Mindaugas Daukšys

Tyre Rubber Additive Effect on Concrete Mixture Strength

Abstract This article describes the observed and examined effect of crumb rubber on the strength (compressive, bending and splitting tensile) of concrete. The tests have shown that the change in the strength of concrete with crumb rubber waste additives can be forecasted from exponential equations. These relationships enable to foresee the regularities of strength properties when a certain amount of crumb rubber of a certain size fraction is added to concrete. The obtained exponential equations show that concrete compressive, flexural and splitting tensile strengths decrease with increasing crumbed rubber additive amount. The testing has also shown that the addition of a small amount of crumbed rubber slightly increases (7%) the tensile splitting strength. The reason is better adhesion of the cement stone with rubber particles compared to the adhesion of sand, which was replaced by crumbed rubber. With higher content of crumbed rubber additive in the concrete, the tensile splitting strength decreases due ...

Dilatancy of cement slurries with chemical admixtures

Abstract The results of experimental investigation of plasticising, air‐entraining and viscosity‐modifying admixtures with different chemical composition influence on rheological properties and dilatancy of cement slurries are presented in the article. Rheological properties of cement slurries were tested by a rotation viscometer with coaxial cylinder, at different gradients of velocity. Dilatancy of cement slurries was determined by the distortion of the rheological curve and index of dilatancy D was calculated according to proposed methods. The results of investigation show that the properties of liquid disperse medium of structural system influence slightly the dilatancy of cement slurries. Plasticising admixtures with a different chemical composition slightly increases but air‐entraining and viscosity‐modifying admixtures slightly reduces the dilatancy of cement slurries.

The effect of cement modification on the rheological properties of cement paste

AbstractExperimental tests have determined the effect of slag, opoka (silica-calcite sedimentary rock), silica fume (SiO2) suspension, dolomite dust and sodium silicate solution (NaSS) together with the polycarboxylatether based plasticizing admixture on the yield stress and viscosity of Portland cement paste the rheological properties of which have been defined applying a rotational viscometer with co-axial cylinders. The tests have revealed that slag, opoka, silica fume suspension and dolomite dust added to cement paste by replacing 10% of Portland cement (by weight) have an effect on the yield stress and viscosity of the paste subject to the form and fineness of additive particles. When 10wt% of Portland cement is replaced with slag cement, the yield stress of Portland cement paste reduces by about 25.9%, and viscosity increases by about 3.5 times compared with the yield stress and viscosity of reference cement paste. The yield stress of Portland cement paste with 0.5% NaSS admixture increases insignif...

Cheminių priedų silanų pagrindu įtaka cementinio akmens savybėms

Santrauka Straipsnyje nagrinėjama cheminių priedų silanų/siloksanų pagrindu įtaka cementinio akmens fizikinėms ir mechaninėms savybėms bei poringumui. Tyrimams buvo paruostos sesios cemento teslos, naudojant skirtingos koncentracijos silanų/siloksanų pagrindu pagamintus cheminius priedus. Tyrimo metu nustatytas cemento teslos sklidumas, cementinio akmens tankis, lenkimo ir gniuždymo stipriai, poringumo parametrai bei atsparumas salciui. Nustatyta, kad naudojant skirtingos koncentracijos silanų/siloksanų pagrindu pagamintus cheminius priedus, cemento teslos sklidumas padidėjo iki 46,3%, lyginant su kontroline tesla. Cementinio akmens tankis sumažėjo iki 2,4%, lenkimo stipris – iki 21,0%, gniuždymo stipris – iki 34,6%, lyginant su kontroliniu bandiniu be silanų/siloksanų pagrindu pagamintų priedų. Cementinio akmens be cheminių priedų silanų/siloksanų pagrindu vandens įgėris (12,16%), atviras ir uždaras poringumai yra panasūs kaip ir cementinio akmens su cheminiais priedais silanų/siloksanų pagrindu. Cementi...

Vandens įgertį mažinančių cheminių priedų įtaka smulkiagrūdžių betonų savybėms@@@The Influence of Silane Based Chemical Admixtures on the Properties of Cement Stone

Santrauka Atliekant eksperimentinius tyrimus, nustatyta vandens įgertį mažinancių cheminių priedų silanų/ siloksanų pagrindu įtaka betono misinio technologinėms bei sukietėjusio betono fizikinėms ir mechaninėms savybėms bei poringumui. Tyrimams buvo suprojektuotos sesios betono misinio sudėtys naudojant skirtingos koncentracijos silanų / siloksanų pagrindu pagamintus cheminius priedus. Nustatyta, kad naudojant skirtingos koncentracijos silanų pagrindu pagamintus cheminius priedus, betono misinio Vebe trukmė sumažėjo iki 1,78 karto, palyginti su kontroliniu misiniu be cheminių priedų silanų pagrindu. Silanų / siloksanų pagrindu pagaminti cheminiai priedai, dedant jų 0,1–0,4 % nuo misinio masės, didesnės įtakos bandinių tankiui neturėjo. Betono bandinių lenkimo stipris sumažėjo apie 27,4 %, gniuždymo stipris sumažėjo apie 34,6 %, o skėlimo stipris sumažėjo apie 34,7 %, palyginti su kontroliniu bandiniu. Betono bandinių be priedų silanų pagrindu vandens įgertis kinta nuo 2,61 % iki 4,09 %, o su priedais sila...

Influence of the granite screenings to the properties of the concrete paving blocks

Abstract The research deals with the granite screenings as fine aggregate influence on the technological properties of concrete mixtures and on the physical and mechanical properties and durability of concrete paving. The following several compositions of concrete mixture for the production of environment arrangements are researched: fine aggregate using only 0/2 fraction sand (B1), 10% of 0/2 fraction sand replacing with 0/2 fraction granite screenings (B2) and using only granite screenings (B3). Concrete mixtures were prepared in the laboratory, and concrete paving blocks – in the factory. The technological properties of concrete mixtures and physical and mechanical properties of concrete paving blocks (made from the mentioned concrete mixtures) were determined; the durability of the products in the cycles of frost resistance was forecasted. The research results reveal that due to the properly selected ratio between sand and granite screenings in the fine aggregate, the characteristics of concrete pavin...

The Influence of Fine Particle Content (Cement Together with Sand Particles up to 0.25 mm) on Rheological Properties of Concrete Mixture

The influence of the fine particle content on the rheological properties of the fresh concrete mixture was studied. The change of cement together with sand particles up to 0.25 mm in mixture composition was taken into the consideration. The amount of fine particles in mixture composition varied in the range from 402 to 639 kg per one cubic meter of the concrete mixture. Technological properties of the concrete mixture were established according to the standardized requirements, rheological properties: yield stresses and viscosity of conventional concrete mixture were calculated based on analytical formulas. According to obtained test results, the increase of fine particle content from 481 to 520 kg in mixture reduced the yield stresses from about 557 to 132 Pa. Further increase of fine particle content from 600 to 639 kg showed the rise of yield stress by 3.87 times. On the other hand, the viscosity of concrete mixture gradually decreased (ca. 5.6 times). To sum up, the rheological properties of the concrete mixture were significantly influenced by the content, packing density, fineness, surface texture and particle size distribution of fine particles.

THE INFLUENCE OF THE SODIUM SILICATE ADMIXTURE ON THE PUMPED CONCRETE FLOWABILITY IN PIPELINES / NATRIO SILIKATO TIRPALO PRIEDO POVEIKIS SIURBLIAIS TRANSPORTUOJAMO BETONO MIŠINIO TEKAMUMUI VAMZDŽIAIS

Santrauka Atliekant eksperimentinius tyrimus nustatytas natrio silikato tirpalo (NST) ir plastiklių poveikis betono misinio tekėjimo vamzdžiu greiciui, nasumui, transportuojant misinius dviejų stūmoklių su S tipo vožtuvu betono siurbliu. Tyrimo metu matuotas 0,406 m3 tūrio pamatų blokų formų užpildymo betono misiniu laikas, esant skirtingam betono siurblio misinio tiekimo slėgiui – 25,5 ir 68,0 bar. Nustatyta, kad įmaisius į misinį NST priedą 0,5% cemento masės kartu su superplastikliu polikarboksilo eterių pagrindu, pasiektas didesnis misinio tekėjimo greitis vamzdynu ir gautas didesnis nasumas esant mažesniam betono siurblio misinio tiekimo slėgiui. Įmaisius į misinį NST priedą 0,5% cemento masės kartu su plastikliu lignosulfonatų pagrindu ir sumažinus cemento kiekį misinyje, betono misinys blogai teka vamzdynu, kai betono siurblio misinio tiekimo slėgis yra mažas – 25,5 bar. Įmaisius į misinį NST priedą 0,5% cemento masės kartu su plastikliu lignosulfonatų pagrindu ir smulkiuoju užpildu naudojant tik 0...