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Lech Czarnecki

Other affiliations: University of Tennessee
Bio: Lech Czarnecki is an academic researcher from Warsaw University of Technology. The author has contributed to research in topics: Polymer concrete & Carbonation. The author has an hindex of 20, co-authored 124 publications receiving 1724 citations. Previous affiliations of Lech Czarnecki include University of Tennessee.


Papers
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Journal ArticleDOI
TL;DR: In this paper, an experimental study of the viscosity and principal normal stress difference of a polystyrene melt filled with aramid (Kevlar), glass, and cellulose fibers is reported.
Abstract: An experimental study of the viscosity and principal normal stress difference of a polystyrene melt filled with aramid (Kevlar), glass, and cellulose fibers is reported. The influence of loading level and mastication on the rheological properties is discussed. The effects of mixing and mastication on fiber damage are considered. Glass fibers break down rapidly to very small aspect ratios, while aramid shows a “kinked” structure, with kinks occurring every 100 μm. A mechanism is proposed for fiber breakage based on buckling during rotation in shear flow. It is found that addition of fibers increases the viscosity in the same manner as a reduction in temperature, and data may be superposed by reduced plotting. This indicates that the viscosity increase is due solely to enhanced viscous dissipation in the matrix and not to interparticle forces as is the case with smaller particles. The principal normal stress difference increases at fixed shear stress with fiber loading. The extent of increase depends upon fiber loading, aspect ratio, and modulus.

225 citations

01 Apr 2006
TL;DR: The 11th International ICPIC Congress on concrete polymers in concrete in combination with cement concrete was held in Berlin, 2-4 June 2004 as discussed by the authors, where new trends and evolutions have been presented and discussed.
Abstract: The search for durable and sustainable construction materials inspires the developments in the world of cement concrete, as well as in the world of concrete-polymer composites. Both worlds recognize, strive for and accept each other's contribution to the synergetic effects that are realized by the combination of classical building materials and polymers. A better knowledge of materials behaviour, especially in the field of admixtures, and a better understanding of curing processes allowed the development of highly performing mineral or modified mineral concretes, mortars and grouts. CPC-science becomes an invaluable element in the development of sustainable construction materials. ICPIC brings together practitioners and scientists, dealing with concrete-polymer composites in all industrial fields, but with emphasis on construction industry. The 11th International ICPIC Congress took place in Berlin, 2-4th June 2004. New trends and evolutions have been presented and discussed. The highlights of the Congress, and the synergies for the construction world that emerge from this congress on polymers in concrete in combination with cement concrete, are presented. (c) 2005 Elsevier Ltd. All rights reserved.

137 citations

Journal ArticleDOI
TL;DR: The 11th International ICPIC Congress on concrete polymers in concrete in combination with cement concrete was held in Berlin, 2-4 June 2004 as discussed by the authors, where new trends and evolutions have been presented and discussed.
Abstract: The search for durable and sustainable construction materials inspires the developments in the world of cement concrete, as well as in the world of concrete-polymer composites. Both worlds recognize, strive for and accept each other's contribution to the synergetic effects that are realized by the combination of classical building materials and polymers. A better knowledge of materials behaviour, especially in the field of admixtures, and a better understanding of curing processes allowed the development of highly performing mineral or modified mineral concretes, mortars and grouts. CPC-science becomes an invaluable element in the development of sustainable construction materials. ICPIC brings together practitioners and scientists, dealing with concrete-polymer composites in all industrial fields, but with emphasis on construction industry. The 11th International ICPIC Congress took place in Berlin, 2-4th June 2004. New trends and evolutions have been presented and discussed. The highlights of the Congress, and the synergies for the construction world that emerge from this congress on polymers in concrete in combination with cement concrete, are presented. (c) 2005 Elsevier Ltd. All rights reserved.

132 citations

Journal ArticleDOI
TL;DR: In this article, a model is proposed for the formation of the microstructure in polymer-modified cementitious materials, with specific emphasis on the synergetic effect between cement particles and polymer particles.
Abstract: A model is proposed for the formation of the microstructure in polymer-modified cementitious materials. Cement hydration and polymer film formation were studied, with specific emphasis on the synergetic effect between cement particles and polymer particles. Alterations at the microstructure level result in macroscopic changes in the properties of the modified material. In this paper, the influence of the polymer addition on the appearance of the cement hydrates and the presence of the polymer film through the cement hydrates are presented in relation to the minimum film forming temperature. Owing to the presence of the cement particles and to cement hydration, film formation can take place at lower temperatures, so that a polymer dispersion with a slightly higher MFT (minimum film forming temperature) can be used. This is important for the physical and mechanical properties of the polymer-modified materials. The findings have been included in an integrated model based on the three-step model of Ohama, in which the polymer film formation and the cement hydration processes are integrated in relation to each other. A time-dependent evaluation of both processes was incorporated. The research presented in this paper was part of a PhD research at the Civil Engineering Department, University of Leuven, Belgium [1].

125 citations

Journal ArticleDOI
TL;DR: In this paper, an experimental study on the rheological properties of compounds of a polystyrene melt with calcium carbonate, carbon black, titanium dioxide, calcium sulfate anhydride fiber, mica, glass beads and aramid, cellulose and glass fibers is presented.
Abstract: An experimental study is reported on the rheological properties of compounds of a polystyrene melt with calcium carbonate, carbon black, titanium dioxide, calcium sulfate anhydride fiber, mica, glass beads and aramid, cellulose and glass fibers. Comparison is made of the shear viscosity, elongational viscosity and principal normal stress difference of these compounds at 20 volume per cent loadings. The polymer matrix and compounds with the smallest particle dimension greater than 10µ exhibit low shear rate Newtonian viscosities. Suspensions with particle sizes 0.5µ and smaller exhibit yield values. Yield values are also observed in elongational flow for systems exhibiting yielding in shear flow. The experimental data are contrasted to both mechanistic theories of suspensions with interaction between particles and a phenomenological plastic-viscoelastic tensor constitutive equation.

99 citations


Cited by
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Journal ArticleDOI
TL;DR: An overview of the developments made in the area of biodegradable composites, in terms of market, processing methods, matrix reinforcement systems, morphology, properties and product development is presented in this article.

1,133 citations

MonographDOI
01 Nov 2011
TL;DR: In this paper, the authors introduce colloid science and rheology, and present an overview of colloid physics and its applications in viscoelastic media. But they do not discuss the role of non-spherical particles.
Abstract: 1. Introduction to colloid science and rheology 2. Hydrodynamic effects 3. Brownian hard spheres 4. Stable colloidal suspensions 5. Non-spherical particles 6. Weakly flocculated suspensions 7. Thixotropy 8. Shear thickening 9. Rheometry of suspensions 10. Suspensions in viscoelastic media 11. Advanced topics.

792 citations

Journal ArticleDOI
TL;DR: In this article, a comparison of the stiffness/weight efficiencies of wood pulp composites with other traditional materials of construction including steel, aluminum, glass-fiber composites, and talefilled polyolefins was made.
Abstract: Wood pulp fibers possess strength and modulus properties which compare favorably with glass fibers when the differences in fiber densities are considered. Softwood pulp fibers with fiber aspect ratios near 100 are readily dispersed into high-density polyethylene or isotactic polypropylene with the aid of carboxyic dispersing agents to form mixtures containing 50 weight-percent wood pulp which can be readily injection molded. The mechanical properties of the molded specimens were similar for all types of pulp including Kraft (bleached and unbleached), mechanical and chemical-mechanical pulps, waste pulps, and reclaim newspapers. Comparisons of the stiffness/weight efficiencies revealed that pulp composites equal or exceed the stiffness of most traditional materials of construction including steel, aluminum, glass-fiber composites, and talefilled polyolefins, while retaining a major material cost advantage. The measured strength values of the pulp composites were less than the theoretically predicted values due to the presence of voids created by the formation of volatiles during processing. Mechanical pulps which were available in dry form were preferred because of lower cost and ease of handling. Wood fibers are non-abrasive so that relatively large concentrations may be incorporated into polyolefins without causing serious machine wear during mixing and fabrication.

408 citations

Journal ArticleDOI
TL;DR: In this paper, a review of emerging supplementary cementitious materials (SCM) sources is presented, along with new developments in characterizing and qualifying SCMs for use and improved knowledge of SCM on long-term concrete performance and durability.

386 citations