Application of the rebound test for the technological control of concrete hollow-core slabs

Haach, Vladimir Guilherme; Paiva, Mariana Acioli do Carmo

doi:10.1590/S1983-41952020000400006

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ORIGINAL ARTICLE • Rev. IBRACON Estrut. Mater. 13 (4) • 2020 • https://doi.org/10.1590/S1983-41952020000400006 copy

Application of the rebound test for the technological control of concrete hollow-core slabs

Aplicação do ensaio de esclerometria para o controle tecnológico de lajes alveolares de concreto

Authorship SCIMAGO INSTITUTIONS RANKINGS

ABSTRACT:

Hollow-core slabs are precast elements produced with very dry concrete, which hinders the molding of cube or cylindrical specimens normally used for the technological control of the material. This paper addresses the use of the rebound test for the technological control of concrete applied to hollow-core slabs. An experimental program divided into two phases was developed. In the first phase, three concrete mixtures were produced and compressive and rebound tests were performed in cylindrical and prismatic specimens for 6 hours to 28 days for the obtaining of a correlation curve. In the second phase, a hollow-core slab was built with one of the concrete mixtures used and the same tests were applied. The results showed the rebound number correlates well with the compressive strength, which confirms the possible application of the test for the technological control of the concrete used in the construction of hollow-core slabs.

Keywords:
non-destructive tests; rebound; hollow-core slab; technological control

	Cement	Sand	Gravel
Bulk density (kg/m³)	1171	1565	1498
Density (kg/m³)	3070	2625	2804

ID	Cement	Sand	Gravel	Water	Water/cement ratio
M1	484.6	630.0	1066.2	227.8	0.47
M2	378.8	780.4	1113.8	227.3	0.60
M3	295.0	834.6	1141.5	224.2	0.76

ID	Age (hours)	Rebound Number		Compressive Strength
ID	Age (hours)	Mean	C.V. (%)	Mean (MPa)	C.V. (%)
M1	8.5	-	-	2.76	9.85
	9.5	-	-	4.54	6.07
	11.5	15.88	10.51	8.38	3.06
	12.5	19.33	8.45	11.54	3.95
	13.5	19.13	8.29	12.90	1.97
	14.5	19.69	10.11	14.18	5.07
	15.5	20.31	7.57	15.69	5.92
	16.5	20.63	7.89	17.17	1.79
	17.5	22.31	6.89	18.23	5.12
	18.5	21.44	8.16	18.79	4.88
	21.5	21.38	8.35	21.06	3.42
	22.5	22.00	5.98	21.89	2.88
	23.5	22.75	8.72	23.97	11.57
	168	26.88	8.69	46.39	7.35
	672	28.07	10.64	52.56	11.17
M2	9.0	-	-	2.92	17.21
	11.0	-	-	4.68	5.42
	12.0	10.56	14.65	5.26	6.82
	14.0	11.75	12.62	7.58	11.75
	15.0	12.13	12.00	8.19	3.07
	16.0	13.75	13.14	8.91	6.06
	17.0	15.81	10.89	9.67	3.51
	18.0	16.13	8.44	10.15	2.00
	19.0	15.27	13.21	11.13	10.91
	20.0	16.69	11.10	11.47	2.54
	22.0	16.94	11.90	13.30	8.07
	23.0	16.88	10.57	14.24	2.87
	24.0	18.31	14.48	15.40	7.73
	168	25.47	10.69	26.86	7.73
	672	26.38	7.31	33.33	3.46
M3	10.5	-	-	1.53	5.45
	11.5	-	-	1.79	5.01
	13.5	-	-	2.40	7.91
	14.5	-	-	2.90	6.02
	15.5	-	-	3.32	3.03
	16.5	10.13	3.37	3.61	2.40
	17.5	10.19	5.34	4.07	6.42
	18.5	11.69	12.77	4.33	8.21
	19.5	12.31	10.15	5.30	10.42
	22.5	13.44	10.51	7.43	5.59
	23.5	13.00	11.92	7.70	2.68
	24.5	15.06	9.22	8.93	3.52
	168	22.88	9.15	24.45	4.62
	672	28.69	10.24	31.21	3.23

ID	Age (hours)	Rebound Number1		Rebound Number2		Compressive strength
ID	Age (hours)	Mean	C.V. (%)	Mean	C.V. (%)	Mean (MPa)	C.V. (%)
M1	9.17	23.19	8.37	23.80	11.14	11.14	3.50
	10.88	23.63	9.26	27.06	12.03	18.02	5.25
	13.90	25.92	6.95	26.77	9.90	21.64	6.26
	15.88	25.93	7.50	24.88	12.62	23.58	2.74
	17.83	27.67	9.33	27.33	10.41	24.21	3.94
	19.93	26.13	9.36	26.27	7.94	26.05	3.60
	22.87	27.31	8.53	27.67	9.82	27.90	3.61
	24.97	27.06	8.58	26.88	11.44	30.14	3.04
	168	28.06	12.31	27.93	10.65	42.88	6.46
	672	31.43	7.14	32.07	6.52	50.82	4.58

Age (hours)	Web¹		Core1		Web2		Core²
Age (hours)	Mean	C.V. (%)	Mean	C.V. (%)	Mean	C.V. (%)	Mean	C.V. (%)
9.17	22.86	9.26	23.44	8.01	22.43	10.25	25.00	9.80
10.88	22.86	8.90	24.22	9.18	28.57	10.07	25.13	9.38
13.90	23.50	15.86	26.00	7.45	29.25	7.58	25.67	8.03
15.88	26.50	8.52	25.56	6.81	25.57	10.31	24.33	14.53
17.83	27.83	8.63	27.56	10.28	25.86	13.10	27.67	11.57
19.93	25.83	6.67	26.33	11.07	26.86	9.72	25.75	5.78
22.87	26.57	10.39	27.89	6.81	26.33	4.60	27.88	9.08
24.97	26.86	8.97	27.22	8.77	27.00	6.05	26.78	14.79
168	26.14	10.46	29.56	11.24	25.40	6.59	29.33	8.86
672	31.29	7.54	32.63	11.22	32.67	6.32	31.00	8.83

Age (hours)	Web x Cores1		Web x Cores 2		With x Without reinforcements
Age (hours)	F-Test	T-Test	F-Test	T-Test	F-Test	T-Test
9.17	0.7345	0.5662	0.8933	0.0572	0.2421	0.4667
10.88	0.8529	0.2273	0.6095	0.0242	0.1347	0.0015
13.90	0.0987	0.1102	0.7683	0.0163	0.1951	0.3506
15.88	0.4876	0.3762	0.4906	0.4528	0.0812	0.2721
17.83	0.7446	0.8469	0.8571	0.2925	0.7214	0.7394
19.93	0.2614	0.7131	0.1675	0.3230	0.5599	0.8735
22.87	0.3240	0.2765	0.1236	0.1962	0.5616	0.6991
24.97	0.9503	0.7669	0.0444	0.8816	0.2889	0.8470
168	0.6540	0.0454	0.4123	0.0106	0.5938	0.9109
672	0.3044	0.4232	0.5539	0.2283	0.8057	0.4401

IBRACON - Instituto Brasileiro do Concreto Instituto Brasileiro do Concreto (IBRACON), Av. Queiroz Filho, nº 1700 sala 407/408 Torre D, Villa Lobos Office Park, CEP 05319-000, São Paulo, SP - Brasil, Tel. (55 11) 3735-0202, Fax: (55 11) 3733-2190 - São Paulo - SP - Brazil
E-mail: arlene@ibracon.org.br

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[1] Corresponding author: Vladimir Guilherme Haach. E-mail: vghaach@sc.usp.br