CN105181527B - A kind of slump cone and Test Method For Workability of Self-compacting Concrete - Google Patents

Abstract

A slump cylinder, which includes a slump cylinder and a reinforcement grid, the slump cylinder is a tower-shaped cylinder with a thin top and a thick bottom, the thickness of the cylinder is 1.5mm, handles are arranged on both sides of the outer wall of the cylinder, and the reinforcement grid is fixed At the bottom of the slump cylinder, the steel bars are ribbed steel bars or smooth round steel bars with a diameter of 12mm, and the net spacing of the steel bars is 41mm or 59mm. Using the above slump cylinder to test the workability of self-compacting concrete is to add the prepared self-compacting concrete mixture into the slump cylinder, quickly extract the slump cylinder vertically to a height of about 300mm, and observe that the concrete passes through the steel bar For the state behind the gate, the fluidity is evaluated by the degree of expansion S _F , the gap passing performance is evaluated by the complete discharge time T _F and the ellipticity δ, and the segregation resistance is evaluated by the visual stability index method VSI. The invention has the advantages of simple structure, convenient and quick use; one test can simultaneously test the fluidity, gap passing property and segregation resistance of the self-compacting concrete.

Description

A slump cylinder and self-compacting concrete workability test method

technical field

The invention belongs to the field of building materials, in particular to a self-compacting concrete workability testing device and testing method.

Background technique

At present, self-compacting concrete (SCC for short) is a new type of high-performance concrete. As the name suggests, self-compacting concrete can fill the formwork voids through steel bars only by its own weight. In order to achieve the expected performance, self-compacting concrete has high requirements for workability. The workability of self-compacting concrete mixtures is divided into three aspects: fluidity, gap passage and segregation resistance. There are corresponding test methods for the performance of the three aspects. The fluidity is generally tested by slump spread and T ₅₀ , and the gap passes The resistance is generally tested by methods such as J ring and L box, and the segregation resistance is tested by sieve analysis test and visual stability index. Each test method can basically only reflect a certain aspect of the workability of self-compacting concrete, and cannot fully cover the three aspects of the workability of self-compacting concrete. Two or three test methods must be used to compare the workability of self-compacting concrete. Comprehensive testing and evaluation. This is not only time-consuming and labor-intensive, but also may lead to poor composite performance of the measured properties. Only when the three aspects of concrete workability meet the requirements can self-compacting be realized. Once the concrete mixture that does not meet the workability standards is poured during on-site construction, it will be difficult to repair afterwards, which will seriously affect the quality of the project. Therefore, it is particularly important to control the workability of self-compacting concrete in advance, and it is urgent to develop a test method suitable for construction site application that can quickly and simultaneously obtain fluidity, gap passage and segregation resistance through only one test.

The slump cylinder is commonly used to test the workability of concrete in the field. Starting from the principle of self-compacting concrete workability test, the slump cylinder is improved, and a workability test method is proposed to test the workability of self-compacting concrete mixture. It can conveniently and quickly test the fluidity, gap passage and segregation resistance of self-compacting concrete, and is suitable for on-site operation.

Contents of the invention

The object of the present invention is to provide a slump cylinder and self-compacting concrete workability testing method which has a simple structure and can be tested conveniently and quickly.

The slump cylinder of the present invention comprises a slump cylinder and a steel bar grid, wherein the slump cylinder is a tower-shaped cylinder with a thin top and a thick bottom, the thickness of the cylinder is 1.5 mm, and it is above the two sides of the outer wall of the cylinder. There are two opposite handles, the steel bar grid is fixed at the bottom of the slump cylinder, the lower skin of the steel bar grid is flush with the bottom of the slump tube, and the longitudinal ribs at both ends of the steel bar section of the steel bar grid are at the same height and arranged at equal intervals , the steel bars are ribbed steel bars or smooth round steel bars with a diameter of 12mm, and the net spacing of the steel bars is 41mm, which is suitable for testing the workability of the self-compacting concrete aggregate with a maximum particle size of 20mm; the net spacing of the steel bars is 59mm, which is suitable for testing the self-compacting concrete The workability of the maximum particle size of the aggregate is 25mm.

Use the above slump cylinder to test the workability of self-compacting concrete as follows:

1) Place the tablet on a flat ground and check whether it is level;

2) Wet the surface of the plate and wipe off the free water on the surface;

3) Place the wetted slump cylinder on the flat plate to coincide with the 210mm diameter circle in the central area;

4) Press down on the slump cylinder, slowly add the self-compacting concrete mixture into the slump cylinder in a continuous manner, do not perform any compaction operation on the mixture in the slump cylinder, and then scrape the slump Sweep the excess mixture on the surface of the upper end of the cylinder, and remove the mixture falling on the flat plate;

5) Quickly and vertically extract the slump cylinder to a height of about 300mm. The self-compacting concrete mixture will stay in the cylinder for a period of time after the slump cylinder is lifted. Oval guide after the tube is released;

6) Record the time T _F for the self-compacting concrete mixture to come out of the cylinder completely. When the mixture no longer flows, measure its diameter D ₁ along the direction of the reinforcement and D ₂ perpendicular to the direction of the reinforcement, and use the degree of expansion S _F to evaluate the fluidity of the concrete;

7) Observe with the naked eye whether there is segregation in the expanded concrete (surrounding bleeding or aggregate accumulation, etc.), give the VSI value, calculate the expansion degree S _F =(D ₁ +D ₂ )/2, and the ellipticity δ=(D ₁ -D ₂ )/(D ₁ +D ₂ ); Evaluate the passability of concrete gaps by using the time T _F and ellipticity δ; Evaluate the segregation resistance of concrete by using the visual stability VSI index method.

Compared with the prior art, the present invention has the following advantages:

1. Simple structure, convenient and fast to use;

2. One test can test the fluidity, gap passage and segregation resistance of self-compacting concrete at the same time;

3. Be able to distinguish the cause of poor clearance.

Description of drawings

Fig. 1 is the front view of the slump cylinder of the present invention.

Fig. 2 is the bottom view of the slump cylinder with a steel bar net spacing of 41 mm according to the present invention.

Fig. 3 is the bottom view of the slump cylinder with a steel bar net spacing of 59mm in the present invention.

Detailed ways

In the schematic diagram of the slump cylinder shown in Figure 1, the slump cylinder 1 is a tower-shaped cylinder with a thin top and a thick bottom, and two opposite handles 2 are arranged above the two sides of the outer wall of the cylinder. Welded at the bottom of the slump cylinder, the lower surface of the reinforcement grid is flush with the bottom of the slump cylinder, and the longitudinal ribs at both ends of the steel bar section of the reinforcement grid are at the same height and arranged at equal intervals. Figure 2 shows a ribbed steel bar with a diameter of 12mm. The net spacing is 41mm, which is suitable for testing the workability of self-compacting concrete aggregates with a maximum particle size of 20mm; Figure 3 shows that the steel bars with a diameter of 12mm are light round steel bars with a net spacing of 59mm, which is suitable for testing self-compacting concrete aggregates with a maximum particle size of 25mm Workability.

Using the above slump cylinder to test the workability of self-compacting concrete:

1) Place the tablet on a flat ground and check whether it is level;

2) Wet the surface of the plate and wipe off the free water on the surface;

3) Place the wetted slump cylinder on the flat plate to coincide with the 210mm diameter circle in the central area;

4) Press down on the slump cylinder, slowly add the self-compacting concrete mixture into the slump cylinder in a continuous manner, do not perform any compaction operation on the mixture in the slump cylinder, and then scrape the slump Sweep the excess mixture on the surface of the upper end of the cylinder, and remove the mixture falling on the flat plate;

5) Quickly and vertically extract the slump cylinder to a height of about 300mm. The self-compacting concrete mixture will stay in the cylinder for a period of time after the slump cylinder is lifted. Oval guide after the tube is released;

6) Record the time T _F for the self-compacting concrete mixture to come out of the cylinder completely. When the mixture no longer flows, measure its diameter D ₁ along the direction of the reinforcement and D ₂ perpendicular to the direction of the reinforcement, and use the degree of expansion S _F to evaluate the fluidity of the concrete;

7) Observe with the naked eye whether there is segregation in the expanded concrete (surrounding bleeding or aggregate accumulation, etc.), give the VSI value according to Table 1, and calculate the expansion degree S _F = (D ₁ + D ₂ )/2, ellipticity δ =(D ₁ -D ₂ )/(D ₁ +D ₂ ); Evaluate concrete gap passability by using time T _F and ellipticity δ; Evaluate concrete segregation resistance by visual stability VSI index method.

Table 1 Value and evaluation of visual stability index (VSI)

According to the adjustment of the amount of cementitious material, sand ratio, tackifier and water reducing agent, five self-compacting concretes in different states were prepared to evaluate the feasibility of improving the slump cylinder. Table 2 is the mix ratio of self-compacting concrete, and Table 3 is the test results.

Table 2 test mix ratio

Table 3 Workability test results

According to the test results in Table 3, the slump cylinder spread of the present invention has a clear correlation with the slump spread test, and the spread S _F can be used to characterize the fluidity of concrete. The steel grid hinders the smooth discharge of the concrete, which increases the discharge time and the elliptical guidance of the concrete after discharge. The time T _F of the complete cylinder is the ability of the concrete to pass through the steel bar, and the ellipticity δ is the degree of ovalization of the concrete after the cylinder. _TF is more sensitive to the poor passability of the gap caused by fluidity, and δ is more sensitive to the poor passability of the gap caused by cohesion. Using _TF and δ to judge the passability of the concrete gap, and can distinguish the cause of the poor passability of the gap Is it insufficient fluidity or insufficient cohesion. The visual stability index (VSI) was used to determine the segregation resistance of concrete mixtures.

The above test verification: S _F is between 600mm ~ 700mm, the fluidity is good; T _F is between 4s ~ 21s, δ ≤ 2.4%, the gap passage is good; VSI ≤ 1, the segregation resistance is good, if in Outside this range, the concrete state needs to be adjusted accordingly. If _TF is large, poor gap permeability is caused by insufficient fluidity; if δ is large, poor gap permeability is caused by insufficient cohesion.

Claims (2)

1. a kind of slump cone, it includes slump cone and reinforcing bar grid, and the slump cone is up-thin-low-thick turriform cylinder, cylinder Body thickness 1.5mm, two opposite handles are equipped with the top of the outer wall both sides of cylinder, it is characterised in that：The reinforcing bar grid are consolidated Slump cone bottom is scheduled on, reinforcing bar grid lower epidermis is concordant with slump cone bottom, and the steel area both ends longitudinal rib of reinforcing bar grid is same One height, and equidistantly arrange, the reinforcing bar is the Ribbed Bar or plain bar of diameter 12mm, and reinforcing bar clear spacing is 41mm, Workability suitable for testing self-compacting concrete maximum aggregate size 20mm；Reinforcing bar clear spacing is 59mm, suitable for test certainly The workability of air-free concrete maximum aggregate size 25mm.

2. the slump cone of usage right requirement 1 is to Test Method For Workability of Self-compacting Concrete, as follows：

Tablet is placed on smooth ground, checks whether level；Wetting planar surface simultaneously dries the Free water on surface；Flat The slump cone of wettability treatment is placed through on plate, is overlapped with center 210mm diameter circles；Slump cone is pushed down, mixing is good Autodensing concrete almixture be slowly added in a continuous manner in slump cone, not in slump cone mixture carry out Any closely knit operation, then strikes off the unnecessary mixture of slump cone end surfaces suitable for reading, and removes the mix on tablet that drops Thing, it is characterised in that：

1) rapid vertical extraction slump cone is highly located to general 300mm, and autodensing concrete almixture lifts in slump cone After can be detained in cylinder a period of time, reinforcing bar grid are ellipse after cylinder along reinforcing bar direction and vertical reinforcing bar direction dissimilarity, is added out Sphering is oriented to；

2) record autodensing concrete almixture goes out a time T completely_F, it is measured when mixture no longer flows along reinforcing bar direction Diameter D₁With vertical reinforcing bar orient diameter D₂, using divergence S_FEvaluate concrete flowability；

3) concrete to detect by an unaided eye after extending provides VSI values, calculates divergence S with the presence or absence of isolation_F=(D₁+D₂)/2, Ovality δ=(D₁-D₂)/(D₁+D₂)；Using going out a time T_FConcrete clearance through is evaluated with ovality δ；It is steady using vision Qualitative VSI index methods evaluate agent on crack resistance of concrete segregability.