scholarly journals Influence of Curing Humidity on the Compressive Strength of Gypsum-Cemented Similar Materials

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Weiming Guan ◽  
Dongsheng Zhang ◽  
Yingyuan Wen ◽  
Xufeng Wang
Keyword(s):  
Compressive Strength ◽  
Simulation Experiment ◽  
Early Stage ◽  
Material Strength ◽  
Similar Materials ◽  
Curing Method ◽  
Time Required ◽  
Curing Procedure ◽  
Reverse Tendency ◽  
Peak Value

The analogous simulation experiment is widely used in geotechnical and mining engineering. However, systematic errors derived from unified standard curing procedure have been underestimated to some extent. In this study, 140 gypsum-cemented similar material specimens were chosen to study their curing procedure with different relative humidity, which is 10%–15%, 40%, 60%, and 80%, respectively. SEM microstructures and XRD spectra were adopted to detect the correlation between microstructures and macroscopic mechanical strength during curing. Our results indicated that the needle-like phases of similar materials began to develop in the early stage of the hydration process through intersecting with each other and eventually transformed into mat-like phases. Increase of humidity may inhibit the development of needle-like phases; thus the compressive strength changes more smoothly, and the time required for the material strength to reach the peak value will be prolonged. The peak strength decreases along with the increase of humidity while the humidity is higher than 40%; however, the reverse tendency was observed if the humidity was lower than 40%. Finally, we noticed that the material strength usually reaches the peak value when the water content continuously reduces and tends towards stability. Based on the above observation, a curing method determination model and experimental strength predication method for gypsum-cemented similar materials were proposed.

scholarly journals Study on proportioning of similar materials for overburden rock in underground gasification model experiment

2021 ◽  
Vol 303 ◽  
pp. 01057
Author(s):  
Lin Xin ◽  
Limin Han ◽  
Mingyu An ◽  
Jian Li ◽  
Chao Li ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Model Test ◽  
Shear Failure ◽  
Similarity Theory ◽  
Orthogonal Experiment ◽  
Material Strength ◽  
Overburden Rock ◽  
Underground Gasification ◽  
Binder Ratio ◽  
Similar Materials

In order to provide an accurate theoretical basis for the underground gasification model test of coal, the similar materials ratio of underground gasification’s overburden rock was studied by orthogonal experiment according to the similarity theory. The results show: the fifth group material ratio meets the model test requirements, the mass ratio of sand, cement and gypsum is 6:1:1, and the compressive strength is 1.36MPa; the material strength is most sensitive to sand as compared to cement and gypsum; the compressive strength decreases as the aggregate–binder ratio increases. When the aggregate–binder ratio remains the same, the compressive strength decreases as the cement-gypsum ratio increases; the compressive strength-elastic modulus curve of the specimen increases linearly and conforms to the sandstone fitting curve in the coal-bearing strata; the failure mode of similar materials is mainly shear failure.

On the use of jerk and snap in condition monitoring of machinery – review and case studies

2021 ◽  
Vol 63 (8) ◽  
pp. 457-464
Author(s):  
S Lahdelma
Keyword(s):  
Condition Monitoring ◽  
Large Scale ◽  
Early Stage ◽  
Time Derivative ◽  
Additional Insight ◽  
Rolling Bearings ◽  
Monitoring Applications ◽  
Derivatives Of ◽  
Insight Into ◽  
Peak Value

The time derivatives of acceleration offer a great advantage in detecting impact-causing faults at an early stage in condition monitoring applications. Defective rolling bearings and gears are common faults that cause impacts. This article is based on extensive real-world measurements, through which large-scale machines have been studied. Numerous laboratory experiments provide additional insight into the matter. A practical solution for detecting faults with as few features as possible is to measure the root mean square (RMS) velocity according to the standards in the frequency range from 10 Hz to 1000 Hz and the peak value of the second time derivative of acceleration, ie snap. Measuring snap produces good results even when the upper cut-off frequency is as low as 2 kHz or slightly higher. This is valuable information when planning the mounting of accelerometers.

scholarly journals Effect of Curing Method on Properties of Lightweight Foamed Concrete

2018 ◽  
Vol 7 (2.29) ◽  
pp. 927 ◽  
Author(s):  
Bishir Kado ◽  
Shahrin Mohammad ◽  
Yeong Huei Lee ◽  
Poi Ngian Shek ◽  
Mariyana Aida Ab Kadir
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
Water Absorption ◽  
Precast Concrete ◽  
Construction Materials ◽  
Splitting Tensile Strength ◽  
Structural Members ◽  
Lightweight Construction ◽  
Foamed Concrete ◽  
Curing Method

Lightweight construction is aimed to achieve a sustainable feature by reducing transportation frequency and construction materials usage during construction phase. Lightweight precast concrete may serve an alternative for the lightweight construction. There are rarely application can be found for structural members as lightweight panels always to be used for secondary or non-load bearing members. This paper presents an experimental study on properties (compressive strength, splitting tensile strength, water absorption) of lightweight foamed concrete (LFC) at two different curing methods. LFC with densities of 1500, 1700, and 1800 kg/m3, cement-sand ratio of 2:1 and water-cement ratio of 0.5 were investigated. The results showed LFC can be produced with the properties ofdensity range of 1500 to 1800 kg/m3 and corresponding compressive strength of 10 to 39 MPa. The higher the density of LFC, the less the water absorption for all the curing method considered, the highest and the lowest water absorption was 11.3% and 2.0% for 1500 kg/m3 cured in water and 1800 kg/m3 cured in air respectively. Compressive strength of LFC increases with age and density while water cured LFC has high compressive strength. Splitting tensile strength increases with density of LFC, but air cured LFC has more splitting tensile strength than water cured of the same density. The highest splitting tensile strength recorded was 3.92 MPa for 1800 kg/m3 cured in air, which was about 16% of its compressive strength at 28 days of curing age. These properties are important and can be applied to LFC precast structural members with air or water curing method which have less references for LFC in structural usage.  

scholarly journals Evaluation of Compressive Strength of Decayed Wood in Magnolia obovata

2010 ◽  
Vol 36 (2) ◽  
pp. 81-85
Author(s):  
Kahoru Matsumoto ◽  
Futoshi Ishiguri ◽  
Kazuya Iizuka ◽  
Shinso Yokota ◽  
Naoto Habu ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Early Stage ◽  
White Rot Fungi ◽  
Brown Rot ◽  
Soft Rot ◽  
White Rot ◽  
Chemical Components ◽  
Cellulose Content ◽  
Magnolia Obovata ◽  
Weight Loss Ratio

To obtain the basic information needed to estimate the degree of decay from compressive strength measured using a Fractometer (CS), relationships between CS and the contents of chemical components were analyzed for Magnolia wood decayed by three types fungi (brown rot, white rot, and soft rot fungi) at various decay levels. Weight loss ratio was significantly, negatively correlated with CS in woods decayed by brown rot and white rot fungi. In addition, a relatively high correlation coefficient was recognized between CS and holocellulose or α-cellulose content, except for wood decayed by soft rot fungus. The results obtained showed that Fractometer can detect the decrease of CS at relatively early stage of decay.

Standardized Development Planning for Satellite Fields in the South of the Sultanate of Oman

2021 ◽  
Author(s):  
Peter in ‘t Panhuis ◽  
Adel El Sabagh ◽  
Hilde Coppes ◽  
John Meyers ◽  
Niels Van der Werff ◽  
...  
Keyword(s):  
Development Strategy ◽  
Early Stage ◽  
Development Planning ◽  
Oil Fields ◽  
Sultanate Of Oman ◽  
The South ◽  
Well Design ◽  
Time Required ◽  
Rule Based Approach ◽  
Petroleum Development

Abstract This article will show how a standardized rule-based approach was used by Petroleum Development Oman (PDO) to shorten the cycle time required to mature the opportunity of implementing waterflood developments in small-to-medium sized satellite oil fields in the South of the Sultanate of Oman. The standardized concept relies on a common development strategy for a portfolio of satellite fields with similar reservoir and fluid characteristics that are still under depletion or in the early stage of waterflood. The targets are early monetization, driving cost efficiency through standardization & replication, and increasing recovery factor through the accelerated implementation of field-wide waterflood. This is achieved by leveraging excess capacity in existing facilities, applying analytical workflows for forecasting, standardizing well design and urban planning, and by applying the learnings and best practices from nearby fields that already have mature developments.

scholarly journals A comparative study on the effect of different activating solutions and formulations on the early stage geopolymerization process

2020 ◽  
Vol 322 ◽  
pp. 01039
Author(s):  
Lais Alves ◽  
Nordine Leklou ◽  
Silvio de Barros
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Early Stage ◽  
Construction Material ◽  
Potassium Hydroxide Solution ◽  
Mechanical And Thermal Properties ◽  
Liquid Ratio ◽  
Promising Alternative ◽  
Precursor Material ◽  
Activating Solution

Concrete is a major construction material that produces high levels of carbon dioxide in its manufacturing process. Hence the construction sector is responsible for relevant environmental impacts. This justifies the need to find materials as green and ecological alternatives to common Portland cement. Geopolymers represent the most promising alternative due to its proven durability, mechanical and thermal properties. This study investigates the effects of solid-to-liquid and alkali activator ratios on the synthesis of slag-based pure geopolymer and their relation to the geopolymerization process. Two activating solutions were used: a) a mixture of sodium hydroxide, sodium silicate, and water; and b) a mixture of potassium hydroxide solution, potassium silicate, and water. As precursor material, ground blast furnace slag was used. Precursors and activators were mixed with solid-to-liquid ratios in range of 1.5 to 2.2. In the first stage of the study, the mechanical properties were evaluated for each activating solution. In the following stage, different formulations, with variations in the water percentage and solid-to-liquid ratio were tested for mechanical properties and SEM observations. Test results indicate that the resulting geopolymer has the potential for high compressive strength and is directly affected by the composition of the activating solution. It can also be observed that compressive strength was affected by solid-to-liquid ratio and % of water added to the mixture, and strength increased with ageing day.

scholarly journals Developing a forecasting model of concrete compressive strength using relevance vector machines

2014 ◽  
Vol 3 (2) ◽  
pp. 224 ◽  
Author(s):  
Mohammad Awwad
Keyword(s):  
Compressive Strength ◽  
Early Stage ◽  
Mixing Time ◽  
Relevance Vector Machine ◽  
Strength Increase ◽  
Concrete Compressive Strength ◽  
Relevance Vector Machines ◽  
Vector Machines ◽  
Strength Material ◽  
Cement Mixture

We analyze results of two experiments that tested effect of adding Silica on the compressive strength of concrete at early stage and after long period. The two experiments evaluated different silica/cement ratios for different mixing periods. Adding Silica to concrete mix produce high early strength material which is highly desirable in airports and highways. More than 90 samples of different silica/cement ratios are tested for compressive strength at 3 and 28 days. Test results showed high early up to 60 MPa. Strength increase is proportional with the increase of silica/cement ratio and mixing time with maximum at ratio of 15/100 and 30 minutes mixing time. A relevance Vector Machine (RVM) model is developed to predict concrete compressive strength using concrete mixture inputs information. RVM model predictions matched experimental data closely. The developed model can be used to predict compressive strength in future periods based on initial information related to cement mixture. Keywords: Relevance Vector Machine, Silicate Percent, Prediction Model, Milling Time, Compressive Strength, Concrete.

Experimental Investigation on the Factors Affecting Proppant Flowback Performance

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Lei Wang ◽  
Heng Wen
Keyword(s):  
Particle Size ◽  
Simulation Experiment ◽  
Early Stage ◽  
Fluid Viscosity ◽  
Significant Issue ◽  
Fracturing Fluid ◽  
Factors Affecting ◽  
Well Production ◽  
Fracture Simulation ◽  
Fractured Well

Abstract Proppant flowback is a significant issue in the field of fractured well production. In order to investigate the influencing relationships among the parameters affecting proppant flowback, the weight of proppant flowback within different conditions was tested by applying a fracture simulation experiment device. During the experiments, the flowback velocity of the fracturing fluid, the viscosity of the fracturing fluid, the proppant particle size, and the effective closure pressure were studied. The experimental results indicated that the flowback velocity of the fracturing fluid is critical for proppant flowback. The weight of the flowback proppant increases as the fracturing fluid flowback velocity increases. Proppant flowback mainly occurs in the early stage of fracturing fluid flowback; more than 75% of the flowback volume of the proppant was carried by 33.33% of the fracturing fluid flowback volume. The weight of the flowback proppant decreases as the flowback fracturing fluid viscosity decreases. Using a larger particle size proppant or upon increasing effective closure pressure also can decrease the weight of the flowback proppant.

scholarly journals Study on the Deterioration of Concrete under Dry–Wet Cycle and Sulfate Attack

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4095
Author(s):  
Fang Liu ◽  
Tonghuan Zhang ◽  
Tao Luo ◽  
Mengzhen Zhou ◽  
Kunkun Zhang ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Sodium Sulfate ◽  
Distribution Curve ◽  
Early Stage ◽  
Sulfate Attack ◽  
Industrial Computed Tomography ◽  
Spectrum Distribution ◽  
Compressive Strength Of Concrete ◽  
Internal Pore Structure ◽  
Internal Pore

In order to study the deterioration and mechanism of dry–wet cycles and sulfate attack on the performance of concrete in seaside and saline areas, the deterioration of compressive strength of concrete with different water cement ratios under different erosion environments (sodium sulfate soaking at room temperature and coupling of dry–wet cycling and sodium sulfate) was studied here. At the same time, ICT (industrial computed tomography) and NMR (nuclear magnetic resonance) techniques were used to analyze the internal pore structure of concrete under different erosion environments. The results show that the compressive strength under different erosion environments increases first and then decreases, and the dry–wet cycle accelerates the sulfate erosion. With the increase of dry and wet cycles, larger pores are filled with erosion products and developed into small pores in the early stage of erosion; in the later stage of erosion, the proportion of larger pores increases, and cracks occur inside the sample. In the process of sulfate soaking and erosion, the smaller pores in the concrete account for the majority. As the sulfate erosion continues, the T2 spectrum distribution curve gradually moves right, and the signal intensity of the larger pores increases.

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