Features of reinforced concrete foundation blocks

There is an opinion that the construction of a foundation for building a house can be significantly accelerated by using a block version of such a foundation. Indeed, the use of concrete foundation blocks in construction can save builders from the need for formwork, preparation of a reinforcing structure, mixing, pouring and placing concrete, greatly simplifying and reducing the cost of the process of foundation work.

Prefabricated foundations from reinforced concrete blocks become a decisive factor in the case when a high speed of construction is required. Concrete blocks with steel bar reinforcement, as an alternative to strip foundations, are used in industrial and residential construction, are used in the construction of private houses, several times reducing the commissioning time of the facility.

However, the acceleration of the pace of construction is not the only argument in favor of a prefabricated block foundation. The fact is that new technologies and the materials used in them make it possible to successfully construct relatively more massive buildings from bricks and wall panels. Concrete blocks are manufactured at precast concrete factories with pre-built technological characteristics and mechanical strength corresponding to GOST 13579-78. Due to this, the foundation made of them is more durable, stable uniform shrinkage and load distribution.

In addition, the construction of a block foundation from foundation blocks makes it possible to significantly reduce the level of rejects caused by violations of technological requirements when creating a reinforcing cage, in the process of pouring and placing concrete in a strip base.

Also, the risk of errors in observing the geometry of the foundation is minimized, arising from the squeezing out of fragments of wooden formwork by the concrete mass or unwanted shrinkage due to the flow of cement laitance into the soil. In addition, this technology significantly reduces the number of manual operations and reduces the risk of deterioration in the quality of concrete pouring due to violation of technological requirements and the timing of concrete work.

The process of concreting a foundation slab or tape is always continuous with a time gap between pouring sessions no more than four hours. A delay in the automatic mixer with a concrete mass somewhere on the road or worsening weather by the time the concrete is poured will most likely lead to problems with the strength of the foundation foundation being built.

Even with strict adherence to the pouring schedule, the required strength is achieved by the concrete material extremely slowly: it must settle and gain a foothold on the reinforcing cage, and the process of complete hardening of concrete, as you know, takes one month.

If reinforced concrete blocks with a safety margin of the order of 50-70% are used for the construction, then the fears of deformations or cracking are reduced to zero, and the construction of a foundation tape or a buried foundation is carried out with minimal losses.

However, the block method may not be recommended for all types of foundations.For example, its use is not possible when erecting a slab foundation or its pile-grillage variety. Sometimes, in the construction of low-rise buildings, a combination of foam blocks and a pile foundation is used, but only as a method of constructing the basement of the building.

Foundation blocks for industrial use. The technology for the construction of foundations from concrete blocks involves the use of block material of two types: for manual masonry and industrial use.

FBS blocks in this series are the main building material. Solid foundation blocks (this is how the abbreviation FBS stands) are used for the construction of wall strip prefabricated foundations.

FBV - auxiliary blocks. At their edges and on the end surfaces, they have technological grooves and protrusions, due to which channels and voids are formed in the structure.

FBP is a hollow foundation block. This variety is used to create lightweight foundation foundations.

All three of the above types of block foundation material can only be used in industrial construction with the use of professional measuring tools and lifting vehicles. This is due to the fact that the mass of the foundation block, belonging even to the smallest size series 12.4.3 tons, is 310 kg. And the most massive are FBS blocks (size series 24.6.6t) weighing 3.5t. Therefore, it is absolutely impossible to lay a strip foundation from such blocks or simply deliver them to a construction site without using special equipment. Moreover, the dimensions of such block products range from 880 × 600 × 580 to 2380 × 600 × 580 mm.

The technology for constructing concrete foundations from ready-made reinforced concrete blocks is almost identical to the method of brickwork or laying of cinder block material. However, there is a difference: the installation of a foundation from blocks is faster than brickwork. For this reason, various industrial and warehouse buildings, garages, overpasses, bunkers, basements and much more are successfully built from such blocks.

The strength and geometric proportions of the building largely depend on the correct laying of the first block row. To install FBS-blocks in it, products of the FL brand must be used. These base concrete slabs are designed for initial preparation, leveling the horizon and at the same time preventing shrinkage of the massive foundation block on a sand cushion at the bottom of the excavation.

FBS-blocks made of silicate concrete are considered the most difficult in the technology of arranging strip prefabricated foundations. Such products are sold with maximum stiffness and mechanical strength.

The idea of ​​building a foundation in the form of a prefabricated block structure is successfully implemented in a home building environment. Here, of course, you need to take into account that a heavy brick or two-story house made of wall blocks must be built on a full-fledged cast foundation tape, but such a large-scale construction does not always happen in the life of an ordinary citizen. More often, the foundation is built under the walls using foam blocks, from which it is customary to build sheds, baths or country country houses.

Taking into account the fact that the overwhelming majority of such buildings are erected without the use of specialized construction equipment, foundation blocks are selected for their foundations, intended for manual laying.Such lightweight concrete products are made from expanded clay concrete, foam concrete and silicate concrete.

If we try to compare the strength parameters of the materials named here, then we can come to the conclusion that the technical characteristics make it possible to use them with confidence for the construction of the MZLF tape. Some difficulty in this arises from the fact that the foundation base of a building made of foam blocks must be light, so that it can be folded on its own, and at the same time have rigidity that allows the box of the constructed building not to crumble from its own mass or wind pressure. In addition, such a foundation should not adsorb water from the ground.

A foam concrete block can stand in water for several weeks, remaining practically dry, because it retains the remnants of a blowing agent inside its porous mass. If you do not protect the concrete base from soil and atmospheric moisture, then the columnar foundation built from foam concrete blocks will crumble two years after the start of operation. The fact is that the residues of the blowing agent actively absorb moisture - and this can lead the concrete material to watering and cracking in the frost in winter conditions.

For the production of foundation blocks, see below.