In-situ concrete and premixed concrete the difference in terms of building projects, convenience and costs?

Question

In-situ concrete and premixed concrete the difference in terms of building projects, convenience and costs?

Answer 1

In-situ concrete is concrete that is cast on site. It can be supplied by a Readymix Plant or batched on site.

A batching plant on site that weighs the materials and has sufficient capacity usually takes up quite a lot of space but the concrete is fresh. If you are a long way from a Readymix supplier and / or it is very hot then on site batching is better as readymix concrete may have started to set in the truck unless you add retarders.

If traffic jams are a major problem then on site batching is also more reliable.

If you have several big casts but lots of time between each then an on site batching plant  will usually not be economic. You would have to design the casts to suit the batching plant capacity (m3/hr output)

Books have been written on the subject.

It also depends on the quality control of the readymix plant and which other projects (and hence demand) is expected during the construction programme.

Answer 2

I think you mean what is difference of mixing concrete on site or use ready mix concrete, there are factors affecting the decision whether you need site mix or ready mix off site,

all relates to site conditions and logistics, also project duration and mobilization plan.

However the cost of the ready mix is higher than mixing on site using the own resources if available, also the quality control plays another role in selection

Answer 3

Depends on by  whom and how the in- situ concrete is being made.

On site if it is just being made by slinging the sand, cement & aggragate in by shovel then it amounts are not strictly accurate. Water is added by guesswork and to the likes of the tradesmen using it. Which means that the strength of each mix will vary everytime. The more water you add the weaker the concrete strenth.

If it is being mixed by specialist machinery (in-situ or specialist plant) then the ingredients and proportions are accurately weighed and the amount of water added is also measured and accurately added. Also we found that pre-mixed concrete was usually mixed better.