DE2120775B - Construction lightweight concrete - Google Patents

Description

Rohdichieklussc Test results - (nominal density) kg / dm ¹ 1.30 1.20 to 1.40 1.50 1.41 to 1.60 UO 1.61 to 1.80 1.90 1.81 to 2.00

It is known to produce a dense construction lightweight concrete that expanded or foamed mineral products of a silicate, clayey and / or carbonate nature such as expanded shale, Expanded clay, etc. or granules from waste products such as fly ash, slurry, etc .. the can also be sintered or steam-hardened, bound with cement paste in a suitable sieve characteristic will. The usual gravel and sand additions for heavy concrete are wholly or in lightweight concrete partially replaced by the above-mentioned lightweight materials, with the rest of the experience of concrete technology can be adopted unchanged.

The bulk densities of the lightweight aggregates are consistently above 0.4 kg / dm ³ , mostly 0.6 to 0.8 kg / dm ³ , sometimes even above, and the grain densities are around twice these values.

With decreasing bulk densities of the aggregates, not only do the concrete densities decrease, but also also the compressive strengths, especially with the coarse aggregates, while reduced grain strength the fine aggregate only has a slight or hardly any effect on the strength of the lightweight concrete, if they are combined with hard, coarse aggregates. When combining heavy, coarser and lighter Finer lightweight aggregates, however, separate the concrete mass, which is all the more pronounced the greater the difference in density of the aggregates and the lower the concrete consistency. The The homogeneity requirements of a structural lightweight concrete cannot be met in this way required security.

The interest in lightweight concrete with the lowest possible density with the highest possible compressive strength wedge is over Great for a variety of reasons, above all because of the increasing thermal insulation properties with decreasing density and the lightening of the vice of buildings. It did not succeed in the previously known ways.

The German Committee for Reinforced Concrete has so far expressly not allowed light * concretes with a bulk density of less than 1.20 kg / dm ³ for use in structural lightweight concrete because it assumes that a dense concrete structure with sufficient reliability is not possible with such concrete compositions.

The invention therefore has the task of proposing a construction lightweight concrete in which this "density threshold" of 1.20 kg / dm ³ - without endangering the tightness of the concrete and without any significant reduction in compressive strength - is significantly below. This is achieved by using highly absorbent, foamed, inorganic, concrete-compatible products with a smooth, unbroken surface, approximately spherical or ellipsoidal in shape with grain sizes of 0.1 to 6 mm. preferably 0.1 to 4.0 mm, and with bulk densities of 0.15 ± 0.10 kg / dm ³ as aggregates are combined with very hard, less absorbent, foamed or expanded or otherwise porous, inorganic lightweight aggregates with grain sizes of 4 to 25 mm and bulk weights of 0.6 ± 0.2 kg / dm ³ and according to the rules of concrete technology with a sufficient amount of cement and water with a water / cement ratio of 0.65 ± 0.25 and within the usual range , mostly steadily increasing sieve characteristics for aggregates are processed. The shaping by means of formwork with vibration with and without load and the setting are carried out in a known manner.

Despite the large differences in density between the finer, extremely light and the coarser, hard ones and heavier aggregates do not segregate during concrete production and pouring instead when the former have a strong absorbency for water. Therefore, in a preferred Embodiment of the invention the absorbency of the foamed, inorganic, concrete-compatible Products after soaking under water for one hour and dripping off for half an hour more than 15 percent by weight.

The shape of the lightweight aggregates with a small grain size of 0.1 to 6 mm, preferably 0.1 to 4 mm, is of the greatest importance for achieving the low-density construction lightweight concrete according to the invention for reasons of space conservation. Absorbent inorganic products of the density of 0.15 ± 0.1 kg / dm ³ required for the small aggregate with not smooth but broken ones

COPY

Surface, ζ. B. perlite, vermiculite among others are not suitable for the production of the lightweight construction concrete due to insufficient space filling of the invention, but such concrete-compatible, inorganic, foamed, granular products with a smooth or slightly rough surface of spherical or ellipsoidal shape with a space filling of more than 45% and high absorbency, whereby the absorbency in the grain is partially different can be.

Light granulates have proven to be particularly advantageous proved that according to German patent specification 1154752 or German Auslegeschrift 1 671266 from fibrous or powdery silicate material by digestion in aqueous alkali silicate solutions in proportion from 0.02 to 0.7: 1 or 0.02 to 0.8: 1, loosening, Drying, granulating and heating to 700 to 900 ° C and, if necessary, in accordance with the German Auslegeschrift 1 671 243 provided with a surface layer made of a high-melting substance and were then subjected to a temperature of 600 to 1000 ° C.

Particularly light alkali silicate particles according to German Offenlegungsschrift 1804137 can also be used are used during their production to avoid a shrinkage process in the plastic state Propellants that split off or vaporize gases at 400 to 700.degree. C. have been added to the particles or gas-generating reactions suffer, and then a predrying at 500 to 700 ° C was foamed.

Also suitable are light granulates according to German Patent 1 908 049, which are made from natural or artificial foamed silicate particles with the addition of lime and formed by reaction in Atmosphere containing water vapor were cured with dissolving or dissolving of the silicate particles.

Because of their small grain size, lightness, controllable absorbency, concrete compatibility and smooth, mainly round grain shape they are excellent with the much heavier, hard, little to combine absorbent, larger granulates based on expanded clay, expanded slate, fly ash, slag, etc., whereby a construction lightweight concrete with significantly improved properties than previously possible is. Because the surface of these small granulates is produced by melting release agents is hardened, abrasion is avoided during the mixing times customary in concrete technology.

The gap in the sieve characteristic of the aggregates for the lightweight construction concrete according to the invention from 0.06 to 0.1 mm can be achieved through low percentages of quartz powder or concrete-compatible fly ash getting closed.

Exemplary embodiments of the lightweight construction concrete according to the invention are those in Concrete recipes contained in the following table, whereby according to the provisional guidelines and the preliminary information sheet I of the German Committee for Reinforced Concrete (in the versions of August 1967 and July 1968):

Foam glass granules of the specified grain size and bulk density with an absorbency of 70 percent by weight are mixed with expanded clay granules of the specified grain size and bulk density with an absorbency of 7 percent by weight and moistened with water. A cement paste consisting of cement Pz 450, electrostatic precipitator ash and water is added to this mixture. The mixture with the consistency K 2 is poured into the formwork provided, with constant shaking. After 28 days, this lightweight construction concrete has reached the values for density, compressive strength and λ value given in the following table.

grain
density Schütt
density kg BeL
Grain-
V0I./I game 1
Bulk
V0I./I Volume
percent kg By S
grain
V0I./I game 2
rubble
V0I./I Volume
percent kg By S]
Grain-
V0I./I ) iel3
Bulk
V0I./I Volume
percent Cement PZ 450 3.12
2.5
1.0
1.0 350
100
180
42
0.7 112
40
180 cT
0 "
Il 300
100
168
61
0.6 96
40
168 cn "
cT
rn
Ό
ο "
Il
N_ 275
100
154
100
0.55 88
40
154 it ¹ Electrostatic precipitator ash 672 332 629 304 629 282 VO
vi
0 "
Il Water of hydration 2.6
0.9
0.8
0.22
0.22 1.6
0.50
0.45
0.11
0.10 169
235
104
14th
28 65
262
130
65
130 105
470
231
127
280 10
40
20th
10
20th 182
278
31
30th 70
347
139
139 109
618
282
300 10
50
20th
20th 187
144
55
47 72
180
250
215 112
320
500
470 N. Core water 550 652 100 521 695 100 433 717 Concrete liquefier 1222
1140
1200 984 1150
988
1040 999 1062,
918
960 999 10 271 250 150 80 25th
35
30th 0.43 0.35 0.30 100 Sand 0/1 Expanded clay 3/7 Expanded clay 7/15 Foam glass granulate
0/2 1/4 172 Dense for
Fresh concrete kg / 1 Dry concrete kg / 1 Nominal value kg / 1 Compressive strength kp / cm ² ..... Thermal conductivity λ
(calculate) = thermal conductivity
ability (according to) +, 20% ..

grain
density Schütt
density kg Ex
Grain-
Vol / 1 el la
Bulk
V0I./I Volume
percent kg Beisr.
Grain-
Voiyi «El 2a
Bulk
V0I./I Volume
percent kg Ex
Grain-
Voiyi iel 3a
Bulk
Voiyi Volume
percent Cement PZ 450 .. 3.12
2.5 350
100 112
40 300
100 96
40 275
100 88
40 Electrostatic precipitator ash 1.0
1.0 180
15th
0.7 180 168
20th
0.6 168 154
30th
0.55 154 Water of hydration 1.6
0.5
0.45
0.90 645 332 105
470
231
358 10
40
20th
30th 588 304 10
50
40 559 282 10 Keni water 2.6
0.9
0.8
1.65 169
235
104
322 65
262
130
195 100 182
278
459 70
347
278 109
618
510 100 187 72
180
465 25th
65 BV 830 652 919 695 144
767 717 100 Σ1 .. 1475
1420
1500 984 1507
1440
1500 999 1098 999 0.60 0.60 1657
1583
1600 Sand 0/1 250 250 0.68 Expanded clay 3/7 250 Expanded clay 7/15 Expanded slate 0/4 Σ2 Fresh concrete ... Dry concrete Face value Thermal conductivity λ
(calculate) = thermal conductivity
ability (according to) + 20% .. Compressive strength kp / cm ²

Explanations to the table

The foam glass granulate according to the invention contained in Examples 1 to 3 (Table 1) is in the examples la to 3a by a conventional lightweight aggregate of the same grain spectrum, namely by expanded slate.

The following table 3 contains a comparison of the characteristic data of the concretes according to Invention (Examples 1 to 3) and that according to the prior art (Examples la to 3a).

Table 3 example

3a

Fresh concrete density .. Dry concrete density nominal value kg / m ³ ...

difference

A values

1222 1140 1200

0.43

1475

1420

1500 0.300 0.60

1150

988

1040

0.35

1507
1440
1500
~ 0.450
0.60

1062 918 960

0.30

1657 1583 1600 ~ 0.650 0.68

With the conventional lightweight aggregate expanded (Examples 1 to 3). The data for the

slate increases the dry concrete density up to almost 50 thermal conductivity show the considerable advantage

1600kg / m ³ (Examples la to 3a), while with the foamed glass granulate according to the invention, in contrast,

low proportion of foam glass granulate in fine grain over conventional aggregates,
range, the density is less than 1000 kg / m ³

Claims (1)

Patent claims: I. Construction lightweight concrete, dadu rc h characterized that highly absorbent, foamed, inorganic, concrete-compatible products with a smooth, unbroken surface approximately spherical or ellipsoidal shape in grain sizes of 0.1 to 6 mm, preferably 0.1 to 4.0 mm, and with bulk densities of 0.15 ± 0.10 kg / dm ³ are combined as aggregates with very hard, less absorbent, foamed or expanded or otherwise porous, inorganic lightweight aggregates with grain sizes from 4 to 25 mm and bulk weights of 0, 6 ± 0.2 kg / dm ³ and according to the rules of concrete technology with a sufficient amount of cement and water with a water / cement ratio of 0.65 ± 0.25 and within the framework of the usual, mostly steadily increasing sieve characteristic for aggregates . • 2. Structural lightweight concrete _f according to claim 1, characterized in that the absorbency of the foamed, inorganic, concrete-compatible products is more than 15 percent by weight after being soaked for one hour under water and dripping off for half an hour. to produce a dense lightweight construction concrete of high compressive strength with densities below 1200 kg'm ^3. This can already be seen from the fact that the provisional guidelines for the execution and testing of lightweight reinforced concrete - version August 1967 - of the German Committee for Reinforced Concrete only allow the following bulk density classes for structural lightweight concrete.