A method for predicting the strength of modified three-dimensional porous graphene recycled concrete

Abstract

The application belongs to the field of civil engineering recycled concrete strength prediction, and relates to a modified three-dimensional porous graphene recycled concrete strength prediction method. A formula is established through a water-binder ratio deformation formula, a water-cement ratio, a paste-aggregate ratio, a replacement rate of recycled aggregate and a water absorption rate. The relationship between the optimal modified three-dimensional porous graphene content and the recycled concrete strength is found, and finally, a recycled concrete strength prediction formula about the paste-aggregate ratio, the water consumption, the replacement rate of recycled aggregate and the water absorption rate and the optimal content of the modified three-dimensional porous graphene is established.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of strength prediction methods of recycled concrete, and particularly relates to a recycled concrete strength prediction method under the action of modified three-dimensional porous graphene. BACKGROUND

[0002] With the rapid advancement of urbanization and the continuous expansion of urban construction scale in China, the construction industry is experiencing a new period of prosperity. However, this has led to a huge amount of construction waste generated annually. For waste concrete, the traditional disposal methods are mainly open-air stacking or landfill. These methods not only occupy a large amount of valuable arable land resources, but also involve high disposal and transportation costs. More seriously, during the collection and stacking of waste concrete, dust and flying sand are easily generated, seriously polluting the atmospheric environment and causing secondary pollution. In addition, the production of concrete itself requires a large amount of sand and gravel aggregate. With the continuous exploitation of natural sand and gravel, natural aggregate resources are becoming increasingly depleted, which poses a serious threat to our ecological environment and further deteriorates the ecological condition.

[0003] Due to the presence of many voids and micro-cracks in recycled concrete, these defects pose a considerable challenge to the strength of the concrete. However, by introducing modified three-dimensional porous graphene, we can significantly improve the internal structure of recycled concrete. This material can effectively fill the voids, reduce the porosity, and reduce the size of the pores, thereby enhancing the compactness of the cement-based material and further improving the strength of the concrete. This innovative method not only overcomes the inherent defects of insufficient strength of recycled concrete, but also provides a new solution to this problem. The development of this technology is expected to promote the pace of recycled concrete in commercial applications, thereby promoting the vigorous development of the recycled concrete industry. For economic construction, the application of recycled concrete will bring significant resource savings and cost reductions; for environmental improvement, it helps to reduce the environmental pressure of construction waste; for social development, the promotion and application of recycled concrete technology will promote the construction industry to develop in a more environmentally friendly and sustainable direction. Therefore, the widespread application of this technology will have far-reaching and immeasurable impact. SUMMARY

[0004] In view of the limitations of the current technology, the core problem to be solved by the present application is to develop a new method for predicting the compressive strength of concrete that simplifies the operation process, shortens the time consumption, and ensures that the prediction results have small errors and high accuracy compared to actual measured values.

[0005] To solve the above technical problems, the present application adopts the following technical solutions:

[0006] Step 1, establish a 28d compressive strength prediction method of recycled concrete containing modified three-dimensional porous graphene, as shown in formula (2):

[0007]

[0008] wherein p represents the paste-aggregate ratio, i.e. w a — water absorption of recycled coarse aggregate; λ r — recycled coarse aggregate replacement rate;

[0009] m” bo — dosage of cementitious material per cubic meter of recycled concrete, in kg / m 3 ;

[0010] m” so — dosage of fine aggregate per cubic meter, in kg / m 3 ;

[0011] m” go — dosage of coarse aggregate per cubic meter of recycled concrete, in kg / m 3 ;

[0012] m” go1 — dosage of coarse aggregate per cubic meter of concrete, in kg / m 3 ;

[0013] m wh — dosage of water per cubic meter of normal concrete mixture, in kg / m 3 ;

[0014] p s — density of fine aggregate, in g / cm 3 ;

[0015] p' g — density of coarse aggregate, in g / cm 3 ;

[0016] p b — density of cementitious material, in g / cm 3 ;

[0017] p w — density of water, in g / cm 3 ;

[0018] a — air content percentage of concrete, taken as 1 when no air-entraining admixture is used.

[0019] Step 2, set the dosage of water m wh and the paste-aggregate ratio p.

[0020] Step 3, set the water absorption w a of recycled coarse aggregate, and set the recycled coarse aggregate replacement rate λ r .

[0021] Step 4, cement and mineral admixture are mixed according to the mixing ratio, mortar-sand ratio is 1:3, and water-binder ratio is 0.5, mortar test is carried out, and 28d mortar compressive strength is recorded.

[0022] Step 5, the related parameters in steps 2, 3 and 4 are substituted into formula (1), and the 28d compressive strength of graphene with different contents is predicted.

[0023] As a further scheme of the application, in the modified three-dimensional porous graphene recycled concrete strength prediction method, the recycled coarse aggregate is obtained by crushing the discarded concrete blocks by a jaw crusher, and the recycled aggregate shaper; the jaw crusher has a feeding port of 150mmx125mm, a feeding particle size of less than 100mm, an adjustable discharging particle size of 5-38mm, and an hourly output of 500-1000kg; the recycled aggregate shaper has a feeding particle size of 0-40mm and an adjustable discharging particle size of 0-31.5mm.

[0024] As a further scheme of the application, in the modified three-dimensional porous graphene recycled concrete strength prediction method, the natural coarse aggregate has a particle size of 4.75-37.5mm, a 37.5mm sieve residue rate of 3%, a 31.5mm sieve residue rate of 15%, a 26.5mm sieve residue rate of 30%, a 19mm sieve residue rate of 45%, a 16mm sieve residue rate of 60%, a 9.5mm sieve residue rate of 80%, and a 4.75mm sieve residue rate of 97%; the recycled coarse aggregate is discarded gravel concrete, and the recycled coarse aggregate has a particle size of 4.75-31.5mm, a 31.5mm sieve residue rate of 3%, a 26.5mm sieve residue rate of 15%, a 19mm sieve residue rate of 30%, a 16mm sieve residue rate of 50%, a 9.5mm sieve residue rate of 80%, and a 4.75mm sieve residue rate of 97%.

[0025] As a further scheme of the application, in the modified three-dimensional porous graphene recycled concrete strength prediction method, the modified three-dimensional porous graphene has a value range of 0-0.06%; in step 2, the paste-aggregate ratio has a value range of 0.35-0.5, and the water consumption has a value range of 160-200kg / m 3 ; in step 3, the water absorption has a value range of 0-8%, and the coarse aggregate replacement rate has a value range of 0-100%.

[0026] As a further scheme of the application, in the modified three-dimensional porous graphene recycled concrete strength prediction method, the modified three-dimensional porous graphene is modified by the following method.

[0027] First, the original three-dimensional porous graphene and polycarboxylic acid superplasticizer with a mass ratio of 1:3 are mixed, and the original three-dimensional porous graphene and distilled water with a mass ratio of 1:75 are added and stirred uniformly; then the original three-dimensional porous graphene and sulfuric acid with a mass ratio of 1:5 are added and stirred, and the PH is controlled at 4-6; finally, the modified three-dimensional porous graphene is obtained by drying in a drying oven, adjusting the temperature of the drying oven to 105 DEG C, and baking for 3h, and grinding with a ball mill for 2h.

[0028] Compared with the prior art, the beneficial effects of the present application are:

[0029] (1) The present application can quickly predict the compressive strength of concrete by using parameters such as slurry-bone ratio, water consumption, water absorption rate of recycled coarse aggregate, replacement rate and modified three-dimensional porous graphene, so as to judge in advance whether it meets the established standard, and then guide the adjustment and optimization of the concrete mix proportion in time.

[0030] (2) The present application provides a theoretical basis for replacing natural aggregate with recycled coarse aggregate.

[0031] (3) The present application not only simplifies and optimizes the experimental steps, effectively reduces the use amount of various raw materials, and also reduces the repeated test time and accelerates the test progress, but also significantly improves the accuracy and reliability of the prediction results. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments will be described in detail below with reference to the specific embodiments of the present application. It should be noted that the embodiments described herein are only a part of examples of the present application, rather than all possible embodiments. Based on these embodiments, all other embodiments that can be deduced by those skilled in the art without creative labor should be considered to fall within the protection scope of the present application.

[0033] In the present embodiment, the recycled concrete production raw materials include cement, water, water reducing agent, three-dimensional porous graphene, fine aggregate and natural crushed stone, and recycled coarse aggregate. In addition, the recycled concrete in the present application is not limited to the above raw materials in the specific implementation. The cement in the above raw materials is ordinary portland cement, and the fine aggregate adopts medium sand with qualified gradation. In the specific implementation, the coarse aggregate can be selected from any one of single gradation, discontinuous gradation or continuous gradation according to the actual engineering requirements. In the present embodiment, the continuous gradation is used, including recycled coarse aggregate with a particle size of 5-40mm.

[0034] Six groups of concrete experiments are carried out to test and verify the strength of concrete, and the concrete raw material mix proportion is shown in Table 1:

[0035] Table 1

[0036]

[0037] The unit of each raw material in Table 1 is kg, wherein the cement is ordinary Portland cement with a mark of P.O 42.5.

[0038] The predicted value (unit: MPa) is calculated by the formula:

[0039]

[0040] The calculated predicted value (unit: MPa) is compared with the measured value (unit: MPa) at 28d, and the comparison is as follows:

[0041] As shown in Table 2:

[0042]

[0043]

[0044] Through in-depth analysis of the data in Table 2, it is found that the error between the predicted value and the measured value in the prediction formula in the present application is controlled within 2.46 MPa when predicting the strength of concrete, wherein the minimum error is only 0.89 MPa, the maximum error is 2.46 MPa, and the average error reaches 1.32 MPa. More worth mentioning is that the average relative error is only 2.64%, and the ratio of the predicted value to the measured value (Ypredicted / Ymeasured) is stable in the range of 0.955-1.022, showing an accuracy of up to 95%. These data fully prove that the prediction formula in the present application not only has a high degree of correlation when calculating the 28d compressive strength of concrete, but also shows excellent prediction precision and accuracy.

[0045] Finally, it needs to be emphasized that the above examples are only intended to illustrate the technical concept of the present application, and do not constitute the only or limiting interpretation of its application. Although we have described the present application in detail by referring to its preferred embodiments, those skilled in the art should realize that various adjustments and changes in form and details can be made according to actual needs without deviating from the core spirit and protection scope of the present application defined by the appended claims.

Claims

1. A method for predicting the strength of modified three-dimensional porous graphene recycled concrete, characterized by Comprising the following steps: Step 1, the establishment of recycled concrete containing three-dimensional porous graphene 28 days compressive strength prediction formula, as shown in formula (1) f” cu,o represents the prepared strength of recycled concrete, with the unit of MPa; a a The value range is 0.52-0.54, a b The value range is 0.19-0.21; f b1 represents the 28d mortar strength of cementitious materials, with the unit of MPa; wherein c is the adjustment coefficient: 1.17, a is the optimal dosage of modified three-dimensional porous graphene, b is the dosage of modified three-dimensional porous graphene: 0.05%; a represents the air content percentage of concrete; p b represents the density of cementitious materials; p w represents the density of water; Step 2, setting the amount of water m wh and the pulp bone ratio p; Step 3, setting the water absorption rate w of the recycled coarse aggregate a , setting the replacement rate λ of the recycled coarse aggregate r ; Step 4, according to the cement and mineral admixture mixing ratio, mortar ratio 1:3, water cement ratio 0.5 mortar test, record 28d mortar compressive strength; Step 5, the relevant parameters in step 2, step 3 and step 4 into formula (1), realize different content of graphene 28d compressive strength prediction.

2. The method for predicting the strength of modified three-dimensional porous graphene recycled concrete according to claim 1, characterized in that, Recycled coarse aggregate using waste concrete chunks, recycled coarse aggregate using jaw crusher crushing - recycled aggregate shaping machine - recycled aggregate shaping machine; jaw crusher feed opening 150mmx125mm, feed size less than 100mm, discharge size 5~38mm adjustable, 500~1000kg per hour output; recycled aggregate shaping machine feed particle size 0~40mm, discharge particle size 0~31.5mm adjustable.

3. The method for predicting the strength of modified three-dimensional porous graphene recycled concrete according to claim 1, characterized in that, Natural coarse aggregate with 4.75~37.5mm particle size, particle size 37.5mm sieve rate of 3%, particle size 31.5mm sieve rate of 15%, particle size 26.5mm sieve rate of 30%, particle size 19mm sieve rate of 45%, particle size 16mm sieve rate of 60% particle size, 9.5mm sieve rate of 80%, particle size 4.75mm sieve rate of 97% particle size; recycled coarse aggregate is waste broken stone concrete, recycled coarse aggregate with particle size 4.75~31.5mm particle size 31.5mm sieve rate of 3%, particle size 26.5mm sieve rate of 15%, particle size 19mm sieve rate of 30%, particle size 16mm sieve rate of 50% particle size, 9.5mm sieve rate of 80%, particle size 4.75mm sieve rate of 97% particle size.

4. The method for predicting the strength of modified three-dimensional porous graphene recycled concrete according to claim 1, characterized in that, In step 1, the modified three-dimensional porous graphene is in the range of 0-0.06%; in step 2, the slurry-bone ratio is in the range of 0.35-0.5, and the water amount is in the range of 160-200 kg / m 3 ; in step 3, the water absorption is in the range of 0-8%, and the coarse aggregate replacement rate is in the range of 0-100%.

5. The method for predicting the strength of modified three-dimensional porous graphene recycled concrete according to claim 1, characterized in that, The modified three-dimensional porous graphene is modified by the following method: First, the mass ratio of 1:3 of the original three-dimensional porous graphene and polycarboxylic acid superplasticizer is mixed, and the mass ratio of 1:75 of the original three-dimensional porous graphene and distilled water is added and stirred uniformly; then the mass ratio of 1:5 of the original three-dimensional porous graphene and sulfuric acid is added and stirred, and the PH is controlled at 4~6; finally, the drying oven is used to dry it, and then the temperature of the drying oven is adjusted to 120℃, and the drying is continued for 3h, and the ball mill is used to grind for 2h to obtain the modified three-dimensional porous graphene.

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