Pozzolans can be blended with lime (or Portland cement) to produce blended cements that can replace pure Portland cement commonly used in building materials such as concrete, masonry block, masonry mortar, bricks, and other construction units.
Utilization of natural pozzolans in civil projects include structural concrete, precast and prestressed elements, mass concrete, concrete pipes, concrete masonry units, controlled low-strength materials, grout, mortar.
The benefits of using natural pozzolans in these applications are discussed in this article.
Uses of Natural Pozzolans in Concrete Applications
1. Structural Concrete
The application of natural pozzolans in concrete structures is either in the form of cement replacement materials or the addition rate of the natural pozzolan.
The natural pozzolans enhance concrete plastic properties, increase the cohesion and workability of the mixture, as a result, reduce segregation and facilitate consolidation, reduce permeability, and improve durability
2. Precast, Prestressed Concrete Elements
Natural pozzolans help precast and prestressed concrete elements to develop high early strength and obtain adequate durability. These are essential criteria in the construction of bridges, buildings, and parking garages in which precast and prestressed concrete elements are utilized.
The high early strength helps early removal of formwork. However, a high level of durability is necessary for structures that expose to moderate to severe conditions.
By and large, precast and prestressed concrete structure subjected to moderate to severe exposure category. High reactivity metakaolin is a natural pozzolans that used in the manufacturing of the precast and prestressed concrete units.
3. Mass Concrete
Nowadays, concrete that is used in the construction of sizeable dams contains natural pozzolans.
It reduces the heat of hydration; as a result, decreases the thermal stresses within the concrete that can cause cracking. The head of hydration reduction.
Additionally, it improves sulfate resistance and declines the potential for expansion from alkali-silica reactions.
4. Concrete Pipes
The use of a natural pozzolan can provide significant benefits in the manufacture of concrete pipe. It reduces the quantity of cement and maintain the necessary workability for pipe manufacturing.
The natural pozzolans improve the density of concrete pipes; minimize permeability.
Finally, the reduction of heat hydration of concrete contains natural pozzolans leads to a low possibility of hairline crack development.
5. Concrete Masonry Units
Natural pozzolans are used to produce concrete masonry units. It improves plasticity and cohesion and hence helps in compaction of concrete used in the production of masonry units. Since natural pozzolans reduce concrete durability, the formation of efflorescence on concrete brick units is decreased.
6. Controlled Low-strength Materials
Mixture of natural pozzolan, Portland cement, water, and fine aggregate used to produce controlled low-strength fill material in place of compacted soil. It does not require compaction to achieve necessary density, strength, and load-bearing capacity.
The main application of the controlled low-strength materials is as a replacement for compacted granular materials where installation and subsequent settlement could be problematic.
Additionally, the controlled low strength materials have been employed for trench backfilling, pipe bedding, foundation sub-base, paving subbase, floor fills, culvert backfill, filling abandoned tanks, manholes and sewer lines.
7. Grout and Mortar
The use of natural pozzolans in grouts is to improve workability, decline heat of hydration, reduce alkali-silica reaction expansion, reduced permeability, improve sulfate resistance, and for economic reasons.
The natural pozzolans in mortar might influence bond strength, setting time, and other crucial properties.