PL233549B1 - Addition for mortars and concretes - Google Patents

Abstract

An additive to mortars and concretes made of common cements as well as special cements has been disclosed, improving the mechanical strength of the hardened material and reducing the amount of cement in the mixture, with properties that accelerate the setting and hardening of concrete. The additive is characterized by the fact that it contains expanded perlite in the range of not less than 90% by weight, with a grain size of 0.1 - 10 µm, preferably obtained in the process of grinding any of its grain fractions, preferably pressed before grinding; auxiliary substances that prevent caking and accelerate the setting and hardening of cement, in the range not exceeding 10% by weight.

Description

Description of the invention

The subject of the invention is an additive to mortars and concretes made of common cements as well as special cements, improving the mechanical strength of the hardened material and reducing the amount of cement in the mixture.

An additive that reduces the permeability and increases the strength of concrete is known from the American patent description No. US8568527 B2. This additive contains ground perlite (pearlite ore) with grain sizes in the range 10-100 µm. It enables the improvement of strength by about 30% after 28 days of concrete hardening. The disadvantage of this solution is the use, in addition to the ground perlite ore, of fine fractions of expanded perlite, which have not been ground after the expansion. Therefore, its high water demand is maintained, which essentially limits the possibility of introducing such an additive into the cement mass.

From the US patent application No. US 20120152539 A1, binders are known which are obtained by grinding cement and unexpanded perlite (perlite ore) together and mixing cement and expanded perlite. They are intended for drilling applications.

EP 2004567 B1 discloses a perlite micro-filler obtained by grinding natural perlite (pearlite ore). It can be used in many industries, primarily as a filler in the production of plastics.

From the study by Yu L.-H., Ou H., Lee L.-L "Investigation on pozzolanic effect of perlite powder in concrete". Cement and Concrete Research 33 (2003) pp. 73-76, it is known to use natural, unexpanded perlite as an additive to concrete, allowing to replace some cement.

From the work of Z T.K. Erdem, C. Meral, M. Tokyay, T.Y. Erdogan “Use of perlite as a pozzolanic addition in producing blended cements Cement and Concrete Composites, 29 (2007), pp. 13-21, is known to use perlite as a component of common cements. Perlite was introduced into cements either by grinding or mixing separately ground perlite and cement. However, the presented solution does not allow the introduction of perlite to obtain strength equal to or better than the strength of the control cement. None of the perlite containing cements achieved a strength higher than the perlite-free cement after 28 days of hydration.

The additive to mortars and concretes according to the invention is characterized by the fact that it is expanded perlite, the grain size of which not less than 90% by weight is 0.1-10 µm, obtained in the process of grinding any of its grain fractions, and pressed before grinding under a pressure of at least 15 MPa.

The advantage of the solution according to the invention is that the fragmentation of the expanded perlite to such small grains, unlike the known solutions, allows to eliminate the unfavorable, in this case, very high porosity of the expanded perlite and to increase the specific surface of the ground grains, which in turn allows to significantly increase its chemical activity in relation to water solution of the liquid phase in cement slurries, mortars and concretes. The use of grains with an average diameter of a few micrometers, in addition to the favorable pozzolanic effect leading to the formation of additional amounts of C-S-H phase, allows at the same time to geometrically seal the pile of grit / mortar / concrete. This allows to limit the porosity of the hardened material, and thus improve the strength and durability of the material produced with its participation.

Due to the fact that expanded perlite of any granulation can be used as a raw material for the production of the additive, it is possible to manage the troublesome perlite waste dust generated in the plants producing and processing expanded perlite. This waste is not widely used, which, combined with its very low bulk density, causes great problems with its disposal.

The additive according to the invention makes it possible to reduce the amount of cement, which is favorable from the point of view of the economics of producing building materials as well as ecology. This allows to reduce the amount of mortars and concretes component, the production of which produces the most CO2 (cement clinker), and thus reduces CO2 emissions in the economy.

The subject matter of the invention is illustrated in the following examples.

P r z k ł a d 1

The additive to mortars and concretes is expanded perlite, crushed in a grinding device, preferably a ball mill to a grain size of 0.1-10 pm, the feed of which was pre-pressed under a pressure of at least 15 MPa, in order to obtain a density of at least 750 kg / m ³ .

The additive was used in mortars in amounts of 5-35% by weight of the cement weight. In the cement maturation periods indicated below, the yield properties were examined

PL 233 549 Β1 of poured mortar. Table 1 shows the results of the tests carried out in terms of the effect of the additive on the properties of the fresh mortar, while Table 2 shows the effect of the additive on the compressive strength of the mortar.

Table 1

Effect of the additive on the properties of the fresh mortar

additive content [% m. cement] spread [mm] air content [%] 0 142 2180 6.3 5 132 2210 5.3 10 126 2220 5.5 twenty 113 2200 7.2 35 103 2160 12.0

The test was based on the PN-EN1015-3 standard: Test methods for mortars for masonry. Determining the consistency of fresh mortar (using a spreader table).

Table 2

The influence of the additive on the compressive strength of mortars

additive content [% m. cement] relative compressive strength [MPa] 1 Day 2 days 7 days 28 days 0 100 100 100 100 5 122 118 120 132 10 143 133 133 147 twenty 124 120 127 165 35 106 117 122 184

The test was carried out on the basis of the PN-EN 1015-11 standard: Test methods for mortars for masonry. Determination of the bending and compressive strength of the hardened mortar.

The additive used in the indicated amounts improves both the early and final strength of the mortar. Subjecting the feed to the pressing process enables an efficient grinding process of the expanded perlite, which is easier compared to the grinding of the pearlite ore.

The conducted research showed that with the increase of the additive in the mortar, its normal strength increases after 28 days of maturation. With a 5% addition, this increase in strength is 32%, and with 35% it is 84%.

Increasing the amount of perlite does not significantly change the bulk density of the mortar, while with the increase in the amount of perlite, the air content increases and the flow rate decreases.

Example 2

The mortar was prepared in accordance with the PN-EN 196-1 standard: Cement testing methods. Strength marking. In the mortar, part of the cement was replaced with an additive in the form of ground perlite dust described in example 1, in the form of an aqueous suspension.

Table 3 shows the effect of replacing some cement with an additive on the properties of fresh mortar. Table 4 shows the effect of replacing some cement with an additive on the compressive strength of mortars.

Table 3

Effect of replacing some cement with an additive on the properties of fresh mortar

additive content (% binder) spread [mm] density [g / απ ’] air volume [%] 0 142 2180 6.3 twenty 128 2140 5.6 35 116 2140 6.9

PL 233 549 Β1

Table 4

Effect of replacing a part of cement with an additive on the compressive strength of the mortar

additive content [% binder] relative compressive strength [MPa] 1 Day 2 days 7 days 28 days 0 100 100 100 100 twenty 85 97 90 133 35 55 69 84 146

The conducted research showed that with the increase of the additive in the mortar, its standard compressive strength increases after 28 days of maturation. The increase in compressive strength of the mortar is not as large as in the example 1 embodiment (table 2), however, the use of the additive allows to save cement consumption while still having high product strength.

Claims (1)

Patent claim 1. An additive to mortars and concretes with properties that accelerate the setting and hardening of concrete, characterized by the fact that it is expanded perlite, of which not less than 90% by weight has a grain size of 0.1-10 gm, obtained in the process of grinding any of its grain fractions, and pressed under a pressure of at least 15 MPa before grinding.