PSI - Issue 74

Lucyna Domagała et al. / Procedia Structural Integrity 74 (2025) 17 – 24 Lucyna Domagała / Structural Integrity Procedia 00 (2025) 000–000

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Fig. 4. Relationshi p between density (D) and thermal conductivity (λ) of fine lightweight aggregate concretes in natural and oven -dry conditions.

4. Conclusions The analysis of the carried out test results indicates that the range of lightweight aggregates available on the market creates possibilities of modeling the properties of fine-aggregate insulating and structural concretes in a very wide range. The tested composites, due to using lightweight aggregates, a high water and cement ratio w/c = 0.8 and additionally a foaming admixture, were characterized by an oven dry density in the range of 520 to 1070 kg/m 3 which was lower by as much as 46 ÷ 74% than the reference normal-weight concrete. Such a significant reduction in the density of the tested composites resulted in the relatively low compressive strength (2.9 - 7.3 MPa) and a very low thermal conductivity coefficient (0.07 - 0.17 W/(m K)). However, in the case of the tested insulating and structural concretes no direct relationship was found between their density and compressive strength. The type of lightweight aggregate, which significantly affects the density of the composite, turned out not to have a clear effect on the compressive strength of composites made with a cement matrix of lower strength. In connection with the above, the production of fine-aggregate insulating and structural concretes made on cement matrices with significant porosity and lightweight aggregates with higher particle density, such as sintered fly ash or expanded clay, should be considered ineffective. In such cases, composites with relatively high density are obtained, which does not significantly improve their strength. However, this type of matrix together with ultra-light aggregates can be successfully used for insulating and structural concretes, for which the priority criterion in design is their low density and high thermal insulation. Among the ultra-light aggregates tested, perlite guarantees the most favourable relationship between strength and density and thermal insulation of insulating and structural concretes. However, the high water absorption of concrete with this aggregate indicates that it cannot be used without protection in conditions of increased humidity. In such cases, a safer and more universal solution is to use expanded glass aggregate.