6.1. Mixing Process

Your RMC transit mixer, it is also an example of free fall non-tilting reversible mixer. So, here also, you can see, there is only one opening. You have spiral blade arrangement inside. So, you have spiral blade arrangement inside. So, when you feed in the material, you have to rotate in one direction. So, when you want to discharge the concrete out, you have to rotate in the opposite direction.

The RMC (Ready Mix Concrete) transit mixer is a type of mixer used in concrete production. It falls into the category of free-fall, non-tilting reversible mixers. This means that it has a drum that doesn't tilt but can rotate in both directions. When you add materials to mix concrete, the drum rotates in one direction to mix everything thoroughly. However, when it's time to discharge the concrete (pour it out), the drum rotates in the opposite direction, which allows the material to flow out due to the design of the spiral blades. These blades help in achieving effective mixing and discharging of concrete.

Think of a RMC transit mixer like a blender where you blend fruits to make a smoothie. When you add fruits and yogurt and turn the blender on, it mixes these ingredients together (like the drum rotating in one direction). When you're ready to pour out the smoothie, you flip a switch to reverse the blades slightly, making it easier to pour out (similarly to how the drum rotates in the opposite direction to discharge the concrete).

So far, we discussed about the free fall mixers. So, they have different categories as we discussed tilting type, non-tilting, non-tilting reversible type. Now, let us move to the next category that is power mixer. So, here, the mechanism is different. Here, you are not dependent upon the free fall of the material. Here, we are dependent upon the rapid rotation.

In the world of concrete mixing, there are several types of mixers. The first group includes free-fall mixers, which can be further divided into tilting, non-tilting, and non-tilting reversible types. Each of these uses gravity to mix the materials. On the other hand, power mixers utilize a different mechanism that relies on rapid rotation instead of gravity. This allows them to mix materials more efficiently and handle stiffer mixes more easily.

Consider making a salad. With a traditional method, you might toss the ingredients using a spoon (like a free-fall mixer using gravity). However, with a salad spinner, you rapidly rotate the basket to mix and dry the salad greens, taking advantage of centrifugal force rather than gravity (similar to how power mixers work).

So, these mixer machines will be rotated at a very high speed. So, there will be some paddles fixed to the shaft inside pan or the drum. So, these paddles will be rotating at a very high speed that enables the rapid mixing and homogeneous mixing of the concrete. So, here, you are going to mixer concrete by rapid rotary motion of the paddles inside the drum. So, this is suitable for stiff and cohesive mixes.

Power mixers are built with paddle mechanisms that rotate at high speeds, allowing them to mix concrete effectively and quickly. This rapid rotary motion is beneficial for creating homogeneous concrete mixtures, especially when dealing with stiff and cohesive mixes, which are harder to blend using free-fall mixers. The high-speed rotation allows these mixers to handle lower slump mixes that would challenge a traditional mixer.

Think about mixing thick cake batter. With a hand mixer set on high speed, you can blend the ingredients uniformly, even if the batter is stiff. In contrast, trying to mix it by hand can lead to clumping and uneven distribution (similar to how a power mixer treats difficult-to-mix concrete).

We are going to see that. First, we are going to discuss about the pan mixer. It resembles the shape of a pan. You can see, there is a vertical shaft here and the paddles are connected to the vertical shaft. So, because of the rapid rotary motion of these paddles, you can have a thorough homogeneous mixing of the concrete.

A pan mixer is designed in the shape of a pan and utilizes a vertical shaft with attached paddles that rotate quickly. This design enables thorough mixing of concrete, achieving a uniform mixture. Because of the paddles’ rotation, even dense mixes can become homogeneous, making them ideal for demanding applications.

When you're mixing dough in a deep bowl with a sturdy spoon, the sides of the bowl can make it hard to incorporate ingredients. A pan mixer acts like having a high-powered spoon that can reach every corner quickly, ensuring a smooth, even mix just like how thorough dough mixing produces a well-blended batter.

So, another important thing, we have to note here is the mixing duration. The mixing duration is very critical. We have to make sure we meet at least a minimum mixing duration as stipulated by the guidelines of the manufacturer.

Mixing duration is extremely important in the process of creating concrete. It is essential to follow the manufacturer's guidelines regarding how long to mix the materials. Insufficient mixing time could lead to uneven mixtures, while too long of mixing can affect the quality of the concrete due to premature setting. Therefore, it is crucial to find a balance to ensure a good quality final product.

Imagine making a smoothie again. If you blend for only a few seconds, you'll end up with chunks of fruit instead of smoothness. On the other hand, if you blend it for too long, the smoothie can get warm and lose its freshness. Proper timing makes all the difference in achieving that ideal texture, just like it does in concrete mixing.

So, the mixer cycle time will depend upon your method of your loading and your type of mixer machine and this size of mixer machine.

When assessing how productive a concrete mixer is, one must calculate the cycle time, which is the sum of loading, mixing, and discharging time. Different loading methods (manual, tilting hopper, or conveyor), the type of mixer, and its size all influence this cycle time. Understanding these components allows for a clearer picture of overall productivity and efficiency.

Consider preparing a meal in a kitchen. If you take too long to chop vegetables, that adds extra minutes to cooking (like the loading time). If your oven takes longer to preheat, that adds to the cooking time as well. Understanding each step helps in optimizing how quickly you can serve the meal, just like optimizing mixer production helps in construction timelines.

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