Static Modulus Of Elasticity Research Articles

Overburden 4D seismic analysis: Influence of stress and pore-pressure changes accounting for elastic contrast between a reservoir and its anisotropic surrounding rocks

Time-lapse (4D) seismic data analysis is widely used to monitor producing hydrocarbon or CO2 storage reservoirs and their surroundings. The influence of potentially significant undrained pore-pressure changes around depleting (or injected) reservoirs appears to be neglected in most previous studies. The 4D seismic response in the overburden depends on the stress changes and strains induced by the reservoir. These alterations may challenge stable infill drilling and well integrity. We have used anisotropic static elastic moduli from laboratory measurements for two different field shales to predict stress changes and strains in the surroundings of a depleting reservoir through geomechanical modeling. These mechanical changes are used to quantify undrained pore-pressure changes using anisotropic poroelastic theory constrained with Skempton parameters. Finally, an empirical rock-physics model quantifies the impact of these poroelastic changes on vertical velocity changes and time strains. This model explicitly quantifies the individual contributions to vertical velocity changes from undrained pore pressure, mean stress, and shear stress above (and below) the depleting reservoir. We find that a stiffer surrounding rock exhibits significantly larger vertical time strains and time shifts in the overburden as compared with softer surrounding rocks because of promoted arching. Undrained overburden pore-pressure changes significantly contribute to overburden velocity changes and time shifts. Ignoring anisotropy in the Skempton parameters can lead to overestimating the overburden undrained pore pressure and time shifts after reservoir depletion. The anisotropy in static stiffnesses significantly impacts the dynamic changes in the vertical direction, and the dynamic changes are particularly pronounced in the vicinity of the reservoir. We find how a tailored rock-physics model can link 4D seismic data and geomechanics to separate stress, strain, and pore-pressure changes — all essential for optimizing drilling and production.

Effect of Moisture Condition of Structural Lightweight Concretes on Specified Values of Static and Dynamic Modulus of Elasticity.

The dynamic modulus of elasticity (Ed), specified by ultrasonic pulse velocity measurements, is often used, especially for concrete built into construction, to estimate the static modulus of elasticity (Ec,s). However, the most commonly used Equations for such estimations do not take into account the influence of concrete moisture. The aim of this paper was to establish this influence for two series of structural lightweight aggregate concrete (LWAC) varying in their strength (40.2 and 54.3 MPa) and density (1690 and 1780 kg/m3). The effect of LWAC moisture content turned out to be much more pronounced in the case of dynamic modulus measurements than for static ones. The achieved results indicate that the moisture content of the concrete should be taken into consideration in modulus measurements as well as in Equations estimating Ec,s on the basis of Ed specified by the ultrasonic pulse velocity method. The static modulus of LWACs was lower on average by 11 and 24% in relation to dynamic modulus, respectively when measured in air-dried and water-saturated conditions. The influence of LWAC moisture content on the relationship between specified static and dynamic moduli was not affected by the type of tested lightweight concrete.

Mechanical Properties and Microstructure of Mechanical Sand Concrete at High Temperature based on Electron Microscopy

For sustainable development, sand-mixed concrete has been paid more and more attention by researchers. In order to study the mechanical properties of sand-gravel concrete, five temperature levels of natural cooling and water cooling were considered, and the mechanical properties of sand-stone concrete after high temperature were tested.. In order to study the mechanical properties of desert sand concrete after high temperature, this paper designs a single factor test with the replacement rate of desert sand as the variable. Five temperature levels are considered, and natural cooling and watering cooling are adopted to test the mechanical properties of desert sand concrete after high temperature. The influences of temperature, desert sand replacement rate, cooling method and fly ash content on compressive strength, axial compressive strength and static compressive elastic modulus of desert sand concrete after high temperature were analyzed, and the deterioration model of strength and elastic modulus of desert sand concrete after high temperature was established. From high temperature post-voltage voltage specimen sampling, X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) observation, from the micro level desert sand concrete after high temperature macro performance deterioration mechanism to explain.

Physical and mechanical characteristics of refractories for the vitrification furnace of highly active waste

The results of experimental measurements of mechanical and physical characteristics of refractory materials are presented: TCLE, thermal conductivity, heat capacity, dynamic and static modulus of elasticity. The study was carried out to select the material for the manufacture of the vault of a glass furnace for curing radioactive waste. It is shown that the materials of the MKRV-53 and AZS- 60SB brands are superior in their characteristics to the material of the BMKrF brand. The obtained results are used for mathematical modeling of the operating modes of the electric furnace arch. Ill. 3. Ref. 7. Tab. 7.

Density Estimation by Drilling Resistance Technique to Determine the Dynamic Modulus of Elasticity of Wooden Members in Historic Structures

(1) The assessment of the mechanical properties of old timber is essential for the proper maintenance of wooden structures. (2) Among the non-destructive properties, the dynamic modulus of elasticity is one of the best predictors of the mechanical characteristics of the members, but it requires the determination of wood density to be determined. (3) Thus, wood density was estimated by drilling resistance measurements, developing species-specific prediction equations for silver fir, chestnut and poplar. (4) The estimated density was combined with the stress wave velocity propagating longitudinally through the wooden piece, and the dynamic modulus of elasticity was calculated. (5) Medium-high coefficient determinations (R2 from 0.79 to 0.94) were found for density estimation, and medium coefficient determinations (R2 from 0.53 to 0.60) were found for the estimation of the static modulus of elasticity using the dynamic modulus.

Prediction of the static elastic modulus of limestone using downhole seismic test in Asmari formation

Prediction of the static elastic modulus of limestone using downhole seismic test in Asmari formation

High temperature behaviour of basalt fibre-steel tube reinforced concrete columns with recycled aggregates under monotonous and fatigue loading

Experimental and numerical investigations were carried out to evaluate the effects of incorporating recycled coarse aggregates (RCA) on the mechanical behaviour of inner steel-tube reinforced concrete columns exposed to high temperature. The specimens were reinforced with basalt fibres (BF) and strengthened by carbon fibre reinforced polymer (CFRP) sheets, which were subjected to mechanical loading in monotonous and cyclic arrangements. Test results show that at room temperature (RT), incorporation of the chopped BF has reduced both the tensile strength and flexural strength of concrete specimens prepared with recycled aggregate concrete (RAC) but not their static elastic modulus. On the other hand, the BF has improved crack resistance of the steel tube reinforced RAC (STRC) column specimens. Also, the reduction in mass and dynamic elastic modulus of BF reinforced STRC specimens are lower than those of STRC at a given RCA replacement ratio and exposure temperature. Furthermore, improvements in mechanical performance under monotonous and fatigue loading was observed for STRC columns reinforced with BF and externally bonded CFRP sheets with high-temperature exposure (HTE). Therefore, it is possible that BF reinforced STRC columns could be used to reduce risk of brittle structural collapse when exposed to fire or elevated temperature.

Study on Damage Characteristics and Failure Modes of Gypsum Rock under Dynamic Impact Load.

The objective of this work was to investigate the damage characteristics and failure modes of gypsum rock under dynamic impact loading. Split Hopkinson pressure bar (SHPB) tests were performed under different strain rates. The strain rate effects on the dynamic peak strength, dynamic elastic modulus, energy density, and crushing size of gypsum rock were analyzed. A numerical model of the SHPB was established using the finite element software, ANSYS 19.0, and its reliability was verified by comparing it to laboratory test results. The results showed that the dynamic peak strength and energy consumption density of gypsum rock increased exponentially with strain rate, and the crushing size decreased exponentially with the strain rate, both findings exhibited an obvious correlation. The dynamic elastic modulus was larger than the static elastic modulus, but did not show a significant correlation. Gypsum rock fracture can be divided into crack compaction, crack initiation, crack propagation, and breaking stages, and is dominated by splitting failure. With increasing strain rate, the interaction between cracks is noticeable, and the failure mode changes from splitting to crushing failure. These results provide theoretical support for improvements of the refinement process in gypsum mines.

Influence of moisture content on the mechanical properties of an ancient high-porosity building sandstone: San Cristóbal's stone (Andalusia, Spain)

San Cristóbal’s is a porous sandstone that is present in masonry structures of numerous historical buildings located in the southwest of Spain (15th–18th centuries). In order to guarantee conservation and structural integrity, most of these structures have been assessed during the last two decades after they presented severe damages in locations affected by moisture. In this study, static and dynamic elastic modulus and uniaxial compressive strength of San Cristóbal’s stone are determined in the laboratory under dry and saturated states, as well as with a moisture content of 40%, to establish the influence of moisture on them. An experimental campaign was conducted on 16 samples of ancient stone, extracted from the core of structural walls and columns during a structural intervention. The results show how the moisture content directly affects the deformability of the stone, especially between dry and 40% moisture content states. The values of the elastic modulus, both static and dynamic, are reduced with average values of 16.98% and 22.85% respectively. The loss of uniaxial compressive strength between the dry and saturated states is established with a mean value of 29.82%. Additionally, empirical relationships between the studied mechanical properties have been developed, reaching coefficients of determination over 0.90 in most cases.

The Effect of Specimen Size on Acoustic Emission Parameters and Approximate Position of Defects Obtained during Destructive Testing of Cementitious and Alkali-Activated Degraded Fine-Grained Materials.

Two sizes of test samples were selected to investigate the effect of size on the level of degradation. The smaller test specimens had dimensions of 40 × 40 × 160 mm, and the larger ones had dimensions of 100 × 100 × 400 mm. Both sizes of test specimens were always made of the same mortar. In one case, Blast Furnace Cement was chosen as the binder. In the other case, it was an alkali-activated material as a possibly more environmentally economical substitute. Both types of material were deposited in three degrading solutions: magnesium sulphate, ammonium nitrate and acetic acid. The reference set was stored in a water bath. After six months in the degradation solutions, a static elastic modulus was determined for the specimens during this test, and the acoustic emission was measured. Acoustic emission parameters were evaluated: the number of hits, the amplitude magnitude and a slope from the amplitude magnitude versus time (this slope should correspond to the Kaiser effect). For most of the parameters studied, the size effect was more evident for the more degraded specimens, i.e., those placed in aggressive solutions. The approximate location of emerging defects was also determined using linear localisation for smaller specimens where the degradation effect was more significant. In more aggressive environments (acetic acid, ammonium nitrate), the higher resistance of materials based on alkaline-activated slag was more evident, even in the case of larger test bodies. The experiments show that the acoustic emission results agree with the results of the static modulus of elasticity.

High-performance concrete based on alkaline earth metal ions-activated slag at ambient temperature: Mechanical and microstructure properties

The current study introduces novel mixing ingredients and techniques for high-performance concrete based on alkaline earth metal ions-activated slag (HPC-AAS) and looks into the use of alkaline earth activators for the first time. Moreover, the use of limestone powder as the fine ingredient in HPC-AAS has been also evaluated. The specimens of HPC-AAS thus prepared were tested to determine their mechanical characteristics (flexural, compressive, and tensile strength), microstructure, water absorption, and the static and dynamic modulus of elasticity. The results showed that the use of 10% calcium oxide as an activator of HPC-AAS was able to provide the desired characteristics for compressive strength (114 MPa) and flexural strength (9.2 MPa) as well as the dynamic and static moduli of elasticity (43.1 and 34.9 GPa, respectively). Microstructure analyses indicated that the highest peaks for calcium silicate hydrate gel (C–S–H) and Si–O-T (T = Si or Al) and the strongest bond between the geopolymer matrix and aggregates were created for HPC-AAS activated with 10% calcium oxide, which produced the highest ratio of silicon to aluminum.

Estimation of physical and mechanical properties of high-strength concrete with polypropylene fibers in high-temperature condition

High-strength concretes (HSC) have been widely applied in civil construction. However, this material does not perform well in fire situations due to spalling, a phenomenon that can be significantly mitigated by adding synthetic fibers to HSC cementitious matrix. Estimating HSC physical and mechanical properties for different compositions and temperatures can therefore be useful, as the structure may be pre-designed without requiring prior material characterization in a fire situation. With this perspective, this paper aimed to propose regression models to estimate eight properties of High-Strength Concrete with Polypropylene Fibers (HSC-PPF), namely compressive strength, tensile strength, static modulus of elasticity, dynamic modulus of elasticity, ultrasonic pulse velocity, electrical resistivity, water absorption, and weight loss, at high temperatures (up to 800 °C). For this, it was evaluated the effective correlation between mechanical responses and independent variables, such as temperature, water absorption, and dynamic modulus, and the accuracy of regression models was assessed. The results obtained indicated that, among the models proposed, the two multiple regressions were better than the simple one for estimating HSC-PPF properties since they presented high adjustments (R2) and low mean absolute percentage (MAPE), and coefficient of variation (CV) errors. This methodology can be used in a wide variety of fiber-reinforced HSCs.

Assessment of concrete road paving blocks with coal bottom ash: Physical and mechanical characterization

Urban road pavements made by interlocking concrete paving blocks (CPB) manufactured using industrial by-products are an improving sustainability goal for light traffic areas. Through physical and mechanical characterization, this paper aims to assess CPB with coarse coal bottom ash (CBA), a novelty in aggregate grading terms. Then, eight dry concrete mixtures (two with CBA and six without CBA) were designed with two water/cement ratios (0.63 and 0.73) to produce rectangular CPB 20 cm × 10 cm × 8 cm (length × width × thickness) by a vibro-press machine. The correlation was established between the CPB compressive strength (fc) and dynamic and static elasticity modulus (Ed and Es, respectively). Negatively, the mixtures 20S-0.73 and 20SG19–0.73, with CBA and water/cement ratio of 0.73, showed CPB with the highest air content at 28 days (11.72 % and 10.90 %, respectively). Positively, the mixes REF-0.73 and 20G19–0.73, with water/cement ratio of 0.73 and the last with CBA, presented the highest fc at 28 days (25.34 MPa and 25.05 MPa, respectively). Furthermore, an R² coefficient of 0.18 was determined between the Es results from empirical equations with fc or Ed. This paper showed that more water might be necessary to better concrete mechanical behavior. Also, it was possible to facilitate the determination of Es for CPB with fc and Ed. However, empirical equations for Es with more data, such as water absorption, air content, and unit mass, are required for a better correlation between concrete’s mechanical and physical properties.

Preparation and Properties of Flame Retardant and Antistatic Foamed Wood–Plastic Composite with APP/ZB System

With the aggravation of fire and smoke pollution, it is urgent to develop green, lower-cost and high-performance Foamed Wood–Plastic Composite (FWPC) to meet the standards of antistatic and flame retardant in practical application. Therefore, the flame retardant and antistatic FWPCs were prepared by compression molding in this study. High-density polyethylene (PE-HD) and Salix wood flour were used as main raw materials, and azodicarbonamide (AC) was used as foaming agent; Nano-carbon black (Nano-CB) was used as antistatic filler, and ammonium polyphosphate (APP) and zinc borate (ZB) were used as flame retardants. The static bending strength and elastic modulus of FWPC-20 were up to 30.01 MPa and 2636 MPa, respectively, which can meet the commercial application of wood–plastic decorative board. The logarithm of surface resistivity and volume resistivity of FWPC-20 was kept at eight, indicating that it has antistatic effect. The residual carbon rate of FWPC-20 increased to 38.58% at 800 °C, indicating that FWPC had high thermal stability. The minimum heat release rate of FWPC-20 was 226.75 kw/m2, and the average heat release rate was 110.53 kw/m2. The total heat release was 66.96 MJ/m2, and the Limit Oxygen Index was 27.3%, which indicated that FWPC-20 had flame retardant and smoke suppression effects. This study provides a low-cost and simple method for the design of flame retardant, antistatic and high-performance FWPC, and has broad application prospects in the fields of packaging and construction.

PROPERTIES OF CONCRETE WITH COATED AGGREGATES UNDER DIFFERENT LOADING CONDITIONS

Properties of concrete can be improved using different coating materials and chemicals. Some of the materials, however, are not effective as there is a weak bond between the coarse aggregate and the cement mortar. Hence, in this research, the mechanical and dynamic properties of concrete with epoxy resin, epoxy-sand and silicon coated aggregates at different volume fractions ranging from 5 to 15 percent were experimentally investigated. The test results indicate that there are improvements in compressive strength of concrete ranging from 10 % to 18 %, in which a maximum strength was achieved by using 15 percent epoxy-sand coating. Furthermore, a 5 % epoxy resin coating, resulting in an increase in compressive and tensile strengths of concrete by 5% and there are enhancements in static and dynamic modulus of elasticity by 2.7 %. In general, concrete specimens made with aggregates coated with epoxy-sand have higher performance in compressive strength as compared to using aggregates epoxy and silicon coated aggregates. Based on the findings of this study, it is recommended that coating of coarse aggregates with epoxy and epoxy-sand can be used as an alternative building and construction material to enhance the mechanical and dynamic properties of concrete.

Effect of Rice Husk Ash on the Mechanical Properties and Microstructure of Concrete Subjected to High Temperatures

Mineral admixtures in portland cement–based concrete, such as rice husk ash (RHA), improve the mechanical strength and durability under normal conditions and ambient temperature. However, more knowledge is needed on the behavior of concretes with these materials when subjected to fire conditions. Fire conditions are characterized by an expressive increase in temperature in the structure in a short period. Thus, this study aimed to evaluate the effect of partial portland cement replacement with RHA in concretes subjected to different temperatures. Parameters examined were mineral composition with X-ray diffraction (XRD), compressive mechanical strength, static modulus of elasticity, and mass loss after heating. The mineral composition of concretes with and without RHA replacement after heating was similar. Partial replacement of cement with RHA improved the mechanical performance with higher compressive strength up to a temperature of 400°C. The static modulus of elasticity degraded more sharply than mechanical strength due to dehydration of cementitious matrix and fissuring. No explosive spalling was observed for all temperatures tested, and the mass loss was similar for both concretes. This indicated no adverse effects in the partial replacement of portland cement with RHA from a mineral point of view.

Research on Fuzzy PID Control of Concrete Press Based on Frequency Conversion Speed Regulation System

In the static compression elastic modulus test of concrete, controlling the value of the loading force is the key to the success of the test. The test requires that the set force value be reached quickly, and the fluctuation should be stable within the test standard range, even in the presence of external interference. There is no oscillation in the transient process, and the best adjustment process is achieved. This article uses a variable frequency speed regulation system to control the value of the loading force, but the hydraulic system is susceptible to fluctuations due to the influence of oil pressure and temperature. Conventional PID control cannot meet its performance requirements. As a result, this article proposes a fuzzy PID for the press’s variable frequency speed regulation system. It uses MATLAB/Simulink and the controller to simulate the system. Simulation experiments show that fuzzy PID control has a better control effect than conventional PID control.

Use of pumice aggregate in cementitious rheoplastic lightweight concrete

Rheoplastic lightweight concrete (RLC) is generally designed for pumping applications as fluid concrete free from segregation. Concrete is produced using polymeric admixtures to enhance concrete workability, strength, drying shrinkage, and durability. This research investigated the suitability of natural porous pumice aggregates in Turkey to obtain rheoplastic lightweight concrete with cement content in normal ranges. To produce and experience rheoplastic concrete mix design data, rheoplastic lightweight concrete mixes were tested with fine pumice aggregate (FPA) and coarse pumice aggregate (CPA) supplied from the Nevşehir region of Turkey. For rheoplastic lightweight concrete with cement contents in the 250 to 400 kg/m3 range, the percentage of fine pumice aggregates required was in the 73.6-81.0% range with complimentary water/cement ratios of between 0.53 and 0.68. The upper compressive strength limit was circa 30 N/mm2 . The research findings determined that the rheoplastic concrete samples with pumice aggregate met the design requirement of a slump value of 200 mm for fresh concrete predicted for fluid concrete forms. While technical properties of hardened concrete such as oven-dry density (1198-1362 kg/m3 ), strength values, static elasticity modulus (9236- 10756 MPa), thermal expansion coefficient (5.354 x10-6/°C - 6.929x10-6/°C) and thermal conductivity value (0.405-0.619 W/mK) decrease with increasing aggregate/cement ratios, they increase with increasing cement dosage. In addition, the high amount of fine pumice in concrete composition results in lower drying shrinkage and wetting expansion with decreasing cement dosage. The technical findings showed that RLC might be produced by using a superplasticizer and air-entraining admixtures and mixtures of different sizes of pumice aggregates.

Mechanical properties of 3D printed concrete with coarse aggregates and polypropylene fiber in the air and underwater environment

In this study, three-dimensional concrete printing (3DCP) was performed for concrete with coarse aggregates in air and underwater environments for a comparative evaluation of the mechanical properties of the obtained samples. The base concrete mix was selected based on normal weight concrete (NWC) with ordinary Portland cement (OPC) as a binder, and the mechanical properties of the printed concrete applied using 3DCP and mold cast concrete were compared for analysis. For printability, fiber-reinforced concrete (FRC) with polypropylene fiber was additionally considered as a variable, and the fabrication method (printing and mold casting) and conditions (air and underwater environments) were varied. For the specimens fabricated using different materials, fabricating methods, and fabricating environments, the apparent density, compressive strength, splitting tensile strength, and stress–strain curves were comparatively analyzed. Considering the static elastic modulus calculated from the stress–strain curve, the correlation between the values obtained using design codes and those obtained via elastic modulus prediction models presented in previous studies was comparatively analyzed. When the concrete fabricated using the mold casting method was compared with the printed specimen, the density of the mold cast concrete was higher by 34 kg/m3 compared to that of the printed specimen, and the specimen fabricated in the air showed a density that was 45 kg/m3 greater compared to that of the specimen fabricated underwater. The compressive strength (28 days) was found to be approximately 8% higher in NWC compared to that in FRC, and the compressive strength of the underwater specimen was about 72% of that of the air specimen.

Мodulus of Elasticity as a Function of a Process in Hereditary Mechanics

The article considers the problem of determining the modulus of elasticity for polymer materials. The measurement process of these materials is considerably complex, mainly due to the fact that they comply with the laws of viscoelasticity. The Boltzmann — Volterra method is applied to the consideration of the behavior of a hereditarily elastic body, namely, to synthetic threads. We revealed that the elastic modulus for polymer materials is not a constant value and depends on the frequency of exposure during the deformation of the material. It is particularly noted that the modulus of elasticity is not a function of the state, but a function of the process. In this regard, it is necessary to consider various modes of deformation, namely static, acoustic, and dynamic modes. The Boltzmann heredity principle is utilized to provide a clear understanding of the concepts of static, dynamic, and acoustic modulus of elasticity. Furthermore, the applicability of the Boltzmann equation to dynamic mechanical processes is analyzed using two methods — the hierarchy of relaxation times and the method of linearization. In addition, the concept of the interaction core of static and dynamic parts of deformation is introduced. This concept helps to explain the relationship between the static and dynamic moduli of elasticity and their impact on material properties.