Core Compressive Strength Research Articles

Graphene nanoplatelet additive impact on compression and bending strength of S-2 glass face-sheet honeycomb sandwich panels: An experimental study

In this study, the three-point bending, edge-wise, and flat-wise strengths of Nomex® sandwich structures with un-doped S-2 glass fiber face-sheet (Neat/S-2/glass) and those with Graphene nanoplatelet-doped S-2 glass fiber face-sheet (GNPs/S-2/glass) were examined parametrically. In the macroscopic images obtained post-experimentation, the damage to the structures’ face layer, core, and interface with GNP (graphene nanoplatelet) additives was visualized. Morphological images depicting the damaged structures were obtained by applying image processing techniques to the macroscopic images. Finally, the fracture mechanisms of fiber/fiber and fiber/matrix interfaces within the shell layers were examined in SEM images. As a result of the study, the addition of GNPs increased the strength of the interfaces between the fiber layers and the fiber core within the face layers of S-2 glass face-sheet Nomex® sandwich structures, leading to a 40% enhancement in bending strength, a 14% improvement in core compressive strength, and a 2.85% increase in edge-wise compressive strength. Moreover, the delamination damage between the face layer and the core, which undermines the structural integrity of the sandwich structure, was not observed in GNPs/S-2/glass sandwich structures. Thus, the damage propagation throughout the sandwich structure contributed to enhancing its load-carrying capacity. The collapse extent of the sandwich structures, determined through image processing, measured 8676 mm in Neat/S-2/glass sandwiches, whereas it amounted to 10,410 mm in GNPs/S-2/glass sandwiches. The inclusion of GNPs additive augmented the collapse strength of the sandwich structure by 19.9%. Utilizing GNPs as a filler in the matrix material has been recognized as a practical approach to enhancing the mechanical strength of sandwich structures.

Sandstone chemical consolidation and wettability improvement using furan polymer-based nanofluid

The oil and gas industry faces a challenge in meeting global energy demand due to sand production in unconsolidated or semi-consolidated reservoirs, leading to equipment wear, production instability, and significant financial burdens. Mechanical and chemical sand control methods are being used among which chemical sand consolidation techniques have emerged as a promising solution. In this research, furan polymer-based nanofluid is investigated as a chemical consolidant to explore its intriguing properties and characteristics and how the quantity of nanoparticles influences the fundamental properties of curing resin and wettability while pioneering a groundbreaking approach to enhancing regaining permeability. According to the findings, a substantial boost in core compressive strength has been achieved as well as an impressive increase in re-permeability, especially for the foam injection case, by the meticulous optimization of nanofluid composition. The results include a remarkable regain permeability of 91.37%, a robust compressive strength of 1812.05 psi, and a noteworthy 15.32-degree shift towards water-wet wettability. Furthermore, silica nanoparticles were incorporated to enhance the thermal stability of the fluid, rendering it more adaptable to higher temperatures. Therefore, Furan polymer-based nanofluid is not only expected to present a solution to the challenge of sand production in the oil and gas industry but also to provide operational sustainability.

A Study on the Statistical Analysis and Artificial Intelligence Model to Improve the Reliability of Safety Inspection

In this study, safety diagnosis results from underground and nuclear power plant structures were collected to evaluate the reliability of on-site structural safety assessments. The analysis of these results revealed a discrepancy between the compressive strength determined by rebound hardness and the core compressive strength, with the former typically being evaluated higher than the latter. Additionally, existing strength prediction models did not adequately explain field data, whereas artificial intelligence models, particularly the support vector machine model, demonstrated improved accuracy and reduced error rates. This indicated the superior performance of support vector machine models in this context.

Effect of ultra‐high performance concrete repair layer thickness on the behavior of concrete columns

AbstractThe use of ultra‐high‐performance fiber reinforced concrete (UHPFRC) to repair or rehabilitate old concrete structures has been shown to be appropriate due to its properties, such as higher compressive strength, ductility, and durability than conventional concretes. One of the studied strengthening techniques is the reinforced concrete columns jacketing by UHPFRC. Some recent research evaluated some parameters, such as the repair thickness and the volumetric ratio of stirrups. However, other important parameters, such as UHPFRC jacketing thickness in different column cross‐sections and the concrete core compressive strength, need to be addressed. In addition, the analytical models presented in the literature are restricted to only one concrete grade. The present study aims to evaluate the behavior of short reinforced concrete columns strengthened with UHPFRC subjected to centered compression. Numerical analyses of three‐dimensional models were performed using the finite element method, validated, and calibrated using experimental results. The influence of the concrete core compressive strength, the UHPFRC jacketing thickness, and the shape of the cross‐section were evaluated. Numerical simulations concluded that the lower concrete core compressive strength columns showed the best relative increase performance. Moreover, the concrete core strength was inversely proportional to the resistance capacity of the repair system. In addition, the increase in repair thickness contributes to the axial strength of the column. Furthermore, the cross‐section influences the distribution of stresses and strains, showing the best performance for circular sections. Finally, regardless of cross‐section type, the proposed equations accurately predicted the numerical results.

Compressive properties of aluminum middle-trabecular beetle elytron plates with a large height-to-thickness ratio core

To develop lightweight and high-strength biomimetic structural materials, the compression characteristics of aluminum middle-trabecular beetle elytron plates (MBEPa) with a large height-to-thickness ratio (β) core were investigated by flat compression tests and finite element simulations, and the results are as follows. 1) Compared with aluminum honeycomb plates (HPa), the core compressive strength and energy absorption of MBEPa with two trabeculae per honeycomb can increase by 12.4 % and 28.6 %, respectively, with an increase of about 1.8 % in the total volume; and for the first time, the MBEPa core structure with a large β was found to have a triple interval deformation morphology with a small C or S shape deformation in the central part. 2) Compared with HPa, MBEPa with six trabeculae has a 9.3 % increase in total volume, 106.7 % increase in compressive strength and 147.3 % increase in energy absorption core. 3) Compared with the BEPs with a small β, with the increase of trabeculae, the compressive property increase of the large-β ones reflects the characteristic of "small in the early stage and large in the later stage". And the strengthening and influence mechanism of trabecula on the compressive properties and deformation was revealed from the perspectives of the aforementioned core deformation characteristics and the constraining effect of skins.

Analysis of the accuracy of in-situ concrete characteristic compressive strength assessment in real structures using destructive and non-destructive testing methods

Estimation of in-situ concrete compressive strength in existing structures is considered as a crucial step in assessing structural capacity. Destructive testing (DT) by coring in conjunction with non-destructive testing (NDT) offers an interesting method for concrete strength assessment in existing constructions. The non-destructive assessment of in-situ strength requires a correlation between NDT measurements and the core compressive strengths. Therefore, the accurate quality of the in-situ strength assessment is a fundamental point. The NDT techniques such as Rebound Hammer (RH) and Ultrasonic Pulse Velocity (UPV) are widely used separately or in combination to estimate the in-situ strength. A series of on-site data (205 data triplets) of non-destructive testing (RH and UPV) and coring have been carried out on structural elements (columns and beams) in an existing building to assess the in-situ concrete strength according to the new standard version procedures (EN 13791-2019) with a comparison to its old version 2007. The analysis highlighted in a real on-site situation the positive effect of the new procedures in the recent version (2019) of EN 13791 on strength assessment, namely: the selection process of coring positions, the required number of cores, and the identification method of the conversion model. However, the statistical procedures proposed in the new version for calculating the in-situ characteristic strength appear to underestimate the results and seem to be excessively conservative as compared to the 2007 version.

Assessing concrete strength loss at elevated temperatures as a function of dielectric variation measured by GPR: an empirical study

ABSTRACT Reinforced concrete (RC) parts, which are exposed to high temperatures for a certain period, undergo physical-chemical changes that deteriorate their mechanical properties. To this end, this study investigates the efficiency of using ground-penetrating radar (GPR) as a non-destructive testing (NDT) method in assessing the core compressive strength loss, elastic modulus decrease, and tensile strength loss of concrete under extreme temperatures. RC specimens are fabricated and exposed to elevated temperatures (300°C, 400°C, 500°C, 600°C, and 700°C). GPR measurements are performed to estimate the relative dielectric permittivity (RDP) of the specimens before fire exposure (BFE) and after fire exposure (AFE). The compressive strengths of the cores extracted from the specimens are obtained also for BFE and AFE cases. Attained RDP values are in conformance with the previous research results and contribute additional evidence to the published literature. As the temperature levels are increased, RDP and strength-related values of concrete specimens decrease. The strength-related parameters are more sensitive to elevated temperatures, whereas the change in the RDP values is rather gradual. Through multiple correlations within 95% confidence intervals, core compressive strength loss, elastic modulus decrease, and tensile strength loss are, individually, estimated as a function of relative RDP change and applied temperature levels. Empirical formulas are obtained with high coefficients of correlation. The relative effects of RDP change and temperature are more pronounced in elastic modulus decrease and tensile strength loss compared to compressive strength loss. Overall, the outcomes of this paper confirm the viability of using the GPR technique for concrete dielectric characterisation in estimating the strength-related properties of concrete exposed to high temperatures, which might reduce the need for destructive testing.

Performance evaluation of composite concrete-filled steel tube columns by steel fibers and different cross-section shapes: Experimental and numerical investigations

Increasing the load-bearing capacity of columns without increasing their dimensions has become an essential issue for engineers. Concrete-filled steel tube (CFST) column is one of the common techniques used in different constructions. This study aims to assess the influence of steel fibers (SF) on the uniaxial performance of CFST columns to improve their behavior. 27 specimens are produced and tested under a uniaxial compressive load. Specimens are made with three cross-section shapes: circular, rectangular, and octagonal. Also, steel fibers are added at the three-volume percentages of 0%, 1%, and 2%. Low, normal, and high-strength concrete is used to manufacture concrete columns to consider the influence of compressive strength. The bearing capacity, load-axial shortening curves, and axial-hoop strain performance of columns are measured. Also, the obtained outcomes are compared with the requirements of current design codes and previous models. Based on the obtained results, new models are developed to predict the uniaxial bearing capacity of CFST columns with different concrete core compressive strengths, cross-section shapes, and SF contents. The results indicated that adding SF led to changing the softening behavior of the column to the hardening behavior due to raising the axial compressive strength of the concrete core. Nonetheless, this impact is more significant in CFST columns with octagonal and square cross-section shapes. Additionally, the proposed formulas in this study, with high accuracy, could be employed to predict the uniaxial bearing capacity of CFST columns with different concrete core compressive strengths, cross-section shapes, and SF contents.

Experimental Study for the Comparison between Core, Schmidt and Cubic Concrete Compressive Strength After Durability Test

Estimating the compressive strength of concrete exposed to different environmental conditions is an essential parameter in judging the quality of concrete and proving its ability to perform as planned. There are various destructive (DT) and non-destructive (NDT) methods for estimating compressive strength. Some NDT and DT procedures, such as Schmidt hammer and core testing, have been used for estimating concrete strength for a long time. These methods consider indirect and predicted tests to evaluate concrete strength in existing structures. Various factors influence these tests, so it is difficult to precisely assess the hardened concrete strength. Thus, this research aims to identify a coherent relationship that connects the results of these tests and correlates them with the results of cube compressive strength by assessing data from laboratory tests conducted under control and durability conditions using statistical techniques. To achieve this purpose, three grades of concrete were considered C250, C450, and C600 Kg/cm2. Six concrete cubes of size (15x15x15 cm) and four concrete columns of size (30x15x50 cm) were cast for each grade and tested to assess the cube, Schmidt hammer, and core compressive strength of concrete. Half of the columns and cubes were cured in drinking water (control condition) and the other half of the samples were subjected to durability cycles for 92 days (durability condition). In the durability condition, the samples were exposed to 10% sodium sulfate solution for a day, placed in a water tank for a day, heated to 100°C at a laboratory furnace for a day and then left at average laboratory temperature for a day to finish one cycle. The results were tabulated and graphed to notice any differences between DT, NDT and cube compressive strength tests. The results showed that the cube strength is higher than the core strength for all grades of concrete under control and durability conditions. The cube test indicates a lower compressive strength than the Schmidt hammer test method at grade C250 under control condition and greater compressive strength in the rest of the grades.

Comparison of the Performance of the Steel Fiber Shotcrete and Cast Concrete considering Accelerator Types and Core Sizes from a Tunnel Site

Shotcrete is considered a substantial long-term product providing a sheltered working environment for tunneling engineering. However, multi-functional problems occur due to the sprayed concrete construction method. Moreover, the performance of the shotcrete placement into the wall of the tunnel is challenging to verify. Currently, accelerators are used in highway tunnels for improving the overall performance of shotcrete. This study evaluated the tunnel shotcrete performance for cement mineral, aluminate, and alkali-free accelerators, as well as steel fiber, which is the main constituent of shotcrete. The workability of concrete and shotcrete in situ has been measured for these combinations. Using 1-month samples, shotcrete was evaluated by means of accelerating agent, compressive strength, core compressive strength, flexural strength, and flexural toughness. In particular, 37 kg and 40 kg of steel fiber were included into the cement and aluminate mix and the alkali-free mix, respectively. Changes in strength and flexural performance of shotcrete were studied under Korean standard. Thus, concrete cylindrical molds were manufactured for the compressive strength test. After 28 days of curing, concrete and shotcrete test panels were manufactured for core compressive strength tests on cylindrical molds with diameters of 100 mm, 75 mm, and 55 mm. Furthermore, beam samples were produced for flexural strength and toughness tests to measure the shotcrete performance. Air void test and steel fiber remaining percentage after shooting were performed to ensure the performance image analysis. Alkali-free incorporated with steel fiber is the best combination for tunnel shotcrete premised on compressive strength, core compressive strength, flexural strength, and toughness test results, along with environmental and worker safety. Finally, the tunnel shotcrete performance was evaluated by regulating and improving the accelerator type with the steel fiber for shotcrete.

Codes applicability of estimating the FRC compressive strength by the core-drilling method

The core-drilling method is a reliable and confident method to evaluate the in-situ compressive strength. Codes and standard relations are developed to evaluate the compressive strength of the traditional concrete. The fiber reinforced concrete (FRC) is different in its behavior and mode of failure when compared to traditional concrete. This paper presents an experimental study on the applicability of these features of FRC. 168 drilled specimens were extracted from 10 different concrete mixes then tested. The investigated parameters were: the fiber type (polypropylene, glass, steel); fiber volume fraction (0.25%, 0.50%, 0.75%); cutting direction (horizontal, vertical); core diameter (100 mm, 150 mm). Standard cubes and cylinders were taken from each mix to evaluate the compressive strength. The results of the drilled cores were verified to more than predicted by code. The results revealed that the existing relationships underestimate the core compressive strength for FRC. A new modification factor was proposed depending on the fiber type and fiber volume fraction to estimate accurately the in-situ core compressive strength.

Ocjena čvrstoće betonskih jezgri pomoću umjetnih neuronskih mreža

The proposed work deals with the use of Ultrasonic pulse velocity technique as an alternative method to identify compressive strength of the core concrete. The use of non-destructive technique without causing damages to the structure is tedious with interpretation of results influenced by various factors. Hence, an empirical relationship is developed using artificial neural network model for creating a regression between pulse velocity and compressive strength of concrete core specimens. Tests were conducted on reinforced concrete cylinders at various orientation angles (0°, 45°, 90°). The tests were conducted based on the design of experiment using the Box-Behnken model. These results were trained using the Levenberg-Marquardt back propagation model with hidden layers. Results indicate that the prediction of core compressive strength for the grade mixes is nearer for the two-level factorial design with R2 = 0.897, and the sum of squared error is found to be 0.9968.

Measurement of core bond strength in reinforced concrete column using magneto rheological fluid assisted Ultrasonic measuring technique

ABSTRACT The present work deals with the investigation of core compressive strength in reinforced concrete column with the slip angle orientation and bond stress relationship using Magneto rheological fluid (MR fluid)-based non-destructive testing principle. Ultrasonic method is used to obtain the crack width and slip angle orientation of the rebar. In addition to that, the bond strength can be determined through the rheological disturbance in the MR fluid medium. Experiments to determine the axial compression behaviour of cylindrical concrete specimens were carried out by placing the MR fluid discs at three distinct zones. Ultrasonic waves were generated and scattered over the MR fluid disc based on two different angles of propagation (90ᴼ and 45ᴼ). The results demonstrated that the percentage of variation in the measured rebar strain for M30/RRD 1.0 is found to be 25.75% of the values measured for M30/RRD 0.5. The maximum bond strength is found to be 24.63 MPa for M30/RRD 1.5 with slip orientation angle of 14ᴼ. Moreover, the minimum difference in the observed values of ultrasound pulse velocity was −0.78 m/s for M20/RRD 1.0 with the magnetic field strength of 40 mT.

Study of a Polyamine Inhibitor Used for Shale Water-Based Drilling Fluid.

Here, we report a water-soluble shale inhibitor for inhibiting shale hydrate formation. The copolymer denoted as thermogravimetric analysis (TGA) was synthesized via triethanolamine, two maleic anhydrides, and glacial acetic acid. The infrared (IR) and gas chromatography (GC) results indicated that TGA is a low molecular weight polymer inhibitor (IR) and is the most commonly used method to identify compounds and molecular structures qualitatively. It is mainly used to study the molecular structure of organic substances and conduct qualitative and quantitative analyses of organic compounds. The main function of GC is for polymer molecular weight analysis. With the aid of shale rolling recovery experiments, particle size distribution experiments, triaxial stress experiment methods, bentonite slurry rate inhibition experiments, and thermogravimetric experiments to evaluate TGA inhibition characteristics, the inhibition effect of TGA is better than that of the traditional inorganic salt inhibitor KCl, polymer amine inhibitor UHIB, and organic cationic shale inhibitor NW-1. When the mass fraction is 0.2%, the cutting recovery rate increases from 18.3 to 94.1%. The compressive strength of the shale core after adding 1% TGA inhibitor is 177.9 MPa, which is close to the original core compressive strength of 186.5. The wet sodium montmorillonite crystal layer spacing after treatment with 0.5%, 1.5%, and 3% TGA aqueous solution is 1.38, 1.35, and 1.35 nm, respectively, and the sodium montmorillonite crystal layer spacing after diesel treatment is 1.34 nm, indicating that the inhibitory effect of TGA on sodium montmorillonite is equivalent to that of diesel and that TGA can effectively inhibit the hydration and dispersion of sodium montmorillonite. At the same time, the crystal layer spacing and the weight loss rate of sodium montmorillonite modified by TGA inhibitors did not change significantly after adsorption of deionized water, which proved that TGA inhibitors could be adsorbed in the crystal layer space of sodium montmorillonite to inhibit hydration and dispersion of sodium montmorillonite. Field test results show that TGA can significantly improve the inhibition performance of the field drilling fluid, and the effect is better than the strong conventional inhibition water-based drilling fluid system, which solves the problems of wellbore instability and considerable friction in horizontal shale sections and provides a new idea and method for efficient shale gas drilling.

Long-Term Compressive Strength Development of Steel Fiber Shotcrete from Cores Based on Accelerator Types at Tunnel Site.

In this study, cement minerals, aluminates, and alkali-free accelerators incorporated with steel fiber were used to scrutinize the influence of accelerating agents on the long-term performance of tunneling shotcrete. Performance tests were identified based on the core compressive strength of mix shotcrete specimens with different types of accelerating agents throughout timeframes of 1, 3, 6, and 12 months. Here, 37 kg of steel fiber was incorporated into the cement mineral and aluminate mixes, and 40 kg of steel fiber was incorporated in an alkali-free mix for the shotcrete mix design. The KSF 2784 and ASTM 214 standards were followed for specimen fabrication and core cutting. For all specimens, shotcrete test panels of 250 × 600 × 500 mm were manufactured for core compressive strength tests conducted using 100, 75 and 55 mm diameter cylindrical molds and a length-to-diameter ratio of 2. The 1-month compressive strength of all test variables satisfied the Korea Expressway Co. standard of 21 MPa. The core compressive strength of the shotcrete specimens showed a tendency to increase with age, but a strength reduction occurred in 6 months and increased again at 12 months. Moreover, the impact of the diameter changes in the shotcrete core specimens was analyzed based on the mixing. For 12 months, a large increase in the core compressive strength occurred, particularly in the alkali-free specimens. The comparison also focused on the relative strength compared with a cast concrete mold and shotcrete core specimens. It is necessary to use alkali-free accelerators considering the long-term performance of tunnels and worker safety.

A study on the effect of reinforcement on the strength of concrete core

Concrete core test is a semi-destructive test, conducted to ascertain the in- situ strength of the hardened concrete of a structure. In such case it is desired to extract cores without reinforcement. If the reinforcements are present in the core, then the core strength does not mean the compressive strength of concrete in the structure from which the core was extracted. The objective of this study was to study the effect of orientation of reinforcement on the compressive strength of concrete core. 10 mm and 12 mm reinforcement were embedded in the test specimens. A set of cores containing different orientations of reinforcement were extracted. The test results indicate that the presence of reinforcement of diameter 12 mm reduces the strength of concrete core from 3% to 30%, while the reinforcement of diameter 10 mm reduces the strength of concrete core from 5% to 36%. The bond between the reinforcement and the core gets affected during the coring action due to which the strength gets reduced in a reinforced core. The reduction of strength of an unreinforced core ranges around 40% when compared to the cube compressive strength. An empirical relationship with several factors influencing the core compressive strength is formulated and the same is validated.

Comparative Study on In Situ and Laboratory Testing of Concrete Cores with Different Height to Diameter Ratios

Abstract The concrete core test is usually conducted to determine the compressive strength of hardened concrete at the site. A laboratory core test takes approximately 2 to 3 days as a result of operations like core cutting, transportation, curing, sawing, sulphur capping, testing, etc. In order to reduce processing time, an attempt was made to test the concrete core compressive strength at the site by fixing an in situ testing machine over the drilled core specimen with the help of anchor fasteners. The research was conducted using two types of in situ testing machines. Cores with diameters of 24 mm and height to diameter (H/D) ratios of 1, 1.5, and 2 were tested using machine 1. Similarly, cores of diameter 24 mm, 42 mm, and 67 mm with H/D ratio 1, 1.5, and 2 were tested using machine 2. The in situ compressive test results were compared with the results from the laboratory test conducted on an equal number of cores. Student t-tests were conducted between the results of both laboratory and in situ core tests. In all the cases, the t-statistical values were less than the t-critical, which indicates that there is no significant difference between both the methods. The results were analyzed for variation of core strength with respect to H/D ratio and diameter. It was observed that in both the in situ and laboratory core testing methods, the core strength decreased with an increase in H/D ratio and increased with an increase in core diameter. However, the variance in strength with increasing core diameter was proved to be not significant with the help of the ANOVA test. Multiplication factors used to determine the equivalent cube strength from the in situ core strength of concrete were calculated for corresponding diameters and H/D ratios.

In-Place Estimation of Concrete Compressive Strength Using Postinstalled Pullout Test – A Case Study

Abstract It was proposed that a 16-story steel framing structure be built on top of an existing 12-year-old 1-story reinforced-concrete structure. The in-place concrete compressive strength of 3 footings and 29 plinths was estimated using a postinstalled pullout test and a core compressive strength test. The influence of different length-to-diameter ratios of the cores and different diameters of cores and the correlation between maximum pullout force and core compressive strength were investigated. The results of the pullout test and core strength test indicate that the concrete compressive strength of footings and plinths was considered structurally adequate as per the acceptance criteria for tested core strength and estimated core strength given by ACI 318, Building Code Requirements for Structural Concrete and Commentary, and ACI 228.1R, In-Place Methods to Estimate Concrete Strength, respectively. Maximum pullout force had a strong correlation with the core compressive strength. The influence of the different length-to-diameter ratio of cores on the strength correlation was not significant if the raw results of the compressive strength tests were corrected by multiplying the corresponding correction factors for the length-to-diameter ratio given by ASTM C42, Standard Test Method for Obtaining and Testing Drilled Cores and Sawed Beams of Concrete. The mixed use of the test results of 3.20 and 3.74-in. (81-mm and 95-mm) cores resulted in a decrease in the R2 of the correlation model, compared to that of the correlation model based on 3.74-in. (95-mm) cores. This was attributed to the potentially increased testing error as the diameter of the cores decreased. Recommendations for successfully performing postinstalled pullout tests in the field were proposed. With the use of pullout tests, the project team was able to determine that the existing structural members had sufficient capacity. A delay in the project schedule was avoided.

Flexural Stiffness of Normal and Sandwich Reinforced Concrete Beam Exposed to Fire Under Fixed Loading

This study focuses on the experimental investigation of normal and sandwich reinforced concrete beam exposed to fire in order to evaluate their flexural stiffness. Two beams specimen of 200×300×4000 mm have been cast and tested under flexural loading. The first one has been a normal concrete beam (N) and the second one has been a sandwich concrete beam (SW) with 50 mm skin thickness and 200 mm core thickness. The skin compressive strength of 25 MPa and the core compressive strength of 15 MPa have been considered. The skin strength has been also applied to the N beam. The beams have been reinforced with a plain bar of 3ϕ12 as a tensile reinforcement and 2ϕ10 as compression reinforcement. Both the tensile and the compression reinforcement have yield strength of 300 MPa. The beams have been tested in a full-size furnace under standard fire testing. Nine thermocouples for measuring temperature have been mounted. An LVDT, which has been protected by fire-resistant material, has been placed at the center of the beam to measure the deflection. The 8.63 kN load has been employed at 1/3 span of the beam. Test results have showed that the flexural stiffness of the beam strongly affected by the accumulative temperature representing temperature and firing time. The strength of the N beam drops significantly after 15 minutes of firing and the beam strength has been totally lost. The firing of 45 minutes has needed to decrease the strength of the SW beam then has decreased gradually until 120 minutes of firing.

A novel chemical-consolidation sand control composition: Foam amino resin system

AbstractA novel chemical-consolidation method based foam amino resin system of sand control systems in the oilfield is reported. This sand control technique is more superior to the conventional method owing to its advantages such as the outstanding resistance and lower density as well as simple process preparation. The apparent density of the foam resin system ranges from 0.528 g/cm3 to 0.634 g/cm3 at room temperature. Moreover, the system has excellent foaming properties and excellent compatibility with the formation fluids. In addition, the foam amino resin sand consolidation system was optimized and investigated. Simultaneously, the sand-fixing performance of the foam resin system was comprehensively assessed. The optimized conditions are as follows: curing temperature, 60°C; curing time, 12 h; consolidated core compressive strength, 6.28 MPa. Furthermore, the consolidated core showed remarkable resistance to the formation fluids. In summary, the foam resin system effectively met the requirements of the sand control and the horizontal wells in the oilfield.