For the production of cement and later mortar, first and foremost a blend of limestone and clay is used often present as a natural mix that is called marl. In addition, different additives or correction materials, such as slag sand, quartz sand, materials containing iron oxide, gypsum, schist or similar are applied to the crushed stone. The portland cement clinker is the burnt component of the cement that is responsible for curing it with water. As complex and customized is the process of making cement, so are the systems and technologies that are required. A common factor, however, always remains in place: The basic material must be crushed.

In a vertical roller mill or ball mill, the pre-crushed materials are further ground. The optimum feed grain size for each one of these mills is different; each normally requiring different pre-crushing systems for the production of the correct feed granulation. If not approached correctly, such mistakes can lead to a significant rise in the needed energy costs associated for the comminution or material pulverizing process.

An important parameter for the production of cement is the LSF (lime saturation factor). The LSF is defined as the rate of the most important chemical component, which has to be kept a constant within narrow limits. By selecting the first stage crushing plant or system the process of influencing the LSF already begins.

Control over the components, such as the limestone and clay (or marl) is indispensable. In many cases, subject to the material characteristics and percentages of each, the limestone and clay can be processed together in a single crusher. Under this condition, a certain level of homogenization is already taking place. To achieve this, the selection of the proper equipment is of vital importance and will further optimize operating costs and the final product. This is ensured by the selection of the complete system, not just a single or individual component. For example, although a compressive type crusher operates with less energy and wear, due to its lower reduction ratio and larger product size, you are faced with the need to include an expensive secondary crushing system to meet the desired product size. Alternatively, under the proper raw material conditions, the flexibility and reduction ratio realized in the primary impactor can produce and offer major advantages. The key is to find that correct and concrete solution; at HAZEMAG you will always find what you are looking for – expertise, experience, a trusting partner and the latest proven technology.

A primary pre-crushing plant normally consists of:

• feed hopper
• hopper discharge unit
• prescreening stage
• primary crusher
• crusher discharge unit

Depending on the characteristics and size of the feed material, these components must be designed in a manner that ensures trouble free operation, reliability and extended service life. These machines must be engineered in a manner that ensures their robust or heavy-duty design, allowing them to deal with the possible entry of metallic, foreign materials such as loader teeth, etc.

The characteristics of the raw material, moisture, inclusions of clays, compressive strength and chemical makeup highly influence not only the selection of aggregates, but also and especially the type of primary crusher that will be utilized. The consideration of mobility for the primary crushing plant is mainly influenced by the raw material resources and the associated transport distances.

Aggregates such as limestone, granite and gravel are essential to maintaining the quality of life around our world. This natural resource is used and enjoyed in nearly all aspects of our daily lives: residential and commercial construction, roads, highways, bridges, airports, fertilizers, toothpaste and even cosmetics. While the average person has a limited amount of knowledge to its origin, aggregate is making a major contribution to improving the quality of life for all of us. For the building industry, HAZEMAG is producing high-quality gravel and sand that are valuable raw materials for different industrial projects.

As varied and different is the geological makeup of this natural resource, so are the systems and technology that are selected in order to meet a vast range of construction specifications and consumer

demands. However, a common factor always remains in place; the basic material must be crushed.

In simple terms, crushing can be defined as the process of changing the size and quality characteristics of the raw stone by the use of an external source, such as a crusher. The targets of crushing are rather easy to define, such as:

■ Target 1: The process of taking the raw material in its natural state and changing its size in order to meet a range of construction specifications associated with concrete, road base, asphalt chips and even finer materials utilized in paints, fertilizers and medicines.

■ Target 2: The process of changing the shape of the raw material in order to meet those construction

specifications that call for the stones to be a more cubical shape.

■ Target 3: The process of increasing the quality of the raw material, known as beneficiation or selective crushing, which enhances the raw material by the elimination of softer, unwanted materials or inclusions.

■ Target 4: The process of increasing the quality of the material, known as upgrading, which eliminates the stones natural cleavages or internal weaknesses.

In order to achieve these targets, the processing plant normally consists of a combination of crushing and screening in multiple stages: primary, secondary and at times tertiary processing. Understandably, aggregate processing systems can be complex and normally require a high investment cost. The decision-making process of selecting the correct equipment is highly important; however, individual pieces of equipment alone do not ensure the success of any project. The ability to produce the products you need at the lowest possible cost are found in the overall system design; a design that offers proven equipment / technology, flexibility, efficient operation, safety / maintenance considerations and the ability of limiting the production of unwanted materials.