JP4262167B2 - Evaluation parameter estimation method for high fluidity concrete - Google Patents

Description

  The present invention relates to a method for estimating an evaluation parameter of high-fluidity concrete, and more particularly to a method for estimating a slump flow value and a 500 mm flow arrival time of high-fluidity concrete only by a simple experiment.

  High-fluidity concrete is a concrete with excellent filling performance that has both high fluidity and material separation resistance, and can be densely filled even in an overcrowded part of a complex-shaped structure or bar arrangement. Has advantages. In addition, high-fluidity concrete is designed according to the shape and dimensions of the target structure, the bar arrangement, the construction conditions, and the like.

  The mixing of high fluidity concrete includes cement, water, fine aggregate (for example, sand having a particle size of less than 5 mm), coarse aggregate (for example, gravel having a particle size of 5 mm or more and 40 mm or less) and additives (high performance AE). Water reducing agents, separation reducing agents, etc.) are kneaded together, but since no blending design method has been established, blending is carried out by trial and error according to the requirements at the construction site. Highly fluidized concrete that has been mixed is evaluated by a slump flow test, etc., and only those that meet the requirements at the construction site are used at the construction site, and the evaluation by the slump flow test meets the requirements at the construction site. If not, re-formulation and evaluation tests will be repeated. In addition, the high fluidity concrete is manufactured in a factory away from the construction site, and is transported to the construction site by a concrete mixer truck or the like.

  The slump flow value test is standardized as JISA1150 (2001) (a method of testing a slump flow value of concrete). This test method involves actually mixing cement, water, fine aggregate, coarse aggregate and admixture to prepare high-fluidity concrete, and performing a predetermined experiment to determine a slump flow value (Sf) and a 500 mm flow arrival time ( Fv) is measured.

  However, in order to prepare high-fluidity concrete by actually mixing cement, water, fine aggregate, coarse aggregate and admixture, a great deal of labor and time are required including procurement of materials (for example, 1 formulation in 6 days). In addition, as a result of the slump flow test after mixing, if an appropriate slump flow value and 500 mm flow arrival time cannot be obtained, re-mixing and re-testing will be required, resulting in an increase in the manufacturing price of high-fluidity concrete. It was.

  Therefore, the present invention provides accurate slump flow value (Sf) and 500 mm flow arrival time (Fv) without actually mixing cement, water, fine aggregate, coarse aggregate and admixture to prepare high-fluidity concrete. It is an object to provide an estimation method that can be well estimated.

  In order to solve the above-mentioned problems, according to the slump flow value and the 500 mm flow arrival time estimation method according to the present invention, a blended mortar in which only coarse aggregate is not mixed is manufactured from the high-fluidity concrete to be measured, and the blended mortar The plastic viscosity, yield value and fine aggregate to water ratio of the mortar were measured, and the plastic viscosity, yield value and fine aggregate to water ratio of the blended mortar were measured. Estimate the aggregate to water ratio, and use the estimated corrected mortar plastic viscosity, yield value and fine aggregate to water ratio to estimate the plastic viscosity, yield value and fine aggregate to water ratio of the screening mortar. The slump flow value and 500 mm flow arrival time are estimated using the estimated plastic viscosity and yield value of the screening mortar.

  According to the present invention, it is possible to accurately estimate the slump flow value and 500 mm flow arrival time of high-fluidity concrete only by producing a comparatively time-consuming blended mortar without actually producing laborious high-fluidity concrete. Therefore, it is possible to save labor and labor for preparing high-fluidity concrete, and it is possible to produce high-fluidity concrete that meets the requirements of the construction site at low cost.

  Hereinafter, an evaluation parameter estimation method for high fluidity concrete according to the present invention will be described with reference to the drawings.

  In the present invention, it takes a great deal of labor to actually produce a high fluidity concrete, because the coarse aggregate needs to be sufficiently kneaded with other materials. Based on the knowledge that it takes less time to create the mortar before mixing (hereinafter referred to as blended mortar), the blended mortar is used to accurately estimate the evaluation parameters of high fluidity concrete. Is.

  Specifically, the blended mortar before the coarse aggregate is mixed is actually manufactured, the rheological properties of the blended mortar are actually measured, the rheological properties of the corrected mortar are estimated based on the measured values, and then corrected The rheological properties of the screening mortar are estimated based on the estimated value of the mortar, and finally the slump flow value (Sf) and the 500 mm flow arrival time (Fv) of the high-fluidity concrete are estimated based on the estimated value of the screening mortar. .

  Hereinafter, the interrelationship between high fluidity concrete, screening mortar, correction mortar, and blended mortar will be described.

Screening mortar refers to a mortar portion obtained by wet screening high-fluidity concrete. Wet screening refers to screening mortar through a kneaded high fluid concrete through a 5 mm wire mesh. When screening is performed through a 5 mm mesh, coarse aggregate remains on the mesh, and other portions pass through the mesh. That is, screening mortar contains water, fine aggregate, cement, etc., and there is a causal relationship between the screening mortar and the slump flow value (Sf) and high flow time (Fv) of high-fluidity concrete. To do. Therefore, from the correlation analysis and factor analysis between screening mortar and high-fluidity concrete, as an influencing factor capable of expressing Sf and Fv of high-fluidity concrete, V _G (unit coarse aggregate amount: L / m ³ ), The plastic viscosity ηw and the yield value τw of the screening mortar were extracted.

The experimental results, since it is a Sf and Fv and V _G is the relationship of the primary proportion is found, represents the slope and intercept in a plastic viscosity ηw and yield value τw screening mortar, just special HYPOTHETICAL equation solution Introduced universality that does not become. According to such a process, the following formulas (1) and (2) in which Sf and Fv of the high-fluidity concrete were expressed by V _G , ηw, and τw were derived.
Sf = (0.136−0.114τw−0.0171ηw) V _G + (628 + 33.4τw + 3.37ηw) Equation (1)
Fv = (− 0.468−0.00393τw + 0.0412ηw) V _G + (176 + 0.714τw−12.9ηw) Equation (2)
Next, considering the relationship between screening mortar and blended mortar, the difference between the two mortars is that the blended mortar lacks the mortar content (water, fine aggregate and cement) attached to the coarse aggregate. is there. Therefore, by analyzing how much the mortar content attached to the coarse aggregate is by experiment, based on the analysis results, it corresponds to the one obtained by subtracting the mortar content attached to the coarse aggregate, Created the concept of corrected mortar.

Furthermore, the ratio of fine aggregate to water ((S / W) w / (S / W) c) is extracted from the correlation analysis between screening mortar and correction mortar as an influencing factor that associates screening mortar with correction mortar. Then, the following formula (3) representing the relationship between the fine aggregate / water of the screening mortar and the fine aggregate / water of the correction mortar was derived.
(S / W) w = (0.0006V _G +0.9091) (S / W) c− (0.0002V _G +0.1726) Equation (3)
Furthermore, it was discovered that the ratio of fine aggregate / water and rheological properties in the screening mortar and correction mortar are linearly proportional, and the ηw and τw of the screening mortar are set to the ratio of fine aggregate / water, The following formulas (4) and (5) represented by the plastic viscosity ηc and the yield value τc were derived.
ηw = (6.88 (S / W) w / (S / W) c−5.57) ηc Equation (4)
τw = (13.5 (S / W) w / (S / W) c-11.4) τc Equation (5)
Next, a linear function indicating the relationship between the corrected mortar and the blended mortar is constructed, and the relationship between the fine aggregate / water ratio of the corrected mortar and the fine aggregate / water ratio of the blended mortar (6) Furthermore, equations (7) and (8) in which ηc and τc of the corrected mortar are expressed by a plastic viscosity ηb and a yield value τb of the blended mortar were derived as shown below.
(S / W) c = 1.02 (S / W) b + 0.198 Formula (6)
ηc = 1.59 ηb−1.33 Formula (7)
τc = 0.978τb + 2.00 (8)
As mentioned above, the slump flow value (Sf) and the 500 mm flow arrival time (Fv) of high-fluidity concrete are related to the blended mortar through an intermediate concept with parametric elements of screening mortar and correction mortar. Became possible.

  In FIG. 1, an example of the procedure of the evaluation parameter estimation method of the high fluidity concrete which concerns on this invention is shown.

First, blending design of high fluidity concrete to be evaluated is performed (step 101). The mixing design of high-fluidity concrete is to determine the mixed cement, fine aggregate, coarse aggregate, admixture (high performance AE water reducing agent, separation reducing agent, etc.) and water distribution and the type of each element. . Thereby, the unit coarse aggregate amount V _G (L / m ³ ) is determined.

  Next, the blended mortar is actually kneaded and prepared, and the plastic viscosity ηb (Pa · s) and the yield value τb (Pa) of the blended mortar are actually measured using the prepared blended mortar (step 102). As described above, the blended mortar refers to the high fluidity concrete before the coarse aggregate is mixed, and is based on the same design as the high fluidity concrete to be evaluated except that the coarse aggregate is not mixed.

  Here, the plastic viscosity ηb (Pa · s) and the yield value τb (Pa) of the blended mortar were measured using an inner disk type rotational viscometer. The measurement was carried out using a rotor with a diameter of 35 mm, rotating in the order of 2.5 rpm → 5.0 rpm → 10 rpm → 20 rpm → 50 rpm → 20 rpm → 10 rpm → 5 rpm → 2.5 rpm. The degree of shear stress was linearly regressed, the intercept was the yield value τb (Pa), and the gradient was the plastic viscosity ηb (Pa · s).

  The fine aggregate to water ratio ((S / W) b) of the blended mortar may be derived from the design value or measured from the blended mortar, but is measured in this embodiment.

  Next, the ratio of fine aggregate to water in the corrected mortar using the ratio of fine aggregate and water in the blended mortar ((S / W) b), the plastic viscosity ηb and the yield value τb measured based on the blended mortar. ((S / W) c), the plastic viscosity ηc and the yield value τc are estimated using the above-described equations (6) to (8) (step 103).

  Next, using the ratio of fine aggregate to water ((S / W) c), plastic viscosity ηc and yield value τc in the corrected mortar obtained based on the equations (6) to (8), the screening mortar The ratio of fine aggregate to water ((S / W) w), plastic viscosity ηw, and yield value τw are estimated using the above-described equations (3) to (5) (step 104).

  Next, using the plastic viscosity ηw and the yield value τw in the screening mortar obtained based on the formulas (3) to (5), the slump flow value (Sf) and the 500 mm flow arrival time (Fv) of the high-fluidity concrete are obtained. Estimation is performed using the above-described equations (2) and (1) (step 105).

In this way, it was possible to estimate the slump flow value (Sf) and the 500 mm flow arrival time (Fv) of the high-fluidity concrete based on the blended mortar before the coarse aggregate was mixed.
(Example)
FIG. 2 shows actual measured values of slump flow values (Sf) and slump flow speeds (Fv) actually created from the designed high-fluidity concrete, and slump flows estimated from the blended mortar based on the present invention. The value (Sf) and the predicted value of the slump flow speed (Fv) are shown. The 500 mm flow arrival time can be uniquely determined from 150 / slump flow speed (mm / s), and the slump flow rate (mm / s) can be uniquely determined from 150/500 mm flow arrival time. .

In FIG. 2, the unit coarse aggregate amount V _G (L / m ³ ), water / binder ratio (%), and fine aggregate volume ratio (%) are design values of high-fluidity concrete, and the plastic viscosity of the blended mortar. ηb (Pa · s), yield value τb (Pa), and fine aggregate to water ratio ((S / W) b) are all actually measured values from the prepared mortar. In FIG. 2, the water / binder ratio (%) was changed to 40.0%, 45.0% and 50.0%, and the fine aggregate volume ratio (%) was changed to 49.0%, 52 A comparison was made for 33 samples with changes of 0.0% and 55.0%.

  The measured values and predicted values at the slump flow speed (mm / s) for each sample in FIG. The average of the difference between the measured value and the predicted value of the slump slow speed (mm / s) is −2 (mm / s), and the standard deviation is 7 (mm / s). When the slump flow rate of high-fluidity concrete is estimated using this estimation formula, 1.45σ (σ indicates a standard deviation) on the probability density function and -10 to 85% probability on the probability density function when processed with a normal distribution. It falls within the range of +10 (mm / s). In JASS5, the difference between the design value and the actual measurement value is set to −10 to +10 (mm / s) or −4.3 to +4.3 (mm / s), and −10 to +10 (mm / s) when 85% is established. If it falls within the range of s), it is considered that it is sufficiently practical.

  FIG. 4 shows the measured values and predicted values in the slump flow (mm) for each sample in FIG. The average of the difference between the measured value and the predicted value of the slump throw (mm) is 12 (mm), and the standard deviation is 31 (mm). When estimating the slump flow rate of high-fluidity concrete using this estimation formula, it enters the range of -50 to +50 (mm) at the probability density of 1.45 σ and 85% on the probability density function when processed with normal distribution. . In JASS5, the difference between the design value and the actual measurement value is set to −75 to +75 (mm) or −50 to +50 (mm), and if it enters the range of −50 to +50 (mm) with 85% establishment, it is sufficient. It is thought that it is sufficient for practical use.

From the above, the estimation formula according to the present invention is such that the unit coarse aggregate amount V _G (L / m ³ ) is in the range of 200 to 360 and the slump flow speed is in the range of 6.54 to 51.7 (mm / s). In addition, it is considered that the slump flow is applicable to estimation within a range of 500 to 800 (mm).

  As mentioned above, since the blended mortar before the coarse aggregate is mixed can be made much easier than the high fluidity concrete after the coarse aggregate is mixed, from the blended mortar according to the present invention, The advantage that the slump flow value (Sf) and 500 mm flow arrival time (Fv) of fluidized concrete can be estimated with high accuracy is great.

It is a figure which shows an example of the procedure of the evaluation parameter estimation method of the high fluidity concrete concerning this invention. It is a figure which shows the estimated parameter value and actual value which were estimated according to this invention. It is a figure for comparing the estimated value of the estimated slump flow speed with an actual measurement value according to the present invention. It is a figure for comparing the estimated value of the estimated slump flow, and the measured value according to this invention.

Claims (4)

In an estimation method for estimating a slump flow value and a 500 mm flow arrival time of a high-fluidity concrete produced from at least coarse aggregate, fine aggregate, cement and water,
Producing mixed mortar in which only coarse aggregate is not mixed from high-fluidity concrete to be estimated,
Using the prepared mortar produced, measure the plastic viscosity, yield value and the ratio of fine aggregate and water,
Using the measured plastic viscosity, yield value and ratio of fine aggregate and water of the blended mortar, the mortar content adhering to the coarse aggregate from the screening mortar obtained by wet screening from the high fluidity concrete to be measured Estimate the plastic viscosity, yield value and fine aggregate to water ratio for the corrected mortar corrected for
Using the estimated plastic viscosity, yield value and fine aggregate to water ratio of the corrected mortar, estimate the plastic viscosity, yield value and fine aggregate to water ratio of the screening mortar,
Using the estimated plastic viscosity and yield value of the screening mortar, estimate the slump flow value and 500 mm flow arrival time in the high-fluidity concrete to be measured,
A method comprising the steps. The fine aggregate to water ratio ((S / W) c), plastic viscosity (ηc (Pa · s) ) and yield value (τc (Pa) ) of the corrected mortar are estimated using the following equations:
(S / W) c = 1.02 (S / W) b + 0.198
ηc = 1.59 ηb−1.33
τc = 0.978τb + 2.00
Here, (S / W) b is the ratio of fine aggregate and water in the blended mortar, ηb (Pa · s) is the plastic viscosity of the blended mortar, and τb (Pa) is the yield value of the blended mortar. The method of claim 1. The fine aggregate to water ratio ((S / W) w), plastic viscosity (ηw (Pa · s) ), and yield value (τw (Pa) ) of the screening mortar were estimated using the following equations: ,
(S / W) w = (0.0006V _G +0.9091) (S / W) c− (0.0002V _G +0.1726)
ηw = (6.88 (S / W) w / (S / W) c−5.57) ηc
τw = (13.5 (S / W) w / (S / W) c-11.4) τc
Here, (S / W) c is the ratio of fine aggregate and water in the corrected mortar, ηc (Pa · s) is the plastic viscosity of the corrected mortar, τc (Pa) is the yield value of the corrected mortar, and V _G The method according to claim 1, wherein (L / m ³ ) indicates a unit coarse aggregate amount of the high-fluidity concrete to be estimated. The slump flow value (Sf (mm) ) and 500 mm flow arrival time (Fv (s) ) of the high-fluidity concrete to be estimated are estimated using the following equations:
Sf = (0.136−0.114τw−0.0171ηw) V _G + (628 + 33.4τw + 3.37ηw)
Fv = (− 0.468−0.00393τw + 0.0412ηw) V _G + (176 + 0.714τw−12.9ηw)
Here, (S / W) w is the ratio of fine aggregate and water of the screening mortar, ηw (Pa · s) is the plastic viscosity of the screening mortar, τw (Pa) is the yield value of the screening mortar, and V _G (L / m < ³ > ) The method as described in any one of Claims 1-3 which shows the unit coarse aggregate amount of the high fluidity concrete of the said estimation object.

Images