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When it comes to sawing, understanding the hardness of materials is crucial for achieving optimal results.  Hardness, which measures a mineral's resistance to abrasion, plays a significant role in identifying and cutting different substances.  By employing minerals of known hardness, we can determine the relative hardness of any other mineral, ensuring precision in our cutting techniques.

Concrete Cutting:

In concrete cutting, assessing the age of the concrete is essential for selecting the appropriate blade type.  Here are the stages to consider:

Stage 1: Green Concrete (10 hours after pour):

At this stage, when the concrete is still setting, using a deep draft segment is crucial.  This prevents abrasive action and the wearing of the core by eliminating the slurry or debris that forms during the cutting process.  The best time to cut green concrete is when it has reached a point where you can step on the slab without leaving an imprint.

Stage 2: Set Concrete (24 hours old):

As the concrete becomes more set or cured, the sand is held more tightly in the mortar, reducing its abrasiveness during cutting.  A slightly softer bond is required, but some level of abrasion can still occur.

Stage 3: Semi-cured Concrete (24-72 hours old):

During this stage, the sand is tightly held in the mortar, further reducing the concrete's abrasive properties.  A softer bond is needed compared to Stages 1 and 2.

Stage 4: Cured Concrete (after 72 hours):

Fully cured concrete has tightly held abrasive sands, making it less abrasive to cut.  When cutting, factors such as density, steel content, aggregate type, and atmospheric conditions need to be considered to determine the optimal usage and cutting properties of the application.

Aggregate Size:

The size of aggregates affects the cutting speed and difficulty.  Larger aggregate sizes result in slower and harder cutting.  Different aggregate types can also impact the wear rates and characteristics of the concrete blade.  In applications such as asphalt over concrete, the use of a mixed grit and grade is necessary to ensure the blade wears at the correct rate for optimal performance.

Asphalt Cutting:

Asphalt behaves differently from concrete, and its abrasive properties vary depending on several factors:

- The hardness of the aggregate affects the cutting speed.

- The sand binder in the asphalt determines the cutting and wearing rate.

- Large aggregates make cutting harder and slower.

- Porous and broken asphalt surfaces accumulate more dirt and sand, increasing abrasiveness.

When cutting asphalt, protective undercut segments are essential to safeguard the core.  Additionally, the depth of the asphalt and the presence of a sub-base must be considered to avoid premature blade wear.

Asphalt over concrete presents a unique set of conditions.  The abrasive nature of asphalt necessitates a hard, wear-resistant bond, while the softer concrete underneath requires a softer bond.  The depth of the asphalt layer and the concrete section further influence the bond selection.  Using a mixed grit diamond with varying sizes and shapes ensures efficient cutting in this application.

By understanding the characteristics and hardness of different materials, we can fine-tune our sawing techniques to deliver effective and precise results, prolonging the longevity of our blades and optimizing cutting performance.