Mobile Concrete Plant

Overview

A mobile concrete plant batches and mixes concrete directly at the job site instead of trucking ready-mix from a fixed plant. The whole machine, the Aggregate Batcher, the Cement Silo & Feed, the Water & Admixture System, the Twin-Shaft Mixer, and the Control Cabin, rides on one road-towable Trailer Chassis. A site crew tows it in, jacks it level, raises the silo, and connects power and water. A typical unit is producing concrete within a working day and needs no concrete foundation, which is what makes it useful for remote roadworks, dams, wind-farm pads, and small precast yards where a permanent plant would never pay back.

Output is in the 30 to 60 cubic metres per hour range. The plant works in discrete batches: it weighs out sand, stone, cement, water, and admixture in the proportions the recipe calls for, drops them into the mixer, mixes for 30 to 40 seconds, and discharges into a truck or a skip. The recipe and all of the weighing are run by the Control Cabin, so one operator can hold the mix consistent batch after batch.

Trailer and setup

The Trailer Chassis is a welded Main Frame in S355 structural steel carrying every other subsystem. For transport it rolls on two Road Axle units, each with a leaf-sprung beam, road wheels, and sealed Ball Bearing hubs running behind Oil Seal units. A Drawbar & Coupling with a pintle eye connects to the towing tractor. On site, four Leveling Jack screws take the load off the tyres and bring the frame level, and four Outrigger Leg legs pin out to widen the footprint so the raised silo stays stable. Levelling matters because every load cell in the plant assumes the structure is plumb.

Aggregate batching

Sand and two stone fractions are stored in the three-compartment Aggregate Bin, a sheet-steel hopper with Bin Divider Plate plates and Hardox Abrasion Liner Plate panels on the high-wear faces. Each compartment empties through a Bin Discharge Gate, a blade driven by a Pneumatic Air Cylinder, and a Bin Wall Vibrator keeps damp sand flowing. Material drops onto the Aggregate Weigh Hopper, which hangs on three Load Cell units. The control system opens each gate until the running weight hits the target, then closes it, so the three aggregates are cumulatively weighed in one hopper. When the batch is complete the hopper gate opens and the Charging Conveyor carries the aggregate up into the mixer. That belt runs on a Belt Gearmotor built from a Stator Assembly, a Rotor Assembly, and a Helical Gear Pair inside a Gearbox Housing.

Cement, water, and admixture

Bulk cement is blown into the Cement Silo & Feed by a tanker. The bolted Silo Shell vents displaced air through a Silo Dust Filter, and a Cement Level Sensor warns when the silo is low. At the cone, fluidizing pads and a butterfly valve feed the Cement Screw Conveyor, whose auger flight is turned by a Screw Gearmotor. The screw doses cement into the Cement Weigh Hopper, again on three Load Cell units, to roughly half a percent. Water is held in the Water Tank and metered by a Water Flow Meter on the line from the Water Pump. Chemical admixtures, plasticizers and retarders, come from the Admixture Dispenser, where a Admixture Dosing Pump meters small volumes against an Admixture Flow Meter.

The mixer

The heart of the plant is the Twin-Shaft Mixer, a forced-action twin-shaft mixer. Two Mixer Shaft assemblies turn in opposite directions inside a lined Mixer Trough, each carrying eight Mixing Paddle blades on Paddle Arm supports. The intermeshing paddles fold the materials together and reach a uniform mix in well under a minute, which is why twin-shaft mixers are preferred for stiff, low-slump concrete. The shafts run through Shaft Seal Gland units packed with Oil Seal elements to keep grout out of the bearings. Drive comes from the Mixer Drive Motor, a three-phase induction motor, through the twin-output Mixer Gearbox, which uses three Helical Gear Pair sets and a stack of Ball Bearing units in its Gearbox Housing to synchronize the two shafts. When the batch is ready the Mixer Discharge Gate drops open under twin air cylinders. The trough floor and walls wear fast, so they are protected by replaceable high-chrome Trough Wear Liner tiles.

Weighing, air, and control

Accurate concrete depends on the Weighing System. Every weigh hopper sits on shear-beam Load Cell units wired through a Load-Cell Junction Box to a Weigh Indicator with an LCD Panel readout. Gate actuation is pneumatic: the Compressed Air System runs an Air Compressor into a receiver and dryer, then a Solenoid Valve Bank routes 8 bar air to each Pneumatic Air Cylinder, with a Pressure Sensor watching line pressure. The Control Cabin ties it together. A Batching PLC reads the load cells and flow meters, drives the solenoids through I/O Module cards full of Relay outputs, and shows the operator a recipe screen on the HMI Terminal. Motor power is switched in the Power Distribution panel, where a Motor Starter with a contactor and thermal overload protects each drive.

Use and variants

Smaller skid-mounted versions drop to about 20 cubic metres per hour for tight urban sites, while larger trailer plants pair with a second silo to switch cement types mid-job. The same architecture scales up to stationary plants by swapping the trailer frame for a foundation and adding aggregate scrapers and storage. Maintenance is mostly wear-driven: paddle tips, trough liners, and the screw flight are the usual replacement items, and the load cells are recalibrated against test weights on a set schedule.