Abstract. In many cases cement based materials demand a higher flowability and workability and this conventionally can't be done without loss of its strength, due to the fact that the common practice to increase the workability is the addition of water. But, nowadays using a third generation superplasticizer (SP) we can achieve the desire flowability without loss of its strength. The action of superplastisizers is to spread efficiently the cement grains and so to wetting better the cement grains giving a more homogeneous mixture with higher strength. Nine different mixtures were prepared adding a small percentage of SP (1%). The conditions to get a self levelling mortar, have to do not only with rheological but also with mechanical demands. The bending and compression test gave the achieving mechanical strength whereas their rheological response came through slump flow and v-funnel flow tests. With the help of a small amount of stabilizer we obtain a robust mixture that deserves the desire response at the field too.
The results of the experimental investigation of the developing expansion and contraction strains of both plastering mortar and Expanded Polystyrene Foam (EPS) coatings, during thermal and drying cyclic loading are presented. The mortar used, is cement based with hydrated lime and fine marble aggregates. The EPS specimens were cut from boards of various qualities, appropriate for the external insulation of buildings. Mortar and EPS specimens were subjected to temperature cyclic changes, during which the occurring expansion and contraction strains were recorded. Based on these data, assumptions were made for the nature and the mechanism of the growing strains, in order to collect the necessary information to develop solutions for the critical problem of mortar cracking when applied over EPS insulating boards.
Abstract. Cement based mortars reinforced by glass and polypropylene fibres were exposed to fire conditions up to 900 o C from 10 min to 2 hours and after their slow cooling, were tested under compression and bending loadings. We can see that three distinct stages are appeared. At first, up to 300 o C, a not absolutely specified behaviour is appeared. Reinforced mortar's mechanical response is depended on temperature level, time duration and type of cement composite. So, its strength can be slightly increased, remains unaltered or can be even reduced. At the following stage from 300 o C up to 800 o C, a gradual general degradation is appeared. Mortar's strength and rigidity are rapidly reduced so low, reaching approximately the 10% of their initial values. At the same time yielding strain is increased, leading to an almost constant toughness. The whole degradation of cement composite is completed at the third stage where a total destruction is appeared. At the temperature level of 900 o C and above the aggregates decomposition is recorded, giving an grained like material.
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