Dragica Jevtić

The properties of the cement screeds with the addition of polypropylene fibres and the shrinkage-reducing admixture

The paper points out the problems of damage that can occur during the preparation and exploitation of a cement screed. There were described the types and properties and presented test results obtained on the samples of cement composites prepared with the addition of fibre reinforcement and shrinkage-reducing admixture. Testing procedure included the following properties: density, compressive strength, ultrasound, coefficient of construction advantages and shrinking, and above all the impact of compaction procedure on the quality of cement screed. The testing results of experimental research show that the use of polypropylene fibres and shrinkage-reducing admixture contributes to the improvement of mechanical and deformation properties of cement screeds and that installation which includes some method of vibration is crucial for screed quality. The above statements are also recommendations in the execution of cement screed in practice.

Study of Fly Ash in Making Cementitious Composites

Applications of fly ash in building industry have very important and relevant problems of origin which are discussed in this paper. Authors have performed tests on mortar, plain concrete and Self Compacting Concrete (SCC) specimens. Experiments showed satisfactory results concerning possible application of fly ash as admixture for cementitious composites. Experimental research was conducted in the Laboratory for materials at the Faculty of Civil Engineering, University of Belgrade.

Thermal Shock Behavior of Sintered Alumina Based Refractories

In many applications, refractories are subjected to rapid temperature changes, which generate thermal stresses. If these stresses are sufficiently large, they can cause catastrophic crack propagation and resultant failure. Many theoretical treatments and experimental measurements have been presented to describe the thermal shock behavior of brittle ceramic materials. D.P.H. Hasselman1,2 and J. Nakayama3,4 applied fracture mechanic concept to refractory thermal shock problems. For the prediction of the thermal shock behavior of the refractory resistance parameters were proposed. Those parameters are based on thermal and mechanic properties. Two groups of resistance parameters were proposed: fracture and damage resistance parameters. In Table 2. equations for calculation resistance parameters are presented1-4.