Integrated cementitious material for high-performance low-carbon concrete

Abstract

The application discloses an integrated cementing material for high-performance low-carbon concrete, which is obtained by uniformly mixing the following raw materials in parts by weight: 35-40 parts of Portland cement clinker powder; 5-6 parts of high-calcium high-iron belite sulphoaluminate cement clinker powder; 5-10 parts of fine limestone powder; 14-20 parts of fine fly ash; 10-15 parts of slag powder; 10-15 parts of steel slag powder; and 5-10 parts of coarse limestone powder. The ingredient parameters of the high-calcium high-iron high-belite sulphoaluminate cement clinker are as follows: the basicity coefficient Cm value is 1.60-1.65, fCaO is 0.5-1.0%, and fSO3 is 0.5-1.0%; the mineral composition is as follows: C2S is 50-60%, C4A3S is 20-25%, C6AF2 is 10-15%, and C 12 A7 is 5-10%. The integrated cementing material has a cement clinker content as low as 33-38%, and the 28d strength can reach 41.0-42.0 MPa.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete, and in particular relates to an integrated cementitious material for high-performance low-carbon concrete. Background Art

[0002] As countries around the world actively pursue carbon reduction, the development and utilization of low-carbon concrete is of vital practical significance. Cement is the primary source of carbon emissions from concrete. Significantly reducing the amount of cement clinker or cementitious materials in concrete and increasing the use of mineral admixtures are the most effective ways to reduce concrete's carbon footprint.

[0003] Chinese patent CN 103193434 A discloses a low-carbon and carbon-absorbing concrete and a preparation method thereof, which uses high-calcium fly ash as a mineral admixture and utilizes the excess f-CaO introduced into the concrete from the high-calcium fly ash to absorb CO2, thereby achieving the purpose of carbon absorption; Chinese patent CN 114890744 A discloses a preparation method for green low-carbon concrete, which uses high-titanium slag powder as a mineral admixture and mainly utilizes the TiO2 and perovskite in the high-titanium slag powder to absorb and reduce CO2 to achieve carbon reduction in concrete; Chinese patent CN 114835455 A discloses a low-carbon concrete and cementitious material, which mainly increases the proportion of primary fly ash in the cementitious material to more than 50%, and reduces the cement content to less than 50%, thereby achieving low-carbon concrete by reducing the amount of cement; Chinese patent CN 108439833A discloses a high-performance low-carbon concrete, which mainly uses slag powder, fine ceramic powder and fly ash as raw materials for cementitious materials, and adds nano-silica and nano-clay to form a micro-aggregate mixture with a reasonable particle size distribution. It is used to replace cement, so that the strength of the concrete can be maintained at the construction requirements and the emission of greenhouse gases such as CO2 can be reduced.

[0004] However, the low-carbon concrete mentioned in the above-mentioned technology has certain technical defects. For example, although the f-CaO in high-calcium fly ash can absorb CO2 to achieve a certain carbon reduction effect, the micro-expansion of f-CaO in the later hydration of concrete can cause hidden dangers to the structural safety of concrete; the activity of high-titanium slag powder is much lower than that of ordinary slag powder, so the amount of cement replacement is very limited; although the first-grade fly ash has very good activity effect and ball effect, the resource of the first-grade fly ash is very limited, accounting for less than 10% of the total amount of fly ash, and the amount of cement in the cementitious material is reduced to less than 50% by using the first-grade fly ash, so the amount of cement clinker or cement that can be saved is very small; although the addition of nanomaterials in concrete can greatly reduce the amount of cement in concrete and reduce the carbon reduction intensity of concrete, the preparation of nanomaterials requires a large amount of energy consumption, and the high carbon emission generated is not taken into account, so the carbon reduction is not truly reduced. In addition, the existing technology has a major technical defect, which is to prepare low-carbon concrete by using four basic materials of cement (or cementitious material), mineral admixture, aggregate and admixture. Because the mixed materials such as slag powder and fly ash are added in the production of cement, there is a repetition or conflict in function with the mineral admixture added in the preparation of concrete, so the overall development of the material is not considered, the performance of the material is not comprehensively designed and considered, which is not conducive to the overall optimization of the performance of the low-carbon concrete material, further reducing the amount of cement clinker in concrete, and achieving the maximum carbon reduction effect. SUMMARY

[0005] In view of the above problems existing in the prior art low-carbon concrete, the application provides an integrated cementitious material for high-performance low-carbon concrete. The application aims to achieve the dual goals of maximum reduction of carbon dioxide emission of concrete and high performance of concrete, and invents an integrated cementitious material with high performance. The four basic raw materials commonly used in traditional concrete technology are simplified to three basic raw materials, and the cement (or cementitious material) required by the concrete and the mineral admixture of the concrete are uniformly prepared into an integrated cementitious material, which can be mixed with aggregate and admixture later.

[0006] The application is achieved in the following manner. An integrated cementitious material for high-performance low-carbon concrete is obtained by uniformly dry mixing the following raw materials in parts by weight: 35-40 parts of Portland cement clinker powder; 5-6 parts of high-calcium high-iron belite sulphoaluminate cement clinker powder; 5-10 parts of fine limestone powder; 14-20 parts of finely ground fly ash; 10-15 parts of slag powder; 10-15 parts of steel slag powder; and 5-10 parts of coarse limestone powder.

[0007] In the above technical solution, preferably, the high-calcium high-iron belite sulphoaluminate cement clinker powder is finely ground to a specific surface area of 380-400 m2 / g.2 / kg obtained;

[0008] High calcium and high iron belite sulphoaluminate cement clinker is fired by limiting its batching rate and mineral composition. It can adapt well to ordinary Portland cement and can significantly improve the early strength of integrated cementitious materials, especially it can promote the early hydration activity of various mineral admixtures added to the integrated cementitious materials. The batching parameters of the high calcium and high iron high belite sulphoaluminate cement clinker are: alkalinity coefficient Cm value is 1.60-1.65, fCaO is 0.5-1.0%, fSO3 is 0.5-1.0%; the mineral composition of the high calcium and high iron high belite sulphoaluminate cement clinker is calculated by weight percentage as follows: C2S mineral content is 50-60%, C4A3S mineral content is 20-25%, C6AF2 mineral content is 10-15%, C 12 A7 mineral content is 5-10%.

[0009] In the above technical solution, preferably, the Portland cement clinker powder is obtained by grinding 95% of ordinary Portland cement clinker and 5% of desulfurized gypsum together, with a specific surface area of ​​380-400m 2 / kg.

[0010] In the above technical solution, preferably, the fine limestone powder is obtained by ultrafine grinding limestone alone, with a specific surface area of ​​800-900m 2 / kg.

[0011] In the above technical solution, preferably, the ground fly ash is obtained by grinding the original fly ash separately, and the specific surface area is 500-550m 2 / kg.

[0012] In the above technical solution, preferably, the slag powder is obtained by grinding water-quenched slag separately, and has a specific surface area of ​​550-600m 2 / kg.

[0013] In the above technical solution, preferably, the steel slag powder is obtained by grinding converter steel slag separately, and has a specific surface area of ​​450-500m 2 / kg.

[0014] In the above technical solution, preferably, the coarse limestone powder is obtained by grinding limestone alone, and has a specific surface area of ​​150-200m 2 / kg.

[0015] The integrated cementitious material prepared by the present invention minimizes the amount of Portland cement clinker used and maximizes the use of mineral admixtures such as limestone powder, fly ash, slag powder, and steel slag powder. At the same time, in order to ensure that the use of a large amount of mineral admixtures does not cause adverse effects such as low early strength of the integrated cementitious material, a new high-calcium and high-iron belite sulphoaluminate cement clinker is added. This new high-calcium and high-iron belite sulphoaluminate cement clinker is different from the sulphoaluminate cement clinker or high belite sulphoaluminate cement clinker in the prior art, which has the disadvantage of poor compatibility with ordinary Portland cement. It can not only cooperate well with the Portland cement clinker in hydration development, but also significantly improve the early strength of the Portland cement clinker system, especially stimulate the early activity effect of fly ash, slag powder, steel slag powder, and limestone powder, so that the early hydration of the integrated cementitious material can meet the requirements of concrete development and reduce defects such as early bleeding of fresh concrete. The particle size composition of integrated cementitious materials is designed according to the requirements of optimal concrete density and coordinated with the particle size gradation of concrete aggregate. The composition of cement clinker and auxiliary cementitious materials is designed according to the hydration and hardening gradient of concrete, so as to significantly improve the performance of concrete while minimizing the amount of cement clinker in concrete, thereby achieving carbon reduction.

[0016] The use of integrated cementitious materials overcomes the shortcomings of previous concrete material designs and simplifies the concrete preparation process. Furthermore, the amount of Portland cement clinker used in integrated cementitious materials is significantly lower than that used in existing cement or cementitious materials, and their excellent performance ensures that the proportion of Portland cement clinker used in the prepared low-carbon concrete is minimized while maintaining good performance, achieving a substantial reduction in carbon emission intensity.

[0017] The advantages and positive effects of the present invention are:

[0018] 1) The integrated cementitious material prepared by the present invention has a cement clinker dosage as low as 33-38%, has good strength, and the 28d strength can reach 41.0-42.0 MPa. It is a low-carbon cementitious material, so that concrete prepared with this integrated cementitious material does not require the addition of other mineral admixtures.

[0019] 2) The integrated cementitious material prepared by the present invention contains high-calcium, high-iron belite sulphoaluminate cement clinker, which can effectively stimulate the early hydration activity of large-volume mineral admixtures, thereby increasing the 3d strength of the integrated cementitious material by 7.7 MPa and the 28d strength by 3.0 MPa, significantly promoting performance optimization.

[0020] 3) The particle size distribution of the integrated cementitious material prepared by the present invention is designed according to the optimal density. The particle distribution of the integrated cementitious material can form good continuity with the particle size gradation of the aggregate in the low-carbon concrete, so that the low-carbon concrete mixture has higher fluidity than ordinary concrete and the concrete expansion is improved by 10-15%.

[0021] 4) Compared with concrete prepared by traditional methods, the low-carbon concrete prepared using the integrated cementitious material of the present invention has a 2-4 MPa increase in compressive strength at each age of C30-C60 grade concrete and a significantly increased expansion when the amount of cementitious material is the same, thus becoming a high-performance concrete.

[0022] 5) The low-carbon concrete prepared using the integrated cementitious material of the present invention reduces the amount of cement clinker by about 14.3% compared with ordinary concrete at different strength levels (C30-C60), that is, the carbon emission intensity of the concrete is reduced by 14.3%, making it a low-carbon concrete.

[0023] 6) Low-carbon concrete prepared using the integrated cementitious material of the present invention does not require the addition of any mineral admixtures during concrete preparation, which simplifies the concrete batching process and further improves the homogeneity and construction performance of the concrete. The secondary hydration reaction of the large amount of mineral admixtures in the cementitious material strengthens the interface transition zone between the hardened cement paste and the aggregate, improving and enhancing the long-term durability of the concrete. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] Example 1 Preparation of high calcium and high iron belite sulphoaluminate cement clinker powder

[0026] According to the weight ratio and batching rate values ​​shown in Table 1, 1.0 ton of raw meal with a fineness of 0.08 mm and a sieve residue of less than 8% was ground and calcined in a rotary kiln at 1350°C to obtain 0.75 ton of high calcium and high iron belite sulphoaluminate cement clinker (raw meal loss on ignition of 25%). After grinding, the specific surface area of ​​380-400 m 2 / kg high calcium and high iron belite sulphoaluminate cement clinker powder.

[0027] Table 1 Raw material proportion and batching rate values

[0028]

[0029] The mineral composition of high calcium calcium iron belite sulphoaluminate cement clinker is shown in Table 2.

[0030] Table 2 Mineral composition of high calcium and high iron belite sulphoaluminate cement clinker

[0031]

[0032] Example 2 Preparation of integrated gelling material

[0033] The components were added into a dry powder mixer in sequence according to the weight ratio shown in Table 3, and the integrated gelling material was obtained after being fully and evenly mixed.

[0034] Table 3 Weight ratio of integrated cementitious materials

[0035]

[0036] The physical properties of the above-mentioned groups of integrated cementitious materials were measured using the standards GB17671-2021 "Test method for strength of cement mortar (ISO method)" and GB / T1346-2011 "Test method for water consumption, setting time and soundness of cement of standard consistency". The results are shown in Table 4.

[0037] Table 4 Physical properties of integrated cementitious materials

[0038]

[0039] As shown in Table 4, the integrated cementitious materials of Groups 1 to 5 achieved a 3-day strength of approximately 20.0 MPa and a 28-day compressive strength of approximately 41.5 MPa, demonstrating relatively good strength and development patterns. However, the integrated cementitious material of Group 6, which did not incorporate high-calcium, high-iron belite sulphoaluminate cement clinker to stimulate the activity of the mineral admixtures, exhibited a 3-day strength of only 12.3 MPa and a 28-day compressive strength of only 38.5 MPa, significantly lower than those of the integrated cementitious materials of Groups 1 to 5. This demonstrates the significant stimulating effect of high-calcium, high-iron belite sulphoaluminate cement clinker on the activity of the mineral admixtures and confirms the superior performance of the integrated cementitious materials of the present invention.

[0040] Example 3 Preparation of low carbon concrete

[0041] In this example, the cementitious material is an integrated cementitious material, prepared according to Group 2 in Table 3. The proportion of Portland cement clinker in the integrated cementitious material is 36%. The fine aggregate is medium-grade machine-made sand with a fineness of 2.5. The coarse aggregate is continuously graded stone aggregate with a particle size of 5-25 mm. The water reducer is a polycarboxylate high-efficiency water reducer with a solids content of 20% and a water reduction rate greater than 30%. The low-carbon concrete strength grades are designed to be C30, C40, C50, or C60. The integrated cementitious material: 360-520 parts; fine aggregate: 800-900 parts; coarse aggregate: 1100-1200 parts; water reducer: 7.0-9.0 parts; water: 160-180 parts.

[0042] Group No. 1:

[0043] The raw materials were weighed according to the following weight parts: 360 parts of integrated cementitious material; 800 parts of fine aggregate; 1100 parts of coarse aggregate; 7.0 parts of water reducer, and 180 parts of clean water.

[0044] The preparation method is as follows: pour the integrated cementitious material, fine aggregate and coarse aggregate into a mixer and stir for 1 minute to mix them evenly; mix the water reducer into water and mix it thoroughly, then pour it into the above mixture and continue stirring for 2-5 minutes to obtain low-carbon concrete.

[0045] Group No. 2:

[0046] The raw materials were weighed according to the following weight parts: 410 parts of integrated cementitious material; 900 parts of fine aggregate; 1180 parts of coarse aggregate; 7.5 parts of water reducer; and 170 parts of clean water.

[0047] The preparation method is as follows: pour the integrated cementitious material, fine aggregate and coarse aggregate into a mixer and stir for 1 minute to mix them evenly; mix the water reducer into water and mix it thoroughly, then pour it into the above mixture and continue stirring for 2-5 minutes to obtain low-carbon concrete.

[0048] Group No. 3:

[0049] The raw materials were weighed according to the following weight parts: 480 parts of integrated cementitious material; 851 parts of fine aggregate; 1200 parts of coarse aggregate; 8.0 parts of water reducer; and 175 parts of clean water.

[0050] The preparation method is as follows: pour the integrated cementitious material, fine aggregate and coarse aggregate into a mixer and stir for 1 minute to mix them evenly; mix the water reducer into water and mix it thoroughly, then pour it into the above mixture and continue stirring for 2-5 minutes to obtain low-carbon concrete.

[0051] Group No. 4:

[0052] The raw materials are weighed as follows: 520 parts of the integrated cementitious material, 800 parts of fine aggregate, 1100 parts of coarse aggregate, 9.0 parts of water reducing agent, and 160 parts of water.

[0053] The preparation method is as follows: the integrated cementitious material, the fine aggregate, and the coarse aggregate are poured into a mixer and stirred for 1 minute to mix uniformly; the water reducing agent is mixed into water and fully mixed uniformly, and then poured into the above mixture and stirred for 2-5 minutes, to obtain the low-carbon concrete.

[0054] In order to fully reflect the performance advantages of the low-carbon concrete of the present application, the concrete prepared by the traditional method using P.O42.5 cement and mineral admixture as the cementitious material is compared synchronously. The P.O42.5 cement has a silicate cement clinker addition ratio of 70% in the composition, a desulfurization gypsum and other mineral admixture addition ratio of 30%, a 3d strength of 26.0 MPa, and a 28d strength of 50.0 MPa; the mineral admixture uses: Ⅱ fly ash with a specific surface area of 320 m 2 / kg, and slag powder with a specific surface area of 420 m 2 / kg.

[0055] Comparison 1

[0056] The raw materials are weighed as follows: 216 parts of P.O42.5 cement, 72 parts of Ⅱ fly ash, 72 parts of slag powder, 795 parts of fine aggregate, 996 parts of coarse aggregate, 6.0 parts of water reducing agent, and 160 parts of water.

[0057] The preparation method is as follows: the P.O42.5 cement, the Ⅱ fly ash, the slag powder, the fine aggregate, and the coarse aggregate are poured into a mixer and stirred for 1 minute to mix uniformly; the water reducing agent is mixed into water and fully mixed uniformly, and then poured into the above mixture and stirred for 2-5 minutes, to obtain the comparison 1 concrete.

[0058] Comparison 2

[0059] The raw materials are weighed as follows: 246 parts of P.O42.5 cement, 82 parts of Ⅱ fly ash, 82 parts of slag powder, 762 parts of fine aggregate, 980 parts of coarse aggregate, 6.5 parts of water reducing agent, and 157 parts of water.

[0060] The preparation method is as follows: the P.O42.5 cement, the Ⅱ fly ash, the slag powder, the fine aggregate, and the coarse aggregate are poured into a mixer and stirred for 1 minute to mix uniformly; the water reducing agent is mixed into water and fully mixed uniformly, and then poured into the above mixture and stirred for 2-5 minutes, to obtain the comparison 2 concrete.

[0061] Comparison 3

[0062] Weigh the following raw materials according to weight: 288 parts of P.O42.5 cement; 96 parts of II fly ash; 96 parts of slag powder; 751 parts of fine aggregate; 954 parts of coarse aggregate; 7.0 parts of water reducer, and 154 parts of clean water.

[0063] The preparation method is as follows: P.O42.5 cement, II fly ash, slag powder, fine aggregate, and coarse aggregate are poured into a mixer and stirred for 1 minute to mix them evenly; a water reducer is mixed into water and mixed thoroughly, and then poured into the above mixture and stirred for 2-5 minutes to obtain comparison 3 concrete.

[0064] Comparison 4:

[0065] Weigh the following raw materials according to weight: 312 parts of P.O42.5 cement; 104 parts of II fly ash; 104 parts of slag powder; 780 parts of fine aggregate; 902 parts of coarse aggregate; 8.0 parts of water reducer, and 150 parts of clean water.

[0066] The preparation method is as follows: P.O42.5 cement, II fly ash, slag powder, fine aggregate and coarse aggregate are poured into a mixer and stirred for 1 minute to mix them evenly; a water reducer is mixed into water and mixed thoroughly, and then poured into the above mixture and stirred for 2-5 minutes to obtain comparative 4 concrete.

[0067] According to GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" and GB / T50081-2019 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete", the slump, expansion, and 3d, 7d, and 28d compressive strength of the concrete prepared in the above examples and comparative examples were measured. The results are shown in Table 5:

[0068] Table 5 Working performance and mechanical properties of low carbon concrete of each group

[0069]

[0070] As can be seen from Table 5, the performance of the low-carbon concrete embodiments provided by the present invention (Groups 1-4) is compared with concrete prepared using conventional methods (Comparisons 1-4). Concrete of different strength grades (C30-C60) is prepared. While maintaining essentially the same concrete slump, the corresponding grades of concrete show a 2-4 MPa increase in strength at each age, and a 10-15% increase in expansion by 60-80 mm, representing superior performance. Compared to the corresponding concrete prepared using conventional methods, the low-carbon concrete (C30-C60) uses 14.3% less cement clinker, meaning the carbon emission intensity of the concrete is reduced by 14.3%, making it a truly low-carbon concrete.

[0071] It should be noted that the above examples are only used to illustrate the technical solutions of the present application, and are not intended to limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some or all of the technical features can be replaced by equivalents, and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An integrated cementitious material for high-performance low-carbon concrete, characterized by: The following raw materials are dry-mixed uniformly by weight: 35-40 parts of Portland cement clinker powder; 5-6 parts of high calcium and high iron belite sulphoaluminate cement clinker powder; 5-10 parts of fine limestone powder; 14-20 parts of ground fly ash; 10-15 parts of slag powder; 10-15 parts of steel slag powder; 5-10 parts of coarse limestone powder; The high calcium and high iron belite sulphoaluminate cement clinker powder is obtained by grinding high calcium and high iron belite sulphoaluminate cement clinker to a specific surface area of ​​380-400 m 2 / kg obtained; The batching parameters of the high-calcium and high-iron belite sulphoaluminate cement clinker are: alkalinity coefficient Cm value is 1.60-1.65, fCaO is 0.5-1.0%, and fSO3 is 0.5-1.0%; the mineral composition of the high-calcium and high-iron belite sulphoaluminate cement clinker is calculated by weight percentage: C2S mineral content is 50-60%, The mineral content is 20-25%, the mineral content of C6AF2 is 10-15%, and the 12 A7 mineral content is 5-10%.

2. The integrated cementitious material for high-performance low-carbon concrete according to claim 1, characterized in that: The Portland cement clinker powder is obtained by grinding 95% of ordinary Portland cement clinker and 5% of desulfurized gypsum together, with a specific surface area of ​​380-400 m 2 / kg.

3. The integrated cementitious material for high-performance low-carbon concrete according to claim 1, characterized in that: The fine limestone powder is obtained by ultra-fine grinding of limestone, with a specific surface area of ​​800-900m 2 / kg.

4. The integrated cementitious material for high-performance low-carbon concrete according to claim 1, characterized in that: The ground fly ash is obtained by grinding the original fly ash separately, and the specific surface area is 500-550m 2 / kg.

5. The integrated cementitious material for high-performance low-carbon concrete according to claim 1, characterized in that: The slag powder is obtained by grinding water-quenched slag separately, and has a specific surface area of ​​550-600m 2 / kg.

6. The integrated cementitious material for high-performance low-carbon concrete according to claim 1, characterized in that: The steel slag powder is obtained by grinding converter steel slag separately, and has a specific surface area of ​​450-500m 2 / kg.

7. The integrated cementitious material for high-performance low-carbon concrete according to claim 1, characterized in that: The coarse limestone powder is obtained by grinding limestone separately, and has a specific surface area of ​​150-200m 2 / kg.

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