Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1984-09-26
1985-10-08
Jacobs, Lewis T.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
524 2, C08K 300
Patent
active
045461325
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of making concrete weather-resistant and particularly to a method in which allowance is made for water absorbed into the pores of concrete to expand when the water freezes.
In the concrete industry, the expansion of freezing water causes problems especially in hydrotechnical structures. Water which is absorbed into the pores of concrete and freezes there produces micro-cracks, which in the course of time reduce the strength of the concrete. Only recently has a realistic picture been obtained of this micro-process, but satisfactory methods for preventing damage have not been known so far.
In order to prevent damage caused by freezing water it is necessary to produce in the concrete, in one way or another, micro-pores which are not filled with water absorbed into the pores of concrete but which allow freezing water to expand into them. In other words, the pores must be made to serve as buffers.
According to one method so far used, air bubbles are formed in concrete. For this purpose, a surface-active agent is added to the concrete mix, and as a result the surface tension of the water decreases, whereby air bubbles are produced in the concrete.
This known method can be said to have the following disadvantages:
the pores are too large in proportion to the capillaries of concrete and decrease the strength of the concrete
the entrained air does not remain homogeneously distributed, and the number of bubbles decreases during transport
the additional air-entraining agent used for the formation of the bubbles is in part absorbed during the preparation and transporting stage of the concrete mix by the carbon of fly-ash, which is nowadays increasingly used as a cement addition. Thus it has proven to be very difficult to obtain the correct quantity of additional entrained air in concrete.
Attempts have been made to reduce the said disadvantage by developing appropriate micro air entraining agents. One such agent is, for example, commercially available Kleenopor SA-8, which consists of plastic blisters. The diameter of the plastic blisters corresponds to the dimensions of the capillaries in concrete, and thus overdimensioned voids will not be produced. This and similar micro air entraining agents have, however, the following disadvantages:
the agent is very expensive
the plastic blisters are very lightweight, and special measures are required for mixing them with the concrete mix
the surface of the plastic blisters is weak, and so in order to avoid breakage of the blisters, the mixing must be carried out in a precisely determined order
the film of the plastic blisters does not tolerate temperatures above +70.degree. C., and therefore the blisters are not suitable for the increasingly common hot-concrete projects, in which the temperature of the concrete mix is +80.degree. C.
By the method according to the present invention it has been possible to eliminate the above-mentioned disadvantages.
In accordance with the invention, a suitable amount, determined through experiments, of a micro-sized rubber powder is mixed with the concrete mix; advantageously the powder has been ground from used automobile tires. The ground rubber may be natural rubber or synthetic rubber or, preferably, mixtures of the same. An advantageous mixture consists of 30% natural rubber and 70% synthetic rubber, for example in the form of styrene butadiene and polybutadiene.
Rubber powder is used precisely in the amount optimized according to need, the amount being between 0.2 and 2% by weight of the amount of cementing agent. The optimum particle size for the powder is between 10 and 250 .mu.m.
The mixing of a rubber powder prepared from used rubber, especially used automobile tires, with concrete mixes is previously known, but not for the same purpose and not with the same results.
The object of Swiss Pat. No. CH-602,515 is to produce more lightweight concrete by mixing with the concrete mix as a filler 10-90% plastic and/or waste rubber with macroscopic dimensions. The main objective is to achieve sufficien
REFERENCES:
patent: 1940528 (1933-12-01), Bond
patent: 2623914 (1952-12-01), Bell et al.
patent: 3301799 (1967-01-01), Rothberg et al.
patent: 4157998 (1979-06-01), Berntsson et al.
Chemical Engineering; Characteristics of Fine Particles; Jun. 1962.
Jacobs Lewis T.
Oy Partek Ab
LandOfFree
Method for making concrete weather-resistant does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for making concrete weather-resistant, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for making concrete weather-resistant will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2220545