In India, the most widely used blocks are AAC (Aerated Autoclaved Concrete) due to their strength, affordability, light weight and ease of construction. They are commonly used in residential, commercial, and infrastructure projects. A few different blocks used across India based on local availability and affordability are as below:-

1. Most widely used in high rise Towers are Aerated Autoclaved Concrete (AAC) Blocks

• Material: Fly ash, cement, lime, gypsum, and aluminum powder.
• Sizes: Various (e.g., 600 × 200 × 150 mm, 600 × 200 × 100 mm).
• Compressive strength:rangee from 3 to 4.5 N/mm²
• Water absorption: 15 to 20%
• Uses:wall Partitions(internal walls), non-load bearing walls within buildings. 

2. Fly Ash Hollow Blocks

• Material: Fly ash, cement, sand.
• Sizes: 400 × 200 × 100 mm, 400 × 200 × 150 mm.
• Compressive strength: 3.5 to 10 N/mm2
• Density : 1500 to 2000 kg/m3
• Water absorption: 10 to 12%
• Uses :suitable for non-load bearing walls and partitions due to its lighter weight and good thermal insulation properties

3. Concrete Hollow Blocks (CHB):

• Material: Cement, sand, aggregates, water.
• Standard Sizes (L × W × H in mm):
• 400 × 200 × 200 (8-inch block)
• 400 × 200 × 150 (6-inch block)
• 400 × 200 × 100 (4-inch block)
• Compressive strength: 3.5 to 15 N/mm2
• Water absorption: 8-10%
• Density: 1100 to 1500 kg/m3
• Uses : They are used in construction for load-bearing and non-load-bearing walls, fences, and other large structures. 

4. CLC (Cellular Lightweight Concrete) Blocks

• Material: Cement, fly ash, foam.
• Compressive strength: 3-10 N/mm2
• Density: 600-1000kg/m3
• Purpose: Lightweight, non-load-bearing walls, eco-friendly.
• Sizes: Similar to AAC blocks.

5. Hollow Clay Blocks (Porotherm Blocks)

• Material: Natural clay, burnt at high temperatures.
• Compressive strength: 3.5 N/mm2
• Density: 700-800 kg/m3
• Water absorption: 12-15%
• Purpose: Heat resistance, lightweight walls.
• Sizes: 400 × 200 × 200 mm, 400 × 200 × 150 mm.