Advanced Materials Research Vol. 897

Abstract: In term of practical applications, it is important to know how to change the modulus of elasticity of concrete, which is in wintertime exposed to low temperatures. The partial results of research are presented and oriented on monitoring the changes of the values of modulus of elasticity in time of frozen and unfrozen concrete specimens.

Abstract: The article deals with the study of the effect of modification of composition of cement-bonded particleboards on their frost resistance. Powder waste from the line for production of cement-bonded particleboards was used for preparation of test units. Conditions of storage under alternating freezing and defrosting in combination with effect of water were specifically created. Subsequently, the fundamental physical-mechanical parameters were assessed.

Abstract: The motivation for utilization of active admixtures in concrete lies primarily in a positive effect on properties of hardened concrete with regard to its durability. Fine parts complement the grain size distribution curve, but also due to subsequent hydration arise phases with better resistance to aggressive substances from surrounding environment. Process of pozzolanic reaction is also associated with a reduction in open capillary porosity, causing a gradual reduction of the permeability of concrete. The paper presents an experimental program focused on the monitoring of evolution of basic and hygric properties of concrete with fine ceramic powder addition.

Abstract: Significant advances in the field of building materials leads to increasingly frequent enforcement of these high performance materials in real constructions. Efforts to maximize the efficient use of non-renewable resources and especially energy-intensive materials lead to efforts to achieve maximum efficiency and usability [. Paper presents results of an experimental program focused on development of fire-resistance composites based on aluminous cement with fine ground ceramic powder (FGCP). Studied fibre composites were loaded by temperature 600 °C and 1000 °C. The influence of applied thermal load on composites was evaluated by means of fracture energy, compressive strength, bending strength and modulus of elasticity in bending.

Abstract: The reduction of the clinker to addition ratio is becoming of main technological importance because energy saving potential by process optimization at the cements manufacture is almost exhausted. The main properties of composite cements of CEM V/A and CEM V/B kinds of Austrian (AT) and Slovak (SK) provenance with cement clinker contents between 45.1 % (CEM V/A-AT) – 52.9 % (CEM V/A-SK) and 26.9 % (CEM V/B-AT) – 30.9 % (CEM V/B-SK), and reference Slovak CEM I 32.5 R cement containing 95 % of the clinker were tested. The composite cements consist of cement clinker with following additions: blast furnace slag, fly ash and natural pozzolan - zeolite. Basic cement properties (normal consistency, initial and final set, volume stability) and fresh mortar properties (workability, volume density, air content) and strength parameters using standard mortars with W/C of 0.5 are introduced. Laboratory-made CEM V/A concrete specimens (AT and SK) demonstrated 90-day cube compressive strength between 49.8 – 50.9 MPa in water and 45.2 – 48.2 MPa in 60 % R.H. dry air; and those of CEM V/B concretes between 39.7 – 40.9 MPa in water and 26.9 – 38.7 MPa in 60 % R.H. dry air opposite to 53.6 MPa in water and 48.3 MPa of the CEM I 32.5 R concrete kept 90 days in 60 % R.H. dry air at (20 ± 1) °C. The use of CEM V/ (A, B) cements for structural concrete is strongly restricted by normative limitations in European countries. In order to improve this circumstance in Austria and Slovakia, the common research project was solved between 2010 and 2012 with the aim to show application possibilities of CEM V/A and CEM V/B cements for common usage in the structural concrete and ready-mixed concrete.

Abstract: Fly ash is currently secondary raw material, which is produced in huge quantities and its applicability is still not optimal. Even though it is used in cement, concrete, mortars, aerated concrete, ceramics, etc., it is still used, more than 80 % of it, for the reclamation of industrial areas and open cast mines. The production of artificial aggregate by clinkering fly ash utilizes at least 90 % of fly ash in the mixture and it is, together with aerated concrete, one of the ways to make the most of the potential of this raw material. This article deals with the description of the nature of individual fly ash types produced in the Czech Republic and the study of its influence on the behaviour during the thermal process. Chemical composition is the decisive parameter; it indicates the ratio of silicon, iron and aluminium oxides, and thus affects the melting point of the entire complex. This article points out the differences among the various fly ash types and it directly shows, using a picture-analysis, the changes in a sample cross-section during annealing.

Abstract: The article describes the results of an experimental research dealing with the use of industrial waste in the form of secondary raw material - polyurethane foam after the end of its life cycle, as a 100% substitute of filler in restoration plaster with thermal insulating effect. The article presents the formulas of restoration plaster and its properties. They are: mortar consistency, volume weight, strength characteristics, thermal conductivity coefficient, coefficient of capillary water absorption, porosity and resistance against salts.

Abstract: This paper is focused mainly on analyzing the possibility of combining direct and indirect lightening of building materials, especially the combination of lightweight porous aggregates in combination with aerated concrete respectively. As a part of indirect lightening the lightweight inorganic aggregate will be described.

Abstract: The paper presents results related to surface treatment of polypropylene fibres with intention to increase its performance in cement composite by exposing such fibres in cold plasma discharge. In was previously demonstrated that such treatment has beneficial effect. Here we focused mainly on the changes in the surface. The study was carried out by electron microscopy, confocal microscopy and microscopy of atomic forces. The results suggest increasing degree of change in the surface as the energy of discharge and time of exposure increase. Atomic force microscopy indicates increase in adhesion force.

Abstract: This article studies the effect of various types of cement on rheological properties of cement pastes. Rheological properties are significantly related to workability of concrete and to requirements of mixing water amount and thus affect the development of strength, durability of concrete and resistance of concrete to extreme conditions and to high temperature. This article describes the influence of cement type, type and dose of superplasticising admixtures on development of torque in time. Torque was monitored by the rotational viscometer Viskomat NT. Theoretical part of the article briefly describes the phenomenons that can accompany mixing and processing of cement pastes. Experimental part is focused on monitoring the rheological behaviour of cement pastes of different formulas by monitoring the evolution of torque in time.