Effects of storage temperature and time on false setting behavior of CPI-S Portland cement

Mota, R. M.; Silva, A. S.; Ramos, V. H. S.; Rezende, J. C. T.; Jesus, E. de

doi:10.1590/0366-69132020663792842

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Articles • Cerâmica 66 (379) • Jul-Sep 2020 • https://doi.org/10.1590/0366-69132020663792842 copy

Effects of storage temperature and time on false setting behavior of CPI-S Portland cement

Efeitos da temperatura e do tempo de armazenamento no comportamento de falsa pega do cimento Portland CPI-S

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The false setting is when cement stiffens prematurely in a few minutes after adding water. Some variables could cause false setting in CPI-S-32 Portland cement, for example, alkali concentration in the cement, the formation of alite (C₃S) with low reactivity, and cement storage temperature and time in silos. Temperature increases cause calcium sulfate dihydrate to dehydrate, forming hemihydrate (CaSO₄.0.5H₂O) or anhydrite (CaSO₄), which causes the false setting. In this study, the influence of cement storage temperature (100, 105, 110, 120, and 130 °C) combined with the cement storage time (30, 60, and 120 min) in a silo was studied regarding the CPI-S-32 false setting behavior. It was verified that temperatures above 110 °C and storage time above 60 min are conditions that favor the false setting of CPI-S-32 cement. Physicochemical analysis, TG/DTG, XRF, and XRD were applied as complementary analyzes for the false setting assays of CPI-S-32.

Keywords:
false setting; CPI-S-32 Portland cement; cement storage temperature; cement storage time

Table I Experimental conditions of the CPI-S-32 sample production.

CPI-S-32 sample	Temperature (ºC)	Time (min)
CPI-S 100.30	100	30
CPI-S 100.60	100	60
CPI-S 100.120	100	120
CPI-S 105.30	105	30
CPI-S 105.60	105	60
CPI-S 105.120	105	120
CPI-S 110.30	110	30
CPI-S 110.60	110	60
CPI-S 110.120	110	120
CPI-S 120.30	120	30
CPI-S 120.60	120	60
CPI-S 120.120	120	120
CPI-S 130.30	130	30
CPI-S 130.60	130	60
CPI-S 130.120	130	120

Table II Loss on ignition (LOI) and chemical composition of raw materials by XRF (wt%).

Raw material	LOI	SiO₂	Al₂O₃	Fe₂O₃	CaO	MgO	SO₃	Other oxides¹
Clinker	0.41	19.84	4.95	3.89	65.06	4.31	0.44	<0.50
Gypsum	19.10	4.91	0.89	0.52	32.90	0.52	40.29	<1.00
Limestone	38.59	7.95	1.44	0.85	45.22	4.63	-	<1.50

Table III Fineness of CPI-S-32 retained in the 75 µm sieve.

Sample	75 μm sieve (%)	NBR 16697 limit (%)
CPI-S-32	0.50	≤12.0

Table IV False setting values obtained for CPI-S-32 at different experimental conditions.

CPI-S-32 sample	False setting* (mm)
CPI-S 100.30	40
CPI-S 100.60	40
CPI-S 100.120	40
CPI-S 105.30	40
CPI-S 105.60	40
CPI-S 105.120	40
CPI-S 110.30	40
CPI-S 110.60	29
CPI-S 110.120	3
CPI-S 120.30	40
CPI-S 120.60	3
CPI-S 120.120	0
CPI-S 130.30	40
CPI-S 130.60	0
CPI-S 130.120	0

Table V Loass on ignition and insoluble residue values of CPI-S.

CPI-S-32 sample	Loss on ignition (%)	Insoluble residue (%)
CPI-S 100.30	4.03	0.76
CPI-S 100.60	4.06	0.62
CPI-S 100.120	3.84	0.80
CPI-S 105.30	4.03	0.95
CPI-S 105.60	3.64	0.77
CPI-S 105.120	3.45	0.97
CPI-S 110.30	4.44	1.07
CPI-S 110.60	4.23	0.75
CPI-S 110.120	4.01	0.92
CPI-S 120.30	3.99	0.94
CPI-S 120.60	3.81	1.01
CPI-S 120.120	3.83	0.76
CPI-S 130.30	3.77	0.86
CPI-S 130.60	3.53	0.91
CPI-S 130.120	3.64	0.82

Table VI Physical requirements of specific mass, normal consistency, initial and final setting times, heat expansion, and specific area of CPI-S-32.

CPI-S-32 sample	Specific mass (g/cm³)	Normal consistency (%)	Initial setting (h:min)	Final setting (h:min)	Heat expansion (mm)	Specific area (m²/kg)
CPI-S 100.30	3.09	25.0	3:10	4:05	0.5	386
CPI-S 100.60	3.10	25.0	3:05	4:00	0.5	385
CPI-S 100.120	3.11	25.2	3:20	4:10	0.5	385
CPI-S 105.30	3.09	25.6	3:05	4:15	0.8	386
CPI-S 105.60	3.12	25.0	2:50	4:15	0.5	384
CPI-S 105.120	3.11	26.4	3:15	4:40	0.0	385
CPI-S 110.30	3.11	25.0	3:00	4:05	0.5	385
CPI-S 110.60	3.11	25.6	3:35	4:25	1.0	384
CPI-S 110.120	3.10	26.6	3:50	5:00	0.0	385
CPI-S 120.30	3.11	25.4	3:05	4:10	0.0	385
CPI-S 120.60	3.12	26.6	3:35	4:45	0.0	385
CPI-S 120.120	3.11	28.0	3:55	5:00	0.0	385
CPI-S 130.30	3.12	26.0	3:55	4:30	0.5	386
CPI-S 130.60	3.12	28.0	3:50	4:55	0.0	386
CPI-S 130.120	3.13	30.4	4:00	5:05	0.0	385

Table VII Chemical composition of CPI-S-32 samples by XRF (wt%).

CPI-S-32 sample	SiO₂	Al₂O₃	Fe₂O₃	CaO	MgO	SO₃	P₂O₅	TiO₂	Na₂O	K₂O	SrO
CPI-S 100.30	18.65	4.56	3.96	65.12	3.79	2.98	0.33	0.24	0.05	0.20	0.08
CPI-S 100.60	18.55	4.62	3.93	65.32	3.71	2.99	0.33	0.24	0.05	0.19	0.08
CPI-S 100.120	18.64	4.50	3.95	65.37	3.72	2.98	0.33	0.23	0.04	0.18	0.08
CPI-S 105.30	18.61	4.62	3.96	65.29	3.76	2.88	0.32	0.24	0.05	0.18	0.07
CPI-S 105.60	18.47	4.51	3.98	65.62	3.70	2.87	0.33	0.24	0.03	0.19	0.07
CPI-S 105.120	18.56	4.57	3.97	65.23	3.84	2.94	0.34	0.24	0.04	0.19	0.08
CPI-S 110.30	18.46	4.57	3.97	65.33	3.72	2.99	0.34	0.25	0.05	0.19	0.10
CPI-S 110.60	18.52	4.58	3.95	65.19	3.83	3.03	0.33	0.25	0.04	0.20	0.08
CPI-S 110.120	18.68	4.56	3.94	65.03	3.87	3.02	0.33	0.24	0.04	0.20	0.08
CPI-S 120.30	18.72	4.63	3.94	65.04	3.79	2.98	0.34	0.24	0.06	0.20	0.07
CPI-S 120.60	18.50	4.53	3.96	65.32	3.75	3.03	0.35	0.23	0.05	0.18	0.07
CPI-S 120.120	18.54	4.52	3.95	65.30	3.80	3.01	0.33	0.23	0.04	0.18	0.08
CPI-S 130.30	18.56	4.56	3.96	65.35	3.76	2.91	0.33	0.24	0.04	0.19	0.10
CPI-S 130.60	18.46	4.53	3.98	65.43	3.79	2.91	0.34	0.24	0.04	0.20	0.08
CPI-S 130.120	18.44	4.52	3.97	65.46	3.78	2.92	0.34	0.25	0.05	0.20	0.08

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