Whether it is to last the test of time for decades to come or to just last a few years before cracking, the mix of the concrete prior to the pour is crucial.
The Core Ingredients
The basic mix for concrete is made up of four key ingredients: cement, sharp sand, aggregate (this can be in the form of crushed stone or of small pieces of gravel) and water. The paste that is made up of the cement and water, is what holds the whole mix together. The other two ingredients, the aggregate and the sand, are what give the concrete its strength, and the way in which the cement, the aggregate and the water interact with each other is what affects the proportions of the mix.
Water-to-Cement Ratio
Excess water in the mix creates voids that evaporate as the concrete dries. This makes the concrete weak. A good mix for a domestic job is 0.5lt of water to 1kg of cement. Add the water gradually to achieve the correct consistency. A very runny mix is too wet.
Drum Versus Hand Mixing
For small repair patches hand mixing with a spade is acceptable but it is important to work quickly to try and avoid air pockets in the mix. The best way to mix small quantities of concrete is to fold the mix as opposed to stirring as this helps to prevent air pockets forming.
Common Mixing Mistakes
The most common mistakes when mixing concrete are adding too much water, not measuring the ingredients out the individual components correctly and letting the mix sit for too long before pouring. The mix will start to set within 30 to 45 minutes of mixing, so you must have your formwork ready.
Ordering Ready-Mixed Concrete
Ready mixed can be easier for large jobs as you can be assured of the correct mix and it saves the hassle of having to find somewhere to store the bulk of the concrete. There is more on Concrete Cheltenham at https://www.monstermixconcrete.co.uk/concrete-cheltenham/.
A well made mix of consistent quality, measured out and poured off quickly is the best for strength.
