Žymantas Rudžionis

Effects of ultrasonic treatment on zeolite NaA synthesized from by-product silica.

The synthesis of zeolite NaA from silica by-product was carried out in the presence of 20 kHz ultrasound at room temperature. Zeolites obtained in this type of synthesis were compared to zeolites obtained by performing conventional static syntheses under similar conditions. The sonication effects on zeolite NaA synthesis were characterized by phase identification, crystallinity etc. The effects of different parameters such as crystallization time and initial materials preparation methods on the crystallinity and morphology of the synthesized zeolites were investigated. The final products were characterized by XRD and FT-IR. It was possible to obtain crystalline zeolite NaA from by-product silica in the presence of ultrasound.

Investigations into effective fly ash used in concrete

Abstract This work presents a study on the influence of thermal‐electrical fly ash on the cement paste hydration processes, investigation into cement stone, mortar, ordinary and self‐compacting concrete, when cement was replaced by fly ash (5–33 %). It was estimated that cement stone and cement paste prepared from fly ash and cement properties were better when polycarboxylic superplasticiser “Visco Crete‐3” was used. It was established that admixture of fly ash influences the processes of cement hydration: the amount of free Ca(OH)2 in cement stone was decreased and amount of stable calcium hydro silicates was increased. It allows to state, that cement stone becomes more corrosion‐resistant and more durable. When fly ash admixture is applied in ordinary concrete production, it is possibility to reduce cement expenditures up to 33 % and in self‐compacting concrete production, segregation and separation of water decreases. Data of investigations on hardened concrete showed that fly ash increases compressive...

COMPLEX ADMIXTURES FOR HIGH-STRENGTH CONCRETE

Abstract The influence of naphthalene formaldehyde superplasticizers (NFS), lignosulfonate plasticizers (LSP) and silica fume on cement paste properties and complex usage of these admixtures for high-strength concrete production are investigated in this research. These admixtures influence the cement hydration products morphology and properties of hardened cement paste. The degree of cement hydration and Ca(OH)2 content in hardened cement paste were determined for analysis of cement hydration process with admixtures. Mechanical properties and porosity of hardened cement paste with the admixtures were tested. Optimal dosages of plasticizing admixtures and silica fume were estimated and the most efficient method of silica fume adding to concrete mixture was proposed. The results of investigation have been used for high-strength concrete production.

The efficiency analysis of foundations for buildings with bearing walls for Lithuanian soil conditions

AbstractThe paper deals with selection of foundations for bearing walls of residential buildings depending on the strength of soil and taking into account the economic benefit. Based on in-situ investigation of soil conditions in different Lithuanian regions and construction technologies, it was found that the cost of foundations comprise 2.5–6% of total costs, and takes up 6–10% of construction time. Strip and pile foundations were analysed taking into account dimensions and mode of production. The proposed case study model enables to save up to 30–50% of foundation costs. It has a significant influence on entire life cycle costs of.