LU500369B1

LU500369B1 - C60 self-compacting and micro-expansion high performance concrete

Info

Publication number: LU500369B1
Application number: LU500369A
Authority: LU
Inventors: Zhe Ma; Xinrong Cheng; Yuchao Xie; Zhi Cheng; Lan Liu
Original assignee: Univ North China
Priority date: 2021-07-01
Filing date: 2021-07-01
Publication date: 2022-01-04

Abstract

The disclosure relates to the field of solid waste utilization, and in particular to a C60 self- compacting and micro-expansion high performance concrete. A composition for making such concrete is provided, comprising: 150 to 174 parts by weight of a ground desulfurization slag, 350 to 406 parts by weight of a cement, 750 to 800 parts by weight of river sand, 850 to 900 parts by weight of crushed stone, 150 to 174 parts by weight of water, and 7.5 to 8.7 parts by weight of a water reducing agent. The ground desulfurization slag and cement serve as a cementing material, and the water reducing agent is 1.5 % by weight of the total weight of the cementing material. The ground desulfurization slag is prepared by grinding and sieving coal gangue desulfurization slag using a ball mill and a square mesh screen with a mesh size of 80 microns, respectively, such that the slag has a specific surface area of not less than 600 m2/kg. The concrete material made from the composition exhibits high strength and can form self- compacting and micro-expansion, and can be widely used in the field of construction.

Description

BL-5268 LU500369 C60 SELF-COMPACTING AND MICRO-EXPANSION HIGH

PERFORMANCE CONCRETE TECHNICAL FIELD

[01] The present disclosure is related generally to the field of solid waste utilization, and, in particular, to a concrete, more particularly a C60 self-compacting and micro- expansion high performance concrete.

BACKGROUND ART

[02] Coal gangue is low carbon dark grey rock that is associated with coal seams, and is generated as a solid waste during the process of coal mining and clean coal production. It accounts for 8 to 20 % of raw coal production, with the average being 12 %, and, as an industrial residue, has the largest accumulation amount and occupied area of land. As coal gangue contains components of high calorific value, such as, carbon, hydrogen, and oxygen, it has been widely used for power generation. The government has introduced a series of policies associated with coal gangue power generation in order to promote energy saving and emission reduction and to encourage the utilization of coal gangue. As a result, a large number of coal gangue power plants have been established. These power plants, however, produce a large quantity of ash while bringing economic advantages through utilization of coal gangue. Coal gangue desulfurization slag is waste residue discharged from the bottom of a circulating fluidized bed combustion (CFBC) boiler after combustion and desulfurization of coal gangue in the boiler. Such residue from coal gangue combustion and desulfurization is produced in an amount greater than the residue from coal combustion and desulfurization via a circulating fluidized bed (CFB) boiler, due to the fact that coal gangue is a lower grade fuel than coal. Moreover, since there is a big difference in structure and chemical composition between coal gangue and ordinary coal, the slags produced therefrom have different properties. Currently, the coal gangue desulfurization slag has a very low utilization rate, leading to a large number of piles on land and thus pollution of environment. It is of important economic value and practical significance to replace cement with an equal amount of coal gangue desulfurization slag for production of high performance concrete (HPC), as this approach can realize a good utilization of such slag and a reduced amount of cement.

[03] On the other hand, prior art concretes suffer from certain disadvantages. Firstly, conventional methods for producing expansion concretes often employ an expanding agent or an expanding cement as an expansion source. Although this can compensate for shrinkage of the concretes or enable self-stress to be generated therein, the strength and stability of the concretes may decrease at later age. Secondly, these concretes cannot form self-compacting and need to be vibrated in use. This not only costs human and financial resources, but also produces noise which is relatively large such that it makes nighttime construction impossible. Lastly, the conventional concretes cannot satisfy both high performance and low cost. 1

BL-5268 SUMMARY LU500369

[04] Thus, in view of the above disadvantages, an objective of the present disclosure is to provide a composition for making a C60 self-compacting and micro-expansion high performance concrete which exhibits high strength and can form self-compacting and enable compensating for any shrinkage thereof. Importantly and advantageously, coal gangue desulfurization slag, often discarded as a waste as mentioned above, is included in the composition, realizing effective utilization of such waste residue and also allowing a reduced cement amount (as will be described hereinafter in detail). Moreover, the concrete prepared from the composition can exhibit improved strength and durability, and provide both economic and environmental benefits.

[05] Accordingly, an objective of the present disclosure is realized by a composition for making a C60 self-compacting and micro-expansion high performance concrete (also referred to as concrete mixture composition or simply composition hereinafter), which comprises: 150 to 174 parts by weight of a ground desulfurization slag, 350 to 406 parts by weight of a cement, 750 to 800 parts by weight of river sand, 850 to 900 parts by weight of crushed stone or gravel, 150 to 174 parts by weight of water, and 7.5 to 8.7 parts by weight of a water reducing agent. The ground desulfurization slag and cement serve as a cementing material, and the water reducing agent is about 1.5 % by weight of the total weight of the cementing material. The ground desulfurization slag is prepared by grinding and sieving coal gangue desulfurization slag using a ball mill and a square mesh screen with a mesh size of 80 microns, respectively. The ground desulfurization slag has a specific surface area of not less than 600 m*/kg.

[06] Further, the ground desulfurization slag may have a specific surface area of 620 to 640 m°/kg.

[07] Further, the composition may comprise: 164.4 parts by weight of a ground desulfurization slag, 383.6 parts by weight of a cement, 784.7 parts by weight of river sand, 876.9 parts by weight of crushed stone, 164.4 parts by weight of water, and 8.22 parts by weight of a water reducing agent; wherein, the ground desulfurization slag 1s prepared by grinding and sieving coal gangue desulfurization slag using a ball mill and a square mesh screen with a mesh size of 80 microns, respectively, and wherein the ground desulfurization slag has a specific surface area of 635 m°/kg.

[08] The cement may be an ordinary portland cement of 42.5 grade.

[09] The crushed stone may be graded crushed stone with a particle size distribution of 5 to 20 millimeters.

[10] The water reducing agent may be polycarboxylate superplasticizer.

[11] The composition according to the present disclosure mainly contains a ground desulfurization slag, a cement, river sand, crushed stone, water, and a water reducing agent. The coal gangue desulfurization slag is activated by the grinding process, so no activator is required. The presence of the ground desulfurization slag in the composition can result in not only a substantially reduced amount of the cement, but also an effectively reduced amount of the water due to the interaction with the water reducing agent. Further, due to the presence of the ground desulfurization slag in the composition, workability and pumpability of the concrete mixture can be increased, and the concrete made from the concrete mixture composition can have higher impermeability and lower hydration heat. 2

BL-5268 Further, such concrete can have an improved pore structure which has much smaller and LU500369 uniform sizes, thereby leading to higher impermeability, excellent resistance to freezing and thawing, and thus improved durability. The coal gangue desulfurization slag used for preparing the ground desulfurization slag may have a SO3 content of 5.91 %, which is present in the form of anhydrite (i.e., II-CaSO4). Anhydrite has a low activity and is less reactive. However, it is activated by the grinding process, and can then be involved in an early stage of a hydration process involved in the making of the concrete to produce ettringite. This causes expansion of ettringite to occur at an earlier stage, avoiding cracking of the concrete material caused by the later hydration stage. Moreover, both the coarse aggregate (crushed stone or gravel) and the fine aggregate (river sand) in the composition are important for bending strength and durability of the concrete material.

[12] The present disclosure provides several advantages over prior art.

[13] Coal gangue desulfurization slag, which is often discarded as an industrial waste, is utilized effectively. In particular, the slag after grinding is used to replace part of the cement for making concrete. Hence, the present disclosure realizes utilization of solid waste (1.e., coal gangue desulfurization slag) and reduced cost of concrete.

[14] The concrete made from the concrete mixture composition of the present disclosure can form self-compacting, so no vibration is required, thereby avoiding noise generation. This makes it possible to carry out nighttime construction, thereby shortening the overall construction cycle. On the other hand, the concrete can enable the pouring time to be reduced, thereby reducing labor intensity of and/or the number of workers and construction cost.

[15] The present disclosure proposes to use desulfurization slag instead of expanding agents or expanding cements that are common for conventional cement mixture compositions, based on self-hardening and expansive properties and pozzolanic activity of the desulfurization slag. The concrete made from the concrete mixture composition of the present disclosure can enable compensating for any shrinkage thereof in the absence of an expanding agent, thereby avoiding cracking of the concrete material and reduction in strength thereof at a late stage caused by addition of an expanding agent. It is found that, when the concrete made from the concrete mixture composition of the present disclosure is used to make high-strength concrete filled steel tubes, the concrete is tightly attached to inner surfaces of the steel tubes and not separated therefrom. Further, the coal gangue desulfurization slag enables the generating time of concrete expansion to be effectively controlled. In particular, due to the coal gangue desulfurization slag, concrete expansion typically occurs at an early stage of curing of the concrete with a quicker expansion at 2, 3, and 7 days curing age, and after 28 days of curing age at a late stage the concrete tends to a steady state, thereby avoiding cracking of concrete caused by expansion thereof at the late stage that wound occur in prior art. Overall, the concrete made from the concrete mixture composition of the present disclosure does not shrink or expand during later use.

[16] The ground desulfurization slag may be present in the cementing material in an amount up to about 30 % by weight. So, the amount of cement required is substantially reduced. On the other hand, the strength of the concrete made by using such slag is surprisingly increased. In particular, the compressive strength of the concrete can reach 3

BL-5268 about 47 MPa at 7 days of curing age, and reach about 62 MPa at 28 days of curing age. LU500369 So, a high-strength concrete is provided.

[17] Further, the high performance concrete made from the composition of the present can provide improved adhesion to steel surfaces, achieving effective interaction therebetween and thus an improved bearing capacity. So, the concrete made from the composition of the present disclosure can be widely used for making concrete filled steel tube and steel reinforced concrete structures.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[18] The present disclosure is further illustrated by the following examples. It should be understood that these examples are only intended to explain the disclosure, and the present disclosure is not meant to be limited thereto.

[19] A composition for making a C60 self-compacting and micro-expansion high performance concrete is provided, which mainly comprises a cementing material, a fine aggregate, a coarse aggregate, water, and a water reducing agent. In particular, the cementing material consists of cement and a ground desulfurization slag, with the ground desulfurization slag present in an amount of about 30 % by weight with respect to the total weight of the cementing material. The cement may be Taiyuan Zhihai cement P.O

42.5, for example. The ground desulfurization slag is prepared from coal gangue desulfurization slag by grinding and sieving such slag using a ball mill and a square mesh screen with a mesh size of 80 microns, respectively. The grinding may be carried out, for example, for 70 to 75 minutes, such that the ground desulfurization slag has a specific surface area of 620 to 640 m*/kg. River sand is used as the fine aggregate, and preferably has a medium particle size. If the particle size of the river sand is too large, it is hardly possible for only the cementing material and the coarse aggregate to provide a relatively continuous particle size distribution; while if the particle size of the river sand is too small, the amount of water required would be increased, forming a viscous concrete mixture which is difficult to be pumped. Crushed stone or gravel is used as the coarse aggregate, which has a hard and dense texture and a low content of flat and elongated particles as well as a low water absorption rate. Preferably, the crushed stone may be graded crushed stone with a particle size distribution of 5 to 20 millimeters. The water may be tap water, for example. The water reducing agent may for example be polycarboxylate superplasticizer, which has excellent compatibility with both the cement and the ground desulfurization slag. In addition, the water reducing agent is about 1.5 % by weight of the total weight of the cementing material.

[20] Coal gangue desulfurization slags discharged from different power plants have different ingredients. This may significantly influence the expansion rate and strength of the concrete made. The desulfurization slag used in the following examples is coal gangue desulfurization slag obtained from Shanxi Pingshuo Coal Gangue Power Plant, which mainly contains, by weight: 42.19 % S10,, 25.90 % ALOs, 10.99 % CaO, 5.91 % SOs,

3.10 % Fe,Os, 1.35 % MgO, 0.84 % TiO, 0.79 % KO, 0.12 % P205, 0.06 % NaxO,

0.03 % MnO, 0.02 % CI, and 0.01 % ZnO.

[21] Example 1

[22] A C60 self-compacting and micro-expansion high performance concrete was 4

BL-5268 prepared from 150 kg of a ground desulfurization slag, 350 kg of cement, 750 kg of river LU500369 sand, 850 kg of crushed stone, 150 kg of water, and 7.5 kg of a water reducing agent. The ground desulfurization slag was prepared by grinding the coal gangue desulfurization slag, as mentioned above, for 70 min via a ball mill such that the slag had a specific surface area of 620 m*/kg.

[23] The crushed stone was poured into a mixer, into which the river sand, cement, and ground desulfurization slag were then poured to be mixed and stirred so as to form a homogeneous solid mixture. 40 to 60 % of the water was poured into the mixer, and then mixed and stirred so that the solid mixture therein was pre-wetted in a complete manner. The water reducing agent was added into the remaining water, and mixed and stirred until a homogeneous solution was formed. The solution was then added to the mixture in the mixer while stirring so as to obtain a C60 self-compacting and micro-expansion high performance concrete.

[24] Example 2

[25] A C60 self-compacting and micro-expansion high performance concrete was prepared from 164.4 kg of a ground desulfurization slag, 383.6 kg of cement, 784.7 kg of river sand, 876.9 kg of crushed stone, 164.4 kg of water, and 8.22 kg of a water reducing agent. The ground desulfurization slag was prepared by grinding the coal gangue desulfurization slag, as mentioned above, for 72 min via a ball mill such that the slag had a specific surface area of 635 m°/kg.

[26] The crushed stone was poured into a mixer, into which the river sand, cement, and ground desulfurization slag were then poured to be mixed and stirred so as to form a homogeneous solid mixture. 40 to 60 % of the water was poured into the mixer, and then mixed and stirred so that the solid mixture therein was pre-wetted in a complete manner. The water reducing agent was added into the remaining water, and mixed and stirred until a homogeneous solution was formed. The solution was then added to the mixture in the mixer while stirring so as to obtain a C60 self-compacting and micro-expansion high performance concrete.

[27] Example 3

[28] A C60 self-compacting and micro-expansion high performance concrete was prepared from 174 kg of a ground desulfurization slag, 406 kg of cement, 800 kg of river sand, 900 kg of crushed stone, 174 kg of water, and 8.7 kg of a water reducing agent. The ground desulfurization slag was prepared by grinding the coal gangue desulfurization slag, as mentioned above, for 71 min via a ball mill such that the reside had a specific surface area of 629 m*/kg.

[29] The crushed stone was poured into a mixer, into which the river sand, cement, and ground desulfurization slag were then poured to be mixed and stirred so as to form a homogeneous solid mixture. 40 to 60 % of the water was poured into the mixer, and then mixed and stirred so that the solid mixture therein was pre-wetted in a complete manner. The water reducing agent was added to the remaining water, and mixed and stirred until a homogeneous solution was formed. The solution was then added into the mixture in the mixer while stirring so as to obtain a C60 self-compacting and micro-expansion high performance concrete.

BL-5268

[30] Example 4 LU500369

[31] A C60 self-compacting and micro-expansion high performance concrete was prepared from 160.2 kg of a ground desulfurization slag, 373.8 kg of cement, 760.2 kg of river sand, 862.3 kg of crushed stone, 160.2 kg of water, and 8.01 kg of a water reducing agent. The ground desulfurization slag was prepared by grinding the coal gangue desulfurization slag, as mentioned above, for 73 min via a ball mill such that the slag had a specific surface area of 638 m°/kg.

[32] The crushed stone was poured into a mixer, into which the river sand, cement, and ground desulfurization slag were then poured to be mixed and stirred so as to form a homogeneous solid mixture. 40 to 60 % of the water was poured into the mixer, and then mixed and stirred so that the solid mixture therein was pre-wetted in a complete manner. The water reducing agent was added to the remaining water, and mixed and stirred until a homogeneous solution was formed. The solution was then added into the mixture in the mixer while stirring so as to obtain a C60 self-compacting and micro-expansion high performance concrete.

[33] Example 5

[34] A C60 self-compacting and micro-expansion high performance concrete was prepared from 163.2 kg of a ground desulfurization slag, 380.8 kg of cement, 770 kg of river sand, 863.7 kg of crushed stone, 163.2 kg of water, and 8.16 kg of a water reducing agent. The ground desulfurization slag was prepared by grinding the coal gangue desulfurization slag, as mentioned above, for 73 min via a ball mill such that the slag had a specific surface area of 638 m°/kg.

[35] The crushed stone was poured into a mixer, into which the river sand, cement, and ground desulfurization slag were then poured to be mixed and stirred so as to form a homogeneous solid mixture. 40 to 60 % of the water was poured into the mixer, and then mixed and stirred so that the solid mixture therein was pre-wetted in a complete manner. The water reducing agent was added to the remaining water, and mixed and stirred until a homogeneous solution was formed. The solution was then added into the mixture in the mixer while stirring so as to obtain a C60 self-compacting and micro-expansion high performance concrete.

[36] Example 6

[37] A C60 self-compacting and micro-expansion high performance concrete was prepared from 168 kg of a ground desulfurization slag, 392 kg of cement, 780 kg of river sand, 870.2 kg of crushed stone, 168 kg of water, and 8.4 kg of a water reducing agent. The ground desulfurization slag was prepared by grinding the coal gangue desulfurization slag, as mentioned above, for 74 min via a ball mill such that the slag had a specific surface area of 639 m*/kg.

[38] The crushed stone was poured into a mixer, into which the river sand, cement, and ground desulfurization slag were then poured to be mixed and stirred so as to form a homogeneous solid mixture. 40 to 60 % of the water was poured into the mixer, and then mixed and stirred so that the solid mixture therein was pre-wetted in a complete manner. The water reducing agent was added to the remaining water, and mixed and stirred until a homogeneous solution was formed. The solution was then added into the mixture in the mixer while stirring so as to obtain a C60 self-compacting and micro-expansion high 6

BL-5268 performance concrete. LU500369

[39] Example 7

[40] A C60 self-compacting and micro-expansion high performance concrete was prepared from 170.1 kg of a ground desulfurization slag, 396.9 kg of cement, 785 kg of river sand, 879.3 kg of crushed stone, 170.1 kg of water, and 8.51 kg of a water reducing agent. The ground desulfurization slag was prepared by grinding the coal gangue desulfurization slag, as mentioned above, for 75 min via a ball mill such that the slag had a specific surface area of 640 m°/kg.

[41] The crushed stone was poured into a mixer, into which the river sand, cement, and ground desulfurization slag were then poured to be mixed and stirred so as to form a homogeneous solid mixture. 40 to 60 % of the water was poured into the mixer, and then mixed and stirred so that the solid mixture therein was pre-wetted in a complete manner. The water reducing agent was added to the remaining water, and mixed and stirred until a homogeneous solution was formed. The solution was then added into the mixture in the mixer while stirring so as to obtain a C60 self-compacting and micro-expansion high performance concrete.

[42] Example 8

[43] A C60 self-compacting and micro-expansion high performance concrete was prepared from 172.5 kg of a ground desulfurization slag, 402.5 kg of cement, 790 kg of river sand, 890 kg of crushed stone, 172.5 kg of water, and 8.63 kg of a water reducing agent. The ground desulfurization slag was prepared by grinding the coal gangue desulfurization slag, as mentioned above, for 73 min via a ball mill such that the slag had a specific surface area of 638 m°/kg.

[44] The crushed stone was poured into a mixer, into which the river sand, cement, and ground desulfurization slag were then poured to be mixed and stirred so as to form a homogeneous solid mixture. 40 to 60 % of the water was poured into the mixer, and then mixed and stirred so that the solid mixture therein was pre-wetted in a complete manner. The water reducing agent was added into the remaining water, and mixed and stirred until a homogeneous solution was formed. The solution was then added into the mixture in the mixer while stirring so as to obtain a C60 self-compacting and micro-expansion high performance concrete.

[45] It was found that the slump flow spread of the fresh concretes prepared in Examples 1 to 8 was SF1 grade. So, the concretes can be used to prepare non-reinforced or rare-reinforced concrete structures that can be poured from an open top of a target object and to prepare vertical concrete structures having a small cross-sectional area and without having to be moved horizontally over a long distance, and can be used in the concrete pumping and pouring construction field.

[46] The concretes prepared in Examples 1 to 4 were tested for compressive strength and expansion rate, and the test results are shown in Table 1. Table 1 shows that the compressive strength of the concretes can reach about 47 MPa at 7 days of curing age and about 62 MPa at 28 days of curing age, and that the concretes expanded fast at 2, 3, and 7 days curing age, and after 28 days of curing age at a late stage the concretes tended to a steady state. Therefore, the concretes exhibited high strength, and expanded at an early stage, instead of a late stage, of curing thereof, thereby avoiding cracking thereof caused 7

BL-5268 by expansion at the late stage. LU500369

[47] Table 1 || Example] | Examplel | Examplel | Example! | | Frecoxpansionrate | 0 | 0 | 0 | 0 | pe [ERE rate pe same men | ar] man

[48] It will be understood that the present disclosure may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the present disclosure is not to be limited to the details given herein and is defined by only the scope as defined by the appended claims. Accordingly, any variations or equivalent arrangements should be considered to be within the scope of the present disclosure as defined by the claims. 8

Claims

BL-5268 WHAT IS CLAIMED IS: LUS00369

1. A composition for making a C60 self-compacting and micro-expansion high performance concrete, comprising: 150 to 174 parts by weight of a ground desulfurization slag, 350 to 406 parts by weight of a cement, 750 to 800 parts by weight of river sand, 850 to 900 parts by weight of crushed stone, 150 to 174 parts by weight of water, and

7.5 to 8.7 parts by weight of a water reducing agent; wherein, the ground desulfurization slag and cement serve as a cementing material, and the water reducing agent is 1.5 % by weight of the total weight of the cementing material; wherein, the ground desulfurization slag is prepared by grinding and sieving coal gangue desulfurization slag using a ball mill and a square mesh screen with a mesh size of 80 microns, respectively; and wherein the ground desulfurization slag has a specific surface area of not less than 600 m*/kg.

2. The composition of claim 1, wherein, the ground desulfurization slag has a specific surface area of 620 to 640 m°/kg.

3. The composition of claim 1, comprising: 164.4 parts by weight of a ground desulfurization slag, 383.6 parts by weight of a cement, 784.7 parts by weight of river sand, 876.9 parts by weight of crushed stone, 164.4 parts by weight of water, and 8.22 parts by weight of a water reducing agent; wherein, the ground desulfurization slag 1s prepared by grinding and sieving coal gangue desulfurization slag using a ball mill and a square mesh screen with a mesh size of 80 microns, respectively; and wherein the ground desulfurization slag has a specific surface area of 635 m°/kg.

4. The composition of any of claims 1 to 3, wherein, the cement is an ordinary portland cement of 42.5 grade.

5. The composition of any of claims 1 to 3, wherein, the crushed stone is graded crushed stone with a particle size distribution of 5 to 20 millimeters.

6. The composition of any of claims 1 to 3, wherein, the water reducing agent is polycarboxylate superplasticizer.

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