DE1671214B1 - Process for the production of fast setting portland cement - Google Patents

Description

1 2

The invention relates to a method for producing the invention are as follows

production of fast-setting portland cement. Findings and the resulting task

Various methods are known to be used:

Preparation of fast-hardening Portland cement, e.g. as a benchmark for the degree of grinding of the unfired one by firing a pre-crushed raw mixture twice, the percentage content of SiO ₂ raw mixture was obtained with an intermediate solid product of the formula γ - 2CaO-SiO ₂ in the respective fractions of the ground material, that presented. Under SiO ₂ content or "SiO ₂ components" the afterburning with an additional amount of lime, both the free SiO ₂ as well as the mixed (Polish patent 43 444 and silicate present, converted to SiO _2, Kieselbritische patent 938 761) . With another 10 acid understood.

The process is carried out by firing a raw cements twice. It was found that the following percentage contents of the known mixes with increased lime content (RH Bogue, go to the production of fast-hardening Portland cements, "The Chemistry of Cement", New York, 1947, 2. Aufzemente der Fraklage, and PP Budnikow and MI Streikow in tionen the regrind of SiO ₂ components, calculated "Journal prikladnoj chimii" (Journal for applied i ₅ on the total content of the regrind of SiO ₂ chemistry - Russian), No. 4, p . 343, 1943). The following components are achieved:
Part of these processes are the increased fuel consumption, the cumbersome way of working and the ^{10 to 15} percent by weight
high manufacturing costs. in the 0.5 to 15 ^ fraction,

The production of fast ₂₀ 55 to 75 percent by weight is also known

hardening portland cement by a single in the 15 to 60 ^ fraction, ^

Firing of the pre-shredded raw mixture, e.g. up to at least 15 percent by weight

to a grain size of less than 50 μ (French. _A νλ Γ. ¹ ^ -Tn t,,, ·

Patent specification 1189,641); Only the 60 to 200 ^ fraction are used.

Easily grindable silicate constituents of the raw 25 (The grist supplied to the firing process segregates, which means that the raw material base is strictly adhered to, usually grain sizes below 0.5 and above the can be neglected.) such in known production of rapid-Portland distribution of the SiO ₂ components of the fractions of the cement of an output Portland performs crushing material for grinding _30, as has been found, when burning the cement clinker, of 57 to 63 weight percent Alit- to a delayed formation of the C ₂ S-form, demzuphase and up to 8 weight percent Tricalcium- sequence contains the CaO realuminate remaining in the free state, crystallizes up to a specific surface and its further interaction with from 3500 to 4000 cm ² / g and a content of SiO _{2 is} delayed, while the initially formed "",. ", __, .., 35 C ₂ S is subjected to a "connecting" recrystallization of 20 to 25 percent by weight (coalescence). These processes corrupt the fraction with grain size <5 μ, ^ _ηαβΓη ^ _{quality of the cement} .

55 to 60 weight percent from the above numerical formation is μ to grounding fraction having particle size of 5 to 30 ,, see that the SiO ₂ ingredient accumulates in the coarser to 6 weight percent * ° f ™ ^n; this is due to the fact that the fraction with grain size> 80 μ. ^d f ^{Korner mt h?} ^ ^em proportion of SiO ₂ -Bestandteilen

are difficult to crush. There is thus a

(IW Kravchenko, "using high-strength relationship between the content of the grains to Λ

fast-setting cements for the production of high SiO ₂ components and the degree of grinding. -

firm emphasis ”, Conference of the International Society

shank for materials testing - RILEM, Moscow, extensive fine grinding of the clinker an advantageous

1964.) adhesive distribution of the SiO ₂ components to the grains

However, this procedure does not guarantee the factions can only be reached if already

Production of fast-hardening Portland cement the grist fed to the firing process

with the required strength properties, which has 50 favorable composition, namely one

a significant influence on the strength of the content of SiO ₂ component of at least 20 Ge

Portland cement the clinker structure and the weight percent in the 0.5 to 15 ^ fraction and

Distribution of cement particles according to grain size at most 8 percent by weight in the 60- to 200-μ-

exercise within the factions. Fraction, i.e. if the salary in question

The 55 on which the present invention is based is significantly increased in the finer fraction, while the task consists in eliminating the above-mentioned coarser fraction is significantly reduced, disadvantages due to the development of a process for the production of fast-hardening Portland cement, while in the middle fraction the content is only insignificant is changed (from 52 to 75 weight percent, the maximum initial and final strength at percent to about 55 to 75 weight percent). The solution to the pre-expenditure essentially consists in minimal water requirements and minimal operating costs; this is to be done by applying an underlying invention,
optimal. Combination ⁵ of the grinding fineness of the raw mixture to the sintering and grinding of the cement and such a distribution of the cement particles 65 holding clinker, which reaches over 55 percent by weight of alite of the grain size, whereby a minimum and a maximum of 8 percent by weight of tricalcium aluminate contains water required by the cement without use, is characterized according to the invention in that any additives are guaranteed. that

(A) the grinding of the unfired raw mixture up to a content of SiO ₂ components, calculated on their total amount, of

(a) at least 20 to 30 percent by weight in the fraction of the grain size of 0.5 to 15 μ and

(b) a maximum of 5 to 8 percent by weight in the fraction of the grain size of 60 to 200 μ and

(B) grinding the clinker up to a particle size distribution of

20 to 25 percent by weight

in the 0.5 to 5 ^ fraction,

55 to 80 percent by weight

in the 5- to 30 ^ fraction,

up to 6 percent by weight

in the 80 to 200 ^ fraction

is carried out, the grain distribution within the fractions by the slope of the two parts of the curve in the diagram of Rosin-Rammler-Sperling with 0.4 to 0.5 for the 0.5 to 5 ^ fraction and 0.8 for the 5- to 30 ^ fraction
is marked.

As explained above, the unfired grist contains the fraction with a grain size of 15 to 60 μ the percentage that remains after summing the 0.5 to 15 μ and 60 to 200 ^ fractions.

The cements produced according to the invention are characterized on the one hand by increased reactivity and consequently a lower water requirement of the cement mixes, on the other hand due to an increased Strength of the concrete combined with a lower need for cement, especially for extraction high quality concrete types.

It is known that the slope of the curve in the diagram of Rosin-Rammler-Sperling in the case of fast-setting cements in the range of 5 to 30 ^ grain fractions is 1.0 to 1.2 (cf. B. B e k e in »cement-lime-gypsum«, 1960, No. 9, pp. 419 to 424). It goes without saying that these are fractions of the ground Clinker.

In contrast, according to the invention, this value is reduced to a maximum of 08 (value B), during the the corresponding value for the fraction should be below 5 μ to 0.5 (value A). It was found, that these values are the optimal ones.

If you decrease the value A by 0.1 to 0.2, namely to 0.2 to 0.3 (instead of according to the invention 0.4 to 0.5) and the value B to 0.5 to 0.7 (instead of at least 0.8 according to the invention), the water content increases (in percent by weight) in the cement paste of normal consistency by 2 to 3%, e.g. up to 28 to 29% (instead of 26%); this leads to an increased need for cement, as shown in the table below will be shown.

Water content

26th

27 to 28

29 and above.

Coefficient of the cement content

for concrete quality classes up to

300 I 400 I 500

In summary, it can be seen that, unexpectedly, according to the invention, a particularly advantageous granulometric Composition of the cement is achieved.

example

Chalk, clay and loam soil with the following composition were used as raw materials:

1.00
1.02
1.04

1.00
1.04
1.07

1.00
1.07
1.12

¹⁰ raw material SiO ₂ Al ₂ O ₃ Fe ₂ O ₃ CaO MgO SO ₃ Glow
loss Chalk.. 2.12 0.47 0.38 53.50 0.68 0.42 42.56 Volume ... 50.09 22.41 4.58 2.01 0.62 3.41 19.20 Clay floor 73.01 10.89 2.51 5.81 1.28 1.32 2.14

Pyrite brandies were also introduced into the raw mix.

The comminution of the raw material took place up to

a fineness of grinding, which by a residue amount on the sieve with δΟ-μ mesh of 6.5% and on marked on the sieve with 200 ^ meshes from 0.5 to 1.5% was.

The raw mixture obtained had the following composition:

30 ^si0 ° Al ₂ O ₃ Fe ₂ O ₃ CaO MgO SO ₃ Glow
loss total 13.52 3.50 2.55 42.54 0.55 1.30 35.50 99.46

In the individual grain size _{fractions, the SiO 2} , calculated on its total amount in the raw mixture, was distributed as follows:

SiO ₂ content in
Weight percent

Grain size in μ
> 60 40 to 60 25 to 40 | 0.5 to 15

7.4

8.9

34.0! 48.7

By restricting the SiO ₂ content in the coarser fractions, the reactivity of the comminuted raw mixture is increased. The increased SiO ₂ content of the finer fractions not only accelerates the sintering process, but also prevents the recrystallization of CaO at temperatures between 1150 and 1200 ^° C. by reducing the temperature of the reaction of CaO and SiO ₂ in the solid phase from 1200 to 1250 ^° C. is lowered to 1100 to 1170 ⁰ C, and ensures a uniform distribution of the minerals in the clinker and the formation of a geometrically regular crystal shape, namely a spherical in Belite and a monoclinic prismatic in Alit.

The raw mixture was fired in the subsequent short sintering zone in the rotary kiln Use of natural gas as a fuel.

The clinker obtained was in the petrographic investigation by pronounced crystallization of the Marked minerals: with Alit the average crystal size is 30 μ, the crystal shape is prismatic and belongs to the monoclinic crystal system; Belite, on the other hand, has crystals of a rounded shape, what indicates the correct choice of firing conditions.

The prismatic monoclinic alite crystals characterize this mineral as a solid solution with the substitution of SiO ₂ for Al ₂ O ₃ with the calculated amount of tricalcium aluminate up to 8% and determine the increased supply of thermodynamic free volume energy. The reduced size of the alite crystals and their larger surface area determine the increased supply of free surface energy. The two factors mentioned contribute to the improvement of the grindability of the clinker and to the enrichment of the fine cement fractions in active clinker minerals, namely in alite and tricalcium aluminate, whereby the speed of the increase in cement strength is additionally increased in shorter setting times.

The clinker is crushed in a cutting mill by the mechanical working conditions is chosen so that the cement obtained has a content of fractions has the following grain composition:

Fractions with grain size in μ Obis 5 I 5 to 71 7 to 10 i 10 to 15 I 15 to 20 20 to 25 ■ 25 to 30 I 30 to 60 60

Cement content in the fractions
in percent by weight

22nd

12 12

10

14th

The grain composition of the cement obtained is indicated in the diagram according to the Rosin-Rammler-Sperling coordinate system by a broken line, section 1 of which shows the weight distribution of the cement particles in fractions 0 to 5 μ and section 2 in fractions 5 to 30 μ. indicates. The angle coefficients, ie the tangent of the angles of inclination Q ₁ and <9 _a , are 0.4 to 0.5 and 0.8, respectively. Such a distribution of cement particles within the fractions mentioned ensures a reduced water requirement of the cement and brings about a greater increase in strength in shorter setting times and a uniform increase in the sequence.

The fast-setting Portland cement produced according to the invention has a compressive strength in samples from the solution with a hard consistency of the composition 1: 3 at the age of 300 to 350 kp / cm ^{2 for} 24 hours, 450 to 500 kp / cm ^{2 for} 3 days and 700 to 800 kp for 28 days / cm ² . The use of such fast-hardening Portland cements in high-strength concretes ensures essential advantages, such as shortening the duration of the hydrothermal treatment of precast reinforced concrete parts until this treatment is dispensed with when using stiff concrete mixtures, reducing cement consumption and producing high-strength concrete.

Claims (1)

Claim: Process for the production of quick-setting portland cement by firing the ground Raw mix up to sintering and grinding of the clinker obtained of over 55 percent by weight Contains alite and a maximum of 8 percent by weight tricalcium aluminate, characterized in that that (A) the grinding of the unfired raw mixture up to a content of SiO ₂ components, calculated on their total amount, of (a) at least 20 to 30 percent by weight in the fraction of grain size from 0.5 to 15 µ. and (b) a maximum of 5 to 8 percent by weight in the fraction of the grain size of 60 to 200 μ. and (B) grinding the clinker up to a particle size distribution of 20 to 25 percent by weight in the 0.5 to 5 ^ fraction, 55 to 80 percent by weight in the 5- to 30 ^ fraction, up to 6 percent by weight in the 80 to 200 ^ fraction is carried out, the grain distribution within the fractions by the slope of the two parts of the curve in the diagram of Rosin-Rammler-Sperling with 0.4 to 0.5 for the 0.5 to 5 ^ fraction and 0.8 for the 5- to 30 ^ fraction is marked. 1 sheet of drawings