Research and application of composite cement in Vietnam (стр. 4 )

The autoclave expansion, expansion of mortar in water at 14 days, sulfate expansion, expansion of mortar immersed in artificial marine water with concentration increased tenfold than natural sea water, strength of mortar cured in water at 6 months and 12 months were measured. Test results of strength are presented in Table 6.

Table pressive strength in Na2SO4 solution with concentration of 5% of the proportions presented in tab.4.

TT	mark	Solution Na2SO4 , concentration of 5%.
Strength at 6 month, MPa	Coefficient of strength variation at 6 month, %	Strength at 12 month, MPa	Coefficient of strength variation at 12 month, %
R flex.	R comp.	K flex.	K comp.	R flex.	R comp.	K flex.	K comp.
1	M025	14.41	43.53	105.11	94.77	17.34	45.66	133.28	109.00
2	M89	12.89	41.50	102.63	97.24	17.46	40.79	132.98	103.55
3	M90	13.36	38.68	117.09	98.05	14.65	34.82	116.83	94.85
4	M91	12.89	32.00	117.50	90.19	14.06	31.97	141.16	104.96
5	M026	14.06	42.43	113.39	93.52	16.29	45.73	117.79	96.64
6	M92	14.65	36.93	120.18	96.42	16.88	38.43	139.85	102.62
7	M93	13.36	35.90	125.56	95.53	17.11	36.65	171.79	106.32
8	M94	12.42	33.50	121.76	102.92	15.23	34.21	142.87	110.25
9	M027	14.44	41.60	115.15	93.21	16.29	44.41	114.88	91.87
10	M95	14.60	38.75	112.22	94.28	15.23	41.6	127.45	113.14
11	M96	13.25	37.20	103.68	93.94	15.59	41.01	117.75	119.35
12	M97	12.19	36.75	106.37	108.15	13.95	38.69	140.06	120.87
13	M028	14.81	41.70	114.90	92.52	16.76	46.27	119.20	113.46
14	M98	14.55	40.87	127.74	103.13	17.11	46.59	144.51	115.32
15	M99	14.30	38.53	126.21	102.20	16.41	46.17	135.96	123.61
16	M100	12.48	36.08	117.29	102.21	14.53	33.38	122.72	107.37
17	M029	15.12	41.20	117.30	92.90	15.82	43.53	110.63	96.28
18	M101	14.53	36.95	122.93	98.85	15.12	36.19	135.85	99.15
19	M102	13.83	36.05	130.84	101.41	15.70	33.10	128.79	98.28
20	M103	12.66	34.10	117.44	104.92	13.83	30.68	132.60	100.85
21	M030	15.7	44.05	115.53	94.63	15.47	45.83	101.58	95.98
22	M104	13.83	39.2	106.14	97.03	16.88	35.08	142.57	97.17
23	M105	13.69	34.75	120.94	98.08	14.30	33.34	116.26	99.40
24	M106	12.89	31.93	126.25	101.04	14.06	34.95	126.33	133.60
25	M031	15.13	44.13	110.36	92.65	15.47	46.39	99.23	94.58
26	M107	16.05	37.30	125.49	96.63	16.76	36.35	110.05	122.68
27	M108	14.77	37.98	128.10	99.74	15.35	32.90	104.78	117.21
28	M109	12.19	35.43	119.98	107.85	14.06	31.80	104.30	119.77
29	M032	15.09	45.35	101.41	93.51	17.93	47.16	126.45	95.00
30	M110	15.70	40.30	114.43	97.98	16.41	39.07	112.94	118.79
31	M111	14.06	37.6	114.68	95.72	16.76	33.94	118.19	111.79
32	M112	11.48	35.68	101.32	101.94	19.45	38.22	165.96	143.31
33	M113	9.77	48.30	98.09	80.57	9.61	39.22	64.07	67.88

Comment from test results of expansion, strength in different curing conditions:

- Sulfate expansion at 12 months of GGBFS cement with more than 60% of clinker is not affected by gypsum content and better than the limit of that according to ASTM C1012 for high sulfate resistant cement blended.

- Addition of lime stone and FA in GBFS cement leads to:

+ Expansion of mortar containing lime stone powder increases in water (test by ASTM C1038) if GBFS content is high (more than 50%), especially if gypsum content is higher. FA doesn’t affect that.

+ Adding FA is cause decreasing sulfate expansion of mortar using GBFS cement, it meets the requirement of standard for high sulfate resistant cement blended. Lime stone doesn’t affect that.

+ FA increases resistance of GBFS cement in sulfate and sea environment but Lime stone doesn’t this effect.

- Composite cement containing 20 ÷30% of clinker and mineral additives such as GBFS and FA promotes strength and resistance in sulfate and sea environment. In these solution, strength of mortar using composite cement is even higher than that in water at age up to 28 days.

3.Vietnamese National standard for composite cement.

Based on research results and realization in actual, Ministry of Science and Technology (MOST) approved and promulgated National Standard for composite cement TCVN 9501: 2013. The main technical requirement of composite cement is showed in table 7.

Table 7. Standard technical requirements of composite cement (TCVN 9501: 2013).

Technical standards	Category
CC30	CC40
Compressive strength, MPa, min: - 3 days - 28 days	12 30	14 40
Setting times, minute: - Initial, not less than - final, not more than	45 420
Finesse, Blaine, cm2/g, min	2800
Autoclave expansion, max,	0.8
Autoclave shrinkage, max, %	0.2 (a)
Dry shrinkage, max, %	0.15(a)
Chloride content, max, %	0.1
SO3 content, max, %	4.0
(a) When purchaser requires

4. Conclusion

Cement demand and cement consumption in Vietnam are rapid grown in the last ten years. Nowadays, Vietnam is the country with high cement production in the world. Together with growth of production, cement should be improved on quality and diversified on types. Research and application of composite cement is need for Vietnam cement industry. Beside creation of a new cement product with high sulfate and marine resistance, this kind of cement using of big industry waste, therefore contributes for decreasing emission of CO2 in cement manufacture. For this aspect, composite cement can be considered as a Green material. With its advanced characteristics, potential of production and use of composite cement in Vietnam is great.

Reference

[1] Master plan of Vietnam cement industry to 2020 and orienting to 2030 years (approved by Prime Minister) . Hanoi, 2011.

[2] Yoshida, N., Present status of sulfate attack in concrete structures –Finding Thaumasite form of Sulfate Attack-, GBRC, 28, pp.32-38, 2003 (in Japanese).

[3] А ; А и др.- Теория цемента - Киев.: 1991.

[4] Luong Duc Long and coworkers.- Research on application of GBFS for cement production in Vietnam, Vietnam Institute for Building Materials, No -3, 2007, pp 10-18,