Influence of Molecular Parameters of Cellulose Ether on Mechanical Characteristics of Cement Slurry

Abstract: This article compares the effects of cellulose ether molecular parameters and measurement on the mechanical properties of cement slurry. The results show that fibin ether increases the pore rate of the cement slurry, reduces the pressure resistance of cement slurry and the resistance of folding strength, and compressive pressure The reduction of the intensity is greater than the resistance of the anti -folding strength; the higher the viscosity or molecular weight of the fibin ether, the greater the surface activity, the lower the strength of the modified cement pulp; The intensity is higher than the strength of the cellulose ether containing methyl ether. As the amount of cellulose ether increases, the pressure resistance of the cement slurry gradually decreases and stabilizes, and the anti -folding strength has experienced increased, decreased, stable and stable and stable and stable. The process of slight increase.

Keywords:cellulose ether; molecular parameters; clustering ratio; cement slurry; mechanical performance

1 Introduction

Fibrin ether is a polymer compound produced by natural cellulose through the etherization process, that is, C-2, C-3, and C-6 hydroxyl groups in cellulose molecules are completely replaced by the ether group or even. -Oor represents ether groups, such as -OH, -Och3, -O (CH2CH2O) NH or -O [CH2CH (CH3) O] NH. Hydroxyeylthyl cellulose ether (HEMC) and hydroxydal methyl cellulose ether (HPMC), of which HPMC and HEMC are the most common.

Cellulose ether has excellent water preservation and thickening effect on new mixed cement base materials, so it is widely used in new cement base materials such as dry mix mortar and dense concrete. Cellulose ether also affects the strength of the hardening cement base material, which usually reduces the pressure resistance and reflective strength of the cement base material. However, when the amount of cellulose ether increases to a certain degree Obviously. Cellulose ether has an air -induced effect on the new mixed cement base material, which will increase the pore rate of the cement base material and reduce the density, which will lead to a decrease in the strength of the cement base material. There is also a determined relationship between the compressive strength of the cellulose ether modified cement slurry and the gas content of the new mixing pulp. However, very low -volume cellulose ether may improve the strength of the cement base material, and fibin ether may also reduce the water -asx ratio due to its plastic increase, thereby improving the strength of the cement base material. It will increase the bonding resistance of cement base and tensile resistance.

Obviously, there are already more literature research on the effects of cellulose ether on the strength of cement base materials. However, in the above studies, the cellulose ether used is often only one, and the content of the substituent is rarely indicated. The types of replacement bases are different, and the mechanical performance results are relatively different, which is not conducive to engineering applications. As mentioned earlier, with the different types and content of the substituent, there are many varieties of fibrin ether. The molecular parameters of cellulose ether (replace the type, content, and molecular weight) of the modified cement slurry will inevitably have a difference. This article studies compares the influence of cellulose ether molecular parameters and measurement on the pressure resistance of cement slurry and reflective strength to further deepen the inherent mechanism of cellulose ether affecting the mechanical properties of cement slurry. Scientific basis.

2. Test

2.1 raw materials

(1) Cement. Ordinary silicate cement produced by Wuhan Huaxin Cement Co., Ltd. is P. O 42.5 (GB 175-2007).

(2) cellulose ether. Eight types of cellulose ether were selected for this test, including 5 HPMC, 1 HEMC, 1 MC and 1 HEC. Cellulose ether Moore replacement refers to the amount of the substances of the etheric agent reactant on the average adding on each glucose unit. The Moore replacement of cellulose ether replacement is provided by the manufacturer, and the viscosity and surface tension are determined by the test test. The surface tension measurement adopts the ring method, and the concentration of the solution during testing is 0.01 %; the viscosity uses the rotation viscosity meter test. The concentration of the solution during testing is 2 %, the temperature is 20 ° C, and the rotation speed is 12 R / min.

(3) Water. Use tap water.

2.2 Test method

(1) The intensity measurement of hardening cement pulp. Fibrin ether and cement first are first mixed in the sample bag according to the specified poly ash ratio (the quality ratio of fibrin ether and cement). After adding the specified quality of water to the mortar mixer Slowly stir 60s, then stop 15s for cleaning, and finally mix 60s. Put the stirred cement puree into the border test model of 40 mm x40 mm x 160 mm, vibrate 60 times on the vibration table, put in an environment with a temperature of 20 ° C and more than 95 %, After the mold, then seal it under 20 ° C to be sealed to the specified age. Test anti -folding strength and compressive strength according to the method specified in the method of "cement glue strength test (ISO method)" (GB / T 17671.1999). In addition to the effect of the intensity of the polyid ratio on the intensity of the cement slurry, the water and ash ratio of all cement slurry is 0.35, and the poly ash ratio is 0.6 %.

(2) Measurement of the apparent density of hardening cement pulp. Take out the trial blocks of the bonded bodies after 28 d and dry it. Take the quality with Tianping. In addition to the volume of the test block (256 CM³), the apparent density of the hardened cement slurry is obtained.

(3) Scan the electron microscope. Take out the trial block of the bonded bodies after 28D, remove the sample from the middle of the cement slurry, and break it with a small hammer to 2.5-50mm. Before the test, remove the cement slurry block from the water-free ethanol, dry the vacuum to the constant heavy weight at 40 ° C, and paste the sample on the copper sample with conductive glue. Observe the micro -appearance of the sample section.

3. Experimental results

3.1 The effect of cellulose ether viscosity / molecular weight on the strength of the cement slurry

HPMC1, HPMC2, and HPMC3 three types of cellulose ether modified cement paste and pure cement pulp at the age of 3 d, 7 d, and 28 d. The parameters are exactly the same, the surface tension of the aqueous solution is very close), and it is produced by the same manufacturer. It is only different. The viscosity of HPMC3 is greater than HPMC2, HPMC3 and HPMC2 viscosity is much greater than HPMC1. Because the greater the fibrin ether, the more molecular weight High, therefore, the effect of cellulose ether viscosity on the strength of the cement slurry actually reflects the effect of cellulose ether molecule on the strength of the cement slurry. It can be observed that the intensity of the three cellulose ether modified cement pulp is significantly less than the intensity of pure cement paste. The 28 D pressure strength of HPMC1, HPMC2 and HPMC3 modified cement pulp is only 58.8 % of pure cement pulp, respectively. , 50.6 % and 44.3 %, 28 D anti -folding strength is 74.3 %, 70.0 %, and 60.9 % of pure cement pulp. Moreover, the decrease in the compressive strength of the fibrin ether on the compressive strength of the cement slurry. It should be greater than the resistance of the anti -folding strength; as far as the three fibrin ether, the higher the viscosity / molecular weight of the fibin ether, the lower the compressive strength and anti -folding strength of the modified cement pulp.

3.2 The effect of cellulose ether replacement base on the intensity of cement slurry

From six types of cellulose ether modified cement paste and pure cement paste of 3D, 7 D, and 28 D pressure resistance from HPMC3, HPMC4,HPMC5, HEMC1, HEC1, and MC1, 3D, 7 D, and 28 D pressure resistance and folding strength of pure cement pulp can be seen. The intensity of sexual cement pulp is less than the strength of pure cement pulp. The 28 D pressure strength is only 44.3 % (HPMC3) to 71.5 % (HEC1) of pure cement pulp. 60.9 % (HPMC3) 92.2 % (HEC1). Similarly, the reduction of the compressive strength of the fibrin ether to the compressive strength of the cement slurry is greater than the reflection strength; in terms of six types of fibin ether, the hydroxyetoin cellulose ether HECL HECL HECL HECL Modified cement slurry in each aging period of compression and reflective strength is significantly higher than that of other three types of cellulose ether of the same age. The pressure and anti -folding strength is close. The 28 D pressure strength is between 24.73-28.32 mpa, and the 28 D anti -folding strength is between 6.75 and 7.76 mPa. In comparison, Hemcl and HPMC5 The intensity of the two types of cellulose ether modified cement pulp is higher, and the strength of HPMC3 modified cement slurry is lower.

3.3 The effect of cellulose ether mixing (clustering ratio)

Under the conditions of different polyal ratio, 3 D, 7D, and 28 D pressure resistance of cellulose ether modified cement pulp can be seen that as the polyladom ratio increases, the pressure resistance of cellulose ether modified cement pulp continues to decrease , But the reduction of the reduction continues to decrease, and gradually stabilizes. When the 3 D pressure strength becomes stable when the clustering ratio is 0.6 %, the pressure ratio of 7 d and 28 d is 0.8 % Time tends to stabilize. Under the conditions of different polyettes, 3 D, 7D, and 28 D anti -folding strength of cellulose ether modified cement pulp can be seen. As the polylachen ratio increases, the anti -folding strength of cellulose ether modified cement paste has increased, and The four processes of reduction, stability, and micro -increase are: increased ash ratio from 0 to O. At 1 %, the anti -folding strength of the cement pulp increases; when the toh -to -ash ratio increases from 0.1 % to 0.4 %, the anti -folding strength of the cement pulp decreases; At the time, the anti -folding strength of the cement slurry remains stable; when the polyal ratio increases from 0.8 % to 1 %, the anti -folding strength of the cement pulp increases slightly.

3.4 The intensity of cellulose ether modified cement pulp and the relationship between apparent density

From the above 8 types of cellulose ether modified cement paste, the 28 D pressure strength, folding strength and apparent density relationship curve of the 28 D ash, the polyal ratio is 0.6 %. It can be observed. There is a clear correlation with the apparent density. The smaller the apparent density of the cement slurry, the lower its compressive strength and folding strength. From the conditions of different clustering ash ratio, the 28 D intensity and apparent density relationship curve of the cellulose ether (HPMC2) can be observed that as the clustering ratio increases, the apparent density of the cellulose ether modified cement pulp can be increased. Continuous reduction, decreased compressive strength, and decreased resistance of the folding strength overall, but in the interval of 0 to 0.1 % and 0.8 % to 1 % in the agglomeration ratio. The decrease in the density density has increased slightly.

3.5 Micro structure of cellulose ether modified cement pulp

From the micro -structures observed by scanning electron microscopy's secondary electronic imaging. These four cement slurry includes pure cement slurry and HPMC1, HPMC4 and HEC1 modified cement slurry. The ratio of 0.6 % is that the number of large pores in the three types of cellulose ether modified cement paste is significantly higher than that of pure cement slurry; three types of cellulose ether modified cement pulp, hydroxycopicidal with lower viscosity The number of pores of the centered cellulose ether (HPMCL) and the hydroxye ethyl ether (HECL) altering cement paste is less than that of hydroxylthyl cellulose ether (HPMC4) with higher viscosity. Combined with the previous experiments, it can be found that the more large pores in the large pores in cellulose ether modified cement paste, the lower the intensity.

4. Analysis and discussion

Because the intensity of cellulose ether modified cement pulp has a significant correlation between its apparent density and the number of large pores, the effect of fibrotin ether on the mechanical properties of cement pulp is mainly because of the significant affecting the cellulose ether, which affects the cement slurry. The pore rate is also in line with the general law of material strength. The effects of cellulose ether on the structure of hardening cement paste Lhn is mainly because fibrin ether affects the formation and stability of the bubbles in the new mixing cement slurry: fibrin ether will increase the viscosity of cement slurry, so bubbles are more likely to be captured by cement pulp caught by cement pulp caught by cement pulp caught by cement pulp caught by cement pulp caught by cement pulp. And stability; as a surfactant, cellulose ether can reduce the surface tension of the liquid phase in the cement slurry. Therefore, the cement slurry is easy to form air bubbles, and cellulose ether will therefore be rich in the qi -liquid interface and stable air bubbles. Therefore, a certain amount of cellulose ether will increase the pore volume of the cement slurry, reduce the surface density, and thereby reducing the strength of the cement slurry. The higher the viscosity of the fibrin, the higher the surface activity (the lower the surface tension of the solution), the lower the strength of the modified cement pulp.

Different cellulose ether, due to different surface activity and viscosity, the pore rate and strength of the modified cement slurry are large. As far as HPMC1, HPMC2 and HPMC3 are concerned, because the viscosity of HPMC1 is very low, the intensity of the modified cement pulp is higher than HPMC2 and HPMC3; In terms of species of fibrin, HEC1 is a hydroxyethyl cellulose ether. The molecule does not contain a high -hydrated methyl -based methyl, and the surface activity is low. Therefore, the strength of the modified cement pulp is relatively high. Both of them contain a high -water -having methyl, and the surface activity is high, so the strength of the cement slurry is low. Among the five types of fiber ether, Hemc1 has the lowest surface activity, so the strength of the modified cement pulp is high, and the viscosity of HPMC5 is significantly low, so the strength of the modified cement pulp is high, but because of it, it is due to its In the molecule, the highest methyl content and the largest surface activity. Therefore, the strength of the modified cement slurry is not significantly higher than that of other four types of fibin ether. The viscosity of HPMC3 is the highest, so the strength of the modified cement pulp is low.

Pores are the weak part of cement slurry. Increase the pore rate of cellulose ether, which will inevitably lead to a decrease in the compressive strength and anti -folding strength of the cement slurry. When the cellulose ether modified cement slurry test block is stressed, the test block is almost the same pressure everywhere, which will be destroyed from the weakest part; when the cement slurry is folded, the bottom surface of the test block will be the largest stress. Test block It will first destroy it near this. The thinnest part of the test block is exactly less likely to be distributed in this smaller area. Therefore, the degree of reduction of fibrin ether on cement slurry is greater than the reflection strength.

The concentration of cellulose ether solution increases, and the surface tension of the solution decreases, but when the concentration of the cellulose ether solution exceeds 0.01 %, the surface tension of the solution is stable, and it will no longer decrease with the increase of the concentration of cellulose ether. This experiment will not be Among them, the lowest amount of fibrin ether (ratio to the mass of cement) is 0.05 %, and the water and ash ratio are 0.35, and the concentration of fibrin ether is 0.14 % in the aqueous solution. A portion of water is consumed, and the concentration of cellulose ether in the aqueous solution is higher. Therefore, as the amount of cellulose ether increases, the surface tension of the liquid phase in the cement slurry will not decrease significantly, but the viscosity will increase significantly, thereby increased significantly, thereby increased significantly, thereby increased significantly, thereby increased significantly, thereby increased significantly, thereby increased significantly. As a result, the pore rate of the cement slurry increases, and the pressure resistance and reflective strength are reduced.

Cellulose ether is an organic polymer polymer. After the water participating in the chemical reactions and evaporation in the cement pulp, the cellulose ether will form a highly tough and intensity polymer microfiber or even polymer film inside the cement slurry. The micro -crack of cement slurry has a "bridge" effect, thereby improving the strength of the cement slurry, especially the folding strength. Knapn et al. Send a cellulose ether film distributed at the laminar gap between layer CA (OH) 2 crystals by scanning electron microscope. The crystal layer is bonded together through the "bridge" to increase the strength of the CA (OH) 2 crystal. Therefore, when the poly ash ratio of cellulose ether modified cement pulp is less than 0.1 %, due to the low amount of cellulose ether, the reduction of the strength of the cement slurry is small, and the enhanced effect of the polymer accounted for the leading effect. Cellor ether ether, and cellulose ether. The resistance of the modified cement pulp is therefore higher than the pure cement slurry. However, due to the decrease in the decrease in the pressure of the fibrin ether than the resistance, the tougher effect of the polymer does not improve the compressive strength of the cement slurry. When the poly ash ratio increases, the fibrin ether occupies the leading role in the reduction of cement pulp strength. Therefore, despite the toughness of the polymer, the folding strength and compressive strength of the cellulose ether modified cement pulp usually will usually be The lower. However, when the poly ash ratio is higher than 0.8 %, the increased effect of fibrin ether on the viscosity of cement pulp tends to stabilize, so the reduction of the strength of the cement slurry has stabilized, but the effect of the polymer's tougion continues to increase, and the anti -folding resistance is resistant. The intensity will increase slightly.

5 Conclusion

(1) When the clustering ratio is 0.6 %, the eight types of cellulose ether used for the test will reduce the compressive strength and reflective strength of the age of the cement slurry. The cellulose ether modified cement slurry 28D compressive strength is only 44.3 % to 71.5 % of pure cement slurry, and the 28D folding strength is only 60.9 % to 92.2 % of pure cement slurry. The reduction of fibrin ether to the compressive strength of the cement slurry is greater than the resistance of the anti -folding strength;

(2) The higher the viscosity of the fibin ether, the higher the surface activity (the lower the surface tension of the solution), the lower the strength of the modified cement pulp. The strength of HEC molecular modifiers is significantly higher than that of MC, HPMC, and HEMC three types of cellulose ether modified cement slurry. MC, HPMC and HEMC three types of cellulose ether modified cement pulp are closer;

(3) With the increase of the polyal ratio, the compressive strength of cellulose ether modified cement paste has continued to decrease, but the reduction of the decrease continues to decrease and stabilizes. And the process of micro -increase.