Anton Geffert

Study of Cement Composites Properties with Filler Based on Wood Pulp

Sustainable building materials are based on the use of renewable materials instead of non-renewable. A large group of renewable raw materials are materials of plant origin containing cellulosic fibres which are used as filler into building material with reinforcement function of composite. This study aimed to establish the mechanical and physical properties of cement composites with organic filler, such as wood pulp. Pulp derived from wood pulping process is very interesting material as reinforcement in cement which contributes to a reduction of pollutants. In this paper, utilization of unbleached and bleached wood pulp in combination with cement matrix with emphasis on the physical and mechanical properties is studied. Varying the producing technology (wood pulp and cement ratio in mixture) it is possible to obtain composites with density from 940 to 1260 kg.m-3 and with compressive strength from 1.02 to 5.44 MPa after 28 days of hardening. The experimental results of mechanical properties indicate that cement composites with using unbleached wood pulp reaches higher values than composites based on bleached wood pulp. The percentage of water uptake increased with increasing the volume ratio of unbleached wood pulp in composite.

The Influence of the Long-Term Storage of Hardwood on the Selected Physical and Mechanical Properties in View of Pulping

Wood is loosely stored to ensure continuous production inside paper mills where it is exposed to the effect of external factors. The impact of storage leads to some changes of mechanical and physical properties of wood, but these changes are not the same in all specimens. In this paper, it has been observed that the long term storage of wood influences the impact strength in bending and the permeability of wood for fluids. During the storage, there was a decrease of impact strength in bending of poplar heartwood by 28.3% and oak by 22.1% and mature beech wood by 37.3%. Also, there was decreased a permeability of wood, poplar sapwood 18.3 % and heartwood of 53.9%; oak sapwood by 20.0% and heartwood by 20.3%; beech sapwood 45.8% and mature wood by 48.2%. By decrease of the observed properties of the stored wood, a deterioration a quality of produced pulp can be expected (a higher Kappa number, amount reject and decrease the mechanical properties of pulp).

The Problems in Delignification of Dry Wood by Kraft Process

The objective of this study was to assess the causes of the problems arising in the CBC kraft cooking of several types of hardwood chips particularly in view of high dry matter but also in view of chip thickness and character of wood.High dry matter of processed chips influences negatively delignification. Similar effect on delignification is achieved by wood character (anatomic and morphological properties of cell elements, chemical composition, portion of heart and sapwood).Chips thickness has the most significant impact on delignification process comparing to other monitored characteristics. The increase of chips thickness by 1-2 mm has significant negative impact on monitored characteristics of kraft cooking – yield, Kappa number and amount of rejects.Displacement CBC kraft procedure is more sensitive on the deviation from standard conditions than conventional kraft cooking.The problems occurring during kraft cooking of different wood chips mixtures with high dry matter by CBC procedure are possible to resolve by technological and organizational precautions – separate chipping and storage of chips of heart and non-heart woods, preparation of thinner chips of heart wood, chips pre-vaporing before kraft cooking.

Engineering Approach for Computation of the Energy Consumption Needed for Defrosting and Subsequent Heating of Frozen Wood Chips

An engineering approach for the calculation of the specific mass energy consumption, which is needed for defrosting and the subsequent heating of the frozen wood chips above the hydroscopic range, (in kWh·t-1), has been suggested. Equations for easy calculation of have been derived, depending on the wood moisture content u, on the fiber saturation points of the wood species at 20 °C and at –2 °C (i.e. at 293.15 K and at 271.15 K), and respectively, on the initial chips’ temperature, T0 , and on the final temperature of the heated after their defrosting chips, T1.For the calculation of the according to the suggested approach and equations a software program has been prepared in MS Excel 2010. With the help of the program calculations have been carried out for the determination of the energy consumption , which is needed for defrosting and subsequent heating of oak, acacia, beech, and poplar frozen chips with moisture content in the range from u = 0.4 kg·kg-1 to u = 1.0 kg·kg-1, initial temperature t0 = –20 °C and t0 = –10 °C until reaching of the chips‘ mass temperature of t1 = 80 °C, t1 = 100 °C, and t1 = 120 °C at the end of the heating.

The Change of Swelling of Pulp Fibres under Recycling

During the process of monitoring of pulp fibres swelling, which is directly related to absorptivity, it was found that with the growing number of recycling cycles this characteristics significantly decreases. This phenomenon, which is considered as negative from the point of view of pulp fibres utilizing for paper manufacturing, could potentially find its positive application in other areas, eg. in the civil engineering for production of lightweight composites, where the reduction of water absorption of natural fibre materials is desirable.