Views: 2 Author: Site Editor Publish Time: 2022-02-21 Origin: Site
The amount of HPMC hydroxypropyl methyl cellulose added to foamed concrete was increased to 0.5% and the slump decreased slightly. The data show that when the content of HYDROXYpropyl methyl cellulose is less than 0.05%, the participation of hydroxypropyl methyl cellulose can significantly improve the fluidity and viscosity of foamed concrete slurry. Hydroxypropyl methyl cellulose dissolves between solid particles and gas bubbles to form moist flexible film, which has excellent smoothing effect in mixing process.
If disillusionment breaks, it can also change the bubble. The uniform "rolling" of the stock into the stock effectively improves the fluidity of the fresh stock: however, when the amount of hydroxypropyl methyl cellulose exceeds 0.5%, the stock becomes too sticky and the fluidity is greatly reduced. Therefore, 0.05% hydroxypropyl methyl cellulose not only ensures slump, but also stabilizes bubbles, which is ambitious. The decrease in the height of the specimen after molding indicates the influence of hydroxypropyl methyl cellulose on the volume stability of foamed concrete. It can be seen that 0.05% hydroxypropyl methyl cellulose is used as the aspirant and the height decreases when the hydroxypropyl methyl cellulose is 0.05%. Anatomically, when hydroxypropyl methyl cellulose is suitable, the volume reduction of the hardened body can be reduced along with the improved fluidity of its slurry.
Hydroxypropyl methyl cellulose HPMC has a certain degree of negative effect on the flexural strength and compressive strength of mortar. With the increase of hydroxypropyl methyl cellulose HPMC content, the flexural strength and compressive strength of mortar gradually decreased. At the same time, hydroxypropyl methyl cellulose HPMC can improve the tensile strength of mortar. When the HPMC content of hydroxypropyl methyl cellulose is less than 0.1%, the tensile strength of mortar increases with the increase of HPMC content. Above 0.1%, the tensile strength does not increase significantly. Hydroxypropyl methyl cellulose HPMC can also significantly improve the shear strength of mortar. 0.2% HPMC mixture can increase the bond strength of mortar from 0.72MPa. Increase to 1.16 mpa. The results show that hydroxypropyl methyl cellulose HPMC can significantly prolong the cooling time of mortar and reduce the slippage of mortar.
This is very beneficial to ceramic tile stickup construction. For unbleached HPMC, when the mortar is cooled for 20min, the bond strength is reduced from 0.72MPa to 0.54MPa, and 0.05% and 0.1% H are added. After cooling PMC for 20 minutes, the bonding strength of mortar is 0.8mpa and 0.84mpa, respectively. Without HPMC mixing, the slippage of mortar is 5.5mm. With the increase of HPMC content, slippage rate decreased continuously. When the mixing amount is 0.2%, the sliding of mortar decreases to 2.1mm. The slippage of tile slurry is greatly reduced. The thin layer structure provides technical support.
Due to the particularity of self-leveling floor structure:
(1) Self-leveling layer is a secondary additional layer;
(2) The thickness of self-leveling layer is usually thinner than that of ordinary floor mortar;
(3) After self-leveling floor construction, the maintenance time is usually very short,
(4) Self-leveling layer needs to resist thermal stress from different materials;
(5) Self-leveling materials are sometimes used on substrates that are difficult to attach. Therefore, even with the help of the interface treatment agent, in order to ensure that the self-leveling layer can be firmly attached to the base for a long time, a certain amount of self-leveling special redispersible polymer powder tank is added to ensure the long-term and reliable adhesion of the self-leveling material. Whether on absorbent surfaces (such as concrete, etc.), organic substrates (such as wood), or non-absorbent substrates (such as metal, etc.) for example, on ship decks, the bond strength of self-leveling materials increases significantly with the increase in the amount of self-leveling special redispersible latex powder (see Table 1). Taking the failure form as an example, the failure of the self-leveling material used for self-leveling special redispersible polymer powder occurred in the self-leveling material or the base plane, but not at the interface, indicating its adhesion.
Hydroxypropyl methyl cellulose has excellent wet mortar viscosity, can significantly increase the adhesion between wet mortar and the base, and improve the mortar flow resistance. It is widely used for plastering mortar, tile bonding mortar and external wall insulation. System. The thickening effect of hydroxypropyl methyl cellulose also increases the resistance to dispersion and uniformity of fresh materials, preventing delamination, segregation and seepage, and can be used for fibre-reinforced concrete, underwater concrete and self-compacting concrete. The thickening effect of hydroxypropyl methyl cellulose on cement-based materials comes from the viscosity of hydroxypropyl methyl cellulose solution.
Under the same conditions, the higher the viscosity of hydroxypropyl methyl cellulose, the better the viscosity of the modified cement-based material, but if the viscosity is too large, it will affect the fluidity and operability of the material (such as gypsum knife). Self-leveling mortar with high fluidity is required, and self-compacting concrete requires adhesion of hydroxypropyl methyl cellulose. Very low.
In addition, the thickening effect of hydroxypropyl methyl cellulose will increase the water consumption of cement-based materials and increase the output of mortar. Hydroxypropyl methyl cellulose aqueous solution, which is highly viscous, has high thixotropy, which is also the main characteristic of hydroxypropyl methyl cellulose. Aqueous solutions of methyl cellulose generally have pseudoplastic, non-thixotropic flow properties lower than their gel temperatures, but exhibit Newtonian flow properties at low shear rates. Pseudoplasticity increases with increasing molecular weight or concentration of hydroxypropyl methyl cellulose, regardless of the type and degree of substitution.