CN105155774A - Duplex channel steel and recycled concrete combination beam - Google Patents

Abstract

The invention discloses a double-layer channel steel-recycled concrete composite beam, comprising a first channel steel and a second channel steel riveted with the first channel steel, the bottom of the first channel steel is provided with a shear connector , the first channel-shaped steel is filled with recycled aggregate concrete; the second channel-shaped steel is fixedly connected by rivets, the thickness of the second channel-shaped steel web is greater than the thickness of the first channel-shaped steel web, and the recycled aggregate concrete The replacement rate of recycled aggregate is 50%. In the present invention, by arranging the lower channel steel to be tensioned and the concrete in the upper channel steel to be compressed, respective performances can be fully exerted, and the composite beam has stronger bending resistance; under the same performance, the weight of the present invention is lighter , which is conducive to improving the earthquake resistance; the invention can reduce the support and formwork in the construction stage, which brings great convenience to the construction; while the lower channel steel fully exerts the tensile strength, it simplifies the building structure, reduces the binding of steel bars, and improves the construction efficiency. construction efficiency.

Description

Double-layer channel steel-recycled concrete composite beam

technical field

The invention belongs to the field of building structures, in particular to a composite beam.

Background technique

With the progress of urbanization in China, the problem of construction waste (waste) has gradually been paid attention to. If a simple stacking method is adopted, the annual construction waste disposal will cover an area of at least 150 million square meters. Recycled concrete as a new material can solve this problem well.

With the development of social economy and building structure, more and more steel-concrete composite structures are used. The steel-concrete composite structure fully exerts the material mechanical properties of concrete under pressure and steel under tension. The application of steel can reduce the size of concrete structures. The excessively large cross-section reduces the self-weight and is conducive to the improvement of seismic performance.

The existing steel-concrete composite beam is to bury the section steel in the concrete. To prevent the flange of the section steel from buckling outwards and cause the concrete on the outside of the flange to crack, a certain thickness of concrete protective layer is required, which will cause the bending resistance of the section steel to be incomplete. , the concrete in the tension area does not play a role but increases the self-weight of the component; the concrete used is mostly reinforced concrete, although reinforced concrete can effectively restrain the joint action of steel and concrete, but most of the binding steel bars are manually bound, and the production efficiency Low, not conducive to factory mechanized production.

Contents of the invention

Purpose of the invention: to provide a double-layer channel steel-regenerated concrete composite beam to solve the above-mentioned problems in the prior art.

Technical solution: a double-layer channel steel-recycled concrete composite beam, characterized in that it includes a first channel steel and a second channel steel riveted with the first channel steel, and the bottom of the first channel steel is provided with anti- Shear connectors, the first channel-shaped steel is filled with recycled aggregate concrete; the second channel-shaped steel is fixedly connected by rivets, the thickness of the second channel-shaped steel web is greater than the thickness of the first channel-shaped steel web, and the recycled The replacement rate of recycled aggregate in aggregate concrete is 50%.

Further, the recycled aggregate concrete includes components in the following weight ratio, water: cement: sand: waste bricks: waste concrete blocks = 1: (2-2.5): (2-2.5): (1-1.2 ): (4.8～5.5).

Further, the recycled aggregate concrete includes components in the following weight ratio, water: cement: sand: waste bricks: waste concrete blocks = 1:2.27:2.27:1.04:5.21.

Further, the recycled aggregate concrete also includes the water demand calculated from the 10-min water absorption rate of the waste concrete aggregate.

Beneficial effects: in the present invention, by setting the channel steel in the lower layer under tension and the concrete in the upper channel steel under compression, their respective performances can be fully exerted, and the bending resistance of the composite beam is relatively strong; under the same performance, the present invention The weight is lighter, which is beneficial to improve the anti-seismic ability; different from the existing structure, the present invention can reduce the support and formwork in the construction stage, which brings great convenience to the construction; while the lower channel steel fully exerts the tensile strength, it greatly simplifies The building structure reduces steel bar binding and improves construction efficiency; various communication and electronic equipment can be easily arranged on the inner side of the lower channel steel, which can increase the net height of the house and improve space utilization. In a further embodiment, recycled aggregate concrete can use recycled construction waste to turn waste into treasure, save resources and protect the environment.

Description of drawings

Fig. 1 is a schematic cross-sectional view of a double-layer channel steel-recycled concrete composite beam according to an embodiment of the present invention.

Fig. 2 is a front view of a double-layer channel steel-regenerated concrete composite beam according to an embodiment of the present invention.

Detailed ways

As shown in Figure 1, a double-layer channel steel-recycled concrete composite beam includes a first channel steel 1 (viewed from the azimuth as the upper channel steel) and a second channel steel 2 riveted with the first channel steel 1 (from the From the perspective of orientation, it is the lower channel steel). The bottom of the first channel-shaped steel is provided with a shear connector 5, and the first channel-shaped steel is filled with recycled aggregate concrete 3.

As shown in Figures 1 and 2, the second channel-shaped steel is fixedly connected by rivets 4, and the thickness of the second channel-shaped steel web is greater than the thickness of the first channel-shaped steel web, so as to prevent the steel web of the second channel-shaped steel from being transmitted by the rivets. buckling under load.

The replacement rate of recycled aggregate in the recycled aggregate concrete is 50%. Further, the recycled aggregate concrete includes components in the following weight ratio, water: cement: sand: waste bricks: waste concrete blocks = 1: (2-2.5): (2-2.5): (1-1.2 ): (4.8～5.5).

In a further embodiment, the applicant has optimized the ratio of recycled aggregate concrete, and the more preferred ratio range is water: cement: sand: waste bricks: waste concrete blocks = 1: (2 ~ 2.5): ( 2～2.5):(1～1.2):(4.8～5.5).

Take concrete with strength grade C35 as an example:

The weight ratio of each component in Example 1 is water: cement: sand: waste bricks: waste concrete blocks = 1:2.27:2.27:1.04:5.21. The standard method is used for detection, and the experimental data are as follows: the slump is 180, the workability is excellent, the 7-day compressive strength is 28.5MPa, and the 28-day compressive strength is 43.5MPa.

1. Determine the preparation strength f _cu,0

f _cu.0 =f _cu,k +1.645σ

When the strength grade of concrete is C35, σ=5.0MPa, then

f _cu,0 ＝48.2MPa

2. Preliminary determination of the water-cement ratio W:C

Since the 28d measured strength f _ce of the cement used in this experiment is unknown, it is expected that the measured 28d strength of the cement can reach 48.0MPa. Coarse aggregate is gravel, A=0.46, B=0.07

$\frac{\mathrm{<span\; class="notranslate">\; W</span>}}{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; Af</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; e</span>}}}{{\mathrm{<span\; class="notranslate">\; f</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; u</span>}<span\; class="notranslate">\; ,</span>\mathrm{<span\; class="notranslate">\; 0</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; AB</span>}}_{\mathrm{<span\; class="notranslate">\; c</span>}\mathrm{<span\; class="notranslate">\; e</span>}}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 0.46</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 48.0</span>}}{\mathrm{<span\; class="notranslate">\; 48.2</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 0.46</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 0.07</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 48.0</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0.44</span>}$

3. Preliminary estimate of unit water consumption

The maximum particle size is 40mm. Because the waste concrete block is subjected to a large external force during the crushing process, and the waste concrete block will produce a large number of cracks during the firing process, the water absorption rate and water absorption rate of the recycled aggregate are much higher than that of the natural aggregate. It is generally believed that the water absorption rate of recycled coarse aggregate is about 5% higher than that of natural aggregate. Therefore, it needs to be adjusted on the basis of the initially set water consumption.

When the maximum particle size is 40mm, m _W0 = 175kg/m ³ , after adjustment, m _W = 184kg/m ³

4. Calculate the amount of cement

(1) $m_C=\frac{m_W}{W/C}=\frac{193}{0.44}=439kg$

(2) $m_C=\frac{m_W}{W/C}=\frac{184}{0.44}=418kg$

5. Preliminary selection of sand rate β _S

(1) The maximum particle size of crushed stone used in concrete is 30mm, the water-cement ratio is 0.44, and the linear look-up table β _S =33.2%

(2) The maximum particle size of crushed stone used in concrete is 40mm, the water-cement ratio is 0.44, and the linear look-up table β _S =30.7%

6. Calculate the amount of sand and equivalent stone m _S , m _G

$\frac{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}}{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; W</span>}}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}<span\; class="notranslate">\; +</span>\frac{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}}}{{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 10</span>}\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 1</span>}$

${\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}}{{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; S</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; m</span>}}_{\mathrm{<span\; class="notranslate">\; G</span>}}}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; 100</span>}\mathrm{<span\; class="notranslate">\; \%</span>}$

Simultaneously combine the above two formulas to solve the required m _S , m _G

7. Calculate the amount of waste bricks and waste concrete blocks that need to be replaced;

This experiment refers to the volume replacement rate (the expected replacement rate is 20% for discarded clay bricks and 80% for discarded concrete blocks). The density ρ _RB of discarded brick blocks and the density ρ _RC of discarded concrete blocks are calculated by the drainage replacement method. Find the mass of the waste brick body and waste concrete block mass needed:: $m_{RB}={\mathrm{\&rho;}}_{RB}\&times;\mathrm{no}\%\frac{m_G}{{\mathrm{\&rho;}}_G},m_{RC}={\mathrm{\&rho;}}_{RC}\&times;m\%\frac{m_G}{{\mathrm{\&rho;}}_G};$ In the formula, m _RB , ρ _RB are the mass and density of waste bricks, n is the volume replacement rate of waste bricks, m is the replacement rate of waste concrete blocks, m+n=1, m _RC , ρ _RC are respectively the mass and density of the discarded concrete blocks;

According to the above calculation, the concrete mix ratio is: m _W : m _C : m _S : m _RB : m _RC = 1:2.27:2.77:1.04:5.21.

Embodiments 2 to 5, the relevant process refers to Embodiment 1, adjusts relevant parameters, and obtains the ratio as follows:

The weight ratio of the components in Example 2 is water: cement: sand: waste bricks: waste concrete blocks = 1:2.11::2.48:1.15:5.25. The standard method is used for detection, and the experimental data are as follows: slump is 160, excellent workability, 7-day compressive strength is 22.5MPa, and 28-day compressive strength is 45MPa.

The weight ratio of the components in Example 3 is water: cement: sand: waste bricks: waste concrete blocks = 1:2.45:2.18:1.18:1.89. The standard method is used for detection, and the experimental data are as follows: the slump is 175, the workability is good, the 7-day compressive strength is 24.5MPa, and the 28-day compressive strength is 47.5MPa.

The weight ratio of the components in Example 4 is water: cement: sand: waste bricks: waste concrete blocks = 1:2.36:2.39:1.09:5.05. The standard method is used to test, the experimental data is as follows: slump 155, excellent workability, 7-day compressive strength 20.5MPa, 28-day compressive strength 48.5MPa.

The weight ratio of each component in Example 5 is water: cement: sand: waste bricks: waste concrete blocks = 1:2.40:2.06:1.12:5.15. The standard method is used for detection, and the experimental data are as follows: the slump is 185, the workability is good, the 7-day compressive strength is 21.5MPa, and the 28-day compressive strength is 46.5MPa.

The recycled aggregate concrete also includes the water demand calculated by the 10-min water absorption rate of the waste concrete aggregate.

The replacement rate of the control group is 0, and the 28d strength is about 48MPa. The strength of this implementation is basically the same, and the performance is better than the existing recycled aggregate concrete formula.

Example 6-8

Other processes refer to embodiment 1, in this group of embodiments,

The processing process of waste bricks is further as follows:

Remove impurities such as glass, plastic and steel bars in recycled aggregates (waste bricks and waste concrete blocks), and crush them with a jaw crusher; use 50mm aperture to sieve, and continue to crush the residue in the sieve, and the residue at the bottom of the sieve Sieve with a 20mm aperture, keep the residue in the sieve, and discard the residue at the bottom of the sieve; rinse the recycled aggregate with water and dry it in the air.

After calculating the ratio of water, cement, sand, gravel and discarded bricks, add recycled aggregate modified materials.

Recycled aggregate modified materials include: water reducing agent, reinforcing agent and expansion agent. The dosage of the water reducing agent is 0.1-0.5wt% of the total batching, the dosage of the reinforcing agent is 3-5wt% of the total batching, and the expansion agent is 1-3wt% of the total batching.

The structural formula of the water reducer is as follows:

Among them, R ₁ , R ₂ , R ₃ , R ₄ and R ₅ are all selected from H or CH ₃ , n is 35-55, m is 25-45, a, b, c and d are positive integers, M is one Valence cations.

The reinforcing agent is silica fume, and the expansion agent is sulphoaluminate.

The preparation method of above-mentioned novel polycarboxylate water reducer, the steps are as follows:

Step 1: Prepare or purchase the macromer, and weigh the raw materials according to the predetermined ratio;

Step 2: Add alkyl polyether, acrylic acid monomer, polymerization inhibitor, catalyst and water coordinating agent to the reaction kettle and raise the temperature to 160°C, carry out esterification reaction for 5 hours under reflux, and obtain an intermediate product; the catalyst is selected from sulfuric acid, One or more of toluenesulfonic acid, solid acid ZrO ₂ , said polymerization inhibitor is selected from one or more of hydroxyanisole, hydroquinone, sulfurized diphenylamine, and said water coordinating agent is selected from One or both of ethyl acetate and isoamyl alcohol.

Step 3: Separate the intermediate product and heat it to 90°C for dissolution, and add other monomers and initiator solutions dropwise at the same time. The dropping time is 1.2 hours. After the dropwise addition, keep warm for 6 hours. After the reaction is completed, cool to 40°C Adjust the pH to 7 with sodium hydroxide solution to obtain the target product.

In embodiment 6, the proportion of water, cement, sand, gravel and waste bricks is the same as that of embodiment 1, adding 0.26wt% water reducer, 4.1wt% reinforcing agent and 1.9wt% expansion agent.

In embodiment 7, the proportion of water, cement, sand, gravel and waste bricks is the same as that of embodiment 2, adding 0.11wt% water reducer, 3.2wt% reinforcing agent, and 2.7wt% expansion agent .

In Example 8, the ratio of cement, sand, gravel and waste bricks is the same as that of Example 3, and 0.45wt% of water reducer, 4.9wt% of reinforcing agent, and 1.2wt% of expansion agent are added.

Using the same test method, the obtained 28d strength data are as follows: 48.8, 53.4 and 55.5.

In this group of embodiments, cleaning the recycled aggregate can remove the dust attached to it, and at the same time, silica fume can reduce the void ratio and void size inside the concrete, improve the cement paste structure on the aggregate interface, and the pozzolanic effect of silica fume And particle filling effect, good adhesion between slurry and aggregate. High-efficiency water reducer can not only reduce the water-cement ratio, but more importantly, make the cement in the mixture more dispersed, so that the porosity and pore distribution after hardening can be further improved. The expansion agent can counteract the shrinkage produced by the recycled aggregate, and solve the problem of large shrinkage of the recycled aggregate concrete in the prior art.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be carried out to the technical solutions of the present invention. These equivalent transformations All belong to the protection scope of the present invention. In addition, it should be noted that the various specific technical features described in the above specific implementation manners may be combined in any suitable manner if there is no contradiction.

Claims (4)

1. A double-layer channel steel-recycled concrete composite beam, characterized in that it includes a first channel steel (1) and a second channel steel (2) riveted with the first channel steel, the first channel steel The bottom of the bottom is provided with a shear connector (5), and the first channel steel is filled with recycled aggregate concrete (3); the second channel steel is fixedly connected by rivets (4), and the web of the second channel steel The thickness is greater than the thickness of the first channel-shaped steel web, and the replacement rate of recycled aggregate in the recycled aggregate concrete is 50%. 2. The double-layer channel steel-regenerated concrete composite beam as claimed in claim 1, wherein said recycled aggregate concrete comprises the following components in weight ratio, water: cement: sand: waste bricks: waste concrete block=1:(2~2.5):(2~2.5):(1~1.2):(4.8~5.5). 3. The double-layer channel steel-regenerated concrete composite beam as claimed in claim 2, wherein said recycled aggregate concrete comprises the following components in weight ratio, water: cement: sand: waste bricks: waste concrete Block = 1:2.27:2.27:1.04:5.21. 4. The double-layer channel steel-regenerated concrete composite beam according to claim 2 or 3, wherein the recycled aggregate concrete also includes the water demand calculated from the water absorption rate of waste concrete aggregates in 10 minutes.