Daniel Dobiáš

Influence of Pozzolana Admixture on Long-Term Chemical Characteristic of Cement Mortars

nfluence of non-flowing model sulphate solution determined for cement mortar with pozzzolana admixture are presented in this paper. In the predetermined time intervals the influence of the aggressive liquid on chemical properties and mineralogical composition was tested. The changes caused by corrosive sulphate environment on the testing specimens were determined in dependence on the different type of cement and used ground clay brick as pozzolana admixture. From the results obtained follows that the additive of ground clay bricks has positively impact on the sulphate resistance.

Measurement of Chloride Permeability in UHPC by Accelerated Method

The chloride permeability of concrete (UHPC) was evaluated by means of the Rapid chloride permeation test and and standard difusion test. The tests are different in the voltage applied for accelerating the transport through the concrete specimen. The permeability strongly depends on quality and curing time of the concrete.

The Influence of Glass Fibers as Dispersed Reinforcement on Hydric Properties of Concrete

In this paper, the effect of different kind of glass fiber on hydric properties of ultra-high performance concrete and normal strength concrete is determined. It was the use several types of micro fine high-dispersible alkali resistant fibers that prevent the formation of shrinkage cracks caused by tensions. Comparative measurements with both concrete without glass fibers are done as well. The main aim of this experimental work is to obtain sufficiently accurate input data for the estimate of durability surface layers of concrete which are connected with water transport and its accompanying effects such as biological degradation, water soluble salt transport or degradation by rainwater absorbing oxides of sulfur and carbon from air.

Resistance of Surface Layers of Concrete against Aggressive Environment

The article deals with the corrosive effects of acids on the selected surface layers of concrete with/ without an epoxy coating. Concrete sample was placed in extreme environments, which represented the 40% sulphuric acid solution. In addition to measuring surface degradation of concrete, this work focused on the depth of acid penetration into the sample. It can be concluded that the long-term effects of aggressive environments severely degrades the concrete surface on the samples causing corrosion of Type II.

Water Transport Properties and Depth of Chloride Penetration in Ultra High Performance Concrete

Properties of water transport and depth of chloride penetration into the Ultra High Performance Concrete (hereafter as UHPC) with mild steel fibres are presented in this paper. The main aim of this experimental part of work is to obtain sufficiently accurate input data for the evaluation of long-term durability of architectural concrete which are connected with water transport and its accompanying effects such as biological degradation or chloride transport. The article also presents the one dimensional chloride diffusion into UHPC which can be potentially dangerous particularly for durability of reinforced concrete structures. For the simulation of aggressive environments the concrete samples were exposed to chloride solution for one year. Measured data were examined in relation to the depth of penetration of chloride ions into the UHPC structure. Comparative measurements with normal strength concrete (hereafter as NSC) are done as well. An about five-time lower value of moisture absorption of UHPC compared to the NSC was observed and further the curve of chloride penetration into the structure is significantly steeper for UHPC samples.

Chemical Changes of Cement Caused by Aggressive Environment

The chemical changes of cement structures exposed to aggressive environments are explored in this paper. In the predetermined time intervals the influence of the aggressive liquid, namely 5% wt. non-flowing sulphate solution, on mineralogical composition was tested. The chemical changes caused by corrosive sulphate environment on the testing specimens were determined in dependence on the different type of cement. From the results obtained follows that different kind of cement has impact on the sulphate resistance.

Investigation of Glass Fibre Reinforced Cement (GFRC) Material Exposed to High Temperatures

In this paper we present the tests of high temperatures resistances of glass fibre cement plates. The aim of the research was to determine the values of tensile strength in bending for samples subjected to annealing at temperatures 200, 300, 400 and 500 °C in endurance at the highest temperature level for 24 hours. The bending strength was performed according to the norm EN 1170-4. The thermal dilatometric analysis was performed in the temperatures till 540 °C.

Effect of Pozzolanic Additive on Pore Structure of Cement Mortar

In this paper are explored the changes of pore structures of mortar with pozzolanic admixture exposed to aggressive environments, namely 5% wt. sodium sulphate solution. Influence of non-flowing sulphate solution on the test specimens were determined in dependence on the different type of cement and used minced clay brick as pozzolanic admixture. Attention is also paid to the properties of the individual components of the mortar. From the results obtained follows that the additive of minced clay bricks has positive impact on the sulphate resistance.

Analysis of Suitability of Mortar Used for Reconstruction

Assessment of suitability of mortar intended for reconstruction based on their characteristics, namely basic, hygric and mechanical parameters, chemical analysis and frost resistance, is presented in this paper. Properties of the load bearing structure as well as natural factors were also taken into account in assessing the suitability of the used mortars. Comparative measurements with original historic plaster are done as well. On the basis of the experiments performed, it can be concluded that not only mortar properties but also environment conditions and technology of application as well as load bearing structure characteristics have a great importance to the service life of the repaired parts of historical buildings.

Investigation of Corrosion of Cement-Based Materials by Using of Rotating Disc Method

The paper introduces the rotating disk method, its features and the scope of application. It also describes the application of this technique in the research of corrosion of cement-based materials caused by aggressive liquid solutions and the effect of flow of solutions on the corrosion rate