Micro-aggregate concrete and mix proportion design method thereof

Abstract

The invention provides micro-aggregate concrete and a mix proportion design method thereof. The mix proportion design method comprises the following steps: manufacturing and collecting machine-made sand dust by utilizing impact breaking, and measuring the fineness, the specific surface area, the fluidity ratio, the methylene blue value and the saturated surface dry water absorption rate of the machine-made sand dust; determining the use amount of a cementing material in the micro-aggregate concrete, and respectively calculating the use amounts of fixed cement, fly ash, mineral powder and machine-made sand dust; calculating actual water consumption; respectively calculating the use amount mg0 of coarse aggregate and the use amount ms0 of fine aggregate in the micro-aggregate concrete by adopting a mass method; adding the machine-made sand dust into a binding material, and calculating the dosage ma0 of an additive; the corresponding mix proportion is selected according to the strength required by the project, the dosage of each component is calculated by using an interpolation method, and the actual mix proportion is determined. The method has the beneficial effects that dust generated by stone crushing is used as micro-aggregate for filling, so that comprehensive utilization of resources is effectively realized, waste discharge and dependence on raw materials are reduced, and the influence on the environment is reduced.

Description

Technical Field

[0001] The invention belongs to the field of building materials, and in particular relates to a micro-aggregate concrete and a mix ratio design method thereof. Background Art

[0002] Traditional concrete is composed of cement, active mineral admixtures, sand and gravel aggregates and other main materials, and its mix design is usually based on strength and durability requirements. However, in some special cases, such as anti-seepage, anti-freeze performance, self-compacting performance or higher durability environments, the application of traditional concrete is subject to certain restrictions. As a new type of building material, micro-aggregate concrete is mainly characterized by the use of micron- or millimeter-sized particles as micro-aggregates to fill the gaps between aggregates in concrete and reduce porosity. This design can significantly improve the compactness of concrete, enhance the surface smoothness and wear resistance of concrete, and improve mechanical properties and durability. However, its mix design method has not been fully studied and applied, and the traditional mix operation process is cumbersome. Moreover, in the current concrete preparation process, the dust generated in the stone crushing process is only used as a by-product and is not utilized. This not only wastes resources and fails to reasonably utilize waste materials, but also requires special micro-aggregates when modifying concrete, which greatly increases the high cost of concrete production and is not environmentally friendly.

[0003] Therefore, there is an urgent need to provide an environmentally friendly micro-aggregate concrete and a mix design method thereof that can utilize the dust generated in the stone crushing process as micro-aggregate, significantly improve the performance of concrete, greatly reduce the cost of concrete production, and be environmentally friendly. Summary of the invention

[0004] In view of the shortcomings of the prior art mentioned above, the purpose of the present application is to provide a micro-aggregate concrete and a mix design method thereof, which can effectively solve the problems in the background technology, utilize dry machine-made sand dust to replace part of the admixture or fine aggregate for filling, thereby improving the performance of concrete and realizing the recycling of solid waste resources.

[0005] In order to achieve the above-mentioned purpose and other related purposes, the present application provides a micro-aggregate concrete, characterized in that the components and dosages include: cementitious material, coarse aggregate, fine aggregate, machine-made sand dust, admixture, and water, and the dosage of the cementitious material is 300-500 kg / m 3 The water dosage is 170~230kg / m 3 , the sand rate is 38% to 43%; the amount of coarse aggregate and fine aggregate is calculated according to the mass method, the amount of the machine-made sand dust is 0.1 to 30% of the amount of the cementitious material; the amount of the admixture is 0.5 to 3% of the amount of the machine-made sand dust incorporated into the cementitious material.

[0006] As a preferred embodiment of the present application, the amount of the gelling material is 300 kg / m3 、350kg / m 3 , 400kg / m 3 , 450kg / m 3 or 500kg / m 3 .

[0007] As a preferred embodiment of the present application, the machine-made sand dust is made of diabase, tuff or basalt.

[0008] As a preferred embodiment of the present application, the dosage of the machine-made sand dust is 10-20% of the dosage of the cementitious material.

[0009] As a preferred embodiment of the present application, the specific surface area of ​​the machine-made sand dust is greater than 300 cm 2 / g, fineness <3.5%, fluidity ratio <90%, saturated surface dry water absorption >20%, methylene blue value ≤6.00g / kg. This is because the sand and gravel raw materials are conveyed to the impact crusher through a belt for crushing, and the dust raised is collected into the dust collector under the action of the induced draft fan. It may contain a large amount of clay minerals. Since the expansive clay has a large specific surface area, it is easy to absorb methylene blue dye, while the specific surface area of ​​non-clay mineral particles in the dust is relatively much smaller (1m 2 / g~3m 2 / g), and does not absorb any visible amount of dyes. Therefore, the methylene blue value can directly determine whether there are expansive clay minerals in the dust and determine their content, and then determine the amount of admixture required during normal construction; the saturated surface dry water absorption rate can reflect the water absorption capacity of dust when the surface is relatively dry, which helps to understand the pore structure characteristics of dust and its adsorption to water, and the fluidity ratio can also reflect the fluidity and processability of different dusts from the side, and is used to evaluate the amount of water required for dust mixing. Fineness and specific surface area can both reflect the particle size and particle size distribution of dust. By reasonably controlling fineness and specific surface area, the mix ratio design of micro-aggregate concrete can be achieved to ensure the quality of the project.

[0010] As a preferred embodiment of the present application, the cementitious material includes fixed cement, fly ash and mineral powder, wherein the mixing ratio of the fixed cement, fly ash and mineral powder is 5:3:2.

[0011] As a preference of the present application, the fine aggregate is artificial sand (also known as machine-made sand) with a fineness modulus of 2.5 to 3.0.

[0012] As a preferred embodiment of the present application, the coarse aggregate is continuously graded crushed stone with a particle size range of 5 to 31.5 mm.

[0013] As a preferred embodiment of the present application, the fixing cement is PO 42.5 ordinary silicate or silicate cement.

[0014] As a preferred embodiment of the present application, the fly ash is selected from Class F II fly ash, with a water requirement ratio of ≤105% and a fineness of ≤30%.

[0015] As a preferred embodiment of the present application, the mineral powder is S95 grade slag powder, with a 28-day activity index ≥95% and a fluidity ratio ≥95%.

[0016] As a preferred embodiment of the present application, the dosage of the admixture is 1.2% of the amount of machine-made sand dust incorporated into the cementitious material.

[0017] As a preferred embodiment of the present application, the amount of the gelling material is 300 kg / m 3 、350kg / m 3 , 400kg / m 3 , 450kg / m 3 or 500kg / m 3 ,in:

[0018] When the amount of cementitious material is m b0 =300kg / m 3 When, the sand ratio α is 42% to 43%;

[0019] When the amount of cementitious material is m b0 =350kg / m 3 When, the sand ratio α is 41% to 42%;

[0020] When the amount of cementitious material is m b0 =400kg / m 3 When, the sand ratio α is 40% to 41%;

[0021] When the amount of cementitious material is m b0 =450kg / m 3 When, the sand ratio α is 39% to 40%;

[0022] When the amount of cementitious material is m b0 =500kg / m 3 When the sand ratio α is 38% to 39%.

[0023] The present application provides a micro-aggregate concrete, characterized in that the components and dosages include: cementitious material, coarse aggregate, fine aggregate, admixture, and water, and the dosage of the cementitious material is 300 kg / m 3 、350kg / m 3 , 400kg / m 3 , 450kg / m 3 or 500kg / m 3 ; The water dosage is 170~230kg / m 3; The amount of coarse aggregate and fine aggregate is calculated according to the mass method, the amount of the machine-made sand dust is 10-20% of the amount of cementitious material; the amount of the admixture is 1.2% of the amount of machine-made sand dust into the cementitious material; the sand ratio is 38-43%, wherein:

[0024] When the amount of cementitious material is m b0 =300kg / m 3 When, the sand ratio α is 42% to 43%;

[0025] When the amount of cementitious material is m b0 =350kg / m 3 When, the sand ratio α is 41% to 42%;

[0026] When the amount of cementitious material is m b0 =400kg / m 3 When, the sand ratio α is 40% to 41%;

[0027] When the amount of cementitious material is m b0 =450kg / m 3 When, the sand ratio α is 39% to 40%;

[0028] When the amount of cementitious material is m b0 =500kg / m 3 When the sand ratio α is 38% to 39%.

[0029] The present application also provides a micro-aggregate concrete mix design method, which is characterized by comprising:

[0030] Use impact crusher to produce and collect machine-made sand dust, and measure the fineness, specific surface area, fluidity ratio, methylene blue value and saturated surface dry water absorption of machine-made sand dust;

[0031] Determine the total cementitious content of cementitious materials in micro-aggregate concrete b0 The cementitious material is a mixture of fixed cement, fly ash and mineral powder. The amount of fixed cement is calculated based on the proportion of each component of the cementitious material in the micro-aggregate concrete and the proportion of machine-made sand dust as micro-aggregate. s , the amount of fly ash m f 、Amount of mineral powder m k , the amount of machine-made sand dust m d0 ;

[0032] Determine the water consumption m according to the slump requirements of the construction concrete w0 , and combined with the saturated surface dry water absorption rate γ of machine-made sand dust w Correct the water consumption and calculate the actual water consumption m w ;

[0033] Use the mass method to calculate the amount of coarse aggregate in micro-aggregate concrete m g0 , the amount of fine aggregate m s0 ;

[0034] Include machine-made sand dust in the amount of cementitious materials and calculate the amount of admixture m a0 :

[0035] m a0 =( m b0 +m d0 )×δ (9);

[0036] In the formula, m a0 m is the amount of admixture per cubic meter of micro-aggregate concrete mixture a0 , unit: kg / m 3 ;

[0037] δ is the dosage ratio of admixture, %;

[0038] Select the corresponding mix ratio according to the required strength of the project, and use the interpolation method to calculate the required amount of each component in the micro-aggregate concrete to determine the actual mix ratio.

[0039] As a preferred embodiment of the present application, the mixing ratio of fixed cement, fly ash and mineral powder is 5:3:2.

[0040] As a preferred embodiment of the present application, the dosage of the machine-made sand dust is 10-20% of the dosage of the cementitious material.

[0041] As a preferred embodiment of the present application, the amount of water in the micro-aggregate concrete is calculated as follows:

[0042] The water consumption m is determined according to the slump requirements of the concrete in the design drawings. w0 ;

[0043] Combined with the dry water absorption rate of the saturated surface of the machine-made sand dust, the water consumption is corrected and the actual water consumption m is calculated. w ;

[0044] m w0 =m w1 (1-β)(1);

[0045]

[0046] m w =m w0 +m d0 ×γ w (3)

[0047] Among them, m w The water consumption per cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0048] m w0 The amount of water per cubic meter of micro-aggregate concrete mixture determined according to the slump requirements of the construction concrete in the design drawings, in kg / m 3 ;

[0049] m w1 The amount of water required for concrete with a slump of 160 mm, in kg / m 3 ;

[0050] m d0 The amount of machine-made sand dust per cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0051] β is the water reduction rate of the admixture, %;

[0052] γ w is the water absorption rate of machine-made sand dust, %;

[0053] ω is the saturated surface dry water absorption rate of machine-made sand dust, %;

[0054] is the reduction factor, %.

[0055] As a preferred embodiment of the present application, the mass method is based on the mass of the micro-aggregate concrete mixture being equal to the sum of the masses of the constituent materials, and the amount of coarse aggregate and fine aggregate can be calculated according to the following set of equations:

[0056] m s +m f +m k =m b0 (4);

[0057] m b0 + m d0 + m g0 + m s0 + m w =m cp (5);

[0058] m s0 =(m cp -m d0 -m b0 -m w )×α+ m d0 (6);

[0059] m g0 =(m cp -m d0 -m b0 -m w )×(1-α) - m d0(7);

[0060]

[0061] Among them, m cp is the assumed mass of micro-aggregate concrete mixture per cubic meter, in kg / m 3 ;

[0062] m b0 The amount of cementitious material in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0063] m s The amount of fixed cement per cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0064] m f The amount of fly ash in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0065] m k The amount of mineral powder in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0066] m d0 The amount of machine-made sand dust per cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0067] m w The amount of water in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0068] m s0 The amount of fine aggregate in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0069] m g0 The amount of coarse aggregate in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0070] α is the sand ratio of micro-aggregate concrete mixture, %.

[0071] As a preferred embodiment of the present application, the amount of the gelling material is 300 kg / m 3 、350kg / m 3 , 400kg / m 3 , 450kg / m 3 or 500kg / m 3 .

[0072] As the preferred embodiment of this application, m cp The value is 2350~2450kg / m 3 ;in:

[0073] When the amount of cementitious material is 300kg / m 3 When the micro-aggregate concrete mixture mass is 2350kg / m 3 ~2360kg / m 3 ;

[0074] When the amount of cementitious material is 350kg / m 3 When the micro-aggregate concrete mixture mass is 2360kg / m 3 ~2370kg / m 3 ;

[0075] When the amount of cementitious material is 400kg / m 3 When the micro-aggregate concrete mixture mass is 2370kg / m 3 ~2380kg / m 3 ;

[0076] When the amount of cementitious material is 450kg / m 3 When the micro-aggregate concrete mixture mass is 2380kg / m 3 ~2390kg / m 3 ;

[0077] When the amount of cementitious material is 500kg / m 3 When the micro-aggregate concrete mixture mass is 2390kg / m 3 ~2400kg / m 3 .

[0078] Compared with the prior art, the beneficial effects of this application are:

[0079] 1. Dust is a byproduct of stone crushing. Using it as micro-aggregate filling can effectively realize the comprehensive utilization of resources, reduce waste emissions and dependence on raw materials, reduce the impact on the environment, and conform to the concept of sustainable development. Compared with conventional natural aggregates, the cost of machine-made sand dust produced when making fine aggregates is usually lower as a filler, which greatly reduces the cost of concrete production, especially in mass production, which helps to control construction costs.

[0080] 2. The present invention uses the machine-made sand dust in the machine-made sand as micro-aggregate, and regards it as an inert powder to fill the cementitious material system, so that the particle gradation design of the system is more reasonable, and the close stacking of the powder particles can be better achieved, and the homogeneity and stability of the concrete material are promoted. Under the premise of ensuring that the 28d compressive strength of the concrete meets the requirements, the overall performance and strength of the concrete are improved, and the workability of the concrete is ensured to meet the requirements of self-compacting performance and pumpability.

[0081] 3. Using dust as micro-aggregate filling can bring benefits in many aspects, from resource utilization, economy to environmental protection and improvement of concrete performance, all of which show its practical application potential and advantages in engineering construction, and effectively simplify the concrete mix design operation process of test personnel, and has a strong promotion and application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] Figure 1 It is a flow chart of the mix ratio design method of the present invention;

[0083] Figure 2 The present invention is 300kg / m 3 The amount of cementitious materials used to prepare the compressive strength of concrete;

[0084] Figure 3 The present invention is 350kg / m 3 The amount of cementitious materials used to prepare the compressive strength of concrete;

[0085] Figure 4 The present invention is 400kg / m 3 The amount of cementitious materials used to prepare the compressive strength of concrete;

[0086] Figure 5 The present invention is 450kg / m 3 The amount of cementitious materials used to prepare the compressive strength of concrete;

[0087] Figure 6 The present invention is 500kg / m 3 The amount of cementitious material used to prepare the compressive strength of concrete. DETAILED DESCRIPTION

[0088] The following describes the implementation of the present application through specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification. The present application can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application.

[0089] It should be noted that the process equipment or devices not specifically specified in the following embodiments are all conventional equipment or devices in the art.

[0090] In addition, it should be understood that one or more method steps mentioned in this application do not exclude the existence of other method steps before or after the combination step or the insertion of other method steps between these explicitly mentioned steps, unless otherwise specified; it should also be understood that the combination connection relationship between one or more devices / apparatuses mentioned in this application does not exclude the existence of other devices / apparatuses before or after the combination device / apparatus or the insertion of other devices / apparatuses between these two explicitly mentioned devices / apparatuses, unless otherwise specified. Moreover, unless otherwise specified, the numbering of each method step is only a convenient tool for identifying each method step, and is not intended to limit the order of arrangement of each method step or the scope of implementation of this application. Changes or adjustments in their relative relationships shall also be regarded as the scope of implementation of this application without substantial changes in the technical content.

[0091] The present application provides a micro-aggregate concrete, the components and dosage of which include: cementitious material, coarse aggregate, fine aggregate, admixture, and water. The dosage of the cementitious material is 300-500 kg / m 3 The water dosage is 170~230kg / m 3 , the sand rate is 38% to 43%; the amount of coarse aggregate and fine aggregate is calculated according to the mass method, the amount of the machine-made sand dust is 0.1 to 30% of the amount of the cementitious material; the amount of the admixture is 0.5 to 3% of the amount of the machine-made sand dust incorporated into the cementitious material.

[0092] The machine-made sand dust is made of diabase, tuff or basalt.

[0093] The dosage of the machine-made sand dust is 15-20% of the dosage of the cementitious material.

[0094] The specific surface area of ​​the machine-made sand dust is > 300 cm 2 / g, fineness <3.5%, fluidity ratio <90%, saturated surface dry water absorption >20%, methylene blue value ≤6.00g / kg.

[0095] The cementitious material includes fixed cement, fly ash and mineral powder, wherein the mixing ratio of the fixed cement, fly ash and mineral powder is 5:3:2.

[0096] The fine aggregate is artificial sand (also called machine-made sand) with a fineness modulus of 2.5 to 3.0.

[0097] The coarse aggregate is continuously graded crushed stone with a particle size range of 5 to 31.5 mm.

[0098] The fixing cement is PO 42.5 ordinary silicate or silicate cement, which complies with relevant national standards.

[0099] The fly ash is selected from Class F II fly ash, with a water requirement ratio of ≤105% and a fineness of ≤30%.

[0100] The mineral powder is S95 grade slag powder, with a 28-day activity index of ≥95% and a fluidity ratio of ≥95%.

[0101] The dosage of the admixture is 1.2% of the amount of machine-made sand dust added to the cementitious material.

[0102] The amount of the gelling material is 300-500 kg / m 3 There are five types, 300kg / m 3 、350kg / m 3 , 400kg / m 3 , 450kg / m 3 , 500kg / m 3 , the sand ratio α is 38-43%, where:

[0103] When the amount of cementitious material is m b0 =300kg / m 3 When, the sand ratio α is 42% to 43%;

[0104] When the amount of cementitious material is m b0 =350kg / m 3 When, the sand ratio α is 41% to 42%;

[0105] When the amount of cementitious material is m b0 =400kg / m 3 When, the sand ratio α is 40% to 41%;

[0106] When the amount of cementitious material is m b0 =450kg / m 3 When, the sand ratio α is 39% to 40%;

[0107] When the amount of cementitious material is m b0 =500kg / m 3 When the sand ratio α is 38% to 39%.

[0108] A mix ratio design method of micro-aggregate concrete in the present application comprises:

[0109] S1 uses an impact crusher to produce and collect machine-made sand dust, and determines the fineness, specific surface area, fluidity ratio, methylene blue value and saturated surface dry water absorption of the machine-made sand dust;

[0110] Specifically, the machine-made sand dust can be selected from diabase (HLY) in Huzhou area of ​​Zhejiang Province, tuff (NHY) in Jingning area, and basalt (XWY) in Lishui area.

[0111] The specific surface areas of the three types of machine-made sand dust are 447 cm 2 / g(HLY),384cm 2 / g(NHY),311cm 2 / g(XWY).

[0112] The dust finenesses of the three types of machine-made sand are 3.1% (HLY), 3.0% (NHY), and 2.0% (XWY) respectively.

[0113] The dust fluidity ratios of the three types of machine-made sand are 78% (HLY), 86% (NHY), and 80% (XWY), respectively.

[0114] The saturated dry water absorption rates of the three types of machine-made sand dust are 22.7% (HLY), 20% (NHY), and 23.2% (XWY), respectively.

[0115] The methylene blue values ​​of the three types of machine-made sand dust are 3.25g / kg (HLY), 1.50g / kg (NHY), and 6.00g / kg (XWY), respectively.

[0116] The particle sizes of the three types of machine-made sand dust are shown in Table 1. Taking the diabase dust sample as an example, its D10 = 1.6 μm, D50 = 12.9 μm, and D90 = 72 μm. According to the distribution of particles from small to large, it means that among all the particle systems that make up the sample, particles less than or equal to 1.6 μm account for 10%; particles less than or equal to 12.9 μm account for 50%; and particles less than or equal to 72 μm account for 90%.

[0117] Table 1 Particle size distribution of machine-made sand dust

[0118] Sample type D10(μm) D50(μm) D90(μm) Diabase 1.6 12.9 72.0 tuff 1.4 12.5 93.4 Basalt 2.3 19.1 110.0

[0119] S2 determines the total cementitious amount of cementitious materials in micro-aggregate concrete m b0 The cementitious material is a mixture of fixed cement, fly ash and mineral powder. The amount of fixed cement is calculated based on the proportion of each component of the cementitious material in the micro-aggregate concrete and the proportion of machine-made sand dust as micro-aggregate. s , the amount of fly ash m f 、Amount of mineral powder m k , the amount of machine-made sand dust m d0 ;

[0120] In this embodiment, the amount of cementitious material used is m b0 300~500kg / m 3 There are five types, 300kg / m 3 、350kg / m 3 , 400kg / m 3 , 450kg / m3 , 500kg / m 3 ; The proportion of fixed cement, fly ash and mineral powder in the cementitious material is 5:3:2.

[0121] Specifically, the amount of cementitious material is 400kg / m 3 Take the example of determining the actual amount of all cementitious materials, that is, the amount of fixed cement in the cementitious material is 50% of the cementitious material amount, the amount of fly ash is 30% of the cementitious material amount, and the amount of mineral powder is 2% of the cementitious material amount. Then the actual amount of fixed cement m s =400×50%=200kg / m 3 ; Actual amount of fly ash m f =400×30%=120kg / m 3 ; Actual amount of mineral powder m k =400×20%=80kg / m 3 ;

[0122] The designed machine-made sand dust dosage is 0%, 10%, 20%, and 30% of the cementitious material dosage. The cementitious material dosage is used as the base for calculation. b0 =400kg / m 3 For example, the calculation of sand making dust dosage, then the dust dosage of 10% is m d0 =400×10%=40kg / m 3 Similarly, the amount of dust for 20% is m d0 80kg / m 3 ; The amount of dust mixed with 30% is 120kg / m 3 .

[0123] S3 Determine the water consumption according to the slump requirements of the construction concrete m w0 , and combined with the saturated surface dry water absorption rate γ of machine-made sand dust w Correct the water consumption and calculate the actual water consumption m w ;

[0124] The water consumption m is determined according to the slump requirements of the concrete in the design drawings. w0 ;

[0125] Combined with the dry water absorption rate of the saturated surface of the machine-made sand dust, the water consumption is corrected and the actual water consumption m is calculated. w ;

[0126] m w0 =m w1 (1-β)(1);

[0127]

[0128] mw =m w0 +m d0 ×γ w (3)

[0129] Among them, m w The water consumption per cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0130] m w0 The amount of water per cubic meter of micro-aggregate concrete mixture determined according to the slump requirements of the construction concrete in the design drawings, in kg / m 3 ;

[0131] m w1 The amount of water required for concrete with a slump of 160 mm, in kg / m 3 ;

[0132] m d0 The amount of machine-made sand dust per cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0133] β is the water reduction rate of the admixture, %;

[0134] γ w is the water absorption rate of machine-made sand dust, %;

[0135] ω is the saturated surface dry water absorption rate of machine-made sand dust, %;

[0136] is the reduction factor, %.

[0137] Specifically, the maximum nominal particle size of the crushed stone in the coarse aggregate is 31.5 mm, and the water consumption for a slump of 90 mm is 205 kg / m 3 Based on, increase 5kg / m for every 20mm increase in slump 3 The slump of high-fluidity concrete mixture is required to be no less than 160mm, that is, the amount of water required for concrete with a slump of 160mm is m w1 222.5kg / m 3 Based on, but the water reduction rate of high-performance admixtures (such as water reducers) β is not less than 25%, here β is 25%; then the water consumption per cubic meter of high-flow concrete is m w0 For: m w0 =m w1 (1-β)=222.5×(1-25%)≈166.9kg / m 3 .

[0138] Taking basalt as an example, the saturated surface dry water absorption rate of the measured machine-made sand dust is 23.2%, which needs to be multiplied by the reduction factor Here Take 0.7 (30% surface floating water, 70% powder open pore water) for calculation, then the water absorption rate of basalt tail powder is Similarly, the water absorption rate of tuff tail powder is 14%; the water absorption rate of diabase tail powder is 15.89%. The actual water consumption of basalt micro-aggregate concrete with a dosage of 20% is m w =m w0 +m d0 ×γ w =166.9+80×0.163≈180kg / m 3 .

[0139] S4 Use the mass method to calculate the amount of coarse aggregate in micro-aggregate concrete m g0 , the amount of fine aggregate m s0 The mass method is based on the mass of the micro-aggregate concrete mixture being equal to the sum of the masses of the constituent materials. The amount of coarse aggregate and fine aggregate can be calculated according to the following equations:

[0140] m s +m f +m k =m b0 (4);

[0141] m b0 + m d0 + m g0 + m s0 + m w =m cp (5);

[0142] m s0 =(m cp -m d0 -m b0 -m w )×α+ m d0 (6);

[0143] m g0 =(m cp -m d0 -m b0 -m w )×(1-α) - m d0 (7);

[0144]

[0145] Among them, m cp is the assumed mass of micro-aggregate concrete mixture per cubic meter, in kg / m 3 ;

[0146] m b0The amount of cementitious material in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0147] m s The amount of fixed cement per cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0148] m f The amount of fly ash in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0149] m k The amount of mineral powder in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0150] m d0 The amount of machine-made sand dust per cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0151] m w The amount of water in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0152] m s0 The amount of fine aggregate in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0153] m g0 The amount of coarse aggregate in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ;

[0154] α is the sand ratio of micro-aggregate concrete mixture, %.

[0155] Specifically, 400kg / m 3 Taking the total cementitious dosage and 10% admixture of machine-made sand dust as an example, the concrete mixture is assumed to have a mass of 2380kg / m 3 , the total amount of coarse aggregate and fine aggregate is:

[0156] m g0 +m s0 =m cp -m d0 -m b0 -m w =2380-40-400-180=1760kg / m 3 .

[0157] Calculated based on a sand ratio of 41%, then:

[0158] Fine aggregate dosage m s0 =(m cp -m d0 -m b0 -m w )×α+m d0 =1760×41%+40=761.6kg / m 3 ;

[0159] Coarse aggregate dosage m g0 =(m cp -m d0 -m b0 -m w )×(1-α)-m d0 =1760×59%-40=998.4kg / m 3 S5: Include machine-made sand dust in the amount of cementitious materials and calculate the amount of admixture m a0 :

[0160] m a0 =( m b0 +m d0 )×δ (9);

[0161] In the formula, m a0 m is the amount of admixture per cubic meter of micro-aggregate concrete mixture a0 , unit: kg / m 3 ;

[0162] δ is the dosage ratio of admixture, %;

[0163] Specifically, considering the interlayer adsorption effect of machine-made sand dust on admixtures, in order to prevent the workability of concrete from deteriorating and vibrating and shaping difficulties, when calculating the admixture dosage, the machine-made sand dust is included in the amount of cementitious materials for calculation. The admixture dosage m a0 =(400+40)×1.2%=5.28kg / m 3 The dosage of admixtures with different gelling amounts is determined according to the performance of the mixture and construction requirements.

[0164] S6 According to the strength requirements of the project, select the mix ratio corresponding to the mechanical properties obtained from the above tests, calculate the accurate total cementitious dosage and micro-aggregate dosage through interpolation method, and conduct re-testing to obtain the actual required mix ratio.

[0165] The amount of the gelling material is 300-500 kg / m 3 There are five types, 300kg / m 3 、350kg / m 3 , 400kg / m 3 , 450kg / m 3 , 500kg / m3 , m cp The value is 2350~2450kg / m 3 ;in:

[0166] When the amount of cementitious material is 300kg / m 3 When the micro-aggregate concrete mixture mass is 2350kg / m 3 ~2360kg / m 3 ;

[0167] When the amount of cementitious material is 350kg / m 3 When the micro-aggregate concrete mixture mass is 2360kg / m 3 ~2370kg / m 3 ;

[0168] When the amount of cementitious material is 400kg / m 3 When the micro-aggregate concrete mixture mass is 2370kg / m 3 ~2380kg / m 3 ;

[0169] When the amount of cementitious material is 450kg / m 3 When the micro-aggregate concrete mixture mass is 2380kg / m 3 ~2390kg / m 3 ;

[0170] When the amount of cementitious material is 500kg / m 3 When the micro-aggregate concrete mixture mass is 2390kg / m 3 ~2400kg / m 3 .

[0171] The mix design method of the micro-aggregate concrete of Examples 1 to 3 and the concrete of Comparative Example 1 is based on the total cementitious material of 400 kg / m 3 For example, the total design density is 2380kg / m 3 , calculated water consumption is 180kg / m 3 The fixed cement, fly ash and mineral powder content in the cementitious material is 5:3:2. The content ratio of machine-made sand dust is 0%, 10%, 20% and 30% of the cementitious material. In order to reduce the exposed gravel and improve the workability of concrete, the sand rate is set to 41% and the admixture content is 1.2%. The mix design is shown in Table 2.

[0172] Table 2 Proportion of each component in micro-aggregate concrete

[0173]

[0174]

[0175] The mix design method of the micro-aggregate concrete of Examples 4 to 6 and the concrete of Comparative Example 2 is based on the total cementitious material of 300 kg / m 3 For example, the total design density is 2360kg / m 3 , calculated water consumption is 180kg / m 3 The fixed cement, fly ash and mineral powder content in the cementitious material is 5:3:2. The content ratio of machine-made sand dust is 0%, 10%, 20% and 30% of the cementitious material. In order to reduce the exposed gravel and improve the workability of concrete, the sand rate is set to 43%, the admixture content is 1.2%, and the mix ratio design is shown in Table 3.

[0176] The mix design method of the micro-aggregate concrete of Examples 7 to 9 and the concrete of Comparative Example 3 is based on the total cementitious material of 350 kg / m 3 For example, the total design density is 2370kg / m 3 , calculated water consumption is 180kg / m 3 The fixed cement, fly ash and mineral powder content in the cementitious material is 5:3:2. The content of machine-made sand dust is 0%, 10%, 20% and 30% of the cementitious material. In order to reduce the exposed gravel and improve the workability of concrete, the sand rate is set to 42%, the admixture content is 1.2%, and the mix ratio is shown in Table 3.

[0177] The mix design method of the micro-aggregate concrete of Examples 10 to 12 and the concrete of Comparative Example 4 is based on the total cementitious material of 450 kg / m 3 For example, the total design density is 2390kg / m 3 , calculated water consumption is 180kg / m 3 The fixed cement, fly ash and mineral powder content in the cementitious material is 5:3:2. The content ratio of machine-made sand dust is 0%, 10%, 20% and 30% of the cementitious material. In order to reduce the exposed gravel and improve the workability of concrete, the sand rate is set to 40%, the admixture content is 1.2%, and the mix ratio design is shown in Table 3.

[0178] The mix design method of the micro-aggregate concrete of Examples 13 to 15 and the concrete of Comparative Example 5 is based on the total cementitious material of 500 kg / m 3 For example, the total design density is 2400kg / m 3 , calculated water consumption is 180kg / m 3 The fixed cement, fly ash and mineral powder content in the cementitious material is 5:3:2. The proportion of dust replacing total sand and gravel aggregate is 0%, 10%, 20% and 30%. In order to reduce exposed gravel and improve the workability of concrete, the sand rate is set to 39%, the admixture content is 1.2%, and the mix design is shown in Table 3.

[0179] Table 3 Proportion of each component in micro-aggregate concrete

[0180]

[0181]

[0182] The compressive strength test of concrete cube specimens was carried out according to GB / T 50081-2019 “Standard for Test Methods for Physical and Mechanical Properties of Concrete”. The specific results are shown in Table 4.

[0183] Table 4 Compressive strength test of micro-aggregate concrete

[0184]

[0185]

[0186] Through the test, it can be found that the cohesiveness of concrete is significantly improved with the increase of the amount of machine-made sand dust. This is because the addition of machine-made sand dust increases the viscosity of the slurry, the cohesiveness of the concrete mixture is increased, and the segregation and bleeding of the concrete is reduced. At the same time, since the specific surface area of ​​dust is much higher than that of sand, as the amount of dust increases, in order to ensure the rheological properties of the concrete mixture, the amount of water and admixture required to encapsulate the dust increases.

[0187] It can be seen from the above table that the strength of concrete shows an increasing trend with the increase of the dosage, and the compressive strength of concrete at the corresponding age is improved compared with that without dust. When the dust dosage exceeds 20%, due to the addition of too much dust, the grading of concrete is unreasonable, the relative content of coarse particles is reduced, and the skeleton effect is weakened, resulting in a decrease in the compressive strength of concrete. That is, the dosage of machine-made sand dust is best at 10% to 20%. It can also be seen from the figure that the extent to which machine-made sand dust improves the compressive strength of concrete increases with the increase of concrete age. Machine-made sand dust is of great help in improving the later strength of concrete. The reason is that the addition of dust gives full play to the "nucleation effect" and "filling effect", that is, the machine-made sand dust particles can absorb the Ca released when tricalcium silicate is hydrated. 2+ ions, reduce the enrichment and directional arrangement of calcium hydroxide crystals at the interface, increase the content of CSH at the interface, provide nuclei for hydration products, and refine the calcium hydroxide grains at the same time, so that they crystallize on the surface of dust particles instead of growing into large crystals with poor bonding in local areas, thereby improving the interfacial bonding performance, forming a dense filling structure and a close stacking system at the microscopic level, and promoting rapid strength growth in the later stage.

[0188] The above examples are to illustrate the embodiments disclosed in the present application and should not be construed as limiting the present application. In addition, the various modifications listed herein and the changes in the methods and compositions in the application are obvious to those skilled in the art without departing from the scope and spirit of the present application. Although the present application has been specifically described in conjunction with a variety of specific preferred embodiments of the present application, it should be understood that the present application should not be limited to these specific embodiments. In fact, various modifications as described above that are obvious to those skilled in the art to obtain the application should be included in the scope of the present application.

Claims

1. A micro-aggregate concrete, characterized in that: The components and dosage include: cementitious material, coarse aggregate, fine aggregate, machine-made sand dust, admixture, and water. The dosage of the cementitious material is 300-500 kg / m 3 The water dosage is 170~230kg / m 3 , the sand rate is 38% to 43%; the amount of coarse aggregate and fine aggregate is calculated according to the mass method, the amount of the machine-made sand dust is 0.1 to 30% of the amount of the cementitious material; the amount of the admixture is 0.5 to 3% of the amount of the machine-made sand dust incorporated into the cementitious material.

2. The micro-aggregate concrete according to claim 1, characterized in that: The dosage of the machine-made sand dust is 10-20% of the dosage of the cementitious material.

3. The micro-aggregate concrete according to claim 1, characterized in that: The specific surface area of ​​the machine-made sand dust is > 300 cm 2 / g, fineness <3.5%, fluidity ratio <90%, saturated surface dry water absorption >20%, methylene blue value ≤6.00g / kg.

4. The micro-aggregate concrete according to claim 1, characterized in that: The cementitious material includes fixed cement, fly ash and mineral powder, wherein the mixing ratio of the fixed cement, fly ash and mineral powder is 5:3:

2.

5. The micro-aggregate concrete according to claim 4, characterized in that: The fixed cement is PO 42.5 ordinary silicate or silicate cement; the fly ash is F class II fly ash, with a water demand ratio of ≤105% and a fineness of ≤30%; the mineral powder is S95 grade slag powder, with a 28-day activity index of ≥95% and a fluidity ratio of ≥95%.

6. The micro-aggregate concrete according to claim 1, characterized in that: The amount of the gelling material is 300 kg / m 3 、350kg / m 3 , 400kg / m 3 , 450kg / m 3 or 500kg / m 3 , the sand rate is 38-43%, of which: When the amount of cementitious material is m b0 =300kg / m 3 When, the sand rate is 42% to 43%; When the amount of cementitious material is m b0 =350kg / m 3 When, the sand ratio is 41% to 42%; When the amount of cementitious material is m b0 =400kg / m 3 When the sand ratio is 40% to 41%; When the amount of cementitious material is m b0 =450kg / m 3 When the sand ratio is 39% to 40%; When the amount of cementitious material is m b0 =500kg / m 3 When the sand rate is 38% to 39%.

7. A mix design method for micro-aggregate concrete according to any one of claims 1 to 6, characterized in that: include: Using an impact crusher to produce and collect machine-made sand dust, and measuring the fineness, specific surface area, fluidity ratio, methylene blue value and saturated surface dry water absorption of the machine-made sand dust; Determine the total cementitious content of cementitious materials in micro-aggregate concrete b0 The cementitious material is a mixture of fixed cement, fly ash and mineral powder. The amount of fixed cement is calculated based on the proportion of each component of the cementitious material and the amount of machine-made sand dust in the micro-aggregate concrete. s , the amount of fly ash m f 、Amount of mineral powder m k , the amount of machine-made sand dust m d0 ; Determine the water consumption m according to the slump requirements of the construction concrete w0 , and combined with the saturated surface dry water absorption rate γ of machine-made sand dust w Correct the water consumption and calculate the actual water consumption m w ; Use the mass method to calculate the amount of coarse aggregate in micro-aggregate concrete m g0 , the amount of fine aggregate m s0 ; Include machine-made sand dust in the amount of cementitious materials and calculate the amount of admixture m a0 : m a0 =(m b0 +m d0 )×δ (9); In the formula, m a0 m is the amount of admixture per cubic meter of micro-aggregate concrete mixture a0 , unit: kg / m 3 ; δ is the dosage ratio of admixture, %; Select the corresponding mix ratio according to the required strength of the project, and use the interpolation method to calculate the required amount of each component in the micro-aggregate concrete to determine the actual mix ratio.

8. The mix design method of micro-aggregate concrete according to claim 7, characterized in that: The amount of water in micro-aggregate concrete is calculated as follows: The water consumption m is determined according to the slump requirements of the concrete in the design drawings. w0 ; Combined with the dry water absorption rate of the saturated surface of the machine-made sand dust, the water consumption is corrected and the actual water consumption m is calculated. w ; m w0 =m w1 (1-b) (1); m w =m w0 +m d0 ×γ w (3) Among them, m w The water consumption per cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ; m w0 The amount of water per cubic meter of micro-aggregate concrete mixture determined according to the slump requirements of the construction concrete in the design drawings, in kg / m 3 ; m w1 The amount of water required for concrete with a slump of 160 mm, in kg / m 3 ; m d0 The amount of machine-made sand dust per cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ; β is the water reduction rate of the admixture, %; γ w is the water absorption rate of machine-made sand dust, %; ω is the saturated surface dry water absorption rate of machine-made sand dust, %; is the reduction factor, %.

9. The mix design method of micro-aggregate concrete according to claim 7, characterized in that: The mass method is based on the mass of the micro-aggregate concrete mixture being equal to the sum of the masses of the constituent materials, and the amount of coarse aggregate and fine aggregate is calculated according to the following set of equations: m s +m f +m k =m b0 (4); m b0 +m d0 +m g0 +m s0 +m w =m cp (5); m s0 =(m cp -m d0 -m b0 -m w )×α+m d0 (6); m g0 =(m cp -m d0 -m b0 -m w )×(1-α)-m d0 (7); Among them, m cp is the assumed mass of micro-aggregate concrete mixture per cubic meter, in kg / m 3 ; m b0 The amount of cementitious material in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ; m s The amount of fixed cement per cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ; m f The amount of fly ash in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ; m k The amount of mineral powder in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ; m d0 The amount of machine-made sand dust per cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ; m w The amount of water in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ; m s0 The amount of fine aggregate in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ; m g0 The amount of coarse aggregate in each cubic meter of micro-aggregate concrete mixture, unit: kg / m 3 ; α is the sand ratio of micro-aggregate concrete mixture, %.

10. The mix design method of micro-aggregate concrete according to claim 8, characterized in that: The amount of the gelling material is 300 kg / m 3 、350kg / m 3 , 400kg / m 3 , 450kg / m 3 , 500kg / m 3 , m cp The value is 2350~2450kg / m 3 ; in: When the amount of cementitious material is 300kg / m 3 When the micro-aggregate concrete mixture mass is 2350kg / m 3 ~2360kg / m 3 ; When the amount of cementitious material is 350kg / m 3 When the micro-aggregate concrete mixture mass is 2360kg / m 3 ~2370kg / m 3 ; When the amount of cementitious material is 400kg / m 3 When the micro-aggregate concrete mixture mass is 2370kg / m 3 ~2380kg / m 3 ; When the amount of cementitious material is 450kg / m 3 When the micro-aggregate concrete mixture mass is 2380kg / m 3 ~2390kg / m 3 ; When the amount of cementitious material is 500kg / m 3 When the micro-aggregate concrete mixture mass is 2390kg / m 3 ~2400kg / m 3 .

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