Lime sand bricks are made from natural raw materials (lime, quartz sand and water). The bricks are used in supporting and non-supporting structures primarily to construct interior and exterior walls, and the brickwork is often exposed.

Lime sand brick has lost market share to competing building materials in Western Europea in recent years, and the decline in new building activity has also affected the industry. However, a number of new production facilities have opened around the world, for example in Eastern Europe and China.

Eirich offers a complete range of products for the industry, ranging from stand-alone machines to turn-key plants complete with state-of-the-art process control and the service you would expect from a partner who has been meeting the industry's needs with innovative solutions for many years.

During the manufacturing process, quicklime and water are placed into a pre-mixer. The lime-to-sand ratio is determined by weight (for example, 1:12). The lime and water are then mixed and fed into a reactor. Water is consumed during the slaking process which produces hydrated lime. Water is added to the mix in a re-mixer to achieve the correct level of moisture for pressing. Any lumps from the reactor are broken down and pigment is added as appropriate. Following mixing, the stone is pressed and then cured at about 200°C and 16 bar. During the curing process, silica dissolves on the surface of the quartz sand grains, forming crystalline binder phases with the lime hydrate binder (C-S-H phases). These phases grow on the grains of sand, forming permanent bonds. No contaminants are produced.

Eirich machines are used both for pre-mixing and re-mixing.

Eirich machinery offers the following advantages:

• Homogeneous distribution of all materials and uniform coating of lime on the sand
• Intensive wetting of the lime with water
• The full surface of the sand grains is activated to form calcium silicate
• Clay agglomerates, which inhibit the formation of high-density calcium silicate with fine pores, are broken down
• Lime agglomerates are reliably broken down
• Uniform brick structure when light aggregates or fly ash are mixed in
• No streaking when pigments are mixed in
• Low high-wear part count (only about 10 % of cost compared to ring trough mixers)

Unlike other mixing systems which are considerably older, EIRICH mixing technology allows users to adapt the mixing tool speed to the particular application. The tools run at higher speeds to break down agglomerates and disperse pigments to produce a uniform stone structure.

Higher mixing power compared to other systems reduces mixing time.

EIRICH PLCs use standard hardware. The company has developed special software modules to optimise the process flow in the lime sand brick industry. This software enhances operational reliability, and it is also suitable for modernisation of existing systems (e.g. replacement of Siemens Simatic S5 with Siematic S7).

The control systems manage the process parameters and collect a full set of data starting with metering of the raw materials and continuing right through to transfer of the processed material to the press. EIRICH weighing and metering equipment is designed to withstand the harsh lime sand brick production environment, and in combination with electronic weighing these systems deliver highly accurate results.

Our large standard range offers the following features:

• Setpoint verification
• Target/actual comparison
• Afterflow optimisation
• Tolerance monitoring
• Scale no motion detection
• Scale empty verification
• Automatic zeroing
• Formula calculation
• Balancing
• Logging (production / consumption)
• Service interval monitoring

The quality of the mix remains uniform despite variations in the moisture content of the raw materials. Using data which is captured by sensors, the controller constantly adjusts the amount of sand, water and lime which is added to ensure uniform moisture content in the mix which is fed into the press.

Two correction methods are available:

Lime/water correction

Different sands can be mixed in specific ratios. After the sand is weighed, it is homogenised in the mixer, and the water content of the batch is determined. The formula is calculated based on the moisture level, and the amount of lime and/or water which is added is adjusted automatically. If the metered quantity of sand already has a surplus of water, the surplus water can be absorbed as hydration water by adding more lime. This operation is also performed automatically by the metering control system, and the additional lime requirement is calculated.

Sand/water correction

Before or during metering of the sand, the sand moisture content is measured in the sand balance or in the silo outlet. The desired quantity of sand and the reduced water requirement are calculated from this value and added accordingly.

CaO log:

For each batch, a batch log and CaO log can be generated. The CaO log records the total fraction in % of all the CaO-laden components of the mix and their theoretical end moisture.

EIRICH has been a high-capability partner for the lime sand brick industry for many years.

With this experience base, EIRICH’s innovative engineering team has developed a range of well-matched machines and equipment which fit seamlessly into efficient, high-availability, eco-friendly production systems and which customers know that they can rely on.

Mixer, balances and control system are all manufactured inhouse. Plant planning and project implementation are also performed completely inhouse - from the first draft to the turn-key delivery

Customers report that they use less quicklime compared to other mixing systems without sacrificing strength (better distribution). Scrap due to surface defects on coloured bricks is greatly reduced (better distribution)

Machines with throughputs up to 130 t per hours are available for pre-mixing and re-mixing applications. More than 100 mixing systems have been installed over the past 20 years.