| Popis: |
The choice of the concrete composition following the set research tasks must satisfy the following requirements: 1-the maximum achievable strength on the given starting materials; 2-the required formability, corresponding to the accepted vibration-impact-peristaltic pressing; 3-a given level of dehydration of the concrete mixture, providing a residual W/C, close to the normal density of the cement paste. The accepted conditions are necessary and sufficient when using the physical-analytical method of designing concrete composition. Distinctive features of the method are the use of a large amount of information and the absence of arbitrary coefficients, technological constants, or parameters. The necessary data for the assignment of concrete compositions are determined according to the data of preliminary laboratory experiments, the given technological parameters of mechanisms and equipment, and the design characteristics of concrete and the structure to be formed. For the experimental study, a total of six independent information streams of initial data are used: 1-physical and mechanical properties of the constituents of concrete (Rc, ρc, ρc°, [V/C], рс, γ3, ρshch, γsh, γshch°); 2-laboratory data of tests of raw materials in concrete mix and concrete (a, b, c, Ku, A, B); 3-design characteristics of concrete mix and concrete (Rb, F, W, OK, Zh); 4-characteristics of the product to be concreted (V, h, l, μ); 5-technological characteristics of equipment, mechanisms, and devices (th, tb, TO, t0); 6-the cost per unit volume of raw materials (Sc, Cn, Ssh, Se, Sg). Obviously, the listed volume of initial information comprehensively characterizes the materials used and the conditions for forming the product. The previously developed technological conditions for forming concrete pipes, in addition to the above, require, when assigning the composition of concrete, to take into account the observance of the balance of masses in the concrete mixture and compacted, modified concrete. This should be manifested in checking the equation of absolute volumes for the original and compacted (dewatered) concrete. |
