Tomasz Ponikiewski

THE INFLUENCE OF SELECTED COMPOSITION FACTORS ON THE RHEOLOGICAL PROPERTIES OF FIBRE REINFORCED FRESH MORTAR

ABSTRACT In the paper the methodology and test results of the investigation are presented and discussed on the influence of fibres on Theological properties of modified standard mortars. The rheological parameters of fibre reinforced fresh mortars (FRFM) - yield value and plastic viscosity were determined. FRFM behaves as a Bingham body, their rheological parameters were determined by using rheometer to pastes and mortars. In the research, an experimental verification of a significance of an influence: W/C ratio, volume fraction of fibres, lengths and kind of materials of fibres on rheological properties of FRFM was investigated. In the paper the results obtained for mixes with polypropylene, steel, carbon and glass fibres are presented. The first step of the procedure was a rheological identification of fiber-mortars, which was completed based on the delimitation of the tension due to an assignment of characteristic dependence - speed of non-dilatational strain, in the form of a curve flow and acceptance of adequate model and rheological equalizations. This equalization is a base to the experimental analyses which influences composition factors of mixtures on the character of their flowing and rheological parameters. The analysis of the results of these measurements permitted on the following qualifications: reliable statistics of rheological parameters from variables, indications of workability forms of mortars with fibres and approximate reliability among rheological parameters of FRFM.

X-Ray Investigation And Modelling Of Steel Fibres In Self-Compacting Concrete

Abstract The paper presents an analysis of cross-sections of beams made of Steel Fiber Reinforced High Performance Self-Compacting Concrete (SFRHPSCC). The analysis was performed by two methods, using our own computer program (destructive method), and computed tomography (non-destructive method). Statistical analysis showed that the orientation of the fibers exhibit exponential distribution. The tests confirmed the correct formation of concrete, maintaining the uniformity of steel fibre distribution.

An image processing approach to determination of steel fibers orientation in reinforced concrete

The paper presents a preliminary study aimed to automatically determine the position and orientation of steel fibers in fiber-reinforced concrete. This is required for assessment of the relation between the methods of forming and resulting concentration, position and orientation of steel fibers. Concrete beams with various types of fibers and method of forming were scanned using Computed Tomography and the resulting volumetric images were subjected to image segmentation. From the obtained label map the position and orientation in 3D of each steel fiber were calculated. This enabled generating 4D histograms visualizing in compact form the overall orientation of the fibers. Statistical analysis showed that the orientation of the fibers exhibit exponential distribution.

Experimental and numerical evaluation of SCC concrete durability related to ingress of chlorides

The article focuses on the sample chloride ingress induced corrosion initiation evaluation of the traditional and self-compacting concrete. Surface electrical resistivity measurements is used as material parameter related to the diffusion coefficient. The presented calculations and results are part of a campaign that includes also steel fibers reinforced concrete however the effect of fibers is not covered herein due to long term experiments. The input parameters for the time-dependent diffusion coefficient model are presented. The time to onset of corrosion including the effect of delay of chloride concentration load and the aging effect is evaluated.

Influence of Temperature on Workability and Compressive Strength of Ordinary Concrete with High Calcium Fly Ash

Abstract The rheological properties of fresh ordinary concrete are closely affected by temperature and time. The paper presents the study of consistency of fresh concrete mixtures made with Portland cement and cement with calcareous fly ash. Two types of admixtures were used. It was proven that the temperature has a clear effect on workability and compressive strength concrete. Influence on workability can be reduced by selecting the appropriate superplasticizer and cement.

Influence of Cements Containing Calcareous Fly Ash as a Main Component Properties of Fresh Cement Mixtures

The main goal of presented research was to examine usability of cements containing calcareous fly ash (W) from technological point of view. In the paper the results of tests concerning the influence of CEM II and CEM IV cements containing fly ash (W) on rheological properties, air content, setting times and plastic shrinkage of mortars are presented and discussed. Moreover, compatibility of plasticizers with cements containing fly ash (W) was also studied. Additionally, setting time and hydration heat of cements containing calcareous fly ash (W) were determined. In a broader aspect, the research contributes to promulgation of the possibility of using calcareous fly ash (W) in cement and concrete technology, what greatly benefits the environment protection (utilization of waste fly ash). Calcareous fly ash can be used successfully as the main component of cement. Cements produced by blending with processed fly ash or cements produced by interginding are characterized by acceptable technological properties. In respect to CEM I cements, cements containing calcareous fly ash worsen workability, decrease air content, delay setting time of mixtures. Cements with calcareous fly ash show good compatibility with plasticizers.

X-Ray investigation and strength measurement of steel fibre reinforced self-compacting concrete beams

Abstract The paper presents a study on self-compacting concrete with two types of steel fibres. Under consideration was the effect the method of forming of beam elements has on the distribution of steel fibres. Formed we beams of dimensions 120×15×15 cm3 and 180×15×15 cm3. The self-compacting mixture contained steel fibres of varying lengths (35 and 50 mm) and varying levels of their volume ratio in the mix (0.5% - 1.0% - 1.5%).

Laser System for Testing Early Shrinkage of Concrete Elements in Conjuction with the Deterioration of the Setting Time

Abstract The paper presents a method for testing the shrinkage of concrete beams with dimensions of 10x10x50cm. Measurements followed from setting into the form until 24 hours after setting. It was used modified TLS system, which originally was meant for the determination of changes in the length of thin-mortar. Simultanously measured were the changes of speed propagation of sound waves by Vikasonic, what allows to specify the setting time of binders. It could be a base for determining the scratch resistance of the concrete in the first 24 hours after casting.

Influence of fibres on rheological and mechanical properties of self-compacting concrete

The paper presents results of tests on self-compacting mixtures with the addition of steel fibres (Steel Fibre Reinforced Self-Compacting Concrete). Four types of steel fibres at 3 levels of the volume ratio are considered. The results include studies on samples belonging to classes of slump flow SF, classes of viscosity T 500 , and rheological tests. The studies were based on application of two rheometers for rheological properties of concrete mixtures - BT2 Rheometer and Viskomat XL. Additionally, a study of compressive strength f cm,28 and flexural strength f fl was carried out on concrete SFRSCC. These studies have confirmed the possibility of using steel fibres in concrete SCC while maintaining the assumed technological parameters for concrete mixtures and, above all, their workability.