Mixing your own concrete is a common consideration when pondering whether to order a small amount of concrete, so here we will attempt to break down the costs involved with both home mixing and Palmix volumetric concrete deliveries. 
It is important to note that a good concrete mix requires particles of aggregates of all sizes. We use a 0/4 washed sand and a 4/20 limestone so from this we can see that a Palmix Concrete mix type contains aggregates in each size from 0mm to 20mm. During the mixing and laying process the materials are combined and any gaps between the bigger sized aggregates are filled with the smaller sized aggregates and the final product once tamped or vibrated will form a solid block with no air pockets. 

Cost for C20 Concrete 

Let’s look at the costs involved in two cubic metres of C20 concrete a common low to mid strength mix type but first we will need to know the quantities of sand, stone, cement and water required. 
From our Concrete trials and Calibration completed by Volumech Technical Services we know that for us to make 1m3 of C20 we will need: 
220 Kg of CEM I Cement 
903 Kg of 0/4 Washed Concrete Sand 
1009 Kg of 4/20 lime stone 
110 litres of Water based on a Water/Cement ratio of 0.5 
1. 4/20 limestone is a blend of stone where the smallest aggregate size is 4mm and the largest is 20mm. 
2. Water to Cement ratio or W/C is probably one of the most important factors in making concrete. Too much water and you will not achieve your desired concrete strength and you will also increase the likelihood of your concrete cracking. 
If you want runny (High Consistence/Slump) concrete to make pouring your footing or foundation easier then you have to either add more cement powder or use a Water Reducing Chemical (WRA) at the batching stage. You can’t just say ‘wet it up drive’ and expect everything to be ok. 
So now we know our quantities lets go and source our materials. This has proven to be quite difficult; I have looked at Selco and Travis Perkins as they are both a national supplier and while I can find a match for our sand and cement the concreting stone seems to be in the 10 -20mm range. As we mentioned above this will leave a gap in aggregate size from 5mm to 9mm so your home mixed concrete will be inferior to Palmix batched on site concrete but there you go.  
Mixing concrete with Ballast is also a popular home option so to be fair we will also do this comparison. 
Firstly, lets look at home mixing using separate sand and gravel. For the materials you will need; 
Bulk bags

Cement Powder 

Rugby High Strength Cement is a direct comparable to the cement we use – CEM 1 52.5N £11.45 + VAT for 25Kgs [read more about cement strengths here] 
The cement we are all probably familiar with, Blue Circle Ordinary Portland Cement (OPC) is a CEM II/A-L 32.5R  
This means it has early strength gain and is diluted with up to 20% Limestone and will reach a strength of 32.5Mpa. (Our Cem I is pure and reaches a strength of 52.5Mpa) 

0/4 Washed Sharp Sand 

Selco 850Kg bags £47.89 + VAT 
Travis Perkins 800Kg bags £59.41 + VAT 

10-20mm Gravel 

Selco 875Kgs £52.65 + VAT 
Travis Perkins 800Kg bags £59.41 

Ballast ½ inch to dust 

Selco 850Kg bags £44.29 + VAT 
Travis Perkins 800Kg bags £59.41 + VAT 

C20 x 2m3 needs 

C20 x 2m3 needs 
440Kg Cement = 17.6 bags @ £11.45 £201.52 
1806Kg Sand = 2.12 Bulk bags @ £47.89 + VAT £101.53 
2018Kg Aggregate = 2.3 Bulk bags @ £52.65 + VAT £121.10 
Total excluding VAT £424.15 
C20 x 2m3 using ballast 
440Kg Cement = 17.6 bags @ 11.45 + VAT £201.52 
3824Kg Ballast = 4.5 Bulk bags @ £44.29 + VAT £199.30 
Total excluding VAT £400.82 
* All prices correct at time of publishing 15/4/24 
These calculation prices obviously don’t take into account several key points: 
1. The time it takes to collect the materials from your local builders’ merchants 
2. The time it takes you to mix on site. 
3. You can’t buy 0.12 or 0.5 of a bulk bag 
4. I haven’t included any water in the mix designs 
5. No allowance either for wear and tear, fuel or electric or hire costs for your mixer 
Did you know that a full wheel barrow is about 0.03m3 so 2m3 will be approximately 60 barrow loads, if each barrow full takes 5 mins to mix this means you could be mixing for up to 5 hours in a standard sized mixer. As a comparison Palmix Concretes Volumetric mix on site lorry can mix a cube of concrete at a rate of 1m3 every 2 minutes. 
You might be surprised to learn that our costs for 2m3 of C20 delivered and mixed on your site could cost as little as £370 + VAT all done and in place as fast as we can pump it or you can move it. If it’s going to be tipped straight into a hole or footing 2m3 will be in there in 4 minutes. 

Our Concrete Sliding Pricing Scale 

We run a sliding scale where pricing is concerned so the more you need the cheaper it is, take a full load from £130 + VAT per cube. NB. Prices can and will change on a regular basis depending on our suppliers. 
With Palmix Concrete our mini mix deliveries and full load deliveries will give you up to an hour to unload and place your concrete so the usual rush, rush, rush of a traditional delivery is a thing of the past with us. If we can make the job easier for you then we will. 
It is important to recognise that you might say I’m not paying £11.50 for a bag of cement and I’ll continue to use OPC (CEMII) at £7 per bag + VAT instead of the CEM I we use and that is a fair comment but remember your mix will be of inferior strength and not a true comparison of our product. 
If we ran the comparison above using CEM II the saving would be £78.32 on each mix using the same quantities but remember you'll need to add more CEM II to achieve the same strength as CEM I. The mix using separate sand and aggregates would then be £345.83 and the ballast mix would be £322.50 all + VAT but you’d still have 5 hours of mixing in front of you! I think it makes sense to save your time and energy to have Palmix deliver your ready-mix concrete however much you require. 

Conclusion - Should I mix my own cement? 

• If you mix at home, unless you aggregate size covers 4mm to 20mm your concrete will not be as good as ours 
• If you use CEM II your concrete will not be as good as ours 
• You can’t mix 1m3 in 2 minutes 
• You won’t save any money mixing at home 
• If you buy bulk bags you will have material left over 
• You probably don’t want to be mixing 2 cube for 5 hours 
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