J. Gołaszewski

Influence of viscosity enhancing agent on rheology and compressive strength of superplasticized mortars

Abstract The results of investigation into the influence of Viscosity Enhancing Agents (VEA) on the rheological properties of mortars, different in cement and superplasticizer properties, are presented and discussed. Rheology results have been evaluated according to the Bingham model, which describes the rheology with 2 parameters: yield value and plastic viscosity. Rheological parameters were measured using Two‐Point Workability Test (TPWT). Additionally, the influence of VEA on compressive strength of mortars is presented. It was found that effects of VEA addition on rheological properties of mortars, as well as on compressive strength of mortars, significantly depend on cement and superplasticizer properties. Basic relation of influence of VEA on rheological properties and compressive strength of mortars in respect to cement and superplasticizer properties were presented and discussed. It is concluded that addition of VEA influences compatibility between cement and superplasticizer. Because addition of...

The Effect of Temperature on the Rheological Properties of Self-Compacting Concrete

In the paper the methodology and results of investigation of the influence of temperature and time on the rheological properties of cement paste and different in cement paste volume fresh self compacting concrete are presented and discussed. The influence of temperature on the rheology of mortar analogous to mortar that fills voids of coarse aggregate in the self compacting concretes was additionally the subject of investigation. It was found that the influence of temperature on rheological parameters of fresh cement paste and concrete may be significantly different, whereas on rheological parameters of fresh mortar and concrete is generally similar for both these materials. Discussion on the test results concern possible mechanisms of temperature influence on rheological properties of fresh cement paste, mortar and concrete. It is concluded that testing cement paste is not sufficient for designing and development of self-compacting concrete in respect to changing temperature. For predicting trends of changes in rheological behaviour of fresh self compacting concrete in changing temperature tests made on mortars are necessary.

The Influence of Cement Paste Volume in Mortar on the Rheological Effects of the Addition of Superplasticizer

Abstract The results of investigation into the influence of polyether type superplasticizer addition on rheological parameters and its changes with time of different in cement paste volume fresh mortars are presented and discussed in the paper. Rheology results have been evaluated according to the Bingham model, which describes the rheology with the parameters: yield value and plastic viscosity. Rheological parameters were measured using Two-Point Workability Test. Because of the similar nature of rheological behaviour of fresh mortar and concrete, presented in paper relationships for mortars can be also used to state the rheological properties of fresh concrete. The obtained results show that the character and range of superplasticizer influence on rheological parameters of mortar is strongly influenced by cement paste volume. Volume of cement paste is also a significant factor affecting range and direction of changes of the rheological parameters of superplasticized mortars with time. The results show, that the character of influence of superplasticizer on rheological parameters of fresh cement paste and on fresh mortar may significantly differ each from other. These differences increase with decreasing volume of cement paste in mortar. On the ground of obtained results the empirical relations joining the rheological parameters of mortars with superplasticizer content were established. Analysis of results covers also comparison between influence of cement paste volume on rheology of mortars with and without superplasticizer. It is concluded that effects of superplasticizer addition on rheology of fresh mortar and concrete should be also considered in respect to cement paste volume. It is difficult to unequivocally predict effects of superplasticizer content on rheology of mortar or fresh concrete basing only on tests made on cement paste, and not making allowance on degree of aggregate filling by cement paste in this mortar or concrete.

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.

Designing the composition of concrete mixtures based on properties of mortar

The research was nanced by the project No. 0842/B/T02/2011/40 from the National Science Centre and the project “DoktoRIS – Scholarship program for innovative Silesia” co- nanced by the European Union under the European Social Fund.

The influence of composition on thixotropic behaviour of cement mortar

This paper presents methods of measurement and results of rheological properties including the thixitropic stiffening of designed cement mortars. The aim of the study is to determine the effect of the type of cement, w/c ratio, and chemical admixtures on the selected rheological properties of mortars. It will allow a better understanding of the nature of previously observed decreasing formwork pressure when using self-compacting concrete.

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.