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CN-117645420-B - Carbonation hardening low-calcium cement and preparation and hardening method thereof

CN117645420BCN 117645420 BCN117645420 BCN 117645420BCN-117645420-B

Abstract

Aiming at the problems of excessive consumption of traditional cement stone and limestone resources, excessive energy consumption and high carbon emission, the invention provides carbonation hardening low-calcium cement and a preparation and hardening method thereof, and provides a hardening method for carbonation maintenance of low-calcium cement through CO 2 . The cement raw material comprises 60-70% of limestone, 15-25% of sandstone or clay or silica fume, 5-25% of phosphogypsum, fluorgypsum or desulfurized gypsum and 0.5-2% of component A. The composition A comprises, by mass, 0-50% of fluorite, 0-50% of barium slag, 0-50% of lithium slag, 0-50% of plant ash and 0-30% of industrial sodium carbonate. The composition of the carbonatized hardened cement clinker mineral is designed to be C 2 S：10-90％、C 5 S 2 $：10-90％、C$：0～5％、C 4 A 3 $ 0-10 percent, etc. The limestone consumption of the cement clinker is lower than that of the ordinary silicate cement clinker, the calcining temperature is reduced by 200-350 ℃ than that of the ordinary silicate cement clinker, the energy consumption and the carbon emission are obviously lower than those of the silicate cement, and the low-calcium cement is cured and hardened through CO 2 carbonating, so that the cement can obtain excellent mechanical properties within 2 hours.

Inventors

  • CHANG JUN
  • DU XIAOYUN

Assignees

  • 大连理工大学

Dates

Publication Date
20260508
Application Date
20231127

Claims (7)

  1. 1. The carbonation hardening low-calcium cement is characterized in that the carbonation hardening low-calcium cement is cement clinker minerals prepared from a plurality of raw materials; The raw materials comprise 60-70% of limestone, 15-25% of sandstone or clay or silica fume, 5-25% of phosphogypsum, fluorgypsum or desulfurized gypsum, 0.5-2% of mineralized component A, and 100% of the sum of the mass percentages of the components; The mineralizing component A comprises, by mass, 0-50% of fluorite, 0-50% of barium slag, 0-50% of lithium slag, 0-50% of plant ash and 0-30% of industrial sodium carbonate, wherein the sum of the mass percentages of the components is 100%; 48-56% of CaO in the limestone, and 70-99.9wt% of SiO 2 in the sandstone, clay or silica fume; the composition of the cement clinker mineral is designed as C 2 S：10%~50%,C 5 S 2 :60-90%,C 0-2% Of the total weight of the components is 100%.
  2. 2. The carbonation hardened low calcium cement according to claim 1, wherein the C 2 S is one or more combinations of β -C 2 S、α' L -C 2 S and amorphous C 2 S.
  3. 3. A method of preparing a carbonation hardened low calcium cement according to any one of claims 1 to 2 and including the steps of: (1) Raw material proportioning calculation and preparation Calculating the raw material consumption according to the mineral composition of each raw material chemical component and the target cement clinker; (2) Raw material grinding and premixing homogenization Limestone, sandstone or silica fume or clay, phosphogypsum or fluorgypsum or desulfurized gypsum, and mineralized component A is dried, mixed, crushed and ground according to the mass fraction proportion, and pre-homogenized to obtain qualified raw materials; (3) And (3) calcining clinker: Calcining the raw materials in a kiln, controlling the calcining temperature to be 1100-1250 ℃, keeping the temperature for 1-5 hours, and rapidly cooling or naturally cooling to obtain low-calcium cement clinker; (4) Calcining the step (3) to obtain cement clinker, rapidly cooling or naturally cooling to room temperature, and grinding to obtain low-calcium cement; In the preparation process of the low-calcium cement, CO 2 -containing gas generated during calcination of the low-calcium cement raw material can be used in the hardening process to realize the recycling of CO 2 .
  4. 4. The method for preparing carbonated hardened low-calcium cement according to claim 3, wherein in the step (1), the fineness of raw materials is controlled to pass through a square sieve with 0.08mm, and the low-calcium cement clinker in the step (4) is ground to a Bo specific surface area of 300-400 m 2 /kg.
  5. 5. A method of setting a carbonation hardened low calcium cement according to any one of claims 1 to 2 and including the steps of: (1) Adding water into the low-calcium cement, and uniformly mixing to obtain a mixture, wherein the mass ratio of the added water to the low-calcium cement is 0.1-0.3:1; (2) Pressing the mixture obtained in the step (1) to obtain a test block, wherein the initial porosity of the pressed test block is controlled to be 5% -35% before hardening; (3) And (3) hardening the test block in an environment containing CO 2 gas for 0.5-24 h to obtain a hardened test block, wherein the gas pressure of the hardening environment is 0.05-0.5 MPa.
  6. 6. A method of setting a carbonation hardened low calcium cement according to claim 5 and characterized in that: in the step (1), the mass ratio of water to low-calcium cement is 0.15-0.2:1; In the step (2), the initial porosity of the pressed test block before hardening is controlled to be 15% -25%; in the step (3), the hardening time is 1-3 hours, and the pressure of hardening ambient gas is 0.1-0.3 MPa.
  7. 7. The method of setting a low-calcium cement according to claim 6, wherein said setting environmental conditions in said step (3) include pure CO 2 gas and industrial waste gas containing CO 2 .

Description

Carbonation hardening low-calcium cement and preparation and hardening method thereof Technical Field The invention belongs to the field of building materials, and relates to low-calcium cement cured and hardened by CO 2 carbonating, and a preparation and hardening method thereof. Background The cement industry belongs to resource and energy intensive industry and is also a high carbon emission industry. The energy consumption of the cement industry mainly comes from the sintering energy consumption in the clinker sintering process, and comprises the following two aspects of (1) the decomposition process of carbonate in raw materials. In the process of firing cement clinker, caCO 3 in raw material is gradually decomposed into CaO by high-temperature calcination at 500-900 ℃, and about 50% of the theoretical heat consumption of calcination is derived from the pyrolysis of calcium carbonate. (2) a high-temperature sintering process of clinker minerals. The main mineral components of conventional portland cement clinker are tricalcium silicate (C 3 S, about 55-65%), dicalcium silicate (C 2 S, about 20-30%), tricalcium aluminate (C 3 a, about 7-15%), and tetracalcium aluminoferrite (C 4 AF, about 10-18%). In order to obtain excellent mechanical strength and early activity, a large amount of C 3 S exists in clinker minerals, and a large amount of limestone resources are needed for firing the minerals. In order to ensure the formation of a high proportion of C 3 S high-calcium mineral phases in the clinker, the sintering temperature of the clinker generally needs to reach about 1450 ℃. Thus, the design of the high calcium mineral (C 3 S) component in cement clinker is the root cause of the high energy consumption and carbon emissions in the conventional portland cement clinker formation process. The cement industry is facing tremendous carbon emission reduction pressure, and is urgently required to seek breakthrough in low-carbon zero-carbon key technology. The invention provides a low-calcium cement clinker mineral system which is cured and quickly hardened by CO 2 carbonating, and provides a hardening method thereof. The limestone consumption of the cement clinker is lower than that of the ordinary silicate cement clinker, industrial wastes such as phosphogypsum and the like can be consumed, the calcining temperature is reduced by 200-350 ℃ compared with that of the ordinary silicate cement clinker, and the energy consumption and the carbon emission are obviously lower than those of the conventional silicate cement. The low-calcium cement can obtain excellent mechanical properties within 2 hours through CO 2 carbonation curing hardening. The cement hardening process absorbs CO 2, realizes the recycling of CO 2, and has great significance for energy conservation and carbon reduction in the cement industry. Disclosure of Invention The invention aims to solve the problems of excessive consumption of limestone resources, excessive consumption of energy and serious carbon emission in the prior art of cement, provides a low-calcium cement mineral composition cured and hardened by CO 2 carbonating and a preparation method thereof, and provides a hardening method for curing low-calcium cement by CO 2 carbonating. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a carbonated hardened low-calcium cement is a cement clinker mineral prepared from a plurality of raw materials. The raw materials comprise 60% -70% of limestone, 15% -25% of sandstone or clay or silica fume, 5% -25% of phosphogypsum, fluorgypsum or desulfurized gypsum, 0.5% -2% of component A and 100% of the sum of the mass percentages of the components. Further, the mineralizing component A comprises, by mass, 0-50% of fluorite, 0-50% of barium slag, 0-50% of lithium slag, 0-50% of plant ash and 0-30% of industrial sodium carbonate. The sum of the mass percentages of the components is 100 percent. Further, the content of CaO in the limestone is 48-56%. The content of SiO 2 in the sandstone or clay or silica fume is 70-99.9wt%. The cement clinker mineral comprises 10-90% of C 2 S (containing one or more of beta-C 2S,α'L-C2 S and amorphous C 2 S), 0-10% of calcium silicate (called C 5S2$)：10-90％、C$：0～5％、C4A3 for short) and the balance of miscellaneous items, preferably 60-90% of C 2S：10％～50％,C5S2, and 0-2% of C, wherein the sum of the mass percentages of the components is 100%. The preparation method of the carbonated hardened low-calcium cement comprises the following steps: (1) Raw material proportioning calculation and preparation And calculating the raw material dosage according to the mineral composition of the target cement clinker according to the chemical components of each raw material. (2) Raw material grinding and premixing homogenization The method comprises the steps of drying limestone, sandstone or silica fume or clay, phosphogypsum or fluorgypsum or desulfurized gypsum, mixing, crushing and grind