Giedrius Girskas

Variation Of Characteristics Of Vibropressed Concrete Pavement Blocks

Abstract Concrete pavement blocks were formed and the following properties were investigated after 7 days of curing: density, tensile splitting strength, freezing-thawing resistance, using de-icing salts in one-sided way, and abrasion resistance. The scattering of the values of density and tensile splitting strength of the concrete pavement blocks in the pallet during the process of manufacture was examined. It was determined that the values of density and splitting tensile strength were similar in the diagonals of the pallet. Bigger changes were seen on the edges of the tray. The variation coefficients of the examined properties ranged from 0.5 % to 15.6 %. The biggest scattering of research results was noted in strength.

The effect of synthetic zeolite on the viscosity of cement paste

Abstract The paper reports the effect of the synthetic zeolite admixture on the viscosity of cement paste. Materials include Portland cement CEM I 42.5 R, synthetic zeolite obtained through low-temperature synthesis under laboratory conditions, polycarboxylate ester based supeplasticizer Muraplast FK 63.30 and tap water. Three compositions of cement paste were made adding 0%, 5%, and 10 wt% of synthetic zeolite. A rotating cylinder viscometer was used for measuring the consistence of the paste; viscosity was measured employing vibrational viscometer SV–10. The consistency test on cement paste showed that spread with no addition of synthetic zeolite made 149 mm, containing 5% of synthetic zeolite the slump was 85 mm and containing 10% of synthetic zeolite spread was 70 mm. The viscosity test also indicated that for the period of 30 minutes, changes in the viscosity of cement paste were as follows: 81.11 mPa s with no addition of synthetic zeolite, 746.5 mPa s containing 5% of synthetic zeolite and 827.1 mP...

Zeolite Influence of Vibropressing Concrete Durability

Durability is one of the main characteristics in the production of high-quality concrete paving blocks in the Baltic region climate zone. Concrete paving blocks are produced by means of vi bropressing , dimensions: 198×98×80 mm . The article describes tests with concrete paving blocks, the top layer of which contains 5% of zeolite admixture obtained from waste of aluminum fluoride production by low-temperature synthesis. The durability of concrete paving blocks was tested according to abrasion resistance, tensile splitting strength, absorption and frost resistance. The test results revealed that 5% of zeolite admixture added to the top layer of concrete paving blocks reduce the absorption, increase the tensile splitting strength and decrease abrasion. The zeolite admixture used in concrete paving blocks reduces the scaling about 4 times after 28 freeze-thaw cycles when 3% NaCl is used as the freezing solution. The test results proved that synthetic zeolite obtained from aluminum fluoride by means of low temperature synthesis can be used as a supplementary cementitious material to increase the durability of concrete pavement elements.

The influence of carbon nanotubes on the properties of water solutions and fresh cement pastes

It is known, that the properties of cement-based materials can be significantly improved by addition of carbon nanotubes (CNTs). The dispersion of CNTs is an important process due to an extremely high specific surface area. This aspect is very relevant and is one of the main factors for the successful use of CNTs in cement-based materials. The influence of CNTs in different amounts (from 0 to 0.5 percent) on the pH values of water solutions and fresh cement pastes, and also on rheological properties, flow characteristics, setting time and EXO reaction of the fresh cement pastes was analyzed in this work. It was found that the increment of the amount of CNTs leads to decreased pH values of water solutions and fresh cement pastes, and also increases viscosity, setting times and EXO peak times of fresh cement pastes.

Identification of Reactivity Level in Aggregates from Lithuanian Gravel Quarry

Abstract The article analyses the reactivity level of aggregates from Lithuanian quarries and their effect on the alkali corrosion in mortars. The reactivity of aggregates was assessed according to Rilem Recommended Test Method: AAR-2. The hardened cement paste and cracked aggregate contact zones were tested by means of optical microscopy. Two gravel aggregates and one sand aggregate from Lithuanian quarries were selected for testing. The tests revealed that according to AAR 2 methodology fine and coarse aggregates from Lithuanian quarries shall be allocated to Group II, i.e. reactive aggregates. The expansion after 14 days exceeds 0.1 % in the case of fine aggregate, the average expansion after 14 days is 0.13 %, and in the case of coarse aggregates the average expansion ranges from 0.11 % to 0.12 %.

The Influence of Commonly Used Plasticizing Admixtures on the Plasticizing Effect of Cement Paste

Abstract The article aims to present a research into the impact of dosage and effectiveness of commonly used plasticizing admixtures. More specifically, it focuses on rheological properties of the cement pastes (yield stresses and plastic viscosities) of different testing times (from 0 min to 90 min after mixing). The following materials were used in the study: Portland cement CEM I 42.5 R, plasticizer P (ligno-sulphonates based), superplasticizer SP1 (modified acrylic polymer based), superplasticizer SP2 (polycarboxylate esters based) and water. Experiments were carried out using rotational rheometer Rheotest RN4.1 with coaxial cylinders. It was observed that larger dosage of SP1 (0.6–1.2 %) results in slower increase in plasticizing effects until the 90 min margin. In conclusion, from the start of mixing until the 90 min margin, the best plasticizing effect and its retention are achieved by superplasticizer SP2. Recommended SP2 dosage varies within the range of 0.6 % to 0.8 %.

The Use of Steel Cord Scrap in Concrete

Abstract Materials used for the study: Portland cement CEM I 42.5 R, 4/16 gravel, 0/4 sand. The fine aggregate in four concrete mixtures was substituted with steel cord scrap added at 1.5 %, 3.0 % and 4.5 %. Water absorption and compressive strength was measured in concrete specimens after 7 and 28 days of curing. Total, closed and open porosity was measured in the modified concrete specimens. The tests of predicted freeze-thaw cycles were done. Test results showed that the substitution of fine aggregate with steel cord scrap results in lower water absorption and higher compressive strength in the modified concrete specimens. The porosity parameters have also changed: the closed porosity has increased and consequently the freeze-thaw resistance of modified concrete has improved.

Porous permeable high-alumina ceramic materials for macro- and microfiltration

AbstractDesigned composition of ceramic mass for high-alumina porous permeable ceramic material for disperse micro hydro systems. The filler used alumina fraction 100–250 microns, as a binder system studied refractory clay Veselovskaya–medicalglass–gibbsite. Formation of material carried by dry pressing at a pressure 60 MPa, the temperature of synthesis was 1250–1350 °C, holding at the maximum temperature – 1 h. The processes occurring in the binder during sintering was investigated. The effect of the sintering temperature of the material, the amount of binder composition on the acid resistance, mechanical strength, porosity and permeability of open high-alumina permeable porous material was investigated. The structure and phase composition of the submissions received, the average pore diameter was 10 mm, it can be used for microfiltration of liquids and gases, the material is homogeneous at the macro level, the structure is represented by an extensive network of channels of pores. Phase composition is re...

Properties of concrete modified by amorphous alumina silicate

AbstractConcrete is the most widely used building material obtained by hardening the mix made of coarse and fine aggregates, cement as the binding material, and water. The basic properties of concrete depend on the quality and properties of cement, w/c ratio and the homogeneity of compaction. Compressive strength is one of the most important properties of concrete. Materials used: Portland cement CEM I 42.5 R, 0/4 fraction sand, 4/16 fraction gravel, amorphous alumina silicate admixture, polycarboxylate ether-based superplasticizer Muraplast FK 63.30, and tap water. Five compositions of concrete mixes containing 0%, 2.5%, 5%, 7.5% and 10% of amorphous alumina silicate admixture by mass of cement were produced. The article analyses the effect of amorphous alumina silicate on the properties of concrete depending on the admixture content. The results revealed that the compressive strength of concrete after 7 days of curing increased by 7.1%, after 28 days of curing increased by 13.3% when the amorphous alumi...

The Dependence of Physical Mechanical Properties of Concrete Pavement Blocks on Coarse Aggregate Type

Abstract The aim of this research is to determine the dependences of the physical mechanical properties of vibropressed concrete (pavement blocks) on the type of coarse aggregate used in the main layer. Sustainability of concrete pavement blocks is a really important matter. Five different batches of pavement blocks were produced, changing the consistence ratio of coarse aggregate in the main layer. There are two types of course aggregate: crushed gravel and granite. The consistence of a facing layer was not changed. All tests: density, tensile split strength, water absorption for vibro-pressed concrete units were made according to EN 1338:2003+AC2006.