QUANTITATIVE EVALUATION METHOD FOR WORKABILITY OF CONCRETE BASED ON BOTTOM RESISTANCE ANALYSIS

Abstract

The present invention relates to a quantitative evaluation method for concrete workability based on bottom resistance, including the following steps: step 1, carrying out a test for bottom resistance of fresh concrete; step 2, drawing a curve of inserting velocity of steel sheet over time; and step 3, quantitatively evaluating a concrete workability based on conditions of the bottom resistance. This method can quantitatively characterize the sinking condition of aggregate of the fresh concrete by effectively carrying out the test for bottom resistance of fresh concrete, calculating the inserting velocity of concrete and drawing the curves of displacement and velocity over time, so as to achieve the quantitative evaluation for concrete workability and overcome the defects of conventional methods that it is difficult to quantitatively characterize the segregation degree of concrete.

Claims

1. A quantitative evaluation method for concrete workability based on bottom resistance analysis, comprising the following steps: step 1: carrying out a test for a bottom resistance of fresh concrete: placing a concrete container on a level platform, filling with the fresh concrete which has been already mixed evenly, removing a residual concrete from a surface of the container and vibrating sufficiently, inserting a steel sheet into a bottom of the concrete, recording a displacement of the steel sheet and a corresponding time; step 2: drawing a curve of inserting velocity of the steel sheet over time: drawing a curve of displacement of the steel sheet over time based on the data of the displacement of the steel sheet and the corresponding time, and by deriving the curve of the displacement of the steel sheet over time to analyze the inserting velocity and time, then drawing the curve of the inserting velocity of the steel sheet over time; and step 3: quantitatively evaluating the concrete workability based on conditions of the bottom resistance: based on the curve of the displacement of the steel sheet over time determined by the test for the bottom resistance, evaluating the concrete workability by using a calculation model of coefficient of colligation for the concrete workability to solve the coefficient of the colligation for the concrete workability, the calculation model of the coefficient of the colligation for the concrete workability is as follows by integral calculation with an interval of v>100 mm/s: $W=\underset{i=1}{\overset{n}{.Math.}}{\int }_{t_{i1}}^{t_{i2}}v\left(t\right)dt$ wherein W is the coefficient of the colligation for the concrete workability, n is a number of the interval, t.sub.i1 is a starting-point of the interval, t.sub.i2 is an end-point of the interval, i=1, 2, . . . , n.

2. The quantitative evaluation method for the concrete workability based on the bottom resistance analysis according to claim 1, wherein water and slurry float up from a segregated bleeding concrete, and sinking stones cement with a base tightly, resistance of aggregate is resulted at the bottom, and by determining a segregation degree of the concrete through a degree of the aggregate sank, cohesion and water retention of the concrete workability are quantitatively evaluated.

3. The quantitative evaluation method for the concrete workability based on the bottom resistance analysis according to claim 1, wherein the test for the bottom resistance of the fresh concrete is as follows: mixing water, cement, grit, crushed stones and a water reducer according to a ratio to prepare the fresh concrete for use, wherein a mass ratio of the water, the cement, the grit to the crushed stones is 1:2.01:4.57:5.90, adding the water reducer having a gelling material mass of 0.22%-0.66%, filling the concrete container with the fresh concrete, upon sufficient vibration, wiping up the surface of the concrete container, fixing the steel sheet and a spring to a digital caliper with screws, pulling a vernier of the caliper to the bottom by using an insertion force provided by the spring, allowing the spring to be in a stress state, releasing the vernier so that a steel ruler on the vernier is inserted to the bottom of concrete with the coiled spring, and automatically recording the displacement of the steel sheet and the corresponding time by connecting the digital caliper to a computer.

4. The quantitative evaluation method for the concrete workability based on the bottom resistance analysis according to claim 1, wherein the test for the bottom resistance of the fresh concrete is as follows: mixing water, cement, grit, crushed stones and a water reducer according to a ratio to prepare the fresh concrete for use, wherein a mass ratio of the water, the cement, the grit to the crushed stones is 1:2.01:4.57:5.90, adding the water reducer having a gelling material mass of 0.44%, filling the concrete container with the fresh concrete, upon sufficient vibration, wiping up the surface of the concrete container, fixing the steel sheet and a spring to a digital caliper with screws, pulling a vernier of the caliper to the bottom by using an insertion force provided by the spring, allowing the spring to be in a stress state, releasing the vernier so that a steel ruler on the vernier is inserted to the bottom of concrete with the coiled spring, and automatically recording the displacement of the steel sheet and the corresponding time by connecting the digital caliper to a computer.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0022] FIG. 1 is a schematic diagram of tests for bottom resistance in Embodiments 1 and 2.

[0023] FIG. 2 is a schematic diagram of a curve of displacement of steel sheet over time in Embodiment 1.

[0024] FIG. 3 is a schematic diagram of a curve of inserting velocity of steel sheet over time in Embodiment 1.

[0025] FIG. 4 is a schematic diagram of a curve of displacement of steel sheet over time in Embodiment 2.

[0026] FIG. 5 is a schematic diagram of a curve of inserting velocity of steel sheet over time in Embodiment 2.

DETAILED DESCRIPTION

[0027] The technical solutions of the present invention are further described in detail in combination with the following embodiments and accompanied drawings.

Embodiment 1

[0028] A quantitative evaluation method for concrete workability based on bottom resistance according to the present invention included the following steps:

[0029] Step 1: Carrying Out a Test for a Bottom Resistance of Fresh Concrete:

[0030] water, cement, grit, crushed stones and a water reducer were mixed according to a ratio to prepare a fresh concrete for use, wherein a mass ratio of the water, the cement, the grit to the crushed stones was 1:2.22:3.65:4.65. The water reducer having a gelling material mass of 0.44% was added. The concrete at this moment had severe segregation and bleeding. A concrete container was filled with the fresh concrete, and upon sufficient vibration, surface of the concrete container was wiped up. A steel sheet and a spring were fixed to a digital caliper with screws, and an insertion force was provided by the spring shown as FIG. 1. A vernier of the caliper was pulled to the bottom, allowing the spring to be in a stress state, and the vernier was released so that a steel ruler on the vernier was inserted to the bottom of concrete with the coiled spring. Displacement of steel sheet and a corresponding time were automatically recorded by connecting the digital caliper to a computer.

[0031] Step 2: Drawing a Curve of Inserting Velocity of Steel Sheet Over Time:

[0032] a curve of displacement of steel sheet over time was drawn based on the data of the displacement of steel sheet and the corresponding time, and by deriving the curve of displacement of steel sheet over time to analyze the inserting velocity and time, then a curve of inserting velocity of steel sheet over time was drawn, shown as FIG. 2 and FIG. 3.

[0033] Step 3: Quantitatively Evaluating a Concrete Workability Based on Conditions of the Bottom Resistance:

[0034] based on the curve of displacement of steel sheet over time determined by the test for bottom resistance, coefficient of colligation for concrete workability W was determined by using a calculation model of coefficient of colligation for concrete workability which was 45 mm, and a corresponding slump was 200 mm and a divergence was 640*520. Severe segregation and bleeding were observed in the concrete already.

Embodiment 2

[0035] A quantitative evaluation method for concrete workability based on bottom resistance according to the present invention included the following steps:

[0036] Step 1: Carrying Out a Test for Bottom Resistance of Fresh Concrete:

[0037] water, cement, grit, crushed stones and a water reducer were mixed according to a ratio to prepare a fresh concrete for use, wherein a mass ratio of the water, the cement, the grit to the crushed stones was 1:2.01:4.57:5.90. The water reducer having a gelling material mass of 0.44% was added. The concrete at this moment had good flowability, and no segregation or bleeding occurred in the concrete through visual inspection. A concrete container was filled with the fresh concrete, and upon sufficient vibration, surface of the concrete container was wiped up. A steel sheet and a spring were fixed to a digital caliper with screws, and an insertion force was provided by the spring shown as FIG. 1. A vernier of the caliper was pulled to the bottom, allowing the spring to be in a stress state, and the vernier was released so that a steel ruler on the vernier was inserted to the bottom of concrete with the coiled spring. Displacement of steel sheet and a corresponding time were automatically recorded by connecting the digital caliper to a computer.

[0038] Step 2: Drawing a Curve of Inserting Velocity of Steel Sheet Over Time:

[0039] a curve of displacement of steel sheet over time was drawn based on the data of the displacement of steel sheet and the corresponding time, and by deriving the curve of displacement of steel sheet over time to analyze the inserting velocity and time, then a curve of inserting velocity of steel sheet over time was drawn, shown as FIG. 4 and FIG. 5.

[0040] Step 3: Quantitatively Evaluating a Concrete Workability Based on Conditions of the Bottom Resistance:

[0041] based on the curve of displacement of steel sheet over time determined by the test for bottom resistance, coefficient of colligation for concrete workability W was determined by using a calculation model of coefficient of colligation for concrete workability which was 71 mm, and a corresponding slump was 200 mm and a divergence was 450*470. Good workability was observed in the concrete.

[0042] Multiple groups of tests were carried out according to the same steps as above, and test results are shown in the table below:

TABLE-US-00001 TABLE 1 Slump, Water Workability Divergence Test Group Water Cement Grit Stones reducer condition (mm) result 1 1 2.01 4.57 5.90 0.22% No 140, 400*380 95 mm segregation or bleeding 2 1 2.01 4.57 5.90 0.44% No 200, 470*450 71 mm segregation or bleeding 3 1 2.01 4.57 5.90 0.66% Slight 200, 540*520 64 mm segregation and bleeding 4 1 2.01 4.57 5.90   1% Severe 240, 700*650 53 mm segregation and bleeding 5 1 2.22 3.65 4.65 0.44% Severe 200, 640*520 45 mm segregation and bleeding

[0043] The test results show that under the condition of the same ratio, the concrete workability was changed by varying an addition amount of the water reducer. As the water reducer was increased, the condition of concrete changed from poor flowability to good workability, and then to severe segregation and bleeding. The test results decrease with the aggravation of concrete segregation and bleeding, and have good discrimination, which can better quantitatively evaluate the workability of concrete.