Menu
Forums
New posts
Search forums
What's new
New posts
New media
New media comments
New profile posts
Latest activity
Media
New media
New comments
Search media
Members
Current visitors
New profile posts
Search profile posts
Log in
Register
What's new
Search
Search
Search titles and first posts only
Search titles only
By:
New posts
Search forums
Menu
Log in
Register
Forums
Cattle Boards
Feedyard Board
A question for you concrete experts....
JavaScript is disabled. For a better experience, please enable JavaScript in your browser before proceeding.
You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an
alternative browser
.
Reply to thread
Help Support CattleToday:
Message
<blockquote data-quote="upfrombottom" data-source="post: 819509" data-attributes="member: 13088"><p>O.K. Mr. nova I won't argue your point about my opinion maybe helping someone, then again I </p><p>really wasn't in the mood for an argument over my opinion and am not so sure I am now, but, nevertheless I will offer one. </p><p></p><p>As far as thickness adding strength, it actually does. The strength that it adds is called shear strength. The thinner the slab, the less the shear force it can withstand. In most cases 4 inches can withstand the shear placed on it by a common automobile, but can't withstand the force of heavy machinery. Shear force is what causes a lot of potholes in roadways. So how would a person design a parking garage with a concrete slab of 4 inches? Well the easiest solution is to lower the ceiling and narrow the entrance so that nothing larger than a common automobile can enter.</p><p></p><p>There has been a great deal of research done trying to find a replacement for the component in concrete that adds the most to the cost, that being Portland cement. There are some that are used to reduce the amount of cement necessary to achieve the desired strength. One of those is fly ash, a waist product of coal burning power plants. Fly ash does not reduce the designed strength of concrete but it does significantly increase the curing time it takes to reach that strength. The fly ash will also increase the working time of concrete which is also desirable in most instances. </p><p></p><p>The tensile strength of the concrete itself is considered to be zero. Most can't understand how a slab lying flat on the ground can have tension force applied to it by driving a vehicle across it. A very easy way to understand it is to hold a pencil by the ends and with your thumbs push up on the center of it until it bends. The top of the pencil is in tension and the bottom is in compression; meaning your stretching the top fibers and compressing the bottom fibers. Since concrete has a great deal of compression strength and no tensile strength it will fracture or crack on the side in tension. By pushing or bending the pencil in the opposite direction the compression and tension will be reversed and it should be easily understood how the horizontal center of the pencil is the most neutral or has the least amount of tension applied.</p><p></p><p>Steel is the most common material used to resist the tensile forces that are placed on the concrete. Fibermesh is also a great reinforcement material but it should not be totally relied upon for its strength. I can remember doing an experiment in the laboratory using fibermesh compared to concrete wire. The tensile strength of the concrete with mesh was actually a little stronger than the concrete using common wire. As far as using wire compared to rebar it depends on the loads being applied to the concrete. Number 3 rebar or 3/8 rebar ( the diameter of rebar is commonly measured in 1/8 inch increments and specified by the number of eighths) put on 18 inch centers gives about 2 times the strength of the concrete wire and it also adds shear strength. If you use concrete wire and add fiber, you can easily get the same results and in most cases at a cheaper cost. </p><p></p><p>Based on all the variables that would have to be known to engineer a design for Mr. whitewing, I won't give a professional opinion, but I will suggest this, go to your concrete supplier and ask them to help you. I don't know the regulations that they have to follow there, but they do have formula's that they go by to design the strength of concrete and if you are not up to doing the job yourself, they can recommend someone reputable that can.</p><p></p><p>One thing that I forgot to add is moisture barrier. All concrete has air pockets and in instances where it is subject to freezing temperatures, an air entraining admixture is put in the mix to increase the amount of pockets. Concrete will wick moisture into the air pockets and if subjected to freezing temperatures it will crumble under the pressure or tension placed on it. The admixture is added to increase the number of pockets to allow a place for the expanding moisture to go. Lack of air entrainment is what causes surface spalding. So in my opinion all slabs that are to be used for storage of a material that is to remain dry should have a moisture barrier under it.</p></blockquote><p></p>
[QUOTE="upfrombottom, post: 819509, member: 13088"] O.K. Mr. nova I won’t argue your point about my opinion maybe helping someone, then again I really wasn’t in the mood for an argument over my opinion and am not so sure I am now, but, nevertheless I will offer one. As far as thickness adding strength, it actually does. The strength that it adds is called shear strength. The thinner the slab, the less the shear force it can withstand. In most cases 4 inches can withstand the shear placed on it by a common automobile, but can’t withstand the force of heavy machinery. Shear force is what causes a lot of potholes in roadways. So how would a person design a parking garage with a concrete slab of 4 inches? Well the easiest solution is to lower the ceiling and narrow the entrance so that nothing larger than a common automobile can enter. There has been a great deal of research done trying to find a replacement for the component in concrete that adds the most to the cost, that being Portland cement. There are some that are used to reduce the amount of cement necessary to achieve the desired strength. One of those is fly ash, a waist product of coal burning power plants. Fly ash does not reduce the designed strength of concrete but it does significantly increase the curing time it takes to reach that strength. The fly ash will also increase the working time of concrete which is also desirable in most instances. The tensile strength of the concrete itself is considered to be zero. Most can’t understand how a slab lying flat on the ground can have tension force applied to it by driving a vehicle across it. A very easy way to understand it is to hold a pencil by the ends and with your thumbs push up on the center of it until it bends. The top of the pencil is in tension and the bottom is in compression; meaning your stretching the top fibers and compressing the bottom fibers. Since concrete has a great deal of compression strength and no tensile strength it will fracture or crack on the side in tension. By pushing or bending the pencil in the opposite direction the compression and tension will be reversed and it should be easily understood how the horizontal center of the pencil is the most neutral or has the least amount of tension applied. Steel is the most common material used to resist the tensile forces that are placed on the concrete. Fibermesh is also a great reinforcement material but it should not be totally relied upon for its strength. I can remember doing an experiment in the laboratory using fibermesh compared to concrete wire. The tensile strength of the concrete with mesh was actually a little stronger than the concrete using common wire. As far as using wire compared to rebar it depends on the loads being applied to the concrete. Number 3 rebar or 3/8 rebar ( the diameter of rebar is commonly measured in 1/8 inch increments and specified by the number of eighths) put on 18 inch centers gives about 2 times the strength of the concrete wire and it also adds shear strength. If you use concrete wire and add fiber, you can easily get the same results and in most cases at a cheaper cost. Based on all the variables that would have to be known to engineer a design for Mr. whitewing, I won’t give a professional opinion, but I will suggest this, go to your concrete supplier and ask them to help you. I don’t know the regulations that they have to follow there, but they do have formula’s that they go by to design the strength of concrete and if you are not up to doing the job yourself, they can recommend someone reputable that can. One thing that I forgot to add is moisture barrier. All concrete has air pockets and in instances where it is subject to freezing temperatures, an air entraining admixture is put in the mix to increase the amount of pockets. Concrete will wick moisture into the air pockets and if subjected to freezing temperatures it will crumble under the pressure or tension placed on it. The admixture is added to increase the number of pockets to allow a place for the expanding moisture to go. Lack of air entrainment is what causes surface spalding. So in my opinion all slabs that are to be used for storage of a material that is to remain dry should have a moisture barrier under it. [/QUOTE]
Insert quotes…
Verification
Post reply
Forums
Cattle Boards
Feedyard Board
A question for you concrete experts....
Top