How do you increase the compressive strength of mortar containing lime and Portland cement?

To increase the compressive strength of mortar containing lime and Portland cement, adding cement is the best approach. Mortar is primarily composed of a binder, such as Portland cement, which gives it its strength. By increasing the amount of cement in the mixture, the overall strength of the mortar can be enhanced.

The cement hydrates during the curing process, creating bonds that contribute to the structural integrity of the mortar. Lime, while beneficial for workability and flexibility, does not provide the same level of compressive strength as Portland cement. Therefore, while lime can improve other characteristics, such as adhesion and resistance to cracking, it is the increased cement content that directly improves compressive strength.

Adding water does not effectively increase compressive strength; in fact, too much water can weaken the mixture if it exceeds the optimum water-to-cement ratio. Adding mortar would not alter the fundamental mix proportions favorably and could lead to inconsistencies. Similarly, adding lime does not directly increase compressive strength; rather, it plays a different role in the mortar's properties.