Influence of the relationships between compressive strengths of mixed and industrialized mortars and concrete blocks on the behavior of masonry prisms

Paulino, Rafaella Salvador; Toralles, Berenice Martins

doi:10.1590/S1983-41952024000500003

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ORIGINAL ARTICLE • Rev. IBRACON Estrut. Mater. 17 (5) • 2024 • https://doi.org/10.1590/S1983-41952024000500003 copy

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10.1590/S1983-41952024000500011

Influence of the relationships between compressive strengths of mixed and industrialized mortars and concrete blocks on the behavior of masonry prisms

Influência das relações entre resistências à compressão de argamassas mistas e industrializadas e blocos de concreto no comportamento de prismas de alvenaria

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The performance of masonry structures depends not only on the quality of blocks and mortars but also on their interactions. This study aims to evaluate the influence of unit and mortar characteristics on the compressive strength of masonry. Prisms were produced using concrete blocks with nominal strengths of 8 and 10 MPa, combined with mixed and industrialized mortars with lower, similar, and higher strengths compared to the blocks. Response surfaces and contour plots were generated to visualize the effects of unit and mortar properties on prism strength. Estimations were performed, and the failure mechanisms of prisms for various combinations of blocks and mortars were analyzed. The failure modes of the prisms were characterized by ductile failure (in weaker mortars), cohesive rupture of the assembly (in intermediate-strength mortars), and brittle failure (in stronger mortars), primarily due to lateral tensile forces acting on the blocks. The findings of this research contribute to the existing knowledge database in the field and can assist in the appropriate selection of blocks and mortars for structural masonry applications.

Keywords:
mixed mortar; industrialized mortar; concrete block prisms; masonry; failure modes

Sieve (mm)	Retained massa (g)	% retained	% retained accumulated
4.8	0.0	0.0	0.0
2.4	5.0	1.0	1.0
1.2	12.5	2.5	3.5
0.6	50.0	10.0	13.5
0.3	252.5	50.5	64.0
0.15	180.0	36.0	100.0
Fineness modulus (-)		1.82	NBR NM 248 [⁴³43 Associação Brasileira de Normas Técnicas, Aggregates – Sieve analysis of fine and coarse aggregates, NBR NM 248, 2003.]
Maximum size (mm)		1.18
Classification (-)		Fine
Unit mass (g/cm³)		1.49	NBR NM 45 [⁴¹41 Associação Brasileira de Normas Técnicas, Aggregates – Determination of the unit weight and air-void contents, NBR NM 45, 2006.]
Specific mass (g/cm³)		2.62	NBR NM 52 [⁴⁴44 Associação Brasileira de Normas Técnicas, Fine Aggregate – Determination of the Bulk Specific Gravity and Apparent Specific Gravity, NBR NM 52, 2002.]
Fineness (Sieve nº 30) (%)		0.3	NBR 9289 [⁴⁵45 Associação Brasileira de Normas Técnicas, Hydrated Lime for Mortars: Determination of Fineness, NBR 9289, 2000.]
Fineness (Sieve nº 200) (%)		10.8	NBR 9289 [⁴⁵45 Associação Brasileira de Normas Técnicas, Hydrated Lime for Mortars: Determination of Fineness, NBR 9289, 2000.]

CP II-F-32		Limit - NBR 16697 [⁴⁶46 Associação Brasileira de Normas Técnicas, Portland Cement: Requirements, NBR 16697, 2018.]
Physical properties
Initial curing period (min.)	195	≥ 60
Initial curing period (min.)	255	≤ 600
Specific surface area (cm²/g)	3290	≥ 2600
Insoluble residue (%)	1.08	≤ 7.5
Compressive strength – 1 day (MPa)	15.0	N/A
Compressive strength – 3 days (MPa)	28.4	≥ 10
Compressive strength – 7 days (MPa)	34.9	≥ 20
Compressive strength – 28 days (MPa)	41.4	≥ 32
Chemical compositions
${A l}_{2} O_{3}$ (%)	4.18	-
Si $O_{2}$ (%)	18.56	-
${F e}_{2} O_{3}$ (%)	2.65	-
CaO (%)	60.11	-
MgO (%)	3.69	N/A
${S O}_{3}$ (%)	2.57	≤ 4.5
Loss on ignition (%)	6.41	≤ 12.5
Free calcium oxide (%)	1.15	-

Prism	Block	Mortar	Condition^*	Number of specimens
PBL1MA	BL1	MA	$f_{m}$ ≤ 0.7 $f_{b}$	3
PBL1MB		MB	0.7 $f_{b}$ ≤ $f_{m}$ ≤ 1.5 $f_{b}$	3
PBL1MC		MC	$f_{m}$ $\geq$ 1.5 $f_{b}$	3
PBL1IA	BL1	IA	$f_{m}$ ≤ 0.7 $f_{b}$	3
PBL1IB		IB	0.7 $f_{b}$ ≤ $f_{m}$ ≤ 1.5 $f_{b}$	3
PBL1IC		IC	$f_{m}$ $\geq$ 1.5 $f_{b}$	3
PBL2MA	BL2	MA	$f_{m}$ ≤ 0.7 $f_{b}$	3
PBL2MB		MB	0.7 $f_{b}$ ≤ $f_{m}$ ≤ 1.5 $f_{b}$	3
PBL2MC		MC	$f_{m}$ $\geq$ 1.5 $f_{b}$	3
PBL2IA	BL2	IA	$f_{m}$ ≤ 0.7 $f_{b}$	3
PBL2IB		IB	0.7 $f_{b}$ ≤ $f_{m}$ ≤ 1.5 $f_{b}$	3
PBL2IC		IC	$f_{m}$ $\geq$ 1.5 $f_{b}$	3

Property	Block
Property	BL1	BL2
Length (cm)	39.13 (0.18)	39.22 (0.14)
Width (cm)	13.98 (0.29)	14.00 (0.00)
Height (cm)	19.02 (0.40)	19.27 (0.42)
Average thickness of longitudinal shells (mm)	35.01 (0.32)	35.12 (0.17)
Average thickness of transverse webs (mm)	32.03 (0.31)	32.04 (0.21)
Water absorption (%)	7.86 (20.49)	8.60 (16.42)
Gross area (cm²)	547.04	549.08
Net area (cm²)	326.64	328.98
Net area / gross area ratio	1.675	1.669
Gross area compressive strength (MPa)	8.33 (6.39)	11.98 (6.20)
Net area compressive strength (MPa)	13.95 (3.82)	19.99 (3.72)
Characteristic compressive strength (MPa)	7.18 (7.41)	10.77 (6.90)

Mortar	Mix proportion (by mass)	Materials						Fresh state
Mortar	Mix proportion (by mass)	Cement (g)	Lime (g)	Sand (g)	Water (ml)	w/c ratio	w/dm ratio	Flow (mm)	Bulk density (g/cm³)	Air content (%)	Water retentivity (%)
MA	1:1.25:6.75	0.389	0.486	2.625	0.731	1.880	0.209	260^a	2.06^A	3.97^a	97.20^A
MA	1:1.25:6.75	0.389	0.486	2.625	0.731	1.880	0.209	(0.38)	(0.25)	(6.01)	(0.16)
MB	1:0.75:5.25	0.500	0.375	2.625	0.665	1.330	0.190	257^a	2.09^A	3.45^a	95.90^A
MB	1:0.75:5.25	0.500	0.375	2.625	0.665	1.330	0.190	(0.45)	(1.26)	(8.13)	(0.70)
MC	1:0.50:4.50	0.583	0.292	2.625	0.624	1.070	0.178	261^a	2.13^A	3.10^a	95.63^A
MC	1:0.50:4.50	0.583	0.292	2.625	0.624	1.070	0.178	(0.38)	(0.86)	(9.68)	(0.16)
IA	-	-	-	-	0.665	-	0.190*	258^a	2.31^a	9.88^b	97.92^B
IA	-	-	-	-	0.665	-	0.190*	(0.97)	(1.55)	(9.98)	(0.28)
IB	-	-	-	-	0.665	-	0.190*	261^a	2.30^a	10.85^b	98.09^B
IB	-	-	-	-	0.665	-	0.190*	(0.77)	(0.27)	(2.71)	(0.19)
IC	-	-	-	-	0.665	-	0.190*	256^a	2.31^a	10.40^b	96.67^B
IC	-	-	-	-	0.665	-	0.190*	(0.45)	(0.22)	(2.35)	(0.16)
Statistical analysis								$ρ$ = 0.191	$ρ$ = 0.003	$ρ$ = 0.531	$ρ$ = 0.015
Statistical analysis								$ρ$ = 0.191	$ρ$ = 0.423	$ρ$ = 0.054	$ρ$ = 0.0003

Mortar	Water absorption (%)		Flexural strength (MPa)		Compressive strength (MPa)		Dynamic modulus of elasticity (GPa)
Mortar	7 days	28 days	7 days	28 days	7 days	28 days	7 days	28 days
MA	14.06 (2.03)	12.90^A (0.69)	1.85 (2.48)	1.65^a (3.22)	4.60 (8.91)	5.17^a (6.38)	6.52 (6.39)	7.12^a (4.79)
MB	13.30 (4.00)	12.82^A (1.90)	3.35 (4.75)	2.96^A (3.71)	7.95 (13.46)	8.98^A (5.01)	10.17 (4.63)	12.18^A (4.79)
MC	12.58 (2.05)	12.40^A (1.62)	4.76 (3.21)	4.22^B (5.81)	11.15 (7.71)	13.61^B (5.81)	12.59 (4.39)	14.66^b (5.72)
IA	17.68 (6.93)	14.64^a (9.41)	2.01 (2.22)	1.82^a (7.40)	2.00 (13.00)	5.68^a (10.74)	7.17 (3.82)	7.48^a (7.44)
IB	14.96 (4.80)	14.25^a (0.40)	4.03 (3.54)	3.56^A (4.21)	6.26 (10.86)	10.75^A (7.91)	12.62 (11.65)	13.85^A (5.75)
IC	13.94 (4.66)	13.25^a (1.79)	5.33 (2.58)	4.74^B (2.59)	10.90 (11.93)	14.48^B (3.25)	13.83 (5.17)	15.89^b (5.53)
Statistical analysis	-	^A $ρ$ = 0.010	-	^a $ρ$ = 0.172	-	^a $ρ$ = 0.161	-	^a $ρ$ = 0.313
	-	^aρ = 0.091	-	^A $ρ$ = 0.009	-	^A $ρ$ = 0.010	-	^A $ρ$ = 0.015
	-	-	-	^B $ρ$ = 0.021	-	^B $ρ$ = 0.016	-	^b $ρ$ = 0.089

Prism	$f_{b}$ (MPa)	$f_{m}$ (MPa)	$f_{p}$ (MPa)	$f_{p}$ ^* (MPa)	$f_{p} / f_{b}$	$f_{m} / f_{b}$	Respected condition	Failure mode
PBL1MA	8.33	5.17	5.35 (5.42)	5.78	0.64	0.62	$f_{m}$ ≤ 0.7 $f_{b}$	Crushing of the mortar
PBL1MB	8.33	8.98	6.95 (2.07)	6.82	0.83	1.08	0.7 $f_{b}$ ≤ $f_{m}$ ≤ 1.5 $f_{b}$	Lateral traction
PBL1MC	8.33	13.61	6.74 (7.09)	7.72	0.81	1.63	$f_{m}$ $\geq$ 1.5 $f_{b}$	Compression of the block
PBL1IA	8.33	5.68	5.16 (6.65)	5.94	0.62	0.68	$f_{m}$ ≤ 0.7 $f_{b}$	Crushing of the mortar
PBL1IB	8.33	10.75	6.70 (7.44)	7.19	0.80	1.29	0.7 $f_{b}$ ≤ $f_{m}$ ≤ 1.5 $f_{b}$	Lateral traction
PBL1IC	8.33	14.48	6.61 (9.24)	7.87	0.79	1.74	$f_{m}$ $\geq$ $1.5 f_{b}$	Compression of the block
PBL2MA	11.98	5.17	6.46 (4.81)	7.45	0.54	0.43	$f_{m}$ ≤ 0.7 $f_{b}$	Crushing of the mortar
PBL2MB	11.98	8.98	7.42 (4.73)	8.79	0.62	0.75	0.7 $f_{b}$ ≤ $f_{m}$ ≤ 1.5 $f_{b}$	Lateral traction
PBL2MC	11.98	13.61	7.21 (3.55)	9.96	0.60	1.14	$f_{m}$ $\geq f_{b}$ **	Compression of the block
PBL2IA	11.98	5.68	6.32 (3.47)	7.66	0.53	0.47	$f_{m}$ ≤ 0.7 $f_{b}$	Crushing of the mortar
PBL2IB	11.98	10.75	7.21 (10.19)	9.28	0.60	0.90	0.7 $f_{b}$ ≤ $f_{m}$ ≤ 1.5 $f_{b}$	Lateral traction
PBL2IC	11.98	14.48	6.75 (6.96)	10.14	0.56	1.21	$f_{m}$ $\geq$ $f_{b}$ ^**	Compression of the block

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E-mail: arlene@ibracon.org.br

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[1] Corresponding author: Rafaella Salvador Paulino. E-mail: rafaellaspaulino@gmail.com