scholarly journals The Impact of the Amount and Length of Fibrillated Polypropylene Fibres on the Properties of HPC Exposed to High Temperature / Wpływ Ilosci I Długosci Fibrylowanych Włókien Polipropylenowych Na Własciwosci Hpc Poddanego Działaniu Wysokiej Temperatury

2010 ◽  
Vol 56 (1) ◽  
pp. 57-68 ◽  
Author(s):  
I. Hager ◽  
T. Tracz
Keyword(s):  
High Temperature ◽  
Surface Water ◽  
Water Absorption ◽  
Transport Properties ◽  
High Performance ◽  
Gas Permeability ◽  
Research Programme ◽  
Polypropylene Fibres ◽  
Residual Transport ◽  
The Impact

Abstract This paper presents the results of research on high performance concretes (HPC) modified by the addition of polypropylene fibres (PP fibres). The scope of the research was the measurement of the residual transport properties of heated and recooled concretes: gas permeability and surface water absorption. Seven types of concrete modified with fibrillated PP fibres were tested. Three lengths: 6, 12 and 19 mm and three amounts of fibres: 0, 0.9 and 1.8 kg/m3 were used. The research programme was designed to determine which length of fibres, used in which minimum amount, will, after the fibres melt, permit the development of a connected network and pathway for gases and liquids.

scholarly journals The influence of type of cement on the degradation of microstructure and transport properties of cement mortars exposed to frost induced damage

2018 ◽  
Vol 174 ◽  
pp. 01014
Author(s):  
Alicja Wieczorek ◽  
Marcin Koniorczyk
Keyword(s):  
Absorption Coefficient ◽  
Pore Structure ◽  
Water Absorption ◽  
Transport Properties ◽  
Cement Mortar ◽  
Gas Permeability ◽  
Water Absorption Coefficient ◽  
Freeze Thaw ◽  
Cement Mortars ◽  
Small Pore

The purpose of the study is to understand how the cyclic water freezing (0, 25, 50, 75, 100 and 150 freeze-thaw cycles) impacts microstructure and transport properties of cement-based materials. Tests were conducted on cement mortars with different water/cement ratios (w/c=0.45 and 0.40) and on two types of cement (CEM I and CEM III) without air-entraining admixtures. The changes of pore size distribution and open porosity were investigated by means of mercury intrusion porosimetry. Additionally, the relationship between intrinsic permeability and the water absorption coefficient of cement mortar samples was analysed. The water absorption coefficient and gas permeability were determined using capillary absorption test and the modified RILEMCembureau method. The evolution of transport coefficients with growing number of freeze-thaw cycles were determined on the same sample. It was also established that change of pore structure (a decrease of small pore volume <100nm and increase of larger pores >100nm) induces an increase of water transport parameters such as permeability and water absorption coefficient. The higher gas permeability corresponds to the higher internal damage. In particular, it is associated with the change of cement mortar microstructure, which indicates damage of narrow channels in the pore structure of cement mortars.

Transport properties of high-performance cementitious composites incorporating micro and nano SiO2 into the binder

2012 ◽  
Vol 19 (4) ◽  
pp. 415-421 ◽  
Author(s):  
Mostafa Jalal
Keyword(s):  
Water Absorption ◽  
Transport Properties ◽  
High Performance ◽  
Chloride Penetration ◽  
Binder Content ◽  
Cementitious Composites ◽  
Capillary Absorption ◽  
Nano Silica ◽  
Self Compacting Concrete ◽  
Concrete Properties

AbstractIn this paper, transport properties of high-performance self-compacting concrete (SCC), as one of the important cementitious composites incorporating micro and nano silica (NS) (SiO2) into the binder, have been investigated. For this purpose, different mixtures were designed with different amounts of silica fume (SF) and NS admixtures. Different binder contents were also investigated to observe the binder content effect on the concrete properties. Corrosion behavior was evaluated by chloride penetration and resistivity tests. Water absorption and capillary absorption were also measured as other durability related properties. The results showed that water absorption, capillary absorption, and Cl ion percentage decreased rather significantly in the mixtures containing admixtures especially the blend of SF and NS. By addition of the admixtures, resistivity of the SCC mixtures increased, which can lead to reduction of corrosion probability.

scholarly journals New Poly(imide)s Bearing Alkyl Side-Chains: A Study on the Impact of Size and Shape of Lateral Groups on Thermal, Mechanical, and Gas Transport Properties

Membranes ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 141
Author(s):  
Fidel E. Rodríguez-González ◽  
Germán Pérez ◽  
Vladimir Niebla ◽  
Ignacio Jessop ◽  
Rudy Martin-Trasanco ◽  
...  
Keyword(s):  
Transport Properties ◽  
Gas Transport ◽  
Gas Permeability ◽  
Tensile Modulus ◽  
Side Group ◽  
Tert Butyl ◽  
Degradation Temperature ◽  
Gas Transport Properties ◽  
The Impact ◽  
Poly Imide

A set of five new aromatic poly(imide)s (PIs) incorporating pendant acyclic alkyl moieties were synthesized. The difference among them was the length and bulkiness of the pendant group, which comprises of linear alkyl chains from three to six carbon atoms, and a tert-butyl moiety. The effect of the side group length on the physical, thermal, mechanical, and gas transport properties was analyzed. All PIs exhibited low to moderate molecular weights (Mn ranged between 27.930–58.970 Da, and Mw ranged between 41.760–81.310 Da), good solubility in aprotic polar solvents, except for PI-t-4, which had a tert-butyl moiety and was soluble even in chloroform. This behaviour was probably due to the most significant bulkiness of the side group that increased the interchain distance, which was corroborated by the X-ray technique (PI-t-4 showed two d-spacing values: 5.1 and 14.3 Å). Pure gas permeabilities for several gases were reported (PI-3 (Barrer): He(52); H2(46); O2(5.4); N2(1.2); CH4(1.1); CO2(23); PI-t-4 (Barrer): He(139); H2(136); O2(16.7); N2(3.3); CH4(2.3); CO2(75); PI-5 (Barrer): He(44); H2(42); O2(5.9); N2(1.4); CH4(1.2); CO2(27); PI-6 (Barrer): He(45); H2(43); O2(6.7); N2(1.7); CH4(1.7); CO2(32)). Consistent higher volume in the side group was shown to yield the highest gas permeability. All poly(imide)s exhibited high thermal stability with 10% weight loss degradation temperature between 448–468 °C and glass transition temperature between 240–270 °C. The values associated to the tensile strength (45–87 MPa), elongation at break (3.2–11.98%), and tensile modulus (1.43–2.19 GPa) were those expected for aromatic poly(imide)s.

scholarly journals The transport properties of cement mortars subjected to freeze-thaw cycles

2018 ◽  
Vol 49 ◽  
pp. 00128
Author(s):  
Alicja Wieczorek ◽  
Marcin Koniorczyk ◽  
Dalia Bednarska ◽  
Kalina Grabowska
Keyword(s):  
Absorption Coefficient ◽  
Water Absorption ◽  
Transport Properties ◽  
Positive Impact ◽  
Gas Permeability ◽  
Cement Matrix ◽  
Capillary Absorption ◽  
Water Absorption Coefficient ◽  
Freeze Thaw ◽  
Cement Mortars

The parameters characterizing the microstructure of cementbased materials, such as porosity or permeability, determine not only durability, but also risk of degradation of the cement matrix due to an aggressive environment. The report presents results of a research on transport properties of cement mortars subjected to cyclic water freezing. Mortars prepared on the basis of two different cements were the object of the research: Portland cement CEM I 42.5R and Portland blast-furnace slag cement CEM III/A 42.5N LH/HSR/NA, with two water-cement ratio (w/c=0.45 and 0.40). The experimental study was carried out in order to determine the relationship between intrinsic permeability and the water absorption coefficient in relation to the number of freeze-thaw cycles. The evolution of transport coefficients was determined using a capillary absorption test and the modified RILEM-Cembureau method. It was established that the degradation processes induced an increase of transport properties. Moreover, the microcracks had a more significant influence on permeability and lesser influence on the water absorption coefficient. The gas permeability of damaged mortar changed very significantly, an increase with several orders of magnitude could be noticed. Moreover, the positive impact of CEM III on ice-induced degradation was also visible.

scholarly journals Does university performance matter for EU programmes in South East Europe

2019 ◽  
Vol 24 (2) ◽  
pp. 1-10
Author(s):  
Suada Ajdarpašić ◽  
Gazmend Qorraj
Keyword(s):  
Success Rate ◽  
High Performance ◽  
Research Programme ◽  
The European Union ◽  
East Europe ◽  
Horizon 2020 ◽  
South East Europe ◽  
University Performance ◽  
The University ◽  
The Impact

This paper examines the educational system in South East Europe (SEE) within the framework of opportunities coming from the European Union, particularly Horizon 2020, a recent EU innovation and research programme. The specific goal of this article is to measure the impact of the performance of universities in South East Europe and the likelihood of obtaining EU programmes, specifically Horizon 2020 projects. The additional aim is to investigate whether high-ranking universities are successful in obtaining Horizon 2020 projects and, more specifically, if university performance is a significant factor in the success rate in obtaining Horizon 2020 projects. In order to analyse this phenomenon empirically, we compare the main public universities of South East Europe and consider their overall performance in relation to EU programmes obtained. The final outcome of the paper is that there is a clear relationship between the university performance and obtaining Horizon 2020 projects. Therefore, the high performance of a university positively correlates with a high success rate in obtaining Horizon 2020 projects for most of the universities.

scholarly journals Analysis of the impact of high temperature on the change in tensile strength of cement mortars with or without polypropylene fibres added

2018 ◽  
Vol 189 (3) ◽  
pp. 109-126
Author(s):  
Tomasz Drzymala ◽  
Michal Reszka
Keyword(s):  
Tensile Strength ◽  
High Temperature ◽  
Point Of View ◽  
Polypropylene Fibers ◽  
Cement Slurry ◽  
Polypropylene Fibres ◽  
Cement Mortars ◽  
Temperature Impact ◽  
The Impact ◽  
Positive Effect

When evaluating concrete, its strength is the most important feature from the practical point of view. In compliance with technological requirements, the strength of concrete depends primarily on its composition, mainly on the content and strength of cement slurry. This is because this concrete component is most susceptible to changes in working conditions in a construction, including high temperature impact on concrete during the fire. The paper presents the results of tests performed on the cement mortar with and without the addition of polypropylene fibers. This treatment allowed for the elimination of the effect of the coarse aggregate by reason of the accuracy of the tested strength characteristics. The studies concerned the impact of high temperature on the change in tensile strength of cement mortars modified with the addition of polypropylene fibers. The analysis of available literature shows that one of the main causes of concrete’s thermal spalling is seen in high tensile stresses. The results of many tests prove that the addition of polypropylene fibers can have a positive effect on the behavior of concrete structures at high temperatures and help reduce spalling. The polypropylene fibers present in a composite may also positively influence the increase in tensile strength. This article discusses the purpose and scope of research, research methods, the experiment plan, test benches, and test results as well. The conclusions of the study were formulated in the final part of the article.

Dietary Vitamin and Stability of Oral Anticoagulation: Proposal of a Diet with Constant Vitamin K1 Content

1997 ◽  
Vol 77 (03) ◽  
pp. 504-509 ◽  
Author(s):  
Sarah L Booth ◽  
Jacqueline M Charnley ◽  
James A Sadowski ◽  
Edward Saltzman ◽  
Edwin G Bovill ◽  
...  
Keyword(s):  
Dietary Intake ◽  
Vitamin K ◽  
High Performance ◽  
Case Reports ◽  
Food Composition ◽  
Dietary Guidelines ◽  
Dietary Vitamin ◽  
Vitamin K1 ◽  
The Stability ◽  
The Impact

SummaryCase reports cited in Medline or Biological Abstracts (1966-1996) were reviewed to evaluate the impact of vitamin K1 dietary intake on the stability of anticoagulant control in patients using coumarin derivatives. Reported nutrient-drug interactions cannot always be explained by the vitamin K1 content of the food items. However, metabolic data indicate that a consistent dietary intake of vitamin K is important to attain a daily equilibrium in vitamin K status. We report a diet that provides a stable intake of vitamin K1, equivalent to the current U.S. Recommended Dietary Allowance, using food composition data derived from high-performance liquid chromatography. Inconsistencies in the published literature indicate that prospective clinical studies should be undertaken to clarify the putative dietary vitamin K1-coumarin interaction. The dietary guidelines reported here may be used in such studies.

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