Evaluation of the influence of sodium and magnesium lignosulfonates on the hydration kinetics of cementitious paste

Torres, I. F.; Torres, S. M.

doi:10.1590/0366-69132022683873268

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Articles • Cerâmica 68 (387) • Jul-Sep 2022 • https://doi.org/10.1590/0366-69132022683873268 copy

Evaluation of the influence of sodium and magnesium lignosulfonates on the hydration kinetics of cementitious paste

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

Motivated by their low cost, lignosulfonate-based water reducers are the most used type of admixture in the concrete industry worldwide. Due to the plurality of types of lignosulfonates (LSs) and the recent update to the Brazilian standard for admixtures for concrete, the objective of this work was to investigate the impact of sodium (Na-LS) and magnesium (Mg-LS) lignosulfonates, raw materials present in the Brazilian market, in pastes and concretes produced with cement type CP II F 40 under different dosages (0.40% and 0.80%). For this, the following tests were performed: adsorption curves, isothermal calorimetry, microanalytical tests (TGA/DTG and DRX), and application in the concrete according to NBR 11768-1 standard. The results showed different hydration evolutions among the pastes produced with these lignosulfonates. As a consequence, despite the similarity in water reduction, it was verified that Mg-LS was more suitable for RA1-R (water reducer-retarder, setting time 120-360 min), while Na-LS was more suitable for RA1 (water reducer, setting time 30-160 min).

Keywords:
characterization; chemical admixture; hydration; lignosulfonate; Portland cement

CaO	SiO₂	Al₂O₃	Fe₂O₃	SO₃	MgO	TiO₂	SrO	P₂O₅	MnO	K₂O	Na₂O	LOI	Total	Na₂Oeq.
55.48	26.58	3.87	6.07	2.05	4.04	0.57	0.14	0.42	0.04	0.16	0.43	4.59	99.85	0.53

Determination	Content (%)
Silicates (C₃S+C₂S)	73.97
Aluminates (C₃A+C₄AF)	12.98
Calcite (CaCO₃)	9.45
Total sulfates (Ca₂SO₄.2H₂O+Ca₂SO₄.1/2H₂O)	2.18
Others	1.42
C₃A/sulfates	1.68

Characteristic	Na-LS	Mg-LS
Aspect	Fine brown powder	Dark brown viscous liquid
pH at 20 °C	6±1	3±1
Solid content (%)	97	51
Density (g/cm³)	-	1.3
Ash (%)*	28.9	10.0
Insoluble material (%)*	<0.1	-
Total sugar (%)*	2.00	12.80
Molar mass M_W (g/mol)	10482	2400
Na (%)*	9.00	0.28
Mg (%)*	-	4.1
N (%)*	-	<1.0
C (%)*	-	44.00
H (%)*	-	3.00
S (%)*	8.50	8.00
SO₃H (%)*	10.8^a	11.2^b
Ca (%)*	0.12	0.11
Chloride (%)*	0.01	0.16
Sulfate (%)*	7.50	4.50

Assignment of vibrational band	Wavenumber (cm^-1)
(OH) ν - axial deformation of H₂O in lignosulfonates	3350 (Na-LS, Mg-LS)
(C-H)_x ν - axial deformation (aliphatic+aromatic)	2944 (Na-LS, Mg-LS)
(C-C) ν - deformation (aromatic ring)	1630 (Na-LS, Mg-LS)
(C=C) ν - deformation (aromatic ring)	1510 (Na-LS, Mg-LS)
(C-H) δ - bending (CH₃+CH₂)	1465 (Na-LS, Mg-LS)
(C-O) ν - ester stretching	1420 (Na-LS, Mg-LS)
(C-H) δ_ang - angular bending of methyl group (CH₃)	1330 (Na-LS)
(C-O) ν - ester stretching	1271 (Mg-LS)
(S=O) ν - stretching SO₂OH (sulfonic group)	1192 (Na-LS, Mg-LS)
(C-O) ν - stretching	1110 (Na-LS, Mg-LS)
(C-OH + C-O-C) ν - stretching (OH aliphatic+ether, sulfonic group)	1044 (Na-LS, Mg-LS)
(C-S) δ - vibration SO₂OH (sulfonic group)	655 (Na-LS, Mg-LS)

Characteristic	Na-LS	Mg-LS
Aspect	Brown liquid	Brown liquid
pH at 20 °C	5.01	3.39
Solid content (%)	40.38	40.21
Density (g/cm³)	1.03	1.03

Admixture type^@	IM coefficient*			Setting time (min)
Admixture type^@	1 day	7 days	28 days	Initial	Final
Water reducer, type 1 (RA1)	-	≥1.10	≥1.15	≥30	≤160
Water reducer, type 1 retarder (RA1-R)	-	≥1.10	≥1.15	≥120	≤360
Water reducer, type 1 accelerator (RA1-A)	≥1.15	≥1.10	≥1.00	≤30	-

Sample	Age	BW (%)	CH (%)
CP II F 40-Reference	90 min	1.74	0.91
	6 h	4.83	3.39
	12 h	11.29	9.10
	24 h	14.33	12.25
	7 d	18.99	16.97
	28 d	21.04	19.39
Mg-LS-0.40	90 min	2.28	0.20
	6 h	3.20	1.17
	12 h	8.15	6.37
	24 h	11.82	9.29
	7 d	19.25	16.74
	28 d	19.78	18.99
Mg-LS-0.80	90 min	2.63	1.05
	6 h	3.30	1.59
	12 h	5.00	2.50
	24 h	10.42	4.02
	7 d	18.84	15.55
	28 d	19.22	18.06
Na-LS-0.40	90 min	1.79	0.68
	6 h	3.34	1.87
	12 h	9.03	6.91
	24 h	10.79	11.01
	7 d	14.76	16.55
	28 d	19.65	19.23
Na-LS-0.80	90 min	2.10	1.18
	6 h	2.77	1.76
	12 h	6.74	4.08
	24 h	12.22	10.61
	7 d	19.40	16.17
	28 d	19.45	18.42

Sample	Setting time (h)	Heat accumulated (J/g cement)
Sample	Setting time (h)	1.5 h	6 h	12 h	24 h	48 h
Reference	4.5	12	39	103	178	243
Mg-LS-0.40	7.1	16	24	55	159	244
Mg-LS-0.80	10.5	19	25	35	123	234
Na-LS-0.40	6.2	13	28	75	170	241
Na-LS-0.80	8.2	14	26	48	153	244

Sample	Water reduction (%)	Air content relative deviation (%)	IM 1 day	IM 7 days	IM 28 days	Setting time relative deviation (min)
Mg-LS-0.40	7.69	-0.3	1.00	1.10	1.00	156
Mg-LS-0.80	8.64	-0.4	0.85	1.10	1.13	360
Na-LS-0.40	7.69	+0.4	0.92	1.05	0.99	102
Na-LS-0.80	10.0	+0.3	0.82	1.10	1.07	222

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