Durability of Lightweight Expanded Clay Aggregate Concrete

AbstractThe paper describes a development and use of lightweight concrete and lightweight self-compacting concrete using artificial lightweight aggregate based on expanded clay for ready mix concrete and precast elements. The objective of this research was to evaluate the lightweight concrete on durability of concretes placed in chemically aggressive liquid and gaseous environments (high concentrations of sulphate, chloride ions, automotive gas, oil and gaseous CO2 and SO2 environments)

Comparison of Properties of Shotcrete Tested Using Destructive and Non-destructive Methods

AbstractThe paper focuses on possibilities of preparation and observation of basic physical parameters of shotcrete prepared in ordinary laboratory mixer, compacted by vibration combined with defined pressure. The aim is assessment of basic properties of shotcrete: compressive strength of young shotcrete, test core strengths and comparison of results with the results of non-destructive tests of compressive strength. At the same time, homogeneity and consistency of shotcrete will be assessed

Effect of Inorganic SiO2 Nanofibers in High Strength Cementitious Composites

The paper deals with the verification of the effect of the addition of inorganic SiO2 nanofibers to cement composites. In the first stage, a stable suspension of SiO2 nanofibers was prepared in an aqueous medium. It is important to distribute nanofibers so that the nanofibers do not appear in the form of clumps and at the same time do not get damaged during the dispersion process. The ultrasonification process was used for dispersion. The dispersed suspension of SiO2 nanofibers and water was dosed together with the superplasticizing admixtures into the dry components of the cement composite and the components were homogenized. The properties of the cement composite with SiO2 nanofibers have been tested – compressive strength, flexural strength, density. Composites with the addition of SiO2 nanofibers at a dose of 0.008 % by weight of cement exhibited an increased compressive strength of up to 33 % and a 19 % greater flexural strength at doses of 0.016 and 0.032 % of cement weight than the reference sample without nanofibers. The presence of SiO2 nanofibers in the composite was monitored by scanning electron microscopy (SEM)

Carbon Nanotubes in Cementitious Composites: Dispersion, Implementation, and Influence on Mechanical Characteristics

For effective utilization of nanoparticles in cementitious composite materials, their perfect dispersion is necessary. Appropriate quantity of ultrasonic energy (US energy), as well as usage of proper and compatible surfactant, is a prerequisite for carbon nanotubes’ (CNT) suitable deagglomeration. US energy was supplied by Bandelin Sonopuls HD 3200 ultrasonic homogenizer. Influence of US energy’s amount on CNT’s dispersion in aqueous medium was monitored in two steps: at first roughly by an optical microscope and in the next step precisely by the measurement of absorbance via UV/Vis spectrophotometry. After the appropriate amount of US energy was found, cement mortars with CNT were prepared and tested. Their physical and mechanical properties were examined and compared to the reference specimens

Comparison of the actual costs during removal of concrete layer by high-speed water jets

This paper describes the process of possible evaluation of costs of using high speed water jet technology for concrete removal methods. High speed water jet technology is a progressive technology of removing damaged concrete used in civil engineering since the 80's of 20th century. It has been changing and developing since that time. But there is little information in literature devoted to the economic evaluation of this technology. Detailed economic analysis is still missing. This paper aims to compare comprehensively in economic terms the costs of removing concrete using the technology of both continuous oscillating and pulsating oscillating water jets. The research was realized in cooperation with research institutions and industrial companies and was supported by state budget of the Czech Republic and from the European Union. The scheme of cooperation of the University, research institutions, industrial companies and government follows the Triple helix model