3.1. Importance of Mixing Duration

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. This is because the mixing duration needed will vary for different types of mixer machines. Your power mixer, the mixing duration needed is lesser when compared to the free fall mixer and also, the duration needed will vary with respect to the capacity of the mixer machine.

The mixing duration is vital for ensuring that concrete is thoroughly mixed. Each type of mixer machine has a specific recommended duration based on its design and intended use. Power mixers require less time to mix concrete compared to traditional free fall mixers. Additionally, the capacity of the mixing technology impacts how long mixing should occur. If the mixing does not reach the minimum duration specified by manufacturers, the mixture may not achieve the desired homogeneity, potentially leading to problems in concrete quality.

Think of mixing a cake batter. If you mix it just for a few seconds, the flour might remain clumpy, and the ingredients won't blend well, leading to a poor texture in the baked product. Similarly, in concrete mixing, not mixing long enough can leave parts of the mixture under-mixed, creating weak spots in the finished concrete structure.

So, generally, if you go for a lesser duration, then what is needed? What will happen? You will not get a homogenous mix that is a main problem and if you go for a very high duration, mixing duration also is not good because as you know that as you add water to the concrete, your cement starts setting. So, it will result in loss of water from the concrete due to evaporation that will affect your workability of the concrete.

Using too short of a mixing time leads to a non-homogenous mixture. This means different parts of the concrete may not contain equal amounts of cement, water, and aggregate, which impairs strength and durability. Conversely, mixing for too long can cause the cement to start setting before the concrete gets placed, losing its workability due to evaporation of water. Thus, there is an ideal window for mixing that needs to be adhered to.

Imagine frosting a cake: if you don’t mix the buttercream long enough, it will have lumps and not spread evenly. But if you mix it too long, it might become too soft and runny, making it difficult to use. With concrete, both insufficient and excessive mixing have detrimental effects, similar to frosting inconsistency.

So, we should go with a manufacturer recommendation. Guidelines for minimum mixing time for each batch is given in the IS 4925. It will apply the mixing time actually starts after all the materials are added into the concrete mixer machine except the full quantity of water is added in the mixer drum that means your mixing time starts counting after all the materials are added into the mixer machine other than the full quantity of water because commonly you can see that the water, you add it in parts.

Adhering to manufacturer guidelines is crucial for achieving optimal mixing. Specific guidelines, such as those found in IS 4925, provide distinct minimum time frames for efficient mixing based on the type of mixer and its capacity. Importantly, the mixing time is recorded only after all ingredients, except for the total quantity of water, have been introduced because water can be added incrementally to maintain workability.

Think about making soup. You don’t dump all the water in at once; you may add it gradually as you stir in vegetables, spices, and broth to avoid splashing and to ensure that everything blends well. In concrete mixing, water is often added in stages for similar reasons, ensuring everything mixes properly without losing the desired consistency.

Another important thing, you have to note here is; all the mixing water should be introduced not later than one-fourth of the mixing time has elapsed that means though, you add the water in stages but entire mixing water should be added not later than one-fourth of the mixing time has elapsed. This is a guideline available IS 4925. We are supposed to follow the guidelines.

Following specified guidelines like those in IS 4925 ensures proper mixing. One key guideline suggests that all mixing water must be added within a quarter of the total mixing time. This allows for adequate distribution of the water throughout the mix, preventing clumping and ensuring that the concrete achieves a uniform consistency.

When preparing a smoothie, adding all the liquid at once helps blend the fruits evenly to avoid chunks. If you delay adding the liquid too long, the blender struggles, leading to uneven blending. In concrete mixing, similar timing for water ensures a more consistent and effective blend.

So, this is what I told you. This table is available. It is taken from IS 4925 which gives you a guideline for concrete batching and mixing. So, you can see that the mixing duration is given in seconds. It varies for different types of mixer machines. Say, for instance, if you go for non-tilting reversible drum type mixer, the mixing duration is more. So, generally, for non-tilting mixer, it is more. When compared to the pan type mixer and the shaft mixer, you can see that the mixing duration is more for the non-tilting reversible drum type mixer.

The IS 4925 provides a valuable table indicating the required mixing durations for various types of mixers. Generally, the non-tilting reversible drum mixer needs a longer mixing time compared to pan-type mixers and shaft mixers. Recognizing these differences is essential for selecting the right equipment and ensuring effective mixing in concrete production.

Imagine different appliances in your kitchen: a blender takes a shorter time to mix liquid ingredients compared to a stand mixer that needs longer for thicker batters. In concrete mixing, just as with kitchen appliances, each mixer type has a different optimal mixing time to ensure that the materials blend evenly.

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