scholarly journals An Experimental Study on Mechanical Properties for the Static and Dynamic Compression of Concrete Eroded by Sulfate Solution

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5387
Author(s):  
Ao Yao ◽  
Jinyu Xu ◽  
Wei Xia
Keyword(s):  
Mechanical Properties ◽  
Longitudinal Wave ◽  
Energy Absorption ◽  
Wave Velocity ◽  
Concrete Structure ◽  
Mechanical Performance ◽  
Dynamic Compression ◽  
Sulfate Solution ◽  
Static Strength ◽  
Longitudinal Wave Velocity

The mechanical properties of the static and dynamic compression of concrete eroded by a 15% sodium sulfate solution were explored with a 70-mm-diameter true triaxial static-dynamic comprehensive loading test system, and an analysis of the weakening mechanisms for the degree of macroscopic damage and microscopic surface changes of eroded concrete were conducted in combination with damage testing based on relevant acoustic characteristics and SEM scanning. The experience obtained in this paper is used to analyze and solve the problem that the bearing capacity of concrete buildings is weakened due to the decrease in durability under the special conditions of sulfate erosion. The results showed that, in a short time, the properties of concrete corroded by sulfate solution were improved to a certain extent due to continuous hydration. When the corrosion time was prolonged, the internal concrete structure was destroyed after it was eroded by sulfate, and its dynamic and static strength, deformability, and energy absorption were reduced to differing degrees, thus greatly inhibiting the overall mechanical performance of concrete; the dynamic compressive strength changed with strain that exhibited a significant strain rate effect; and, under the influence of sulfate erosion and hydration, the longitudinal wave velocity increased first and then decreased. The longitudinal wave velocity was slower than that of concrete under normal environment and distilled water immersion condition. SEM and acoustic wave analysis indicated that the internal concrete structure was destroyed after it was eroded by sulfate, and its dynamic and static strength, deformability, and energy absorption were reduced to differing degrees, thus greatly inhibiting the overall mechanical performance of concrete.

scholarly journals Experimental Study on Physicochemical and Mechanical Properties of Mortar Subjected to Acid Corrosion

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Runke Huo ◽  
Shuguang Li ◽  
Yu Ding
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Longitudinal Wave ◽  
Uniaxial Compressive Strength ◽  
Wave Velocity ◽  
Chemical Reaction ◽  
Longitudinal Wave Velocity ◽  
Mortar Sample ◽  
Leading Role ◽  
Corrosion Time

The 28 days cured cement mortar samples were soaked in HCl (pH = 1 and 2) and H2O (pH = 7) solutions for 90 days. By monitoring the ion concentration of H+ and Ca2+ and measuring the changes in weight loss, longitudinal wave velocity, and uniaxial compressive strength values of the corroded mortar, the physicochemical and mechanical properties of the mortar specimens were studied. Experimental results indicate that the process of the mortar sample subjected to HCL erosion has apparent stage characteristics. In the initial stage of corrosion, the chemical reaction increased the porosity of the specimen, which leads to the decrease of longitudinal wave velocity of the samples. At the same time, the corrosion solution continuously penetrates into the mortar pore system, which leads to the increase of the mass, and it is considered that the diffusion process plays a leading role during this period. Moreover, the colloidal compounds generated by the chemical reaction can not only fill the pore space but also block the continuous reaction, which led to the increase of the longitudinal wave velocity of the specimen. With the prolonging of corrosion time and infiltration path, the pH value and the concentration of Ca2+ tend to be stable, the diffusion action is weakened, and the chemical reaction is continuous, which led to the decrease of the mass and wave velocity gradually. It is considered that the chemical reaction plays a leading role in this process. Based on the induction and analysis of the test results, a generalized porosity model regarding the increase of the porosity and the decrease of effective bearing area of the mortar sample was proposed. The relation between the uniaxial compressive strength and the corrosion time of the corroded mortar is deduced, and the unknown parameters are determined based on the regression analysis of the test data.

scholarly journals Dynamic Mechanical Properties and Energy Dissipation Analysis of Sandstone after High Temperature Cycling

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Qi Ping ◽  
Chuanliang Zhang ◽  
Hongjian Sun ◽  
Xu Han
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
High Temperature ◽  
Longitudinal Wave ◽  
Wave Velocity ◽  
Incident Energy ◽  
Temperature Cycling ◽  
Longitudinal Wave Velocity ◽  
Cycle Times ◽  
The Impact

In order to study the effect of high temperature cycling on the physical and mechanical properties of rock materials, a box-type resistance furnace was used to conduct high temperature cycling at 400°C 10 times on sandstone specimens in coal mine, and the impact compression tests under 8 loading rates were carried out using a split Hopkinson bar (SHPB) device. Results showed that, with the increase of cycle times, the gray white sandstone specimen gradually showed reddish brown spots, and the volume of specimen increased, while the mass, density, and longitudinal wave velocity decreased; in addition, the volume increase rate, the mass decrease rate, the density decrease rate, and the longitudinal wave velocity decreased rate with cycle times showed quadratic function relationship. The dynamic compressive stress-strain curve of sandstone specimens subjected to high temperature cyclic action under impact load was obviously different from that under normal temperature. The dynamic elastic modulus was obviously larger than that under static load. The failure mode of dynamic and static specimens showed brittleness and ductility characteristics, respectively. In the SHPB test, the impact pressure, reflected energy, transmitted energy, and absorbed energy of the rock specimen all increased linearly with the increase of incident energy. The dynamic compressive strength, elastic modulus, and strain rate of sandstone specimens were positively correlated with the incident energy, while the dynamic strain showed negative correlation.

Determining the Thermal Shock Elastic Behavior of Mullite Ceramic Regenerator Material by Ultrasonic Testing

2014 ◽  
Vol 633 ◽  
pp. 472-475 ◽  
Author(s):  
Tian Tian Sun ◽  
Yan Xia Wang ◽  
Hai Yun ◽  
Dong Huan Zhang ◽  
Qing Hui Shang
Keyword(s):  
Thermal Shock ◽  
Longitudinal Wave ◽  
Shear Wave ◽  
Wave Velocity ◽  
Temperature Difference ◽  
Shear Wave Velocity ◽  
Modulus Of Elasticity ◽  
Longitudinal Wave Velocity ◽  
Mullite Ceramic ◽  
Mullite Ceramics

Mullite material is a material commonly used in honeycomb regenerator, because in the process of using material under big temperature difference effect, so have a great demand for its thermal shock resistance. The used mullite ceramics were made by the direct solid phase sintering method, and the modulus of elasticity of the mullite ceramics measured by ultrasonic pulse-echo method in a thermal shock and thermal fatigue experiment, respectively. In the air-cooling condition, the study found the mullite ceramic without thermal shock that the longitudinal wave velocity and shear wave velocity respectively 3970(m/s) and 2492(m/s). After 45 times thermal shock of temperature difference of 800°C, longitudinal wave velocity and shear wave velocity decreased to 3910(m/s) and 2457(m/s), and the value of the modulus of elasticity changed 1020MPa. By observing the change of the elastic modulus value rule, can know the elastic deformation of thermal shock on the material performance of thermal shock damage. Moreover, the results can provide the data basis for the calculation of the residual strength and the numerical simulation of thermal stress.

scholarly journals Damage Constitutive Model and Mechanical Performance Deterioration of Concrete under Sulfate Environment

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Peng Liu ◽  
Ying Chen ◽  
Zhiwu Yu ◽  
Zhaohui Lu
Keyword(s):  
Mechanical Properties ◽  
Bearing Capacity ◽  
Elasticity Modulus ◽  
Mechanical Performance ◽  
Sulfate Solution ◽  
Concrete Surface ◽  
Ultimate Bearing Capacity ◽  
Stress Strain ◽  
Before And After ◽  
Relationship Model

The effects of erosion mode, erosion age, and concentration of sulfate solution on mechanical properties of concrete were investigated. The dimensionless relationship model of the stress-strain of concrete on the basis of randomness was proposed. The variation of the elasticity modulus and Poisson’s ratio of the concrete surface attacked by sulfate was studied, and a novel method of using a superficial parameter to characterize the performance change of the concrete surface was recommended. The results showed that the dimensionless relationship model of stress-strain of concrete could be used to represent the variations of mechanical properties of concrete. The differences of load-displacement of concrete before and after sulfate attack were reflected as the change of curve’s slope and ultimate bearing capacity, and the slope of a straight section of the lateral and longitudinal strain curves of concrete surface also varied. The increment rates of ultimate bearing capacity of concrete attacked by 1% and saturated sulfate solution were about 30% and 10%, respectively. However, the decreasing ratio of the ultimate bearing capacity of concrete attacked by saturated sulfate solution was approximately 25%. The damage factor of the elasticity modulus of the concrete surface of C20 and C40 was 0.185 and −0.19, respectively. The obtained results could provide a support for investigating the variations of stress-strain relationship and mechanical performance of concrete under a sulfate environment.

Ultrasonic Study on Crystal Orientation Effects Upon Point Defect Growth Caused by Cross Slip Under Plastic Deformation

2004 ◽  
Author(s):  
Michiaki Kobayashi
Keyword(s):  
Plastic Deformation ◽  
Longitudinal Wave ◽  
Wave Velocity ◽  
Crystal Orientation ◽  
Pure Shear ◽  
Cross Slip ◽  
Polished Surface ◽  
Longitudinal Wave Velocity ◽  
Velocity Change ◽  
Change Tendency

Concerned with the longitudinal wave velocity changes under plastic deformation in pure shear state, the experimental results of longitudinal wave velocity are categorized to two types: (i) simple decreasing change tendency at polished surface specimens, and (ii) chaotic change tendency at unpolished surface specimens. In the present paper, the effects of surface roughness and crystal orientation on the amount of cross slip under plastic deformation are studied via finite element polycrystal model (FEPM) from the viewpoint of longitudinal wave velocity change showing a sensitive response to the point defects caused by cross slip.

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