PSI - Issue 68

Zoi S. Metaxa et al. / Procedia Structural Integrity 68 (2025) 184–189 Z.S. Metaxa et al. / Structural Integrity Procedia 00 (2025) 000–000

187

4

mixtures. Overall, at all different curing ages, the flexural strength of the XPS-modified mortars decreases with increasing XPS content. For example, the reference mixture (0 vol.% XPS) exhibits a flexural strength of 7.32 MPa at 28 days, which is reduced to 5.42 MPa for the mixture with 100 vol.% XPS content. It should be pointed out that despite the reduction in flexural strength, at the age of 28 days all investigated mixtures maintained flexural stress values above 5 MPa, which, according to the literature, is considered to be the lower limit for considering a high strength mortar suitable for structural applications (Liu et al., 2024).

+

,

*

! " # $ %C%'%(C%C)C*"! !+! )+! )+' '+! '+' #+! #+' *+! *+' (+! !"#"$%C#'(%)(C*+%,C-+.."("$%C/01C2'$%"$% ,'!,-./01,2P4 ,#!,-./01,2P4 ,*!,-./01,2P4 ,(!,-./01,2P4 ,$!,-./01,2P4 ,%!!,-./01,2P4 ,0,!,-./1,2P4 ,%!,-./01,2P4 ,C!,-./01,2P4 ,"!,-./01,2P4 ,)!,-./01,2P4

!"#"$%C#'(%)(C*+%,C-./C0'$%"$%C12PC4)5S7

F

(

#

'

,

+

C

+,+!+-./,M+12P +%!+-./,M+12P +'!+-./,M+12P +(!+-./,M+12P +*!+-./,M+12P +$!!+-./,M+12P

%

4/5S789/+:X85::+<=29[

!"#$%&'"(F*&#+,*-(./M'1

$

!"!! !"!# !"$! !"$# !"%! !"%# !"C! !"C# !

5S789:,X<=[,?X<=[]

?8.::]59A+AB:C/9a5E5cX+

(a)

(b)

Fig. 1. (a) Flexural strength: development of XPS-modified mortar mixtures over 3, 7, and 28 days of curing and (b) flexural stress versus crosshead displacement of XPS-modified mortar mixtures at 28 curing days.

Fig. 1b shows typical flexural curves (mechanical stress over crosshead displacement) for several XPS-modified mortar mixtures. The slope of the stress-displacement curves is considered to be analogous to the modulus of elasticity, reflecting the relative stiffness of each mixture. Mixtures with lower XPS content, such as the 0 vol.% (in black colour) and 20 vol.% (in red colour) XPS mixtures, show a steeper initial slope, indicating higher stiffness and likely possess a higher modulus of elasticity. In contrast, mixtures with higher XPS content, such as the 100 vol.% (in dark blue colour) and 80 vol.% (in green colour) mixtures, exhibit more gradual slopes in the initial part of the curve, indicating lower stiffness. This suggests that these mixtures have a lower modulus of elasticity, meaning they deform more easily under the same applied mechanical load. The XPS addition, being a lightweight and flexible material, contributes to this reduction in the overall stiffness of the investigated materials. 3.2. Density measurements The relationship between flexural strength and density measurements for XPS-modified mortars at 28 days of curing, with XPS content ranging from 0 vol.% to 100 vol.% is shown in Fig. 2a. As density decreases (corresponding to an increase in XPS content), flexural strength also decreases. The regression line showed at the insert of the graph, demonstrates well that a strong correlation exists between density and flexural strength. The reference mixture with 0 vol.% XPS has the highest density (~2115 kg/m³) and flexural strength (7.32 MPa), while the 100 vol.% XPS mixture shows the lowest values for both properties (~1480 kg/m³ and 5.42 MPa, respectively). Despite the mechanical strength decrease with increased XPS content, all mixtures maintain flexural strength values above the 5 MPa threshold for structural applications, while achieving a decreased density so as to be also considered as lightweight mortar (Dixit et al., 2019). The strong correlation implies that these mortars offer potential for applications where reducing weight is critical, while maintaining acceptable structural performance.