What is a transit mixer? | Q & A

What Is a Transit Mixer?

A transit mixer is a specialized truck-mounted rotating drum vehicle used to transport ready-mix concrete (RMC) from the batching plant to the construction site while keeping the concrete in a workable, uniform condition.

Purpose of a Transit Mixer

• Prevents segregation of concrete during transport

• Maintains uniform mix and workability

• Delays setting until concrete reaches site

How a Transit Mixer Works

• The drum rotates continuously:

  • Charging direction → during mixing/transport

  • Discharging direction → during unloading

• Rotation speed:

  • Slow rotation during transport

  • Higher rotation during discharge

Key Features

• Rotating drum with internal helical blades

• Driven by truck engine or auxiliary motor

• Discharge chute for controlled placing

Typical Capacity

• Usually 4 m³ to 8 m³ per load (varies by region)

Site Engineer Checks on Arrival

• Delivery challan (time, grade, quantity)

• Slump value

• Drum rotation condition

• No unauthorized water addition

One-Line Interview Answer (Perfect)

A transit mixer is a rotating drum truck used to transport ready-mix concrete from the batching plant to the site while maintaining its workability and uniformity.

Common Interview Follow-Up

Q: Can concrete be mixed in a transit mixer?
A: Yes, final mixing and agitation occur during transit.

Site Tip for Fresh Engineers

• Note batching time vs arrival time

• Reject concrete if transit time exceeds limits without approval