Abnt Nbr 5580 Pdf |BEST| Download 4 👊
Abnt Nbr 5580 Pdf Download 4
This study employs concrete with vermiculite as a component of low cost to fulfill the demand on construction infrastructure, according to the provisions of the Brazilian standard ABNT NBR 6118 [ 3 ] that represents a particular class of concrete with a maximum capacity of 55 MPa for compressive strength. In addition, in this study the concrete used for testing is the commonly reinforced concrete (RC). In order to produce the concrete samples, two types of aggregates and three different concrete strengths have been used: 1040D concrete on medium sand concrete strength, 1040E concrete on fine sand concrete strength and 1040F concrete on gravel concrete strength. The first one were prepared as per the requirements of NBR 6118 [ 3 ] and NBR 12655 [ 4 ], and the second and third ones were prepared in accordance with the procedure proposed by the NBR 1996 [ 23 ] and the procedure in the ABNT NBR 6118 [ 3 ] for concrete with vermiculite. Thus, concrete, in the first type (1040D concrete on medium sand), aggregates with the following fineness (LN) values: 0.1639 (sand), 0.1528 (6R), 0.1539 (medium R), 0.1460 (3R) and 0.1414 (2R). In the second type (1040E concrete on fine sand), aggregates with the following fineness (LN) values: 0.1710 (sand), 0.1650 (6R), 0.1672 (medium R), 0.1614 (3R) and 0.1488 (2R). In the third type (1040F concrete on gravel concrete), aggregates with the following fineness (LN) values: 0.1888 (sand), 0.1796 (6R), 0.1730 (medium R), 0.1647 (3R) and 0.1488 (2R).
According to the ABNT NBR 5684, for design of buildings constructed with steel reinforcing bars, it is established that the design using a residual compressive strength of 1500 MPa, decreased up to 1250 MPa, may be considered sufficient, considering the implementation of a safety factor of 2.2 times, in compliance with the EN 12390: 2010, for buildings of brick, stone, concrete, pre-cast concrete or of complex construction, with two to four floors. There are other standards with the same specifications, as EN 11092: 2010, which is the one that considers the buildings of brick and concrete constructions, through its annex II. Acknowledging that the effects of thermal action are already present in the initial state of the tensile load and the durability of these walls can be affected, it is not specified in the standard, once the design procedure is performed keeping in mind the protection against fire, considering the use of design methods that allow to predict the functional behavior of the concrete, as estimated by the effects of thermal action on the tensile strength [ 5, 6 ]. The importance of studying the stabilization processes of a retrofitted concrete colonnade is that it is possible to know how to predict the minimum engineering condition for the design of the new stage, based on the residual design condition of the wall existing after the reinforcement incorporated [ 7 ].
For this purpose, the daily temperature rises the concrete and its degradation is determined by thermal stress, when the concrete begins to change the state of hydration and develops a friable and lime-air condition, allowing the free circulation of water that makes possible the elimination of the air, which indicates the beginning of the curing process. Once the cement is affected by a high temperature and the lime it is supersaturated, it begins to react with atmospheric carbon dioxide and water forming hydroxide and new calcium sulfate, which is typical of the monosulphate and disulphate. The process comes to an end when the equilibrium has been established, in the case of disulphate, where calcium sulfate has been formed and has replaced calcium chloride and calcium hydroxide, and in the case of the monosulphate, where it has been formed as a by-product of a reaction between calcium sulfate and water. abnt nbr 5580 pdf download 4 Thus, the development of the thermal action is divided into three stages, as follows: 1) The equilibrium between the cement hydration and the formation of hydroxide solution, when the time of reaction is the smaller, that is to say, when the total mass of the cement is greater than 90%, and in this condition, the cement, called friable and lime-air, begins to change the state of hydration. 2) The time of reaction is higher than 90%, but less than 95%, and the cement begins to be friable and lime-air when the mass of cement reaches the maximum established for the functional mix, that is, between 65 and 80% [ 8 ]. 3) When the time of reaction is equal to 95%, this is considered to be the stable condition and it indicates the end of the curing process, when the time the cement is considered to be in equilibrium, that is, equal to 120 minutes, time defined as the time for curing the concrete.