Hydrocolloids or the gums are used in cement to act as water-retention agents, thickener and binder, suspending agent, lubricant and friction reducing agent. Hydrocolloids can also act as air entraining agents, reducing weight without sacrificing strength and eliminating need of other additives. All these end uses require prolonged retention of water in order to permit proper hydration and setting of the cement and consequent development of high bond strength.
In cements mortars, hydrocolloids extends the open time or the workability of the cements, it improves water retention, increase adhesion to masonry, and reduce capillary absorption of water from the mortar, into bricks or blocks. This results in the mortar of higher strength. The artisan needs good workability of the mortar mix he is using. Set retardation of cement can be controlled depending upon the choice of type and molecular weight of hydrocolloid.
Performance and utility of cement mortars are drastically reduced if water loss takes place prematurely from the cement mix by a porous absorptive building material e.g. the bricks or a block. When hydrocolloids are used in cement-masonry mortar, it is possible to extend the ratio of sand to cement as high as 7:1, thus offsetting the cost of hydrocolloid, while achieving 3-4 fold increase in bonding strength of mortar.
Sodium carboxymethylcellulose (CMC) is used in grouting cements to suspend mineral fillers and metallic powders. It acts as set retardant for neat cements employed under condition of high temperature and pressure by reducing loss of water. It is preferably used in conjunction with a wetting agent, when it acts as a valuable additive in forming cellular cement for structural work. In the USA there is a practice to pump ready mix concrete in construction industry. Addition of about 125g of a suitable hydrocolloid to about a thousand liters of concrete can result in faster pumping at lower pressure and with reduced blockage.