Effect of hydroxypropyl methylcellulose ether on the properties of inorganic light aggregate thermal insulation mortar

Abstract: Inorganic lightweight aggregate thermal insulation mortar is a new type of inorganic thermal insulation material. The research shows that: hydroxypropyl methyl cellulose ether (HPMC) has a great influence on the performance of inorganic light aggregate thermal insulation mortar. In this paper, cellulose ethers of different viscosities are added to the thermal insulation mortar to find out its influence on the performance of the thermal insulation mortar.

Key words:hydroxypropyl methylcellulose ether; performance of thermal insulation mortar

In recent years, many domestic literatures have reported the application and development of cellulose ether to cement mortar, but there is not much information on the influence of hydroxypropyl methylcellulose ether (hereinafter referred to as cellulose ether) on the performance of thermal insulation mortar. . This paper studies the dry density, compressive strength, thermal conductivity, softening coefficient, frost resistance Performance and other performance indicators.

1. Raw materials and test methods

1.1 Raw materials

(1) Cement: Xiushan P.O.42.5 cement. Its specific surface area is 355m²/kg, the water consumption of standard consistency is 27.2%, the 3-day flexural strength is 5.7MPa, the 28-day flexural strength is 8.7MPa, the 3-day compressive strength is 27.7MPa, and the 28-day compressive strength is 49.3MPa

(2) Fly ash: Class II ash, its fineness is 0.045mm, sieve residue is 14.1%, loss on ignition is 1.4%, water demand ratio is 100%, stability is qualified, sulfur trioxide content is 1.0%, free calcium oxide content 0.4%.

(3) Vitrified microbeads: It is an inorganic glassy mineral material, which is crushed into ore sand from volcanic ash and processed by a special puffing and burning method. Vitrified microbeads are vitrified and closed surface, irregular spherical, and inorganic particle materials with porous cavity structure inside. Its bulk density is 121kg/m³, cylinder compressive strength is 200KPa, thermal conductivity is 0.0611W(m K), volume water absorption is 35%, and volume floating rate is 95%.

(4) Cementing material: refers to other materials that make up inorganic lightweight aggregate insulation mortar except vitrified microbeads, including inorganic cementing materials such as cement and fly ash, and functional additives such as hydroxypropyl methylcellulose.

(5) Hydroxypropyl methyl cellulose ether: Cellulose ether is a general term for a series of cellulose derivatives produced by natural cellulose as raw material through alkalization and etherification reactions under certain conditions. It is a cellulose molecular chain The product in which the hydroxyl group is replaced by an ether group. The three cellulose ethers used in this paper are mainly different in viscosity, so they have a certain impact on the water retention and compressive strength of the thermal insulation mortar.

1.2 Test method

Laboratory environment: temperature (23±2)°C, relative humidity 55%~85%. The test method of thermal insulation mortar is carried out according to DB33/T1054-2008 "Technical Regulations for Inorganic Light Aggregate Thermal Mortar and System".

2. Test results and discussion

2.1 Test results

(1) The composition of the cementitious material remains unchanged, the mix ratio is basically the same, and the test results of the inorganic lightweight aggregate thermal insulation mortar with different dosages of ZQ-8 cellulose ether.

(2) The composition of the cementitious material remains unchanged, the mix ratio is basically the same, and the test results of the inorganic light aggregate thermal insulation mortar with different dosages of ZQ-10 cellulose ether.

(3) The composition of the cementitious material remains unchanged, the mix ratio is basically the same, and the test results of the inorganic lightweight aggregate thermal insulation mortar with different dosages of ZQ-15 cellulose ether.

2.2 The composition of the cementitious material remains unchanged, the mix ratio is basically the same, and the influence of different dosages of the same variety of hydroxypropyl methylcellulose ether on the performance of inorganic light aggregate thermal insulation mortar

When the amount of cellulose ether mixed with the same variety is changed, its main indicators will also change accordingly. When the amount of ZQ-8 cellulose ether is mixed with thermal insulation mortar at 0.15% and 0.1%, its data is A-type thermal insulation mortar; however, when its content is reduced to 0.05%, its data has exceeded that of A-type thermal insulation mortar , manifested as an overweight product. The thermal insulation mortar mixed with ZQ-10 cellulose ether behaves as Type B thermal insulation mortar when the dosage is 0.15%, and it behaves as Type A thermal insulation mortar when the dosage is 0.1% and 0.05%. The thermal insulation mortar mixed with ZQ-15 cellulose ether behaves as type B thermal insulation mortar when the dosage is 0.15%, and it behaves as type A thermal insulation mortar when the dosage is 0.1% and 0.05%. From this, it can be concluded that the main properties of the thermal insulation mortar can be changed by changing the amount of cellulose ether when the composition of the cementitious material remains unchanged and the mix ratio is basically the same. When the content of cellulose ether is reduced, the dry density, compressive strength, thermal conductivity and softening coefficient of the insulation mortar all increase to a certain extent, but its antifreeze performance also decreases to a certain extent with the decrease of the content of cellulose ether. The increase in dry density, compressive strength, thermal conductivity, and softening coefficient is related to the composition of the cement and the specific mix ratio, and the decrease in frost resistance is also related to it.

2.3 The composition of the cementitious material remains the same, the mix ratio is basically the same, the influence of the same dosage and different varieties of hydroxypropyl methylcellulose ether on the performance of inorganic light aggregate thermal insulation mortar

Comparing the test results of ZQ-8, ZQ-10, and ZQ-15 at a dosage of 0.15%, it is found that due to the different types of cellulose ethers, their main properties also change accordingly. Comparing the test results of ZQ-8, ZQ-10 and ZQ-15 at the dosage of 0.1% and 0.05%, the same changes were also found. The main difference between different varieties of cellulose ether is its viscosity. Due to its different viscosity, the water retention performance of cellulose ether also changes accordingly. As a result, the performance of the thermal insulation mortar changes at the same consistency. Among them, ZQ-8 has the lowest viscosity, followed by ZQ-10, and ZQ-15 has the highest viscosity. When the viscosity of cellulose ether increases, the dry density, compressive strength, thermal conductivity, softening coefficient, and antifreeze performance of thermal insulation mortar will decrease to a certain extent, and the extent is related to the specific composition and mix ratio of cement.

3. Conclusion

When the composition of the cementitious material remains unchanged and the mixing ratio is basically the same, it is recommended to add cellulose ether reasonably. When adding it, its influence on dry density, strength, thermal conductivity and other properties should be fully considered. At the same time, it is not possible to blindly pursue heat preservation. Blindly increasing or decreasing the content of cellulose ether due to certain properties of the mortar will affect the product performance of the thermal insulation mortar and affect the energy-saving effect of the product in the project.