Archive for October, 2018

Seal Screed

Monday, October 29th, 2018

The surface of the leveled concrete layer, taking into account the subsequent its precipitation during vibroobrabotki should be 3-5 mm above the rails of Lighthouse. Missed concreted strip after removal of Lighthouse rails using concreted strip as formwork and guides. When laying concrete mixture in the ground near to covering the pillars of roofing installed gasket to prevent deformation of the floor with a possible draft of the building. Cutting surfaces on separate cards are not allowed. Seal the mixture produced screed CO-131a, CO-132, SB-163, etc., which move on rails lighthouse by flexible rods.

Given the small thickness of the concrete mixture in a coating time of vibration should be minimal (before the moisture on the surface), so as excessive vibration can lead to stratification and sedimentation of a mixture of coarse aggregate. Speed of movement screeds usually set 0.5-1 m / min. When you move the screed at its lower edge must be formed roller height of 2-5 cm to reduce the effort moving screed vibrator motor shaft rotation must be sent in the direction of screed. In places inaccessible to the screed (near-wall zones, areas between foundations and equipment, etc.), concrete mix is compacted rammers weighing not less than 10 kg. Before resuming the laying of concrete mix after the break, the vertical edge of the hardened coating is cleaned of dust and dirt and washed with water. In the field of working joints and smoothing concrete seal to spend as long as the seam will be invisible.

After compaction, concrete and setting it to the point where the surface while walking are It follows easily produce a primary treatment coverage smoothers and smoothing machines SB-103 SB-170, equipped with wheels smoothers. Formed during the initial processing finishing the horizon are corrected minor defects in laying and compacting concrete. At the end of 6.1 h after the initial processing of produce secondary processing machine with cover-135, SB-170, OM-700 as a working body which used blades.

Aggressive Media

Sunday, October 28th, 2018

The corrosion rate of metals and metal coatings in atmospheric conditions is determined by the combined action of several factors: the presence on the surface phase and adsorption films of moisture, air pollution korrozionnoagressivnymi substances, changes in air temperature and the metal, the formation of corrosion products and other assessment and calculation of the corrosion rate should be based on the length and material the corrosive effects of the metal the most aggressive factors. Depending on the factors influencing the rate of corrosion, it is appropriate following division of the operating conditions of metals subjected to atmospheric corrosion: 1. Enclosed with the internal sources of heat and moisture (heated rooms), 2. Enclosed with no internal sources of heat and moisture (unheated rooms), 3. The open atmosphere.

On degree of exposure to metals corrosion protection should be divided into non-aggressive, slightly aggressive, and sredneagressivnye silnoagressivnye. To determine the degree of aggressiveness in atmospheric corrosion Wednesday must take into account the operating conditions of metal structures and buildings. The degree of aggressiveness of the environment in relation to structures within the heated and unheated buildings, buildings without walls and constantly aerated buildings defined by the possibility of moisture condensation, as well as temperature and humidity conditions and the concentration of gas and dust inside the building. The degree of aggressiveness of the environment in relation to structures in the open air, not protected from direct contact with precipitation, the climate zone and the concentration of gases and dust in the air. Taking into account the influence of meteorological factors and aggressive gases developed classification of the degree of aggressiveness of media in relation to the structural metal, which are presented in Table 1. Thus, the protection of metallic structures from corrosion is determined by the aggressiveness conditions of their ekspluatatsiiyu. The most reliable protective systems of metal structures are aluminum and zinc coatings.