DIY cinder block: mixes, molds, vibrators

Recommendation points

• Price or quality: what’s wrong with a home cinder block
• Mold for cinder block
• Vibration shrinkage is an integral part of the technological process
• Slag-cement mixture: proportions, dosage, additives
• We prepare the equipment and start production

The idea of ​​home production of cinder blocks is by no means new. Nevertheless, not everyone decides to make it with their own hands. In this article we will talk about in which cases the manufacture of a cinder block with your own hands is considered justified and what is needed for this, consider the production technology.

Price or quality: what’s wrong with a home cinder block

A well-known truth: the greater the mass of the mixture, the more accurate the observance of the proportions. Unfortunately, with small volumes of home production, the heterogeneity of the mixes is too high, which means that there can be no talk of any standardization. This has a detrimental effect on product quality..

The second side of the question: imperfect equipment. The technological cycle in factories has been carefully calculated by research institutes, even the humidity of the air during molding, the amplitude and frequency of vibration are taken into account.

Industrial sanitation is also important: at home, drying and storage conditions are violated, not to mention more difficult stages..

But at the same time, the responsibility of structures from a home cinder block is low, which means that some quality control rules can be neglected. Together with the high profitability of such production, this gives an obvious advantage. It turns out that for individual housing construction, an artisanal cinder block is the best fit, but there can be no talk of selling it.

Mold for cinder block

The main guarantee of a successful cinder block production is a high-quality shape. It should be welded from steel sheet 3 or 4 mm, have a clear geometry. The internal dimensions of the mold are 190x190x390 mm. About 30% of the volume should fall on the void formers (OP) – plugged pipe sections 60 mm, processed with angle grinders to obtain a cone. OP can also be done in any other shape.

Outside, the form is bordered by a steel strip, a kind of side is obtained. Inside the form, there is a jumper made of the same strip, connecting the two short sides of the rectangle. On this jumper, the OP are attached.

The form should have a neck for easy pouring. A clamping lid is inserted inside the mold, divided into two halves. It has slots into which, when lowering, the shape jumper and OP will pass. The cover should be fitted as closely as possible so that the gap at the walls does not exceed 1–2 mm.

In the best design, the clamping cover has a lever clamping mechanism, and the mold is mounted on tubular guides along which it can easily rise above the formed block without touching it. This machine makes the production of cinder blocks fast and very convenient..

Vibration shrinkage is an integral part of the technological process

The main difficulty in making a cinder block at home is the use of vibration shrinkage. As in vibrating tables, cinder block machines use platform vibrating motors. They are sometimes difficult to find, and the cost is high, so craftsmen use improvised means – old two-shaft engines from washing machines with homemade balancer weights. The vibrator is attached to the mold body with bolts or welded studs.

Vibration shrinkage cannot be neglected, it is of exceptional importance in the manufacture of high quality products. A poorly compacted mass can hide air streaks, leading to splitting of the product after drying. Without shrinkage, cinder concrete has a low density, which means that the wall mass loses not only strength, but also resistance to freezing, blowing and getting wet.

Slag-cement mixture: proportions, dosage, additives

Each master has his own recipes for cinder concrete and ways to prepare it. For small production volumes, a concrete mixer of 0.3–0.5 m will suffice³ mixtures. First, about half a bucket of water should be poured into it and cement should be added, then sand and the lumps should be completely dissolved. After adding gravel and slag, various additives, then thoroughly knead.

The mixture should be as dry as possible so that the molded product does not “blur” Ideally, add water in small portions until the concrete starts to form well when clenched into a fist. In this case, a lump thrown on solid ground should completely crumble into small crumbs..

The generally accepted ratio for the mixture is 2 parts of sand and fine gravel, 7 parts of slag, 1.5 or 2 parts of high-quality Portland cement of the M500 or M400 brand, respectively. You can safely use plasticizers, but you should not abuse them. Remember that it will not be possible to achieve a special gain in strength anyway, and this is not necessary, but it will not be superfluous to increase moisture and frost resistance.

Do not be afraid to experiment with the composition of cinder concrete. As a filler, not only blast-furnace slag can be used, but also granite screenings, expanded clay chips or specially prepared sawdust. There are a lot of materials and additives, therefore the properties of finished blocks vary in a wide range.

We prepare the equipment and start production

It is better to make cinder blocks in a covered and well-ventilated area with a hard and flat floor. The production site needs to be freed of debris, several dozen OSB plates with a size of 30×50 cm must be prepared, they will be placed under each molded cinder block.

So, the form is installed on a substrate and filled with concrete to the brim, then you need to turn on the vibrator for 20-30 seconds. After shrinkage, add concrete, turn on the vibrator again and press the mold cover until it rests against the inner walls limiting the height of the block. Further, with the vibrator turned on, the form is removed from the product and the entire machine is shifted by 35–40 mm, where the OSB is again placed and a new block is formed.

The blocks should stand motionless for about a day in a place that excludes their accidental deformation. They can then be transferred to pre-drying. After a week of aging, the blocks can be stored in several rows. The time for complete solidification of cinder concrete is four weeks. Ideal conditions – no direct sunlight and a temperature of 20-25 ° С.