A prediction method for shrinkage deformation of steel slag concrete

Abstract

The invention discloses a method for predicting shrinkage deformation of steel slag concrete, which relates to the technical field of concrete and aims to solve the problem of lack of a method for predicting shrinkage deformation of steel slag concrete in the prior art. The method comprises: (1) obtaining the autogenous shrinkage value of concrete without steel slag; considering the limiting and restraining effect of steel slag aggregate on the autogenous shrinkage of concrete, calculating the equivalent aggregate-cement ratio of steel slag concrete based on the elastic modulus of steel slag aggregate and natural aggregate; and constructing an autogenous shrinkage prediction model of steel slag concrete; (2) obtaining the drying shrinkage value of concrete without steel slag; considering the limiting and restraining effect of steel slag aggregate on the drying shrinkage of concrete, calculating the equivalent aggregate volume fraction of steel slag concrete based on the elastic modulus of steel slag aggregate and natural aggregate; and constructing a drying shrinkage prediction model of steel slag concrete; and (3) constructing a total shrinkage value prediction model of steel slag concrete based on the autogenous shrinkage prediction model of steel slag concrete and the drying shrinkage prediction model of steel slag concrete to predict the shrinkage deformation of steel slag concrete.

Description

Technical Field

[0001] The invention relates to the technical field of concrete, and in particular to a method for predicting shrinkage deformation of steel slag concrete. Background Art

[0002] The use of steel slag, a solid waste discharged from the steelmaking process, as coarse / fine aggregate can replace natural aggregate to mix concrete, which is called steel slag concrete. The application of steel slag concrete can not only solve the problem of large steel slag accumulation and low utilization rate in my country (currently the utilization rate of steel slag in my country is only 35%), but also alleviate the problem of large demand for natural sand and gravel in engineering projects and shortage of actual natural sand and gravel resources (in 2020, my country's demand for sand and gravel is as high as 187 tons, while the actual available amount is only 100 tons). Due to the large elastic modulus of steel slag aggregate, steel slag aggregate will limit the shrinkage deformation of concrete, making the shrinkage performance of steel slag concrete significantly different from that of ordinary concrete. Steel slag aggregate reduces the drying shrinkage of concrete by 16% to 33%, and reduces the autogenous shrinkage of concrete by 17% to 44%.

[0003] Concrete is composed of cement paste and aggregate. In essence, the shrinkage deformation of concrete is mainly caused by the shrinkage of cement paste, while aggregate hardly produces shrinkage deformation and only plays a role in limiting the shrinkage of cement paste. The limiting effect of aggregate on the shrinkage of cement paste is determined by the elastic modulus of aggregate: the larger the elastic modulus of aggregate, the greater the limiting effect of aggregate, which ultimately reduces the shrinkage deformation of concrete. In order to further clarify the long-term deformation and shrinkage cracking of steel slag concrete structural components, a shrinkage deformation prediction method for steel slag concrete is urgently needed. Summary of the invention

[0004] The technical problems to be solved by the present invention are:

[0005] The prior art lacks a method for predicting shrinkage deformation of steel slag concrete.

[0006] The present invention adopts the following technical solutions to solve the above technical problems:

[0007] The present invention provides a method for predicting shrinkage deformation of steel slag concrete, which specifically comprises the following steps:

[0008] (1) The calculation of the autogenous shrinkage value of steel slag concrete includes the following steps:

[0009] Obtain the autogenous shrinkage value of concrete without steel slag;

[0010] Considering the limiting effect of steel slag aggregate on the autogenous shrinkage of concrete, the equivalent aggregate-cement ratio of steel slag concrete is calculated based on the elastic modulus of steel slag aggregate and natural aggregate.

[0011] Based on the autogenous shrinkage value and equivalent cementitious ratio of concrete without steel slag, a prediction model for autogenous shrinkage of steel slag concrete was constructed.

[0012] (2) The calculation of the drying shrinkage value of steel slag concrete includes the following steps:

[0013] Obtain the drying shrinkage value of concrete without steel slag;

[0014] Considering the limiting effect of steel slag aggregate on the drying shrinkage of concrete, the equivalent aggregate volume fraction of steel slag concrete is calculated based on the elastic modulus of steel slag aggregate and natural aggregate.

[0015] Based on the drying shrinkage value of concrete without steel slag and the equivalent aggregate volume fraction, a drying shrinkage prediction model for steel slag concrete was constructed.

[0016] (3) Based on the autogenous shrinkage prediction model and drying shrinkage prediction model of steel slag concrete, a total shrinkage value prediction model for steel slag concrete is constructed.

[0017] Furthermore, the calculation method of the equivalent cementitious ratio (a / c)equ of the slag concrete in step (1) is:

[0018]

[0019] In the formula, a CSA and a FSA are the mass of natural aggregate, coarse aggregate and fine aggregate per unit volume of slag concrete, kg / m 3 ; c is the total mass of cementitious material per unit volume, kg / m 3 , E SA and E NA are the elastic moduli of slag aggregate and natural aggregate, GPa, respectively.

[0020] Furthermore, the autogenous shrinkage value of the steel slag concrete in step (1) is The prediction model is:

[0021]

[0022] In the formula, k a / c is the influence coefficient of the equivalent water-binder ratio of steel slag aggregate, that is:

[0023]

[0024] is the mass of natural aggregate in concrete per unit volume without steel slag, kg / m 3 , is the autogenous shrinkage value of concrete without steel slag (×10 -6 ).

[0025] Furthermore, the equivalent aggregate volume fraction (V A )equ is calculated as:

[0026]

[0027] In the formula, V CSA and V FSA are the volume fractions of natural aggregate, steel slag coarse aggregate and steel slag fine aggregate in steel slag concrete, respectively.

[0028] Furthermore, the drying shrinkage value of the steel slag concrete in step (2) is The prediction model is:

[0029]

[0030] In the formula, is the influence coefficient of equivalent aggregate volume fraction of steel slag aggregate, that is:

[0031]

[0032] In the formula, is the volume fraction of natural aggregate in concrete without slag, is the drying shrinkage value of concrete without steel slag (×10 -6 ).

[0033] Furthermore, the total shrinkage value prediction model of steel slag concrete in step (3) is:

[0034]

[0035] Furthermore, the autogenous shrinkage value of concrete without steel slag is obtained by experimental testing or calculated based on the autogenous shrinkage model of European standard BS EN 1992.

[0036] Furthermore, the drying shrinkage value of concrete without steel slag is obtained by experimental testing or calculated based on the autogenous shrinkage model of European standard BS EN 1992.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention establishes a calculation method for the equivalent cement-binder ratio and equivalent aggregate volume fraction of steel slag concrete, taking into account the limiting and constraining effect of steel slag aggregate on the autogenous shrinkage and drying shrinkage of concrete, and based on this, constructs a prediction model for the autogenous shrinkage and drying shrinkage of steel slag concrete. In the process of developing a prediction model for shrinkage deformation of steel slag concrete, the present invention only uses theoretical deduction to establish a shrinkage model, and does not need to obtain relevant correction coefficient values ​​through fitting methods based on experimental data. Experiments show that the method of the present invention can accurately predict the autogenous shrinkage and drying shrinkage deformation of steel slag concrete in a closed environment or a dry environment, and has wider practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a flow chart of a method for predicting shrinkage deformation of steel slag concrete in an embodiment of the present invention;

[0040] Figure 2 This is a comparison chart of the predicted results of the shrinkage deformation of steel slag concrete (i.e., autogenous shrinkage) with the experimental measured results for the predicted results of the shrinkage deformation of steel slag concrete with a closed water-binder ratio of 0.3 by the prediction method of the steel slag concrete in the embodiment of the present invention;

[0041] Figure 3 This is a comparison chart of the predicted results of the shrinkage deformation of steel slag concrete (i.e., autogenous shrinkage) with the experimental measured results for the predicted results of the shrinkage deformation of steel slag concrete with a closed water-binder ratio of 0.5 according to the prediction method of the steel slag concrete in the embodiment of the present invention;

[0042] Figure 4 This is a comparison chart of the predicted results of the shrinkage deformation of steel slag concrete (i.e., total shrinkage) with the experimental measured results for the open steel slag concrete with a water-binder ratio of 0.3 by the prediction method of the shrinkage deformation of steel slag concrete in the embodiment of the present invention;

[0043] Figure 5 The figure is a comparison chart of the predicted results of the shrinkage deformation of steel slag concrete (i.e., total shrinkage) with the experimental measured results for the open steel slag concrete with a water-binder ratio of 0.5 according to the prediction method of the shrinkage deformation of steel slag concrete in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the scheme of the present invention, exemplary implementations or embodiments of the present invention will be described below in conjunction with the accompanying drawings. Obviously, the described implementations or embodiments are only implementations or embodiments of a part of the present invention, not all of them. Based on the implementations or embodiments of the present invention, all other implementations or embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present invention.

[0045] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0046] Specific implementation plan 1: Figure 1 As shown, the present invention provides a method for predicting shrinkage deformation of steel slag concrete, which specifically includes the following steps:

[0047] (1) The calculation of the autogenous shrinkage value of steel slag concrete includes the following steps:

[0048] Obtain the autogenous shrinkage value of concrete without steel slag;

[0049] Considering the limiting effect of steel slag aggregate on the autogenous shrinkage of concrete, the equivalent aggregate-cement ratio of steel slag concrete is calculated based on the elastic modulus of steel slag aggregate and natural aggregate.

[0050] Based on the autogenous shrinkage value and equivalent cementitious ratio of concrete without steel slag, a prediction model for autogenous shrinkage of steel slag concrete was constructed.

[0051] (2) The calculation of the drying shrinkage value of steel slag concrete includes the following steps:

[0052] Obtain the drying shrinkage value of concrete without steel slag;

[0053] Considering the limiting effect of steel slag aggregate on the drying shrinkage of concrete, the equivalent aggregate volume fraction of steel slag concrete is calculated based on the elastic modulus of steel slag aggregate and natural aggregate.

[0054] Based on the drying shrinkage value of concrete without steel slag and the equivalent aggregate volume fraction, a drying shrinkage prediction model for steel slag concrete was constructed.

[0055] (3) Based on the autogenous shrinkage prediction model and drying shrinkage prediction model of steel slag concrete, a total shrinkage value prediction model for steel slag concrete is constructed.

[0056] Concrete is composed of two parts: cement paste and aggregate. In essence, the shrinkage deformation of concrete is mainly caused by the shrinkage of cement paste, while aggregate hardly produces shrinkage deformation, and only plays a role in limiting the shrinkage of cement paste. The limiting and restraining effect of aggregate on the shrinkage of cement paste is determined by the elastic modulus of aggregate: the larger the elastic modulus of aggregate, the greater the limiting and restraining effect of aggregate, which ultimately reduces the shrinkage deformation of concrete. Different from the previous empirical model, the present invention starts from the limiting and restraining effect of steel slag aggregate on the shrinkage of cement paste, and develops a prediction model for the shrinkage deformation of steel slag concrete based on the shrinkage mechanism.

[0057] Specific implementation scheme 2: The calculation method of the equivalent cementitious ratio (a / c) equ of the slag concrete in step (1) is:

[0058]

[0059] In the formula, a CSA and aFSA are the mass of natural aggregate (including coarse aggregate and fine aggregate), steel slag coarse aggregate and steel slag fine aggregate in unit volume of steel slag concrete, kg / m 3 ; c is the total mass of cement, mineral admixtures and other cementitious materials per unit volume, kg / m 3 , E SA and E NA Elastic modulus of steel slag aggregate and natural aggregate, GPa, when there is no clear test result The other aspects of this embodiment are the same as those of the first embodiment.

[0060] Specific implementation scheme 3: Autogenous shrinkage value of steel slag concrete in step (1) The prediction model is:

[0061]

[0062] In the formula, k a / c is the influence coefficient of the equivalent water-binder ratio of steel slag aggregate, that is:

[0063]

[0064] It is the mass of natural aggregate (including coarse aggregate and fine aggregate) in concrete per unit volume without steel slag, kg / m 3 , is the autogenous shrinkage value of concrete without steel slag (×10 -6 ). The rest of this embodiment is the same as the second specific embodiment.

[0065] Specific implementation scheme 4: Equivalent aggregate volume fraction (V A )equ is calculated as:

[0066]

[0067] In the formula, V CSA and V FSA are the volume fractions of natural aggregate (including coarse aggregate and fine aggregate), steel slag coarse aggregate and steel slag fine aggregate in steel slag concrete respectively. The rest of this embodiment is the same as the specific embodiment three.

[0068] Specific implementation scheme 5: Drying shrinkage value of steel slag concrete in step (2) The prediction model is:

[0069]

[0070] In the formula, is the influence coefficient of equivalent aggregate volume fraction of steel slag aggregate, that is:

[0071]

[0072] In the formula, is the volume fraction of natural aggregate (including coarse aggregate and fine aggregate) in concrete without steel slag. is the drying shrinkage value of concrete without steel slag (×10 -6 ). The rest of this embodiment is the same as the specific embodiment 4.

[0073] Specific implementation scheme 6: Total shrinkage value of steel slag concrete in step (3) The prediction model is:

[0074] The rest of this implementation plan is the same as the specific implementation plan five.

[0075] Specific implementation scheme seven: The autogenous shrinkage value of concrete without steel slag is obtained by experimental testing. If there is no clear test result, it is calculated based on the autogenous shrinkage model of European standard BS EN 1992. The rest of this implementation scheme is the same as the specific implementation scheme one.

[0076] Specific implementation scheme eight: The drying shrinkage value of concrete without steel slag is obtained by experimental testing. If there is no clear test result, it is calculated based on the autogenous shrinkage model of European standard BS EN 1992. The rest of this implementation scheme is the same as the specific implementation scheme one.

[0077] Example 1

[0078] According to the steel slag concrete mix ratio in Table 1, steel slag concrete and concrete test blocks without steel slag aggregate with a side length of 100mm×100mm×400mm were made. After curing for 24 hours, the test blocks were demolded. After demolding, three layers of aluminum foil with glue were used to seal the six surfaces to ensure that the concrete could not exchange moisture with the external environment, so that the concrete only produced self-shrinkage without drying shrinkage. An embedded strain gauge PMFL was used at the center point of the test block to monitor the development of shrinkage strain. A constant temperature and humidity environment with a relative humidity of 55% and a temperature of 22°C was set. In this embodiment, two concrete water-cement ratios of 0.3 and 0.5, three steel slag replacement rates of 0%, 50% and 100% were set, and the steel slag coarse aggregate replaced the natural aggregate in equal volume. The apparent densities of the raw materials are: cement 2500kg / m 3 , natural coarse aggregate 2765.6kg / m 3 , natural fine aggregate 2571.0kg / m 3 、Steel slag coarse aggregate 4133.9kg / m 3 , water reducing agent 1200kg / m 3 , water 1000kg / m 3The cement type is PO42.5 cement. The weight of each component and the average 28-day cylindrical compressive strength of concrete are shown in Table 1.

[0079] Table 1

[0080]

[0081] Pick The equivalent cementitious ratio (a / c) of steel slag concrete is calculated as:

[0082]

[0083] The autogenous shrinkage of steel slag concrete is calculated as:

[0084]

[0085] Among them, the autogenous shrinkage value of concrete without steel slag aggregate is The measurement was performed using the embedded strain gauge PMFL in this embodiment.

[0086] The comparison between the predicted results of the autogenous shrinkage of steel slag concrete with a water-binder ratio of 0.3 calculated by the method in this embodiment and the actual measured results is as follows: Figure 2 The comparison between the predicted results of the autogenous shrinkage of steel slag concrete with a water-binder ratio of 0.5 calculated by the method of this embodiment and the actual measured results is shown in Figure 2. Figure 3 As shown, it can be seen that the result of the steel slag concrete shrinkage deformation prediction method of the present invention is relatively accurate.

[0087] Example 2

[0088] According to the steel slag concrete mix ratio in Table 2, steel slag concrete and concrete test blocks without steel slag aggregate with a side length of 100mm×100mm×400mm were made. After curing for 24 hours, the test blocks were demolded. After demolding, the concrete test blocks were placed in a constant temperature and humidity environment with a relative humidity of 55% and a temperature of 22°C. In this example, there is moisture exchange between the concrete and the external environment, so that the concrete produces both autogenous shrinkage and drying shrinkage. Two stainless steel terminals with standard holes on the four surfaces of the test block, the terminal spacing is 200mm, and a detachable mechanical strain gauge (DEMEC) with a gauge length of 200mm is used to measure the shrinkage deformation of the concrete specimen. The deformation measured in the test is the total shrinkage, that is, the sum of autogenous shrinkage and drying shrinkage. In this embodiment, two concrete water-cement ratios of 0.3 and 0.5, three steel slag replacement rates of 0%, 50% and 100%, and steel slag coarse aggregate replaces natural aggregate in equal volume. The apparent densities of the raw materials are: cement 2500kg / m 3 , natural coarse aggregate 2765.6kg / m 3 , natural fine aggregate 2571.0kg / m 3 、Steel slag coarse aggregate 4133.9kg / m3 , water reducing agent 1200kg / m 3 , water 1000kg / m 3 The cement type is PO42.5 cement. The weight of each component and the average 28-day cylindrical compressive strength of concrete are shown in Table 2.

[0089] Table 2

[0090]

[0091] Pick Calculate the equivalent cementitious ratio of steel slag concrete:

[0092]

[0093] Calculate the equivalent aggregate volume fraction of steel slag concrete:

[0094]

[0095] Calculate the equivalent cementitious ratio of steel slag concrete:

[0096]

[0097] The drying shrinkage of steel slag concrete is calculated as:

[0098]

[0099] The total shrinkage of steel slag concrete is calculated as:

[0100]

[0101] Among them, the drying shrinkage value of concrete without steel slag aggregate is In this embodiment, a detachable mechanical strain gauge (DEMEC) with a gauge length of 200 mm is used for measurement.

[0102] The total shrinkage prediction results of steel slag concrete with a water-binder ratio of 0.3 calculated by the method in this embodiment are compared with the experimental measured results. Figure 4 The total shrinkage prediction results of steel slag concrete with a water-binder ratio of 0.5 calculated by the method of this embodiment are compared with the experimental measured results. Figure 5 As shown, it can be seen that the result of the steel slag concrete shrinkage deformation prediction method of the present invention is relatively accurate.

[0103] Although the present invention is disclosed as above, the protection scope of the present invention is not limited thereto. Those skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for predicting shrinkage deformation of steel slag concrete, characterized by: The specific steps include: (1) The calculation of the autogenous shrinkage value of steel slag concrete includes the following steps: Obtain the autogenous shrinkage value of concrete without steel slag; Considering the limiting effect of steel slag aggregate on the autogenous shrinkage of concrete, the equivalent aggregate-cement ratio of steel slag concrete is calculated based on the elastic modulus of steel slag aggregate and natural aggregate. Based on the autogenous shrinkage value and equivalent cementitious ratio of concrete without steel slag, a prediction model for autogenous shrinkage of steel slag concrete was constructed. (2) The calculation of the drying shrinkage value of steel slag concrete includes the following steps: Obtain the drying shrinkage value of concrete without steel slag; Considering the limiting effect of steel slag aggregate on the drying shrinkage of concrete, the equivalent aggregate volume fraction of steel slag concrete is calculated based on the elastic modulus of steel slag aggregate and natural aggregate. Based on the drying shrinkage value of concrete without steel slag and the equivalent aggregate volume fraction, a drying shrinkage prediction model for steel slag concrete was constructed. (3) Based on the autogenous shrinkage prediction model and drying shrinkage prediction model of steel slag concrete, a total shrinkage prediction model of steel slag concrete is constructed; Equivalent cement ratio (a / c) of slag concrete in step (1) equ The calculation method is: In the formula, a CSA and a FSA are the mass of natural aggregate, coarse aggregate and fine aggregate per unit volume of slag concrete, kg / m 3 ; c is the total mass of cementitious material per unit volume, kg / m 3 , E SA and E NA are the elastic modulus of slag aggregate and natural aggregate, GPa, respectively; The autogenous shrinkage value of steel slag concrete in step (1) The prediction model is: In the formula, k a / c is the influence coefficient of equivalent water-binder ratio of steel slag aggregate, that is: is the mass of natural aggregate in concrete per unit volume without steel slag, kg / m 3 , is the autogenous shrinkage value of concrete without steel slag (×10 -6 ); The equivalent aggregate volume fraction (V A ) equ The calculation method is: In the formula, V CSA and V FSA are the volume fractions of natural aggregate, steel slag coarse aggregate and steel slag fine aggregate in steel slag concrete respectively; Drying shrinkage value of steel slag concrete in step (2) The prediction model is: In the formula, is the influence coefficient of equivalent aggregate volume fraction of steel slag aggregate, that is: In the formula, is the volume fraction of natural aggregate in concrete without slag, is the drying shrinkage value of concrete without steel slag (×10 -6 ).

2. The method for predicting shrinkage deformation of steel slag concrete according to claim 1, characterized in that: The total shrinkage prediction model of steel slag concrete in step (3) is:

3. The method for predicting shrinkage deformation of steel slag concrete according to claim 1, characterized in that: The autogenous shrinkage value of concrete without slag is obtained by experimental testing or calculated based on the autogenous shrinkage model of European standard BS EN 1992.

4. The method for predicting shrinkage deformation of steel slag concrete according to claim 1, characterized in that: The drying shrinkage of concrete without slag is obtained by experimental testing or by calculation based on the autogenous shrinkage model of European standard BS EN 1992.

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