CS272394B1 - Admixture into concrete mixture formed by industrial waste - Google Patents

Abstract

Additive for concrete mix made of industrial waste. The solution uses the discovered properties of industrial waste for significant increasing the load capacity of piles. Industrial additive waste in quantities of 10 - 30 kg per 1 nP the finished concrete will increase its volume 4 to 10% and thereby transverse stretching the pile shaft, which will greatly increase the value cloak friction

Description

The invention relates to an additive to a concrete mix consisting of industrial waste containing alumina dust for the production of deep foundation structures, in particular piles.

Until now, piles are made of relatively high-quality concrete, the strength of which can rarely be used to transfer loads to the subsoil, because they are statically stressed mainly by pressure, less bending and, exceptionally, tension. It is therefore clear that the computational difficulty. pilots decide the limit state of the cross-section of the cross-section only when founding on a practically 'incompressible subsoil (rock). In the predominant cases of foundations of structures on piles of larger diameters embedded in more load-bearing soil, possibly floating, they transfer these vertical loads to the soil by mantle friction and the share of the pile heel in the load transfer is minimal. At the same time, the strengths of the concrete from which the piles are made reach relatively high values and are practically unusable. In practice, the dependence of mantle friction on the shear strength of soils is confirmed. The value of shear strength of soils according to the known expression 7 ^ = ^ x, tg ^ + c * (1) is directly dependent on _the magnitude of the horizontal force of the shear parameters of the soil - the angle of internal friction of cohesion c '. The authors came to the conclusion that the value of expression (1) can be influenced not only by the technology of large-diameter piles and their equipment, but also by the properties of the concrete mixture used. It is obvious that the value of x can be increased by using a concrete mixture with expansion effects. The increase in horizontal stress is caused by prestressing the soil in the immediate vicinity of the pile shaft due to the increase in the volume of the mixture, and thus the transverse expansion of the pile body. The application of known expandable cements is hindered by their difficult availability, but mainly by their relatively high price. The effect of the pure AI component is also known, which in contact with the other components contained in the concrete mixture causes its acquisition. However, the use of pure AI powder is very limited in terms of cost and difficult availability in the corresponding quantity.

The essence of the invention is that an additive consisting of industrial waste in the composition of 60 to 70% by weight, alumina Al 2 O 3, 6 to 10% by weight, sulfur dioxide SiO 2, 0.5 to 70% by weight is added to the other components in the concrete mixture. 1% by weight, iron oxide FeO, 0.2 to 0.4% by weight, copper Cu, 0.2 to 0.6% by weight, zinc Zn, 0.5 to 1% by weight, sodium Na, 0.5 to 1 % by weight of potassium K, 4% by weight of aluminum Al in a weight amount of 10 to 30 kg per 1 m 2 of mixture. The increase in volume change reaches the value of 4 to 9, the volume weight of concrete is around 21 kN.m ^ _{and the} cubic strength reaches 10 to 14 MPa after 28 days of hardening, which corresponds to concrete class BI (B135) in the sense of ČSN 73 12 Ol, respectively 73 20 01. In the production of large-diameter piles, it is necessary to ensure that the interval between adding industrial waste to the concrete mixture and filling the well for the pile is as short as possible, because the acquisition of the mixture occurs mainly at the time of its solidification - the most suitable method is separate concreting - prepact concrete.

The new technology for the production of piles with the use of the properties of industrial waste makes it possible to significantly increase the bearing capacity of piles, possibly to make pilots shorter, but with the same bearing capacity, which is achieved with long piles in the classic design.

Example of a specific design: «»

A large-diameter pile with a diameter of d = 0.6 m is embedded to a length of 1 = 5 m in the gravel class. B 10, relative bearing 1 ^ = 0.7. The pile is drilled rotationally, lined with a casing, which will be pulled out of the borehole before concreting. Pile concreting technology - prepact-concrete.

Concrete quality - concrete cl. III. with an admixture of industrial waste causing 3% acquisition of the mixture.

Mechanical parameters of soil: angle of internal friction / = 34θ specific gravity Ť? - 19 kN.m “ ³ horizontal modulus of deformation Eg = 10 MPa Poisson's ratio ⁼ °» ² 5

Mechanical properties of concrete: modulus of elasticity _ Fý = 26,500 MPa

Poisson's ratio = 0.15

Limiting mantle friction:

·. · Q _su = 0.7. T. d. 1. . 0.5. 1. tg ^ '= = 0.7. T. 0.6.5.19.2,5.tg 34 ° = 211.40 kN

At a 3% volume acquisition of the concrete mix, the pressure increase on the shell will be: _

26.5.10.10 ³ .0.01 = --------------------------------------- - = 87 kPa

10 (1 + 0.15) (1-0.3) - 26.5.10. (1 + 0.15)

Value of honeycomb friction increased due to transverse contraction of the pile shaft:

= 0.7. T, d J. (. 0.5. 1 + pi). tg f =. = 0.7 .7Γ. 0.6.5. (19.2.5 + 87) .tg34 ° = 598.5 kN

Conclusion: The value of honeycomb friction increased 2.8 times due to new properties of the concrete mixture.

- large-diameter pile with a diameter of d = 0.75 m is embedded in a layer of soft to hard clay class. D 21 for length 1 = 7.2 m.

The pilot is concreted with prepact concrete class. III with an admixture of industrial waste causing 3% acquisition of the mixture.

Mechanical parameters of soil: angle of internal friction specific gravity horizontal modulus of deformation Poisson's coefficient

Mechanical parameters of concrete:

modulus of elasticity

Poisson's ratio $ = 10 ° = 18 kN.m ^-3 Eg = 3 MPa Pj = 0.4

Fj, = 26,500 MPa = 0.15

CS 272 394 Bl

Marginal mantle friction:

^Q SU ⁼ ° » ⁷ * ^d * ¹ · ^ 2 · °» 5. i. (1-sin ^). tg $ =. = 0,7 0,75.7,2.18.3,6. (1 - sinlO ⁰ ) .tglO ⁰ = 112,12 kN

At 3% volume acquisition of the mixture, the pressure increase on the pile shell will be:

^Pz 'B ₅ (l * p _ř ) (1-2 fy l-Bj.tl * P _ř )

26,5.3.10 ³ .O, 01

----------------------------------------- = 21.43 kPa 3. (1 +0.15). (1-2.0,15) - 26,5.1O ^J. (1 + 0,4)

Casing friction value increased due to transverse contraction of the pile shaft:

= 0, i. 7Γ. d. 1. (<ý $. 0,5. l. (l-sin ^ ') + P ₂ )). t _e />' = = 0,7 .T. 0,75.7,2. ((18.3,6. (1-sinle ⁰⁾ + 21.43)). tglO ⁰ = 156.99 kN.

Conclusion: The value of skin friction increased 1.4 times due to the new properties of the concrete mixture.

Claims (1)

OBJECT OF THE INVENTION Concrete admixture, consisting of industrial waste, containing alumina dust, which is added to the concrete mixture in an amount of 10 to 30 kg per 1 m ^{3 of} concrete mixture, characterized in that it consists of 60 to 70% by weight of alumina AlgO 2. 6 to 10% by weight, sulfur dioxide SiO ₂ , 0.5 to 1% by weight, iron oxide FeO, 0.2 to 0.4% by weight, copper Cu, 0.2 to 0.6% by weight, zinc Zn, O , 5 to 1% by weight, sodium Na, 0.5 to 1% by weight, potassium K, 4% by weight, aluminum Al.