What additional material can be used in neat cement grout to improve its properties?

Bentonite clay is often used in neat cement grouts as an additive to enhance its properties. When added in controlled amounts, typically up to five percent by weight, bentonite can significantly improve the workability and performance of the grout. It acts as a thickening agent, increases adhesion, and helps to prevent shrinkage, which is particularly beneficial in water well applications.

Bentonite has excellent water retention capabilities and can help to increase the viscosity of the grout, resulting in better sealing qualities around the well casing. This is particularly important in preventing the migration of contaminants through the annular space between the casing and the borehole. The addition of bentonite clay thus ensures greater integrity and durability of the well structure over time.

In contrast, other materials like silt or ordinary clay additives may not provide the same level of improvement in the grout properties as bentonite does, and in some cases, they could even compromise the performance of the grout. Sand, while sometimes used in other applications, is not suitable for this purpose as it does not offer the same benefits that bentonite clay provides in terms of hydraulic properties and sealing capabilities.