Portland cement is generally used as cementitious material for dry mix mortar, and the amount of cementitious material generally accounts for 20% ~ 40% of dry mix mortar; Most of the fine aggregate is quartz sand, and the amount is large. Generally, it needs to be pretreated such as drying and screening to ensure that its particle size and quality meet the requirements of the formula; Sometimes, fly ash and slag powder are mixed as admixtures; Generally, the dosage of admixture is very small, about 1% ~ 3%, but it has great effect. It is often selected according to the requirements of product formulation to improve the workability, layering, strength, shrinkage and frost resistance of mortar.
Cellulose ether:
As a kind of basic additive in mortar formulation, it can provide good water retention, increased adhesion strength and improved workability. Wildly used in many kinds of dry mix mortar products.
Redispersible polymer powder:
Increase the flexibility, workability, bonding strength and water proofing of mortar. It has good effect in the application of wall plaster, tile adhesive, EIFS and self-leveling mortar etc.
Water reducer:
The basic function of water reducer is to reduce the water demand of mortar and thus improve the compressive strength of mortar. The main water reducing agents used in dry powder mortar are casein, naphthalene water reducing agent, melamine formaldehyde condensate and polycarboxylic acid. Casein is a kind of superplasticizer with excellent performance, especially for thin-layer mortar.
Retarding agent:
There are two kinds of coagulants: accelerator and retarder. Accelerator is used to accelerate the setting and hardening of mortar. Calcium formate and lithium carbonate are widely used. Aluminate and sodium silicate can also be used as accelerator. Retarder is used to slow down the setting and hardening of mortar.
Waterproof agent:
Waterproof agents mainly include: ferric chloride, organosilane compounds, fatty acid salts, polypropylene fibers, styrene butadiene rubber and other polymer compounds. Ferric chloride waterproof agent has good waterproof effect, but it is easy to cause corrosion of reinforcement and metal embedded parts. The insoluble calcium salt formed by the reaction of fatty acid salt and calcium ion in the cement phase is deposited on the wall of the capillary tube to block the pores, and at the same time, these capillary tube walls become hydrophobic surfaces, thus playing a waterproof role.
Fibers:
The fibers used for dry powder mortar include alkali resistant glass fiber, polyene fiber (polypropylene fiber), high-strength and high-modulus polyvinyl alcohol fiber (vinylon fiber), wood fiber etc. The fibers are distributed irregularly and uniformly in the cement matrix, and are closely combined with the cement, so as to prevent the formation and development of microcracks and compact the mortar matrix, so as to make it waterproof and excellent impact and crack resistance.
Defoamer:
The powdered defoamers used in dry mix mortar are mainly polyols and polysiloxanes. In addition to adjusting the bubble content, the application of defoamer can also reduce the shrinkage problem.
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