Research and application of composite cement in Vietnam (стр. 3 )

2.4.1 Consistency, setting times and strength.

The results of test for consistency, setting times and strength of the proportions presented in tab.4 are showed in table 5.

- For cement with high ratio of clinker to GBFS (50 ÷ 60%): When adding lime stone setting times decreases and strength at 3 days increases. Recommendable content of lime stone in composite cement is about 5%, and the ratio of lime stone to clinker is 9÷10%. Cements with low ratios of clinker to GBFS cement don't have this characteristic. For this cement, adding lime stone make decreasing strength of cement with any additional content of lime stone even it’s 5% of composite cement.

- Fly ash prolongs setting times and decreases strength of cement at 3 and 28 days.

- The optimum content of gypsum in cement dependent on GGBFS content. When GGBFS content increases, optimum content of gypsum shall be increased. For tested cement at 40%, 50%, 60%, 70% GGBFS in composite cement, optimum gypsum contents are 3.5%, 4.0%, 4.5% and 5% respectively.

Table 5. Consistency, setting times and strength of the proportions presented in tab.4.

TT	Mix ID	Consistency, %	Setting time, Min	Flexural strength, MPa	Compressive strength, MPa
Initial	Final	3 days	28 days	3 days	28 days
1	M025	26.6	80	180	5.92	11.90	18.69	37.89
2	M89	26.0	75	175	5.73	11.25	17.65	35.96
3	M90	27.1	85	200	4.88	11.04	17.20	34.04
4	M91	26.6	75	210	5.28	10.14	16.47	32.66
5	M026	26.3	85	190	6.57	11.99	18.80	38.56
6	M92	27.5	75	180	6.09	11.98	17.74	37.21
7	M93	27.1	85	205	6.30	10.86	17.62	34.61
8	M94	27.6	75	215	6.13	10.48	16.59	32.65
9	M027	26.3	95	210	6.83	11.68	17.64	36.09
10	M95	27.3	95	205	6.79	11.59	17.35	33.62
11	M96	27.3	100	225	5.44	12.08	16.92	32.88
12	M97	27.6	90	230	5.34	10.79	16.18	32.47
13	M028	26.6	90	215	6.50	12.14	17.42	37.49
14	M98	27.1	80	205	5.63	11.95	17.15	35.07
15	M99	27.3	90	215	5.30	10.63	16.56	32.95
16	M100	26.6	85	225	4.98	10.30	15.21	32.14
17	M029	26.6	70	160	5.31	10.83	17.56	37.69
18	M101	26.6	115	190	4.85	10.68	16.29	33.92
19	M102	26.6	120	210	5.21	10.49	15.21	31.53
20	M103	26.8	115	235	5.02	9.56	13.52	27.90
21	M030	26.3	80	160	5.91	11.13	18.49	39.61
22	M104	27.0	115	200	5.50	10.68	16.12	34.37
23	M105	27.0	130	225	5.27	10.16	15.58	32.74
24	M106	27.0	125	240	4.71	10.03	14.42	30.39
25	M031	26.0	85	170	6.40	11.37	19.18	40.32
26	M107	27.0	125	225	5.70	11.45	17.56	35.37
27	M108	27.1	135	250	5.11	10.63	16.26	33.58
28	M109	27.1	130	250	4.82	10.26	15.30	30.21
29	M032	26.3	75	175	5.28	11.37	17.01	38.41
30	M110	27.1	130	235	4.63	11.05	16.17	33.61
31	M111	27.0	145	255	4.50	10.16	13.97	29.60
32	M112	27.0	140	250	4.02	10.32	13.64	27.12
33	M113	26.8	135	225	5.99	10.77	26.79	51.89

2.4.2 Durability in aggressive environments