scholarly journals Experimental Investigations on the Long Term Material Properties of Rubberized Portland Cement Concrete

2021 ◽  
Vol 11 (22) ◽  
pp. 10868
Author(s):  
Ionut-Ovidiu Toma ◽  
Sergiu-Mihai Alexa-Stratulat ◽  
Petru Mihai ◽  
Ana-Maria Toma ◽  
George Taranu
Keyword(s):  
Research Work ◽  
Experimental Investigations ◽  
Rubberized Concrete ◽  
Portland Cement Concrete ◽  
Natural Sand ◽  
Significant Drop ◽  
Fine Aggregates ◽  
Tensile Splitting Strength ◽  
Non Destructive

The paper presents the results of a research work aimed at assessing the long-term strength and elastic properties of rubberized concrete. The parameters of the research were the rubber replacement of fine aggregates and the age of testing the specimens. Compressive and splitting tensile strength of concrete cylinders were obtained at the age of 5 years, coupled with the static and dynamic modulus of elasticity of all concrete specimens. Additionally, the material damping coefficient was assessed by means of non-destructive tests. The density of the rubberized concrete decreases with the percentage replacement of natural sand by rubber aggregates. A significant drop in the values of density after 5 years was observed for specimens made with rubberized concrete. The static and the dynamic moduli of elasticity decrease with the increase in rubber content. A similar trend is observed for the compressive and tensile splitting strength.

Experimental Research on Resistance to Frost of Rubberized Concrete

2012 ◽  
Vol 193-194 ◽  
pp. 1414-1417
Author(s):  
Jin Hua Xu ◽  
Si Li Chen ◽  
Ying Wang ◽  
Ming Liu
Keyword(s):  
Elasticity Modulus ◽  
Fine Aggregate ◽  
Rubberized Concrete ◽  
Portland Cement Concrete ◽  
Destructive Testing ◽  
Dynamic Elasticity Modulus ◽  
Dynamic Elasticity ◽  
Different Grain Size ◽  
Different Content ◽  
Non Destructive

According to mixture proportions design, rubber concrete specimens were produced, which were used for test of resistance to frost. In this study, different grain size and different content rubber were mixed in Portland cement concrete. Quick freeze-thaw test was carried to rubberized concrete. The research shows that appropriate proportional fine aggregate replaced by the discarded tires powder and grain can improve concrete resistance to frost, although concrete compressive strength, flexural strength and dynamic elasticity modulus decrease with increasing of rubber content. The improving effect of rubber powder is better than rubber grain. Furthermore, it is demonstrated that the dynamic elasticity modulus obtained by Non-destructive testing can commendably evaluate the frost resistance of rubberized concrete.

scholarly journals Influence of material degradation on weld seam quality in hot gas butt welding of polyamides

2021 ◽  
Author(s):  
Max Bialaschik ◽  
Volker Schöppner ◽  
Mirko Albrecht ◽  
Michael Gehde
Keyword(s):  
Weld Seam ◽  
Experimental Investigations ◽  
Heating Process ◽  
Butt Welding ◽  
Hot Gas ◽  
Process Gas ◽  
Glass Fiber Reinforced ◽  
Extrusion Welding ◽  
Different Gases

AbstractThe joining of plastics is required because component geometries are severely restricted in conventional manufacturing processes such as injection molding or extrusion. In addition to established processes such as hot plate welding, infrared welding, or vibration welding, hot gas butt welding is becoming more and more important industrially due to its advantages. The main benefits are the contactless heating process, the suitability for glass fiber reinforced, and high-temperature plastics as well as complex component geometries. However, various degradation phenomena can occur during the heating process used for economic reasons, due to the presence of oxygen in the air and to the high gas temperatures. In addition, the current patent situation suggests that welding with an oxidizing gas is not permissible depending on the material. On the other hand, however, there is experience from extrusion welding, with which long-term resistant weld seams can be produced using air. Investigations have shown that the same weld seam properties can be achieved with polypropylene using either air or nitrogen as the process gas. Experimental investigations have now been carried out on the suitability of different gases with regard to the weld seam quality when welding polyamides, which are generally regarded as more prone to oxidation. The results show that weld strengths are higher when nitrogen is used as process gas. However, equal weld strengths can be achieved with air and nitrogen when the material contains heat stabilizers.

Investigations into the Precessing Vortex Core Phenomenon in Cyclone Dust Separators

1994 ◽  
Vol 208 (2) ◽  
pp. 147-154 ◽  
Author(s):  
P Yazdabadi ◽  
A J Griffiths ◽  
N Syred
Keyword(s):  
Vortex Core ◽  
Reynolds Numbers ◽  
Frequency Parameter ◽  
Experimental Investigations ◽  
Swirl Number ◽  
Significant Drop ◽  
Precessing Vortex Core ◽  
Dust Separator ◽  
The Relationship

Experimental investigations have been carried out to examine the effect of downstream pipework configurations on the precessing vortex core (PVC) generated within the exhaust region of a cyclone dust separator. Characterization of the PVC using a non-dimensionalized frequency parameter (NDFP) was used to determine the relationship between Reynolds number and geometrical swirl number of the cyclone. The results show that the NDFP tends towards an asymptotic value for Reynolds numbers of about 50 000 and high swirl numbers (> 3.043). This value is reached earlier with lower swirl numbers. It was concluded that any exhaust pipework configuration produced a significant drop in the PVC frequency, and certain configurations either delayed or promoted the development of the PVC.

Methods for Separation of Copper Oxide Nanoparticles From Colloidal Suspension in Dodecane

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
Mohammed H. Sheikh ◽  
Muhammad A. R. Sharif
Keyword(s):  
Energy Storage ◽  
Copper Oxide ◽  
Phase Change ◽  
Phase Change Materials ◽  
Research Work ◽  
Cuo Nanoparticles ◽  
Health Hazards ◽  
Suspension Stability ◽  
Reduced Pressure

Phase change materials (PCM) are used in many energy storage applications. Energy is stored (latent heat of fusion) by melting the PCM and is released during resolidification. Dispersing highly conductive nanoparticles into the PCM enhances the effective thermal conductivity of the PCM, which in turn significantly improves the energy storage capability of the PCM. The resulting colloidal mixture with the nanoparticles in suspension is referred to as nanostructure enhanced phase change materials (NEPCM). A commonly used PCM for energy storage application is the family of paraffin (CnH2n+2). Mixing copper oxide (CuO) nanoparticles in the paraffin produces an effective and highly efficient NEPCM for energy storage. However, after long term application cycles, the efficiency of the NEPCM may deteriorate and it may need replacement with fresh supply. Disposal of the used NEPCM containing the nanoparticles is a matter of concern. Used NEPCM containing nanoparticles cannot be discarded directly into the environment because of various short term health hazards for humans and all living beings and unidentified long term environmental and health hazards due to nanoparticles. This problem will be considerable when widespread use of NEPCM will be practiced. It is thus important to develop technologies to separate the nanoparticles before the disposal of the NEPCM. The primary objective of this research work is to develop methods for the separation and reclamation of the nanoparticles from the NEPCM before its disposal. The goal is to find, design, test, and evaluate separation methods which are simple, safe, and economical. The specific NEPCM considered in this study is a colloidal mixture of dodecane (C12H26) and CuO nanoparticles (1–5% mass fraction and 5–15 nm size distribution). The nanoparticles are coated with a surfactant or stabilizing ligands for suspension stability in the mixture for a long period of time. Various methods for separating the nanoparticles from the NEPCM are explored. The identified methods include: (i) distillation under atmospheric and reduced pressure, (ii) mixing with alcohol mixture solvent, and (iii) high speed centrifugation. These different nanoparticle separation methods have been pursued and tested, and the results are analyzed and presented in this article.

scholarly journals North European Export Industry and the Shadows of Sulphur Directive

2016 ◽  
Vol 17 (1) ◽  
pp. 9-17 ◽  
Author(s):  
Esa Hämäläinen ◽  
Olli-Pekka Hilmola ◽  
Andres Tolli
Keyword(s):  
Paper Industry ◽  
Research Work ◽  
Transportation Cost ◽  
Paper Mill ◽  
Export Industry ◽  
Eu Directive ◽  
Oil Markets ◽  
Regulation Change ◽  
European Export

Abstract EU Directive of MARPOL Annex VI and its economic impact on the Nordic paper industry is theme of this research work. Empirical data for analysis purposes was gained from a large Nordic paper mill that exports bulk products mainly to Europe (70 % of its volume). The study shows that in the end the industry’s location still has an economical effect, and that the location has a distinct impact on competition through rising transportation costs. Environmental regulation continues and fosters long-term upwards trajectory of transportation cost, which has been experienced by the paper mill earlier during years 2001-2009. Sulphur regulation change to cleaner grades of maritime diesel did not turn as heavy cost increase in the 2015, however, possibility to gain cost benefits in rapidly deteriorating oil markets were not reached either. Therefore, in depressed industrial product markets, like paper industry, implications were such that margins of export industry remained low.

Influences on the Hydrophobicity of Concrete Surfaces Treated with Alkyl Trialkoxysilanes

2014 ◽  
Vol 20 (6) ◽  
pp. 405-412
Author(s):  
U. Antons ◽  
M. Raupach ◽  
O. Weichold
Keyword(s):  
Uv Radiation ◽  
Cement Hydration ◽  
Alkaline Media ◽  
Water Repellent ◽  
Portland Cement Concrete ◽  
Accelerated Carbonation ◽  
Surface Layers ◽  
Hydrophobic Layer ◽  
Furnace Slag

Abstract The paper focuses on how alkaline media, UV radiation, and carbonation as well as on-going cement hydration affects hydrophobic treatments of concrete and influences the properties of these water-repellent layers. Single-sided nuclear magnetic resonance measurements show that layers formed by impregnating samples with alkyl trialkoxysilanes are stable even under long-term exposure to alkaline solution and UV radiation, with the damage of the latter being limited to the topmost surface layers. Microstructural changes during accelerated carbonation of blast furnace slag cement based concrete have a major impact on the hydrophobic layer properties, while the carbonation of Portland cement concrete has no influence. On-going hydration additionally influences the hydrophobic layer properties.

The Long-Term Effects of Grief on Marital Intimacy following an Infant's Death

1996 ◽  
Vol 33 (1) ◽  
pp. 1-19 ◽  
Author(s):  
Laurie N. Gottlieb ◽  
Ariella Lang ◽  
Rhonda Amsel
Keyword(s):  
Home Visit ◽  
Sexual Intimacy ◽  
Long Term Effects ◽  
Emotional Intimacy ◽  
Significant Drop ◽  
Marital Intimacy ◽  
Grief Responses ◽  
Changes Over Time

This follow-up study examined how marital intimacy changes over time in bereaved couples and how their marriages are affected by the death of their infant. A group of thirty-one bereaved couples who two to four years earlier had lost an infant (> 20 weeks gestation and < 1 year of age) were revisited in their home twenty-four months after the initial home visit. Couples did report a significant drop in sexual intimacy at follow-up compared to before the loss and at the initial home visit. Moreover, wives reported less emotional intimacy overall, than did their husbands. In contrast to wives whose own initial grief responses predicted their feelings about their marriages two years later, intensity of husband's initial grief response did not affect their relationship with their wives but, rather a more powerful predictor was their wives' initial reactions, the early state of their marriage (whether they had considered separating), and whether or not they had warning of the impending death. Finally, there is some evidence that women are affected in part, by their husbands' grief.

A sustainable approach to optimum utilization of used foundry sand in concrete

2018 ◽  
Vol 25 (5) ◽  
pp. 927-937 ◽  
Author(s):  
Khuram Rashid ◽  
Sana Nazir
Keyword(s):  
Compressive Strength ◽  
Modulus Of Elasticity ◽  
Research Work ◽  
Hardened Concrete ◽  
Prediction Formula ◽  
Foundry Sand ◽  
Foundry Sands ◽  
Fine Aggregates ◽  
Optimum Utilization ◽  
Conservation Of Natural Resources

AbstractConservation of natural resources, healthy environments, and optimal utilization of waste materials are intimate needs of the present time, and this research work was carried out to fulfill these needs. In this experimental and analytical study, concrete was prepared by replacing natural fine aggregates with two types of used foundry sands by 10%, 20% and 30% (by volume). The properties of fresh and hardened concrete were investigated and compared with a replacement amount of fine aggregates from 0% to 30%. Compressive strength was evaluated after 7, 28 and 63 days of moist curing. Along with compressive strength, the modulus of elasticity was also investigated and a reduction in compressive strength and modulus of elasticity was observed with the increase in the amount of used foundry sand. A prediction formula was proposed to predict the compressive strength, and verified by current experimental observations and also with a large database that was also established in this work. The prediction formula may be considered as very helpful for predicting the potential of using used foundry sand as an aggregate in concrete.

Species interactions in mixed-community crystalline biofilms on urinary catheters

2007 ◽  
Vol 56 (11) ◽  
pp. 1549-1557 ◽  
Author(s):  
Sarah M. Macleod ◽  
David J. Stickler
Keyword(s):  
Urinary Tract ◽  
Species Interactions ◽  
The Other ◽  
Experimental Investigations ◽  
Crystal Formation ◽  
Urinary Catheters ◽  
E Coli ◽  
Pure Cultures ◽  
Providencia Stuartii

Previous experimental investigations of the crystalline biofilms that colonize and block urinary catheters have focussed on their formation by pure cultures of Proteus mirabilis. In the urine of patients undergoing long-term catheterization, P. mirabilis is commonly found in mixed communities with other urinary tract pathogens. Little is known about the effect that the other species have on the rate at which P. mirabilis encrusts catheters. In the present study, a set of data on the nature of the bacterial communities on 106 catheter biofilms has been analysed and it was found that while species such as Providencia stuartii and Klebsiella pneumoniae were commonly associated with P. mirabilis, when Escherichia coli, Morganella morganii or Enterobacter cloacae were present, P. mirabilis was rarely or never found. The hypothesis that the absence of P. mirabilis from some biofilm communities could be due to its active exclusion by other species has also been examined. Experiments in laboratory models showed that co-infection of P. mirabilis with M. morganii, K. pneumoniae or E. coli had no effect on the ability of P. mirabilis to encrust and block catheters. Co-infection with Ent. cloacae or Pseudomonas aeruginosa, however, significantly increased the time that catheters took to block (P <0.05). The growth of Ent. cloacae, M. morganii, K. pneumoniae or E. coli in the model for 72 h prior to superinfection with P. mirabilis significantly delayed catheter blockage. In the case of Ent. cloacae, for example, the mean time to blockage was extended from 28.7 h to 60.7 h (P ≤0.01). In all cases, however, P. mirabilis was able to generate alkaline urine, colonize the biofilms, induce crystal formation and block the catheters. The results suggest that although there is a degree of antagonism between P. mirabilis and some of the other urinary tract organisms, the effects are temporary and whatever the pre-existing urinary microbiota, infection with P. mirabilis is thus likely to lead to catheter encrustation and blockage.

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