PSI - Issue 23

Lucyna Domagała / Procedia Structural Integrity 23 (2019) 342 – 347 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 2. The influence of heating temperature on changes of mean density for different types of insulating-structural concretes.

Fig. 3. The influence of heating temperature on changes of mean compressive strength for different types of insulating-structural concretes.

3.2. Properties of composites subject to heating

Mean results of density and compressive strength tests carried out on specimens subject to heating at high temperatures are presented in Fig. 2 and Fig. 3. Results of flexural strength tests revealed the same decrease trends as compressive strength ones, but due to their low values they should not be quantitatively analyzed. As it was expected rising a heating temperature caused the decrease of both density and compressive strength. Finally the density loss after heating in 400 o C ranged from 15 % for LAC1 to 26 % for LAC3 and LAC4. Such a high density decrease, many times greater than in the case of normal-weight concrete or structural lightweight concretes, resulted mainly from evaporation of large amounts of water accommodated in porous open structure of tested insulating structural concretes. Nevertheless, it can be noted that final density values after heating in temperature of 400 o C were even lower than oven-dry density values given in Table 2. In the case of concretes LAC3 and LAC4 the difference between density determined after final heating and oven-dry density was only 20 kg/m 3 while for LAC1 and LAC2 containing polystyrene aggregate it was ca five times higher. These differences resulted from a certain dehydration of cement paste and burning of polystyrene granulate. Analyzing the fracture of specimens after heating at particular temperatures no visible changes were observed in the case of concretes made of expanded glass and reinforced or not with glass fibres (LAC3 and LAC4). Meanwhile, concretes containing polystyrene aggregate and reinforced with polypropylene fibres (LAC1 and LAC2) revealed that all fibres were melted already at 200 o C and specimens heated at 300 o C showed that polystyrene granulate