concrete by Flor Azabache

Concrete is made up of a mixture of 4 components being such a binder (cement) coarse aggregate (crushed rock or boulder), fine aggregate (sand) and water. There are different types of concrete and these are characterized by possessing resistance, eg H21 characteristic whose resistance is 210 kg/cm2. The concrete strength is given by the relationship between the water both the cement and coarse aggregate as fine stone generate a skeleton, so a concrete boulder does have the same resistance as a concrete with gravel, it is not equal ratio of water - cement. Reinforced concrete is called in this way when the concrete is placed armor (Irons), these suits have the function of absorbing the tensile stresses in the structure, the concrete solicitation itself can not solve.

Concrete is a construction material sufficiently resistant to be worked in its liquid form, which can take almost any form. This material consists essentially of water, cement and other additives, which were later added a fourth ingredient called additive. Although cement is commonly called, are not to be confused, and indeed those mixtures that do dump trucks in construction are actually concrete, ie cement with additives to alter its properties.

When all of the mixing elements are included, is carried out the so-called sick to cement, process in which the fifth element is introduced, the air. Thanks to this procedure, the concrete becomes a mass that can be easily molded, however, care must be taken not to take too long, because after a few hours, the concrete hardens. Because of this, running time, this material loses its plasticity, becoming increasingly hard to completely harden.

There is the possibility of making certain modifications to the solid and liquid forms of concrete. This is achievable since the addition of certain elements in dosage form, and thus, power control, for example, the curing time of the material, shortening or lengthen it, according to the requirements of the manufacturer. Moreover, thanks to this same mechanism can reduce water demands of the mixture, include more air, or increase the chances of its workability.

Concrete is a very popular building material that, thanks to the plasticity of its liquid and solid form resistance, turns out to be the ideal material for outdoor work. Thus, the concrete behaves like material that allows us to live in houses firm and reach them driving through streets, highways and bridges. You can even say that this is the element that gives strength to our homes, streets and many places in which we conduct our lives.

It is common that instead of using a special cement to meet a particular case, this is can change some properties adding an element called additive. An additive is a material different from the normal concrete composition, ie a material which is added immediately before, after or during the realization of the mixture for the purpose of improving the properties of concrete, such as strength, manageability, curing, durability, etc.

nowadays, many products are on the market, and there are in liquid, solid, powder and paste. although its effects are described by the manufacturers, each of them should be checked carefully before using the product because their qualities are yet to be defined.

The most common additives used today can be classified as follows: 1.-entraining is a type of additive which when added to the concrete mixture produces an increase in air content causing, on one hand, an increase in workability and resistance to freezing and secondly The reduction in bleeding and segregation. Some of these products are: Inclusair LQ, Sika-Air, Air-Fest, Vinres 1143, Resicret 1144, etc.

2. - Fluidizers: These additives produce an increase in the fluidity of the mixture, or can reduce the water required for a given mix consistency, resulting in an increase in workability, while maintaining the same slump. Also, can cause increased resistance to freezing as both sulfates and improve grip. Some of these are: Festerlith N, N Dispercon, dENSICRET, Quimiment, Adiquim, Resecret 1142 and 1146, Adicreto, Sikament, Plastocreto, etc. 3. - Setting retardants: These additives delay the setting time in the initial mixing and, therefore, affect its strength at early ages. This may decrease the initial resistance. Recommended for warm climates, large volumes or long transportation times. Some of these are: Resicret 1142, Durotard, Hard-Rock N-14, R Festerlith, Sonotard, Festard, Retarsol, Adicreto R, R Densiplast, etc. 4. - Resistance accelerators: These occur, as the name implies, a breakthrough in the initial setting time by accelerating strength at early ages. Recommended for use in low temperatures to advance descimbrados. In addition, lower resistance puden final. Among these products are: Rrmix, Festermix, Secosal, Dispercon A, Rapidolith, Daracel 1145, Sikacrete, Fluimex, etc.

5.-stabilizers volume: produce a controlled expansion offset the contraction of the mixture for the setting and then this. Recommended for use in equipment support bases, fillings and resanes. Some of these products are: Vibrocreto 1137, Pegacreto, Inc 1105, Expancon, Ferticon Imp, Kemox B, C Interplast, Ferrolith G, Fester grouth NM, Ferroset, etc. 6. - Hardeners: These additives increase resistance to wear caused by impact and vibration. Reduce the formation of dust, and some of these are: Master Plate, Anviltop, Lapidolith, Ferrolith IT, Ferrofest H, duracrete, etc.

There are also other additives such as waterproofing membranes and adhesive curing. within these products have for the waterproofing, Fluigral Pol, Festegral, Impercon, Sikalite, etc. For membranes, Curacreto, Curafilm 1149, curalit, etc. and, for the adhesives used to bond old concrete with new Adhecon B, Fester bond, Pegacreto, Epoxicreto NV, Ligacret, etc. In common applications where additives are used, are the following: a) Construction of cisterns and tanks that are used in waterproofing. b) To carry high altitudes concrete by pumping can be applied fluidizing additives and / or setting retarders. c) in the repair of damaged structures where old concrete should be linked with new adhesive additives are used.

d) In casting, where temperatures are low, we use air entraining admixtures for concrete for the effect of freezing resistant. e) For the correct and efficient anchorage of equipment and machinery used expanders additives, which provide dimensional stability to anchor parts. Obviously re-emphasize that the use of additives must be knowing, in the first instance, the requirement and, thus, to properly define the product to be used. It is also extremely important to know well the characteristics of the additive that we use to get the desired results. Generally concrete additives modify specific properties to suit the work.

MEMBERS: ANGELICK VARGAS FERNANDO REINOSO FLOR AZABACHE 2013