽  
Epoxy Resin ◽  
Cement Mortar ◽  
Light Radiation ◽  
Mortar Specimen ◽  
High Durability ◽  
High Bond ◽  
High Bond Strength ◽  
Peak Value

The epoxy resin based repairing material(REM) is suitable for repairing cracks and holes in concrete or broken concrete due to its high bond strength and high durability. The compressive strength and flexile strength are 76.4MPa and ＞12.5MPa at 28d, and the retest strength still remain 73.4MPa and ＞12.5MPa respectively. The fracture location of cement mortar specimen bonded by RME is at cement mortar, that is, the bond strength between REM and cement mortar is more than mortar itself. The compressive strength of RME keeps 93.3% under ultraviolet light radiation (Peak Value 308nm, 49.5 W/m2) for 1700h.

scholarly journals Effect of Graphene Oxide/Graphene Hybrid on Mechanical Properties of Cement Mortar and Mechanism Investigation

Nanomaterials ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 113 ◽  
Author(s):  
Hongfang Sun ◽  
Li Ling ◽  
Zhili Ren ◽  
Shazim Ali Memon ◽  
Feng Xing
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Graphene Oxide ◽  
Flexural Strength ◽  
Pore Size Distribution ◽  
Cement Mortar ◽  
Underlying Mechanism ◽  
Mortar Specimen ◽  
Degree Of Hydration ◽  
Cement Mortars

This paper evaluated the effect of graphene oxide/graphene (GO/GR) hybrid on mechanical properties of cement mortar. The underlying mechanism was also investigated. In the GO/GR hybrid, GO was expected to act as a dispersant for GR while GR was used as reinforcement in mortar due to its excellent mechanical properties. For the mortar specimen, flexural and compressive strength were measured at varied GO to GR ratios of 1:0, 3:1, 1:1, 1:3, and 0:1 by keeping the total amount of GO and GR constant. The underlying mechanism was investigated through the dispersibility of GR, heat releasing characteristics during hydration, and porosity of mortar. The results showed that GO/GR hybrid significantly enhanced the flexural and compressive strength of cement mortars. The flexural strength reached maximum at GO:GR = 1:1, where the enhancement level was up to 23.04% (28 days) when compared to mortar prepared with only GO, and up to 15.63% (7 days) when compared to mortar prepared with only GR. In terms of compressive strength, the enhancement level for GO:GR = 3:1 was up to 21.10% (3 days) when compared with that of mortar incorporating GO only. The enhancement in compressive strength with mortar at GO:GR = 1:1 was up to 14.69% (7-day) when compared with mortar incorporating GR only. In addition to dispersibility, the compressive strength was also influenced by other factors, such as the degree of hydration, porosity, and pore size distribution of mortar, which made the mortars perform best at different ages.

A Comparison of Plates With and Without Locking Screws in a Calcaneal Fracture Model

2005 ◽  
Vol 26 (4) ◽  
pp. 309-319 ◽  
Author(s):  
Martinus Richter ◽  
Thomas Gosling ◽  
Stefan Zech ◽  
Mohamad Allami ◽  
Jens Geerling ◽  
...  
Keyword(s):  
Cyclic Loading ◽  
Calcaneal Fracture ◽  
Biomechanical Study ◽  
Fracture Model ◽  
Calcaneal Fractures ◽  
Mean Values ◽  
Loading Direction ◽  
Load To Failure ◽  
Loading Methods ◽  
The Stability

Background: We compared different plates in an experimental calcaneal fracture model under biocompatible loading. Methods: Four plates were tested: a plate without locked screws (Synthes), and three different plates with locked screws (Newdeal, Darco, Synthes). Synthetic calcanei (Sawbone) were osteotomized to create a fracture model, and the plates were fixed onto them. Seven specimens for each plate model were subjected to cyclic loading (preload 20 N, 1,000 cycles with 800 N, 0.75 mm/s), and load to failure (0.75 mm/s). Motion, forces, plastic deformation of the plate, and consequent depression of the posterior joint facet were analyzed. Results: During cyclic loading, all plates with locked screws showed statistically significant lower displacement in the primary loading direction than the plates without locked screws. Mean values (mm) of maximal displacements for each plate during cyclic loading were as follows: Synthes, 3.5; Darco, 4.5; Newdeal, 5.0; Synthes without locked screws, 7.5; ( p < 0.001). No statistically significant differences between the plates were found in relation to loads to failure and corresponding displacement. Conclusion: This is the first biomechanical study to assess the stability of different plates currently in use in our practice for the fixation of calcaneal fractures. Our results showed that plates with locked screws provided greater stability during cyclic loading than the plate without locked screws.

scholarly journals Size Effect of Concrete Specimens on the Acoustic Emission Characteristics under Uniaxial Compression Conditions

2017 ◽  
Vol 2017 ◽  
pp. 1-12
Author(s):  
Jianbo Wu ◽  
Enyuan Wang ◽  
Xuekun Ren ◽  
Mingwei Zhang
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Uniaxial Compression ◽  
Stress Level ◽  
Peak Stress ◽  
Deformation And Failure ◽  
Nonlinear Growth ◽  
Concrete Materials ◽  
Felicity Ratio ◽  
Loading Methods

Acoustic emission (AE) experiments under uniaxial compression and cyclic loading-unloading compression conditions were performed using different sizes of cubic concrete specimens. The influences of the loading methods and the concrete sizes on the mechanical parameters and the concrete AE activities were analyzed. The loading method was found to have great impact on the deformation, failure, and energy dissipation of concrete materials. With the increase of the material size, the uniaxial compressive strength of the concrete specimens gradually decreased, while the corresponding strain of peak strength increased first and then decreased. The elasticity modulus fluctuated irregularly. Under the uniaxial compression conditions, five AE patterns corresponding to the deformation and failure of the concrete materials were observed. A significant nonlinear relationship was found between the AE and the stress level. The cumulative AE rings at the peak stress showed nonlinear growth with the increase of the concrete size. Based on an established relationship between the cumulative AE rings and the stress level, the necessary conditions for the existence of the quiet AE period were given. Under the uniaxial cyclic loading-unloading compression conditions, the Felicity ratio decreased first and then increased as the stress increased. The research results have some guiding significance to AE-based monitoring of internal stress evolution of coal, rock, and concrete materials and thereby enable assessment of their stability.

Mechanical Strength and Microstructure Analysis of Cementitious Wheat Straw Composite

2013 ◽  
Vol 357-360 ◽  
pp. 766-772
Author(s):  
Lin Zhang ◽  
Fu Sheng Liu ◽  
Ji Yong Song ◽  
Yan Bin Zhang ◽  
Gang Gang Dong
Keyword(s):  
Mechanical Strength ◽  
Wheat Straw ◽  
Thermal Insulation ◽  
Bending Strength ◽  
Cement Mortar ◽  
Alkali Treatment ◽  
Sem Images ◽  
Mortar Specimen ◽  
Increased Strength ◽  
Straw Composite

Wheat straw alkali treatment has impacts on the strength of cement mortar and glazed hollow beads insulation mortar. The results show that the bending strength and bending strength of cement mortar specimen with 4% wheat straw are respectively 58.3% and 40.9% of the benchmark specimen, but bending-press ratio of the latter is 1.42 times of the former. The SEM images reflect the straws influences on the cement hydrate morphology, status and the influence of the number on cement mortar and glazed hollow beads insulation mortar. Compared with the latter, the former C-S-H gel is loose fibrous, failure to form a good network. In the thermal insulation mortar consistency and stratification of the same circumstances, with straw dosage increased, strength first increases, then declining. And folding pressure than in straw dosage is less than 24% more ideal. The SEM pictures show that network C-S-H gel decrease and loose fibrous C-S-H gel increased. At the same time, AFt gradually become attenuate and curly.

scholarly journals Influence of Plantain Pseudostem Fibres and Lime on the Properties of Cement Mortar

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Humphrey Danso
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Linear Correlation ◽  
Calcium Silicate Hydrate ◽  
Cement Mortar ◽  
Sem Analysis ◽  
Mortar Specimen ◽  
Eds Analysis ◽  
Positive Linear Correlation ◽  
Strength Improvement

This study investigated the properties of cement mortar with lime reinforced with plantain pseudostem fibres. Experimental specimens with 0, 0.25, 0.5, 0.75, and 1% fibre contents by weight of sand and 10% lime content by weight of cement were prepared and tested on 7, 14, 21, and 28 days of curing for density, tensile strength, compressive strength, SEM, and EDS. The 0.25% plantain pseudostem fibre reinforced mortar achieved 23.4% compressive strength improvement over unreinforced mortar specimens. There was between 6.89 and 13.80% increase in tensile strength of the plantain pseudostem fibre reinforced mortar over the unreinforced mortar specimens. A positive linear correlation was found between the compressive strength and tensile strength of cement mortar reinforced with plantain pseudostem fibres and lime with coefficient of determinant (R2) values between 0.909 and 0.869. It was also observed that the plantain pseudostem fibre reinforced mortar specimen had some microcracks and voids from the SEM analysis. Furthermore, EDS analysis showed the presence of calcium silicate hydrate with a Ca/Si ratio of between 1.02 and 2.49, and Al/Si ratio of between 0.76 and 0.81 as the main oxide. It therefore concluded that the incorporation of plantain pseudostem fibre and lime positively influenced the properties of the cement mortar with the 0.25% fibre content being recommended for construction application.

scholarly journals Interaction Analysis of Collinear Two Cracks with Unequal Length under Uniaxial Traction

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Bin Yu ◽  
Jingyi Xi ◽  
Zhonghui Chen ◽  
Lingfan Zhang
Keyword(s):  
Numerical Analysis ◽  
Compression Test ◽  
Cement Mortar ◽  
Interaction Analysis ◽  
Key Factors ◽  
Intensity Factors ◽  
Collinear Cracks ◽  
Mortar Specimen ◽  
Large Crack ◽  
Unequal Length

The interaction among different sizes of cracks in materials is one of the key factors leading to the damage of brittle materials. Based on the Kachanov method, the expressions for the stress intensity factors of two collinear cracks with unequal length were obtained and the interaction effect was analyzed. A compression test of a cement mortar specimen containing two cracks and numerical analysis using RFPA2D were performed. The results indicate that the crack interaction can almost be neglected when the crack distance reaches the length of the large crack; the two respective collinear cracks in the specimen grow and do not affect each other when the crack distance reaches the large crack length. The results of compression test and numerical analysis are both in agreement with the theoretical result.

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