METHOD FOR PREPARING GENERAL-PURPOSE CEMENT

Abstract

A method for preparing a general-purpose cement is provided. Raw materials containing all of SiO.sub.2, Al.sub.2O.sub.3, CaO, MgO and Na.sub.2O (or K.sub.2O) are mixed to obtain a raw meal, which is dried and ground into a raw meal powder. The raw meal powder is oxidatively calcined at no less than 1210 C. to reach a stable phase state, and rapidly cooled to obtain a clinker predominated by glass phase. The clinker is mixed with NaOH, KOH or a combination thereof and ground to obtain the general-purpose cement. Alternatively, the clinker is ground to obtain a clinker powder, which is mixed with an aqueous NaOH solution, an aqueous KOH solution or a combination thereof for use. The NaOH and/or KOH is/are added such that a weight ratio of NaOH+0.713KOH to the clinker powder is 0-0.03:1.

Claims

1. A method for preparing a general-purpose cement, comprising: step (1) mixing one or more raw materials to obtain a raw meal containing SiO.sub.2, Al.sub.2O.sub.3, CaO, MgO, and Na.sub.2O or K.sub.2O; and subjecting the raw meal to drying and grinding to obtain a raw meal powder; step (2) oxidatively calcining the raw meal powder at no less than 1210 C. for a time long enough to obtain a stable phase state, followed by cooling to obtain a clinker predominated by a glass phase; wherein a mass percentage of SiO.sub.2+Al.sub.2O.sub.3+Fe.sub.2O.sub.3+CaO+MgO+Na.sub.2O+K.sub.2O in the clinker is no less than 93%, and in every 100 parts (by mass) of SiO.sub.2+Al.sub.2O.sub.3+Fe.sub.2O.sub.3+CaO+MgO+Na.sub.2O+K.sub.2O, a mass distribution is: SiO.sub.2 31.544.8, Al.sub.2O.sub.3 6.119.9, Fe.sub.2O.sub.306.2, CaO 22.545.0, MgO 1.216.0, Na.sub.2O+K.sub.2O 1.08.3; and step (3) mixing the clinker with NaOH, KOH or a combination thereof followed by grinding to obtain the general-purpose cement; or grinding the clinker to obtain a clinker powder, and mixing the clinker powder with a NaOH aqueous solution, a KOH aqueous solution or a combination thereof for use; wherein NaOH, KOH or a combination thereof is added such that a weight ratio of NaOH+0.713KOH to the clinker is 0-0.03:1.

2. The method of claim 1, wherein in the clinker, a weight ratio of CaO+MgO to SiO.sub.2+Al.sub.2O.sub.3 is 0.6-1.0:1.

3. The method of claim 1, wherein in the clinker, a weight ratio of SiO.sub.2 to Al.sub.2O.sub.3 is 2.0-7.0:1.

4. The method of claim 1, wherein in the clinker, a weight ratio of MgO to CaO is 0.03-0.66:1.

5. The method of claim 1, wherein in step (2), the cooling is performed by air blast cooling or water quenching.

6. The method of claim 1, wherein in step (3), a weight percentage of a sieve residue of the general-purpose cement is no more than 5% after passing through a 75-m square hole sieve; and a weight percentage of a sieve residue of the clinker powder is no more than 5% after passing through the 75-m square hole sieve.

Description

DETAILED DESCRIPTION OF EMBODIMENTS

[0026] The present disclosure will be further described below in conjunction with the embodiments, but the scope of the present disclosure is not limited thereto.

EXAMPLES

(1) Clinker Preparation and Grinding

[0027] According to the difference in chemical composition, raw materials of raw meal including 12 types of potassium sodium aluminosilicate, kaolinite, analytical pure sodium carbonate, calcium carbonate, silicon dioxide (quartz), iron oxide and natural dolomite listed in Table 1 were prepared. The above raw materials were dried at 105 C. to constant weight and subjected to chemical composition detection, with the detection results listed in Table 1. In Examples 1-14, the raw materials of each raw meal were mixed according to formulas shown in Table 2, and ground to obtain a raw meal powder. A weight percentage of a sieve residue of raw meal powder was no more than 10% after passing through a 75-m square hole sieve. The raw meal powder was placed in a corundum crucible, calcinated under heating in a silicon carbide muffle furnace with a heating rate of 10 C./min, and kept at a constant temperature for 1, 2 and 3 h at 1210-1350 C., respectively. After the temperature keeping was completed, the corundum crucible was immediately taken out of the silicon carbide muffle furnace and rapidly cooled by air blast cooling or water quenching to obtain a clinker predominated by a glass phase. The clinker was ground to obtain a clinker powder. A weight percentage of a sieve residue of the clinker powder was no more than 5% after passing through the 75-m square hole sieve. By means of a powder X-ray diffraction method, it was found that when a temperature keeping time of the same raw material at a highest calcination temperature was changed, the phase characteristics of clinker samples kept at the constant temperature for 2 h and 3 h were the same, while there were some differences in clinker samples kept at the constant temperature for 1 h. Therefore, the temperature keeping time at the highest temperature during clinker calcination was determined as 2 h. A total weight percentage of SiO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3, CaO, MgO, Na.sub.2O and K.sub.2O in the clinker powder was no less than 93%, and in every 100 parts (by mass) of SiO.sub.2+Al.sub.2O.sub.3+Fe.sub.2O.sub.3+CaO+MgO+Na.sub.2O+K.sub.2O, a mass parts distribution is: SiO.sub.2 31.544.8, Al.sub.2O.sub.3 6.119.9, Fe.sub.2O.sub.3 06.2, CaO 22.545.0, MgO 1.216.0, Na.sub.2O+K.sub.2O 1.08.3, and a weight ratio of CaO+MgO to SiO.sub.2+Al.sub.2O.sub.3 was 0.6-1.0:1, a weight ratio of SiO.sub.2 to Al.sub.2O.sub.3 was 2.0-7.0:1, and a weight ratio of MgO to CaO was 0.03-0.66:1 (see Table 3 for details).

TABLE-US-00001 TABLE 1 Chemical composition of raw materials (Unit: wt %) Raw materials of raw meal SiO.sub.2 Al.sub.2O.sub.3 TFe.sub.2O.sub.3 CaO MgO K.sub.2O Na.sub.2O Others Potassium sodium 65.8 12.6 7.4 3.0 0.8 0.9 9.5 0.0 aluminosilicate 1 Potassium sodium 58.1 25.7 3.9 1.5 0.4 0.5 9.8 0.1 aluminosilicate 2 Potassium sodium 46.7 21.2 5.8 4.0 8.5 1.6 12.3 0.0 aluminosilicate 3 Potassium sodium 69.5 10.9 2.8 1.9 0.7 1.2 13.0 0.0 aluminosilicate 4 Potassium sodium 72.4 8.8 1.0 3.2 0.8 0.8 13.2 0.0 aluminosilicate 5 Potassium sodium 62.5 10.4 5.6 4.4 3.7 0.8 12.6 0.0 aluminosilicate 6 Potassium sodium 62.4 20.3 3.1 1.4 0.7 2.2 9.9 0.0 aluminosilicate 7 Potassium sodium 72.5 13.9 0.6 1.0 0.3 0.8 11.0 0.0 aluminosilicate 8 Potassium sodium 46.6 42.7 1.5 0.4 0.4 0.5 7.9 0.0 aluminosilicate 9 Potassium sodium 51.6 38.7 0.6 0.3 0.3 0.3 8.2 0.0 aluminosilicate 10 Potassium sodium 48.0 27.0 4.9 0.4 0.6 6.2 12.9 0.0 aluminosilicate 11 Potassium sodium 48.8 37.3 0.2 0.2 0.1 0.2 13.2 0.0 aluminosilicate 12 Kaolinite 42.7 38.3 0.5 0.3 0.3 0.6 0.5 16.7 Dolomite 31.6 20.2 48.3 Sodium carbonate 58.5 41.5 Calcium carbonate 56.0 44.0 Quartz 100.0 0.0 Iron oxide 100.0 0.0 Note: TFe.sub.2O.sub.3 refers to total sum of Fe.sub.2O.sub.3 converted from equivalent iron in different valence states.

TABLE-US-00002 TABLE 2 Raw material weight ratios and calcination conditions of cement raw meal (Unit: %) Potassium sodium Calcination Rapid Clinker aluminosilicate Sodium Calcium Iron temperature cooling No. No. Content Kaolinite carbonate carbonate Quartz oxide Dolomite ( C.) method 1 1 3.0 35.0 10.0 10.0 4.0 38.0 1300 Air cooling 2 2 45.0 20.0 7.0 28.0 1240 Air cooling 3 3 43.0 13.0 4.0 40.0 1300 Water cooling 4 4 30.0 15.0 55.0 1300 Air cooling 5 5 31.0 15.4 2.6 10.0 1.0 40.0 1210 Air cooling 6 6 44.0 5.0 3.0 48.0 1260 Water cooling 7 7 30.0 9.0 3.0 55.0 3.0 1350 Water cooling 8 8 42.0 9.0 2.0 36.0 11.0 1250 Air cooling 9 9 10.4 0.4 55.0 26.2 3.0 5.0 1300 Water cooling 10 10 14.0 3.0 50.0 25.0 8.0 1300 Water cooling 11 11 32.0 50.0 13.0 5.0 1300 Water cooling 12 12 12.0 20.0 50.0 13.0 5.0 1300 Water cooling 13 12 7.0 8.0 50.0 25.0 10.0 1300 Water cooling 14 12 12.0 10.0 50.0 23.0 5.0 1300 Water cooling

TABLE-US-00003 TABLE 3 Chemical compositions of clinker Clinker Chemical composition .sup.a(wt. %) (CaO + MgO)/ SiO.sub.2/ MgO/ No. SiO.sub.2 Al.sub.2O.sub.3 Fe.sub.2O.sub.3 CaO MgO K.sub.2O Na.sub.2O Others (SiO.sub.2 + Al.sub.2O.sub.3) Al.sub.2O.sub.3 CaO 1 37.7 19.3 6.2 24.9 10.9 0.3 0.7 6.8 0.6 2.0 0.44 2 42.7 14.9 2.3 26.7 7.5 0.3 5.7 0.0 0.6 2.9 0.28 3 32.1 12.1 3.3 28.9 15.6 0.9 7.1 0.0 1.0 2.6 0.54 4 38.4 12.7 1.3 25.3 16.0 0.6 5.6 3.1 0.8 3.0 0.63 5 39.9 11.9 1.9 26.5 11.5 0.5 7.8 3.1 0.7 3.4 0.43 6 42.9 8.5 3.3 22.5 14.9 0.5 7.3 1.0 0.7 5.0 0.66 7 31.5 13.3 1.4 45.0 1.2 1.0 6.6 1.9 1.0 2.4 0.03 8 44.8 12.1 0.4 31.4 3.1 0.5 7.6 1.7 0.6 3.7 0.10 9 42.4 6.1 4.3 44.3 1.4 0.1 1.4 0.0 0.9 7.0 0.03 10 44.2 7.4 0.1 41.9 2.3 0.1 4.0 0.0 0.9 5.9 0.05 11 37.6 11.4 2.1 39.3 1.6 2.6 5.5 0.0 0.8 3.3 0.04 12 38.0 16.8 0.2 41.0 1.5 0.2 2.3 4.0 0.8 2.3 0.04 13 44.3 7.9 0.1 43.4 2.9 0.1 1.3 1.6 0.9 5.6 0.07 14 44.8 11.2 0.1 40.1 1.4 0.1 2.2 2.0 0.7 4.0 0.04 .sup.athe percentage of individual oxides when a sum of SiO.sub.2, Al.sub.2O.sub.3, Fe.sub.2O.sub.3, CaO, MgO, Na.sub.2O and K.sub.2O is 100%, and Others refer to a content of other chemical components in the clinker.

(2) Hydration and Curing of Cement Ingredients

[0028] Analytically-pure NaOH and/or KOH was/were dissolved in as little water as possible and cooled to room temperature. NaOH, KOH or a combination thereof was added such that a weight ratio of NaOH+0.713KOH to the clinker was 0-0.03:1. The clinker powder was added in the alkaline solution and stirred for 2-5 min to obtain a slurry. Water was added in the slurry during stirring to reduce the slurry consistency such that the slurry was liquefied during subsequent vibration. The slurry was placed in a 404040 cubic steel mold and vibrated to compact. The slurry as well as the mold was placed into a standard cement curing box and cured at 20 C. and 90% humidity for 1 day followed by demolding to obtain a cement paste test block. In a case where a strength of the slurry did not meet a demolding requirement after 1 day of curing, the demolding was delayed, and the slurry was cured in moisture for 7 days and then soaked in water for 28 days. An unconfined compressive strength of the test block at 3 days, 7 days and 28 days was tested respectively. The ingredients and compressive strength of the cement paste were shown in Table 4. It can be seen from Table 4 that the resulting clinker powder exhibits a certain self-gelling property, that is, it can be solidified by only adding water and has excellent compressive strength. Moreover, the strength of cement increases with the increase of the alkali content. A maximum compressive strength of the cement paste after 28 days reaches 106.0 MPa.

TABLE-US-00004 TABLE 4 Ingredients and compressive strength of cement paste at different ages after room temperature curing Cement paste composition Mass ratio to Compressive strength at Clinker clinker (wt. %) Liquid/solid different ages (MPa) No. NaOH KOH ratio 3 days 7 days 28 days 1 0.5 0.5 0.29 7.2 11.3 21.6 1.0 1.0 0.29 14.5 18.6 37.0 3.0 0 0.29 48.1 62.3 88.5 2 0 1.0 0.25 21.1 26.2 56.7 2.0 0 0.25 28.3 35.9 67.9 3 0 1.0 0.25 29.7 40.8 50.8 4 0 0 0.25 1.5 2.8 13.1 0 2.0 0.25 35.9 55.6 62.8 5 0 0 0.22 5.1 13.5 25.6 1.0 1.0 0.22 23.9 49.7 68.5 0 4.0 0.22 34.1 65.8 86.6 6 2.0 0 0.29 40.8 60.9 76.3 7 0 1.0 0.28 19.5 26.4 33.1 0 3.0 0.29 35.8 48.2 65.4 8 1.0 0 0.27 12.2 18.6 26.9 2.0 0 0.28 18.8 19.8 31.5 9 2.0 0 0.28 13.5 23.7 32.8 10 1.0 0 0.26 15.6 26.4 31.4 11 0.5 0 0.26 11.2 21.3 26.7 12 2.0 0 0.25 24.8 48.5 64.8 13 2.0 0 0.28 30.4 73.9 106.0 14 2.0 0 0.28 52.6 61.4 88.5 0.5 0 0.28 37.8 47.2 70.1