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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tem perature in the range of 1000 ÷ 1350 ° C. As a result, light weight concretes at higher temperatures tend to heat up more slowly, and the temperature rise is accompanied by a lower risk of cracking and lower deformation resulting in more uniform stress distribution. Nevertheless, the performance of lightweight concretes under high temperature conditions depends on: the heating temperature, its increase in time, the type of aggregate, concrete strength and moisture content. Insulating-structural concretes are special type of lightweight composites of relatively low compressive strength (> 3.0 MPa) and low thermal conductivity coefficient (< 0.7 W/m K). The most popular technology of production insulating-structural building composites are autoclaved aerated concrete (AAC) or open structure lightweight aggregate concrete (LAC). Besides typical lightweight aggregates of mineral origin used for structural concretes, e.g. expanded shale and clay or sintered fly ash, LAC may be produced using extremely porous granulates as perlite, polystyrene or expanded glass (Clarke and Yaneske (2009), Sharei et al (2017), Domagała et al (2017)). This type of concretes is especially often applied for thin-walled decorative and insulating elements. Due to their non-structural function they are rarely tested for resistance to high temperature, although in many cases they perform at elevated temperatures. The aim of the research was to assess the resistance of different types of insulating-structural concretes to high temperature. The selected concretes had compositions similar to those applied in practice for production of precast thin-walled protective and decorative elements which may also play a role of insulating claddings for stoves, fireplaces or other heat sources. 2.1. Constituent materials and mix compositions Four series of insulating-structural concretes (LAC1 ÷ LAC4) were prepared for tests. As aggregates natural sand, perlite, recycled polystyrene granulate and expanded glass were applied. A bulk density of sand, perlite, polystyrene and expanded glass, determined according to EN 1097-3, was equal to 1540 kg/m 3 , 100 kg/m 3 , 180 kg/m 3 and 290 kg/m 3 , respectively. The maximum aggregate size did not exceed 2 mm due to its application for thin-walled concrete elements. All aggregate types used for concrete preparation are presented in Fig.1. 2. Experimental details

Perlite

Natural sand

Expanded glass

Polystyrene

Fig. 1. Fine aggregates used for production of insulating-structural concretes.

Table 1. Compositions of insulating-structural concretes, kg/m 3 Concrete type Cement Water Natural Sand 0/2 mm Perlite 0.5/2.0 mm

Polystyrene 0.5/2.0 mm

Expanded Glass 0/1mm

Glass Fibres 12 mm

Polypropylene Fibres 12 mm

Foaming Agent

LAC1 LAC2 LAC3 LAC4

490 490 310 310

330 330 320 320

620 310

45 45

45 90

0 0

0 0

1.0 1.0

0

1.5 1.5 1.5

0 0

0 0

0 0

305 305

1.5

0 0

0