CN110615636A

CN110615636A - Benchmark polycarboxylic admixture and method for evaluating cement performance

Info

Publication number: CN110615636A
Application number: CN201810627555.7A
Authority: CN
Inventors: 白明科; 李海宏; 赵健
Original assignee: Yaobao Special Cement Technology Development Co Ltd
Current assignee: Yaobao Special Cement Technology Development Co Ltd
Priority date: 2018-06-20
Filing date: 2018-06-20
Publication date: 2019-12-27

Abstract

The invention provides a standard polycarboxylic acid admixture and a method for evaluating cement performance, which are used for evaluating cement adaptability. The standard polycarboxylic admixture is characterized in that: the paint consists of the following components in percentage by weight: mother liquor of polycarboxylic acid admixture: 15-25%, retarder: 1-3%, water: 75-85%. The standard polycarboxylic admixture provided by the invention has good adaptability with cement, stable and reliable quality, and can effectively evaluate the adaptability of cement and admixture and the working performance of concrete in time.

Description

Benchmark polycarboxylic admixture and method for evaluating cement performance

Technical Field

The invention relates to a standard polycarboxylic admixture and a method for evaluating cement performance, belonging to the technical field of building materials.

Background

With the continuous development of the construction industry, the requirements of the construction industry on high retention, durability, adaptability and construction performance of cement are higher and higher, and higher requirements are also provided for the additive which is an important component of concrete. For the admixture, besides good use effect (such as the water reducing agent should have the effects of improving cement strength, reducing mixing water consumption and saving cement consumption), the admixture also needs to have good adaptability with cement. However, in the using process, the varieties and the types of the additives on the market are various, the respective qualities of the additives are different, and even the additives produced by different manufacturers with the same brand and the different types are greatly different. The water reducing rate of the admixture used by the laboratories of part of key projects and commercial mixing stations is low and the quality is unstable, so that the cement performance is misjudged when the admixture is used for testing the adaptability of the cement. When the components, varieties or manufacturers of the additives used in key projects or commercial mixing stations change, the adaptability of the additives and cement fluctuates and changes, so that the judgment result of the cement performance is influenced. The problem of poor adaptability of the admixture and the cement is very common, and great inconvenience is brought to lean production of the cement.

If no uniform additive product is used for measuring and judging the adaptability of the cement and the additive, the fluctuation condition of the cement quality cannot be mastered in advance, and the increasing demand of the market on high-quality cement cannot be met. Therefore, cement manufacturers urgently want to evaluate the adaptability of cement and additives by preparing an additive formula which has good adaptability with cement and stable and reliable quality as a reference.

Disclosure of Invention

In view of the above problems of the prior art, the present invention provides a standard polycarboxylic acid admixture for evaluating the adaptability of cement and admixture.

One aspect of the invention provides a benchmark polycarboxylic acid admixture, which comprises the following specific technical scheme:

a benchmark polycarboxylic admixture is composed of the following components by weight percent: mother liquor of polycarboxylic acid admixture: 15-25%, retarder: 1-3%, water: 75-85%.

Further preferably, the purity of the retarder is more than or equal to 98%.

Further preferably, the solid content of the polycarboxylic acid admixture master batch is 42.5%.

Further preferably, the retarder is any one of white sugar, molasses, citric acid, sodium phosphate and sodium gluconate.

The preparation process of the standard polycarboxylic admixture comprises the following steps: uniformly mixing the polycarboxylic admixture master batch and the retarder component, adding water, fully dissolving and uniformly stirring to obtain a finished product.

In another aspect of the present invention, a method for evaluating cement is provided.

The saturated doping amount point of the reference admixture is determined by adopting a clean slurry fluidity method (substitution method) test in JC/T1083-. Specifically, the standard P.O42.5 cement and the standard polycarboxylic acid additive are stirred and mixed uniformly according to a proportion, then the slurry is slowly poured into a round die positioned in the middle of a glass plate to slowly fill the round die with the slurry, then the slurry higher than the top surface of the round die is scraped and smoothed by a scraper, the round die is lifted immediately, after about 1min, the length of the longest diameter direction of the oval slurry and the length of the longest diameter direction of the oval slurry in the vertical direction are measured by a vernier caliper, the longest diameter direction and the length of the oval slurry in the vertical direction are averaged to obtain initial fluidity, after the initial fluidity is measured, the slurry on the glass plate is immediately recovered into a specified container, and the container opening is sealed by a preservative film to prevent water from. And re-stirring after 30min and 60min, and sequentially measuring the fluidity of the slurry under each mixing amount after 30min and 60min according to the method. The technical indexes of the cement obtained by mixing the standard polycarboxylic acid admixture and the standard P.O42.5 cement in proportion are shown in Table 1:

TABLE 1 technical index of cement obtained by mixing a reference polycarboxylic acid admixture with a reference P.O42.5 cement in a proportion

The doping amount of the additive is an abscissa, the fluidity of the cement paste is an ordinate, a curve graph is drawn, then trend lines of curves of two straight line segments are drawn, and the abscissa of the focus of the two trend lines is a saturated doping amount point. The saturated addition point of the standard polycarboxylic acid admixture is shown in the attached figure 1. The initial admixture saturation doping point of the standard polycarboxylic acid admixture is 2.1%, the admixture saturation doping point in 30min is 2.25%, the admixture saturation doping point in 60min is 2.25%, and the final average admixture saturation doping point is 2.2%.

The control standard is determined according to the compatibility test of the cement and the admixture and the saturated mixing amount point as follows: the initial fluidity of the cement paste is more than or equal to 230mm, the fluidity of the cement paste is more than or equal to 210mm after 30min, and the fluidity of the cement paste is more than or equal to 190mm after 60 min.

The invention has at least the following beneficial effects: the additive has the characteristics of high water reducing rate, stable quality, good cement adaptability and the like, and can be used as an efficient standard additive for evaluating the cement adaptability.

Drawings

FIG. 1 is a graph showing the tendency of determining the saturation addition point of a reference polycarboxylic acid admixture.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

The standard polycarboxylic admixture comprises the following components in percentage by weight: mother liquor of polycarboxylic acid admixture: 15-25%, retarder: 1-3%, water: 75-85%.

To evaluate the performance of the benchmark polycarboxylic acid admixture of the present invention, the following examples were conducted:

example 1

A benchmark polycarboxylic admixture is composed of the following components by weight percent: mother liquor of polycarboxylic acid admixture: 20%, retarder: 2%, water: 78 percent. The mother liquor of the polycarboxylic acid admixture is commercial polycarboxylic acid mother liquor.

Different cement net slurry fluidity tests are carried out according to the net slurry fluidity method (substitution method) test in JC/T1083-2008 & lttest method for compatibility of cement and additives'. The 13 cements tested were P.O42.5 cements from Yao Bai Special Cement group Ltd, the addition amount was 2.2% (based on the weight of the cement after curing), and the test results are shown in Table 2.

TABLE 2 comparison of Performance of benchmark polycarboxylic acid admixture on P.O42.5 Cement products from molecular Co

As is apparent from the results of Table 2, the reference polycarboxylic acid admixture of the present invention has a net paste fluidity at an intermediate level as compared with that of the comparative admixture (Cojie polycarboxylic acid admixture used), and is suitable for the control of the water retentivity and fluidity of cement and the control of the sustainability of the stability of cement properties.

Example 2

A benchmark polycarboxylic admixture is composed of the following components by weight percent: mother liquor of polycarboxylic acid admixture: 20%, retarder: 2%, water: 78 percent.

Concrete tests were conducted on 8 kinds of P.O42.5 commercial cement cements from respective sub-companies of Yao and Bai Special Cement group Co., Ltd. using the reference polycarboxylic acid admixture and the commercial polycarboxylic acid admixture, and the result was shown in Table 3, wherein the reference polycarboxylic acid admixture was added in an amount of 2.2% (based on the weight of the cement after setting).

TABLE 3 comparison of Performance of Standard and commercial polycarboxylic acid admixtures to P.O42.5 commercial Cement of molecular Ltd

As can be seen from the comparison of the results of the slump expansion and compressive strength tests of the concrete between the standard polycarboxylic acid admixture and the commercial polycarboxylic acid admixture in Table 3, the adaptability of the standard polycarboxylic acid admixture and the cement is in an intermediate level and meets the standard of the adaptability evaluation and control of the cement.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A benchmark polycarboxylic admixture is characterized in that: the paint consists of the following components in percentage by weight: mother liquor of polycarboxylic acid admixture: 15-25%, retarder: 1-3%, water: 75-85%.

2. The benchmark polycarboxylic acid admixture according to claim 1, which is characterized in that: preferably, the purity of the retarder is more than or equal to 98 percent.

3. The benchmark polycarboxylic acid admixture according to claim 1, which is characterized in that: the mother liquor of the polycarboxylic acid admixture had a solid content of 42.5% by weight.

4. The benchmark polycarboxylic acid admixture according to claim 1, characterized in that: the retarder is any one of white sugar, molasses, citric acid, sodium phosphate and sodium gluconate.

5. The method for preparing the standard polycarboxylic acid admixture according to any one of claims 1 to 4, wherein the finished product is obtained by mixing the components according to the weight percentage and uniformly stirring and dispersing the mixture.

6. The method for evaluating the performance of cement by using the reference polycarboxylic acid admixture as claimed in any one of claims 1 to 4, wherein the reference P.042.5 cement and the reference polycarboxylic acid admixture are stirred and mixed in proportion, then the slurry is slowly poured into the round die positioned in the middle of the glass plate, so that the round die is slowly filled with the slurry, then the slurry higher than the top surface of the round die is scraped and leveled by a scraper, the round die is lifted immediately, after about 1min, the length of the longest diameter direction of the elliptical slurry and the vertical direction thereof are measured by a vernier caliper, the initial fluidity is obtained by averaging the longest diameter direction and the vertical direction of the elliptical slurry, and after the initial fluidity is measured, the slurry on the glass plate is immediately recovered into a specified container, and the container opening is sealed by a preservative film to prevent water loss; and re-stirring after 30min and 60min, and sequentially measuring the fluidity of the slurry under each mixing amount after 30min and 60min according to the method.

7. The method of claim 6, wherein: the dosage of the standard polycarboxylic admixture is 1.0-3.0% of the dosage of the cement.