The composition of concrete, except binding element (as a rule, cement) includes various fillers. Their use improves technical characteristics of concrete and also reduces its cost. Sand, gravel, crushed stone can be them. By production of light concrete the expanded aggregate the haydite which is formed when roasting clay or slate is also widely used.
The choice of sand for construction jobs
The fine aggregate – sand, finds the broadest application at concrete making. However different types of sand significantly differ in quality and operating ability. For example, the best sand for construction – river which practically does not demand additional cleaning. However the price is significantly higher than it. Beach sand also rather clean, however always contains the remains of sinks which reduce durability of ready concrete. Besides, it needs to be washed out, removing salts, and it increases sand cost.
Such washing is especially necessary by production of reinforced concrete, otherwise armature because of salts will quickly rust.
The sand extracted in mountain pits usually contains significant amount of clay and large stones of which it is necessary to get rid by means of washing or sifting.
By production of cement slurry it is desirable to use sand with average particle size not less than 1.2 mm, and at concrete making – with average size not less than 2.0 mm. If the weight of 1 m3 (cube) of dry sand is about 1300 kilograms (or slightly more), such sand can be considered ideal for construction jobs.
Coarse construction aggregates
Gravel, crushed stone and haydite belong to coarse aggregates. The choice of filler of a specific type is caused, first of all, by type of concrete which needs to be made. The ready-made product has to have the maximum allowed durability, iznoso- and frost resistance, to be waterproof. By production of massive building constructions when it is possible to use very coarse aggregate, usually apply gravel. If it is required to make easy masonry units, use haydite. When it is necessary to improve functional performance of external topping coat (for example, warm and sound insulation), and at the same time to reduce the weight and volume of design, apply perlitovy concrete.
In such concrete role of filler is played by volcanic breed perlite – or in natural look, or in so-called "bellied".
If you have to buy components for concrete preparation, previously find out what material will be the most suitable to you as filler, and count how many cement is required (from calculation that the ready concrete mix has to contain about 15% of cement on weight).