Starch ether is a polyacrylamide compound extracted from natural plants. It has the same chemical structure and similar properties as cellulose ether. Starch ether is mainly used in construction mortars. They can affect the consistency of mortars based on gypsum, cement, and lime and change mortars’ workability and sagging resistance. Starch ether is usually combined with non-modified and modified cellulose ether. It is suitable for neutral and alkaline systems and compatible with most additives in gypsum and cement products, such as surfactant, MC, starch, and water-soluble polymers such as polyvinyl acetate.
The main product characteristics of starch ether are improving sag resistance, workability and achieving greater mortar yield. The conventional dosage of starch ether in mortar is 0.01% ~ 0.1%.
The basic properties of starch ether are as follows:
Solubility: Soluble in cold water
Viscosity: 300MPa·s～800MPa·s;
Color: white or light yellow;
Particle size (sieve mesh diameter φ0.180mm): ≥98%;
Moisture: ≤10%.
Starch ether is mainly used in handmade or machine-blasted mortars based on cement and gypsum—Caulks and adhesives, tile adhesives, masonry mortars, etc.
Lime paste and micro-foaming agent
The lime paste is used as a water-retaining thickener in cement mortar. It has the advantages of good water retention and low price. It can effectively avoid the mortar shelling and falling off caused by the high water absorption of masonry (such as bricks) in use. Lime plaster is a traditional building material widely used in masonry mortars and plastering mortars. However, due to the poor water resistance of lime and unstable quality, the prepared mortar can have low strength and poor adhesion, thus affecting the quality of the masonry project. Moreover,the dust will be more prominent when lime powder is added, and the working conditions at the construction site will be poor and affect the quality of the masonry project environment.
Microfoaming agents can improve the workability of mortar by adding air-entraining agents such as rosin soap to the cement mortar to replace part or all of the lime. Adding microfoaming agents to the mortar can increase the volume of the slurry and improve the workability . The water consumption is also reduced accordingly. The appropriate amount of micro-bubbles generated after stirring can significantly reduce the contact points between the aggregate particles of the mixture, reducing the friction between particles. The mortar has good cohesion and is easy to construct. However，the amount of foam agent added should be manageable, as excessive addition will significantly reduce the strength and adhesion of the mortar.
Admixtures for Cement, Concrete, and Mortar
Concrete admixtures refer to substances added during the mixing process of concrete to improve the properties. The dosage of admixtures should generally be at most 5% of the cement mass.
Concrete is a composite material made of cementing materials and aggregates mixed in proportion, cured, and hardened under certain environmental conditions. Concrete can be divided into inorganic cementing materials and organic cementing materials according to the classification of cementing materials. Admixtures for concrete and mortar only act on concrete that uses cement as a binder among inorganic binders to improve the performance of concrete . With the continuous emergence of various admixtures, especially water-reducing admixtures, the large-scale application of pumping agents can improve the different properties of cement concrete and contribute to developing the construction technology of cement concrete. And the development of new varieties of concrete has created good conditions.
