scholarly journals Combined Effect of Multi-Walled Carbon Nanotubes, Steel Fibre and Glass Fibre Mesh on Novel Two-Stage Expanded Clay Aggregate Concrete against Impact Loading

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 720
Author(s):  
Gunasekaran Murali ◽  
Sallal R. Abid ◽  
Mugahed Amran ◽  
Roman Fediuk ◽  
Nikolai Vatin ◽  
...  
Keyword(s):  
Glass Fibre ◽  
Steel Fibre ◽  
Lightweight Concrete ◽  
Concrete Strength ◽  
Strength Properties ◽  
Combined Effect ◽  
Two Stage ◽  
Steel Fibres ◽  
The Impact ◽  
Fibre Mesh

The use of expanded clay aggregate (ECA) for developing lightweight concrete results in strength-reduction properties. However, the ECA-based concrete strength properties can be improved by adding steel fibre (SF), glass fibre mesh (GFM) and multi-walled nano-carbon tubes (MWCNT). The combined effect of MWCNT, GFM, SF and ECA-based concrete and its strength properties is still unexplored. It is worth drawing a logical conclusion concerning the impact on the strength of concrete by incorporating the materials mentioned above. Two-stage expanded clay aggregate fibrous concrete (TECAFC) is a new concrete type and an emerging research area in material engineering. The casting method of TECAFC includes the two essential phases as follows. First, ECA and fibres are filled into the empty cylindrical mould to develop a natural skeleton. Second, the grout comprising cement, sand and MWCNT, are injected into the developed skeleton to fill voids. In this research, eight mixtures were prepared with 0.1 and 0.2% of MWCNT, 2.5% dosage of SF and three different layers of GFM inserted between the two layers of concrete. These eight mixtures were divided into two series of three mixtures each, in addition to two reference mixtures that include no SF or GFM. The first series of mixtures was comprised of 0.1% of MWCNT and 2.5% of SF and one, two and three layers of GFM insertion. The second series was the same as the first series and the dosage of MWCNT was taken as 0.2%. All cylindrical specimens were tested under drop mass impact as per the suggestions made by the ACI Committee 544. The test results showed that incorporating steel fibres and GFM improved the cracking and failure impact resistance by more than 270 and 1100%, respectively, and increased the impact ductility index by more than 220%, significantly contributing to steel fibres.

scholarly journals Mix Proportion of Lightweight Straw Ceramsite Concrete

CONVERTER ◽  
2021 ◽  
pp. 110-117
Author(s):  
Yanxia Huang
Keyword(s):  
Compressive Strength ◽  
Lightweight Concrete ◽  
Concrete Strength ◽  
Engineering Application ◽  
Volumetric Method ◽  
Comprehensive Utilization ◽  
Mix Proportion ◽  
Concrete Mix ◽  
Straw Burning ◽  
The Impact

To reduce air pollution of straw burning, and also to improve the ratio of straw comprehensive utilization, this paper presents a lightweight concrete with straw based on the mix proportion research. Firstly, the mix proportion of lightweight ceramsite concrete was designed by a volumetric method. Then, a series of lightweight ceramsite concrete mix proportion experiments were conducted to verify the validity of the design and to evaluate the effect of the admixtures on the performance of the concrete. Finally, the lightweight straw ceramsite concrete mix proportion experiments were conducted by adding straw to lightweight ceramsite concrete for studying the impact of the straw amount on the concrete strength and density. The experimental results show that the compressive strength of lightweight straw ceramsite concrete can reach the requirement of engineering application. The concrete strength and density were descended obviously with the increasing of straw amount. It was suggested that the straw amount should be limited in 20% of the concrete volume.

Experimental Tests of Steel Fibre Reinforced Concrete Beams under Drop-Weight Impacts

2014 ◽  
Vol 626 ◽  
pp. 311-316 ◽  
Author(s):  
Yi Fei Hao ◽  
Hong Hao ◽  
Gang Chen
Keyword(s):  
Reinforced Concrete ◽  
Steel Fibre ◽  
Concrete Beams ◽  
Plain Concrete ◽  
Fibre Reinforced Concrete ◽  
Steel Fibres ◽  
Steel Fibre Reinforced Concrete ◽  
Impact Tests ◽  
Drop Weight ◽  
The Impact

Concrete is a brittle material, especially under tension. Intensive researches have been reported to add various types of fibres into concrete mix to increase its ductility. Recently, the authors proposed a new type of steel fibre with spiral shape to reinforce concrete material. Laboratory tests on concrete cylinder specimens demonstrated that compared to other fibre types such as the hooked-end, deformed and corrugated fibres the new fibres have larger displacement capacity and provide better bonding with the concrete. This study performs drop-weight impact tests to investigate the behaviour of concrete beams reinforced by different types of steel fibres. The quasi-static compressive and split tensile tests were also conducted to obtain the static properties of plain concrete and steel fibre reinforced concrete (FRC) materials. The quasi-static tests were carried out using hydraulic testing machine and the impact tests were conducted using an instrumented drop-weight testing system. Plain concrete and concrete reinforced by the commonly used hooked-end steel fibres and the proposed spiral-shaped steel fibres were tested in this study. The volume dosage of 1% fibre was used to prepare all FRC specimens. Repeated drop-weight impacts were applied to the beam specimens until total collapse. A 15.2 kg hard steel was used as the drop-weight impactor. A drop height of 0.5 m was considered in performing the impact tests. The force-displacement relations and the energy absorption capabilities of plain concrete and FRC beams were obtained, compared and discussed. The advantage and effectiveness of the newly proposed spiral-shaped steel fibres in increasing the performance of FRC beam elements under impact loads were examined.

scholarly journals Behaviour of Micro Reinforced Concrete with Hooked End Steel Fibres subjected to Impact Loads

2019 ◽  
Vol 8 (3) ◽  
pp. 3453-3461
Keyword(s):  
Impact Energy ◽  
Volume Fraction ◽  
Impact Load ◽  
Concrete Strength ◽  
Initial Crack ◽  
Target Strength ◽  
Hardened Concrete ◽  
Steel Fibres ◽  
Drop Weight Test ◽  
The Impact

Reinforced cement concrete is a common material used for building constructions. In this work a trial has been created to utilize steel fibres in RCC members to extend strength and conjointly to extend resistance to impact load. Hooked end steel fibres (HESF) are used here for the preparation of concrete specimens. Concrete grade of M30 is selected and mix design was carried out for target strength of 38.25 N/mm2 . Varied volume fractions of HESF such as 0%, 1%, 2%, 3% and 4% were added to concrete. Cube, beam and cylindrical specimens were cast with good compaction and cured fully as per standards. Hardened concrete strength of all the specimens with different quantities of HEFS were tested. Simple drop weight test was conducted on the specimens reinforced with different percentages of steel fibres. The impact load is produced by means of dropping a weight of 5.5 kg from 400 mm height. Impact energy of the specimens is derived from number of blows required to produce initial crack (N1) and number of blows to cause complete failure (N2). Impact energy of the specimens with different quantities of fibres are compared. Results indicated that the concrete specimens with 3% volume fraction of fibre has shown best performance and it is also seen that the increase in volume of fibre beyond 3% has resulted in reduced impact energy

A Study on Lightweight Multifunctional Concrete Made Using Waste PET Bottles

2012 ◽  
Vol 193-194 ◽  
pp. 964-969
Author(s):  
Yoshinori Kitsutaka ◽  
Yuichi Uchida
Keyword(s):  
Weight Reduction ◽  
Lightweight Concrete ◽  
Functional Materials ◽  
Concrete Specimen ◽  
Strength Properties ◽  
Recycling Rate ◽  
Pet Bottles ◽  
Complicated Process ◽  
High Level ◽  
The Impact

Polyethylene terephthalate containers (PET bottles) are recycled into fibers and sheets, but the complicated process requires a high level of technology and large cost resulting in a low recycling rate of PET. Weight reduction of concrete has been demanded for certain uses. In view of this, lightweight concrete embedding raw PET bottles is conceivable. It may be used for void slabs and lightweight wall panels for dwelling units. Also such bottles filled with functional materials can add a new function to concrete. In this study, the basic physical properties of lightweight multifunctional concrete embedding used PET bottles were investigated. A method of placing concrete with embedded PET bottles was examined. PET bottles fixed to the mold at their caps withstood the impact and the pressure during concrete placing with no deformation and the filling capability of concrete was confirmed. The weight reduction of the reinforcing concrete panel embedding PET bottles was approximately 16%. The strength properties of concrete embedding PET bottles were examined and the compressive strength of the specimen embedding bottles with the smallest intervals between bottles was 55% of that of the solid concrete specimen.

Does kraft hardwood and softwood pulp viscosity correlate to paper properties?

TAPPI Journal ◽  
2016 ◽  
Vol 15 (10) ◽  
pp. 643-651 ◽  
Author(s):  
ROBERT J. OGLESBY ◽  
HUMPHREY J. MOYNIHAN ◽  
RICARDO B. SANTOS ◽  
ASHOK GHOSH ◽  
PETER W. HART
Keyword(s):  
Physical Properties ◽  
Strength Loss ◽  
Strength Properties ◽  
Clear Correlation ◽  
Paper Properties ◽  
Physical Strength ◽  
Pulp Viscosity ◽  
Softwood Pulp ◽  
The Impact ◽  
Related Paper

The impact of commercially prepared, fully bleached pulp viscosity variation on handsheet physical properties was evaluated at different levels of pulp refining. Hardwood pulps from the same brownstock species mix, cooking parameters, and kappa numbers were processed through two different commercial bleach plants: one with a D0(EP)D1D2 sequence and the second with an OD0(EOP)D1 sequence. Additionally, a commercial softwood (predominately Scotts pine) brownstock pulp bleached by an OD0(EP)D1D2 sequence was employed in this study. Pulps with viscosities ranging from 14 to 21 mPa∙s were refined in a Valley beater to two freeness levels, and the associated handsheet physical properties were measured in this study. Over the pulp viscosity range of 14 to 21 mPa∙s, no clear correlation was found to exist between pulp viscosity and related paper physical properties. Finally, a series of laboratory prepared bleached pulps were purposely prepared under non-ideal conditions to reduce their final viscosities to lower values. Handsheets made from these pulps were tested in their unbeaten condition for physical strength properties. Significant and rapid strength loss occurred when the measured pulp viscosity dropped below 12 mPa∙s; overall strength properties showed no correlation to viscosity above the critical 12 mPa∙s value.

Evaluation of Hydraulic Fracturing Models and Their Limitations to Predict No-Drill Zones for Horizontal Directional Drilling

2018 ◽  
Author(s):  
Saeed Delara ◽  
Kendra MacKay
Keyword(s):  
Hydraulic Fracturing ◽  
Safety Factor ◽  
Standard Procedure ◽  
Accurate Determination ◽  
Strength Properties ◽  
Analytical Models ◽  
Alternative Methods ◽  
Directional Drilling ◽  
Horizontal Directional Drilling ◽  
The Impact

Horizontal directional drilling (HDD) has become the preferred method for trenchless pipeline installations. Drilling pressures must be limited and a “no-drill zone” determined to avoid exceeding the strength of surrounding soil and rock. The currently accepted industry method of calculating hydraulic fracturing limiting pressure with application of an arbitrary safety factor contains several assumptions that are often not applicable to specific ground conditions. There is also no standard procedure for safety factor determination, resulting in detrimental impacts on drilling operations. This paper provides an analysis of the standard methods and proposes two alternative analytical models to more accurately determine the hydraulic fracture point and acceptable drilling pressure. These alternative methods provide greater understanding of the interaction between the drilling pressures and the surrounding ground strength properties. This allows for more accurate determination of horizontal directional drilling limitations. A comparison is presented to determine the differences in characteristics and assumptions for each model. The impact of specific soil properties and factors is investigated by means of a sensitivity analysis to determine the most critical soil information for each model.

scholarly journals Robust Inferences from a Before-and-After Study with Multiple Unaffected Control Groups

2013 ◽  
Vol 1 (2) ◽  
pp. 209-234 ◽  
Author(s):  
Pengyuan Wang ◽  
Mikhail Traskin ◽  
Dylan S. Small
Keyword(s):  
Sensitivity Analysis ◽  
Control Groups ◽  
Two Stage ◽  
Time Effects ◽  
Unaffected Control ◽  
Group Time ◽  
Before And After ◽  
Group Variation ◽  
The Impact ◽  
Before And After Study

AbstractThe before-and-after study with multiple unaffected control groups is widely applied to study treatment effects. The current methods usually assume that the control groups’ differences between the before and after periods, i.e. the group time effects, follow a normal distribution. However, there is usually no strong a priori evidence for the normality assumption, and there are not enough control groups to check the assumption. We propose to use a flexible skew-t distribution family to model group time effects, and consider a range of plausible skew-t distributions. Based on the skew-t distribution assumption, we propose a robust-t method to guarantee nominal significance level under a wide range of skew-t distributions, and hence make the inference robust to misspecification of the distribution of group time effects. We also propose a two-stage approach, which has lower power compared to the robust-t method, but provides an opportunity to conduct sensitivity analysis. Hence, the overall method of analysis is to use the robust-t method to test for the overall hypothesized range of shapes of group variation; if the test fails to reject, use the two-stage method to conduct a sensitivity analysis to see if there is a subset of group variation parameters for which we can be confident that there is a treatment effect. We apply the proposed methods to two datasets. One dataset is from the Current Population Survey (CPS) to study the impact of the Mariel Boatlift on Miami unemployment rates between 1979 and 1982.The other dataset contains the student enrollment and grade repeating data in West Germany in the 1960s with which we study the impact of the short school year in 1966–1967 on grade repeating rates.

scholarly journals Evaluation of the Impact of Organic Fillers on Selected Properties of Organosilicon Polymer

Polymers ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1103
Author(s):  
Sara Sarraj ◽  
Małgorzata Szymiczek ◽  
Tomasz Machoczek ◽  
Maciej Mrówka
Keyword(s):  
Tensile Strength ◽  
Natural Fiber ◽  
Accelerated Aging ◽  
Strength Properties ◽  
Visual Observation ◽  
Walnut Shell ◽  
Pistachio Shell ◽  
Thermoplastic Matrix ◽  
Static Tensile ◽  
The Impact

Eco-friendly composites are proposed to substitute commonly available polymers. Currently, wood–plastic composites and natural fiber-reinforced composites are gaining growing recognition in the industry, being mostly on the thermoplastic matrix. However, little data are available about the possibility of producing biocomposites on a silicone matrix. This study focused on assessing selected organic fillers’ impact (ground coffee waste (GCW), walnut shell (WS), brewers’ spent grains (BSG), pistachio shell (PS), and chestnut (CH)) on the physicochemical and mechanical properties of silicone-based materials. Density, hardness, rebound resilience, and static tensile strength of the obtained composites were tested, as well as the effect of accelerated aging under artificial seawater conditions. The results revealed changes in the material’s properties (minimal density changes, hardness variation, overall decreasing resilience, and decreased tensile strength properties). The aging test revealed certain bioactivities of the obtained composites. The degree of material degradation was assessed on the basis of the strength characteristics and visual observation. The investigation carried out indicated the impact of the filler’s type, chemical composition, and grain size on the obtained materials’ properties and shed light on the possibility of acquiring ecological silicone-based materials.

scholarly journals Influence of Rapid Heat Treatment on the Shrinkage and Strength of High-Performance Concrete

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4102
Author(s):  
Jan Stindt ◽  
Patrick Forman ◽  
Peter Mark
Keyword(s):  
Heat Treatment ◽  
High Performance ◽  
High Performance Concrete ◽  
Treatment Time ◽  
Precast Concrete ◽  
Concrete Strength ◽  
Shrinkage Strain ◽  
Temperature Treatment ◽  
Production Flow ◽  
Steel Fibres

Resource-efficient precast concrete elements can be produced using high-performance concrete (HPC). A heat treatment accelerates hardening and thus enables early stripping. To minimise damages to the concrete structure, treatment time and temperature are regulated. This leads to temperature treatment times of more than 24 h, what seems too long for quick serial production (flow production) of HPC. To overcome this shortcoming and to accelerate production speed, the heat treatment is started here immediately after concreting. This in turn influences the shrinkage behaviour and the concrete strength. Therefore, shrinkage is investigated on prisms made from HPC with and without steel fibres, as well as on short beams with reinforcement ratios of 1.8% and 3.1%. Furthermore, the flexural and compressive strengths of the prisms are measured directly after heating and later on after 28 d. The specimens are heat-treated between 1 and 24 h at 80 °C and a relative humidity of 60%. Specimens without heating serve for reference. The results show that the shrinkage strain is pronouncedly reduced with increasing temperature duration and rebar ratio. Moreover, the compressive and flexural strength decrease with decreasing temperature duration, whereby the loss of strength can be compensated by adding steel fibres.

scholarly journals A Two-Stage Joint Model for Nonlinear Longitudinal Response and a Time-to-Event with Application in Transplantation Studies

2012 ◽  
Vol 2012 ◽  
pp. 1-18 ◽  
Author(s):  
Magdalena Murawska ◽  
Dimitris Rizopoulos ◽  
Emmanuel Lesaffre
Keyword(s):  
Empirical Bayes ◽  
Cox Model ◽  
Data Sets ◽  
Two Stage ◽  
Nonlinear Mixed Effects Model ◽  
Resistance Evolution ◽  
Longitudinal Response ◽  
Longitudinal Measurements ◽  
Subject Specific ◽  
The Impact

In transplantation studies, often longitudinal measurements are collected for important markers prior to the actual transplantation. Using only the last available measurement as a baseline covariate in a survival model for the time to graft failure discards the whole longitudinal evolution. We propose a two-stage approach to handle this type of data sets using all available information. At the first stage, we summarize the longitudinal information with nonlinear mixed-effects model, and at the second stage, we include the Empirical Bayes estimates of the subject-specific parameters as predictors in the Cox model for the time to allograft failure. To take into account that the estimated subject-specific parameters are included in the model, we use a Monte Carlo approach and sample from the posterior distribution of the random effects given the observed data. Our proposal is exemplified on a study of the impact of renal resistance evolution on the graft survival.

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