Jozef Junak

Cement Materials Based on Cellulosic Fibers for Plasters

Abstract This paper presents physical and mechanical properties of cementitious composites/plasters containing cellulosic fibers in portion 2.0% and 5.0% of filler replacement after 28 days of hardening. Cellulosic fibers (Greencel) originated from bleached wood pulp and unbleached waste paper used in this experimental work were characterized from the point of view cellulose structure. Experimental investigations reveal that adding cellulosic fibers reduces composites density (up to 8.2 %) in comparison with composites without any fibers. Moreover, the presence of wood pulp and recycled fibers in composites cause higher values of water absorbability than sample without fibers. Also, the decrease in compressive strength values for tested fiber cement plasters was observed (14.1 - 18.0 MPa) in comparison to reference sample (26.6 MPa). But the identified compressive strength values are in accordance with European standard (5 MPa) for plasters.

Sustainable hemp-based composites for the building industry application

Sustainability goals are essential driving principles for the development of innovative materials in the building industry. Natural plant (e.g. hemp) fibers represent an attractive alternative as reinforcing material due to its good properties and sustainability prerequisites. In this study, hemp-based composite materials, designed for building application as non-load bearing material, providing both thermal insulation and physico–mechanical properties, are presented. Composite materials were produced by bonding hemp hurds with a novel inorganic binder (MgO-based cement) and then were characterized in terms of physical properties (bulk density, water absorption), thermal properties (thermal conductivity) and mechanical properties (compressive and tensile strength). The composites exhibited promising physical, thermal and mechanical characteristics, generally comparable to commercially available products. In addition, the hemp-based composites have the advantage of a significantly low environmental impact (thanks to the nature of both the dispersed and the binding phase) and no negative effects on human health. All things considered, the composite materials seem like very promising materials for the building industry application.Sustainability goals are essential driving principles for the development of innovative materials in the building industry. Natural plant (e.g. hemp) fibers represent an attractive alternative as reinforcing material due to its good properties and sustainability prerequisites. In this study, hemp-based composite materials, designed for building application as non-load bearing material, providing both thermal insulation and physico–mechanical properties, are presented. Composite materials were produced by bonding hemp hurds with a novel inorganic binder (MgO-based cement) and then were characterized in terms of physical properties (bulk density, water absorption), thermal properties (thermal conductivity) and mechanical properties (compressive and tensile strength). The composites exhibited promising physical, thermal and mechanical characteristics, generally comparable to commercially available products. In addition, the hemp-based composites have the advantage of a significantly low environmental impact ...

Utilization of Crushed Glass Waste in Concrete Samples Prepared with Coal Fly Ash

This article is aimed on the study of glass bottle cullet influence on the compressive and flexural strength development of products prepared as the partial natural aggregate replacement by crushed glass waste. For this study, eight different mixtures containing coloured glass cullet as a full replacement of natural aggregate fractions 0/4, 4/8 and 8/16 mm and two comparative mixtures were prepared. In four of these mixtures, 25% of Portland cement were replaced by coal fly ash. After 7, 28 and 90 days of hardening, samples were tested on flexural strength and compression strength. Results showed, that specimens containing full replacement of fraction 8/16 mm of glass cullet reached the highest compressive strength 43.32 MPa corresponding to concrete strength class C 30/37. Partial cement replacement by coal fly ash leads to low compressive strength after 7, 28 and 90 days of curing. Use of coloured glass bottle cullet in concrete should not have negative impact on the strength characteristics of hardened concrete and should have positive effects for preparing quality fair-faced concrete surfaces.

Natural aggregate totally replacement by mechanically treated concrete waste

Abstract This paper presents the results obtained from the research focused on the utilization of crushed concrete waste aggregates as a partial or full replacement of 4/8 and 8/16 mm natural aggregates fraction in concrete strength class C 16/20. Main concrete characteristics such as workability, density and compressive strength were studied. Compressive strength testing intervals for samples with recycled concrete aggregates were 2, 7, 14 and 28 days. The amount of water in the mixtures was indicative. For mixture resulting consistency required slump grade S3 was followed. Average density of all samples is in the range of 2250 kg/m3 to 2350 kg/m3. The highest compressive strength after 28 days of curing, 34.68 MPa, reached sample, which contained 100% of recycled material in 4/8 mm fraction and 60% of recycled aggregates in 8/16 mm fraction. This achieved value was only slightly different from the compressive strength 34.41 MPa of the reference sample.

Effects of physical treatment of hemp fibers on fiber structure and biocomposite properties

This article concerning natural cellulose fibers as reinforcement in composite materials in civil engineering. In this paper, the attention is given to industrial hemp specifically to the woody part of hemp plant called hemp hurds. The properties of natural fibers are mainly determined by the chemical and physical composition, such as structure of fibers. The objective of presented research is to characterize raw and physically treated hemp fibers using Fourier transform infrared spectroscopy method. These natural fibers were used as filler into biocomposites and MgO-cement was used as alternative binder. Physico — mechanical properties (compressive strength, thermal conductivity, absorbability) of prepared composites were determined.

Color pigments in concrete and their properties

Nowadays, color concrete pigments are used to revive space in the construction of new buildings, reconstruction existing buildings and squares. Color pigments represent a partial weight replacement of the binder. Color pigmented concrete also has properties like traditional concrete namely high strength, good durability and weather resistance for its variable use. In this paper, characterization and classification of color pigments, using and their influence on the properties of concrete is given. The experimental part of concrete composites studying (with color pigments) includes testing of physical and mechanical properties in comparison to reference sample (without color pigments).