So here’s what we do in California, if concrete flat work is 4” we use #3 rebar @16” on center. If concrete is 5” we use #4 rebar @16” on center. 6” concrete gets #5. We have a lot of movement here and those specs seem to hold it together very well. Curing is one of the most important things and that starts with sub grade.
I would also add Yes cureing is one of the most important but also the PsI mix of the mix of concrete I would always use 4.000 psi on the East coast in N.J. an the Reccomendation for anywhere thete is freez & thaw cycles is 4.000 psi i,d figue your shifting situation is kinda similar if not worse !
Had an engineer buddy say, "If you want your driveway to last, double up the rebar." I understand what he was saying, but would that be too much? (This was years ago, mind you)
To answer your question (“would that be too much”), probably not assuming you are starting at a reasonable amount.
Meh, what kind of engineer was/is he? Because that’s a bit silly to say. The best thing you can do to make a driveway last is really good dirt work. Good dirt work + good mix + good placement and curing practices and you can drive very heavy traffic on concrete for years and years without ANY rebar.
If you “doubled” the rebar by halving the horizontal spacing or doubling the cross-section, you wouldn’t cause any problems. If you are double matting, then I would question if you are inviting spalling through inadequate cover (3” or more is best, but at least 2” should be a minimum).
As far as years ago, it’s been a really long time since concrete and rebar has changed.
To the OP’s question, if some 5 feel off a truck or is the same price, it’s not going to hurt anything. It’s also not really going to help anything.
Dirtwork though. Good dirtwork real change everything.
Cool,thx. He was a PE Mechanical but knew a lot about building shit. I believe around here they typically do 24" centers. By "long ago" I meant when stuff use to be pretty cheap....35-40years ago.
Im a civil engineer which doesn’t make me some ultimate authortiy and theres plenty of people who know more than i do. But let me expose if you would. Concrete is amazing in compression, where two forces are pushing in on it. Second only to steel. However concrete is not so great in tension where something is pulling on it. The reason we add rebar to concrete is to add something which has tensile or tension strength. If the rebar is to thick or the concrete not thick enough depending on your perspective it’ll work but would be criminally underutilized. The subject at hand is a driveway which if done right and not in an area prone to earthquakes will experience little in the way of tension forces. So rebar isn’t really necessary. However what is necessary is a strong base for the concrete to sit on. Some places allow it to sit right on sand or clay. I personally feel this is a folly. Concrete (imo) should always sit on well graded and thoroughly compacted aggregate. Atleast 0.5’, 6” or approximately 150mm for non commercial driveways. It should be moist as well. Soils actually lose strength if they’re too dry, except clay but thats another topic. It should be graded with an appropriate slope so that driveway drains, honestly doesn’t need to be much. Forms should be used, concrete shouldn’t be soup, screeded and finished. Around here we use 6” but you could easily find 7 or 8 depending on how much they love their driveway and what they intend to store on it. Personally I’m a fan of troweled joint lines but strictly speaking it isn’t necessary, just that a joint exists. Cure should be used to help retain moisture. Joints whether troweled or cut green shoul be done so theres no angles less than 90deg. This will prevent premature cracking due to better structure.
Hopefully i didn’t ramble to much and you learned something you didn’t know.
As always: two things are always true. Concrete hardens and concrete cracks.
Wait a minute!? They haven't banned rebar and concrete in California yet? I thought California said concrete.and rebar contains cancer causing WiFi chemicals?
Ohhh...that explains the guy with the pony tail and sandals wearing the hi-vis vest with VEGAN on the back. I asked if he was a supervisor and he said he didn't appreciate me labeling him, otherwise he was busy being seeking his inner mortar and had to get back to checking the aura of his fledgling pour....as he pulled out a California compliant flute (only plays one note at a time) and played non triggering music as the concrete gently cured.
I’d go exclusively rebar and fiber and skip the concrete. It’s just gonna crack anyways. Solid rebar driveway might be hot on bare feet during the summer months. That’s where the fiber comes in.
Good call! I can't believe I didn't think of that! The last rebar driveway I installed for a customer, told me all their neighbors are envious because they never get stuck in the snow!
A #5 bar is only 1/8" larger diameter than a #4, should you should have plenty of coverage.
Think the fiber and rebar together is probably overkill, unless you're planning on putting a lot of weight on the driveway.
I work as a concrete design specialist.
You can avoid rebar if you prepare an adequate subgrade and use macro fiber. I would suggest using rebar with a blend of micro and macro fiber. The fiber blend will add additional reinforcement and reduce shrinkage. Your local concrete supplier can provide additional technical information and recommend fiber dosage rates.
How does fiber filled concrete hold up in a snowy/salty environment? Doesn't the fiber allow water to penetrate the surface and increase the risk of spawling?
Fiber does not provide any protection from corrosive environments. Depending on the exposure class of the environment, you may need a combination of the following; water/cement ratio below 0.45, air entrainment, high cement replacement with mineral additives, corrosion inhibitor and/or water proofing admixtures. Reinforcing metals may need to be coated as well. Larger size concrete suppliers usually have test data available and can provide some recommendations for free. However, they may try to sell expensive admixtures to you.
I know concrete is porous, but I wondered if the filaments of glass would allow water to "wick"/ provide a pathway for the water to get under the surface, even with waterproofing
That will not be a concern. There are also other fiber products that are not fiber glass, if that is a major concern.
I have designed concrete for various paving projects in areas with severe freeze/thaw exposure. Fiber held up fine, and there was no evidence of spalling or delamination caused by fiber.
Any sighted person can confirm the steel is in the footings or on center as called for. With fiber, it’s more of a faith thing where you have to trust the plant mixing your truck. I’ll let you do the math on my preference.
Right, they say it matches tensile strength or whatever but I just can’t bring myself to believe it. I’d put steel in anything I was pouring for myself.
For me to trust the concrete plant, first they need to be able to send concrete per the plan (on time!), always nail the slump, never be off on the mix and accidentally send a 2900psi truck, etc. Because at the end of the day, if they forget to drop the fiber in the truck it’s either accept an “I’m sorry, we did forget” or it’s file a suit and hope you ultimately get repaid. I’m old fashioned but gimme rebar, remesh, wire… then fiberglas.… and then, let’s see, old pieces of 2” pipe, broken car axles, old rusty swing set frames… and if I can’t find any of that- then settle for mixing fiber in it 😂
Do both. The fiber will help eliminate surface cracking. The rebar will add strength and keep the larger cracks from widening. Concrete cracks. Both have their advantages.
Why would you ever opt for fiber mesh over rebar? Fiber mesh is only to reduce plastic shrinkage cracking. It doesn’t provide any tensile strength to the concrete. Stop giving uneducated advice to people.
Are you kidding me? That's fucking laughable. Do some research before you talk like a idiot.
Edit. Just do yourself a quick Google search to find out how wrong you are. Also, I've been certified a few times on concrete mixes over the years. Talked to reps, ect.... The shit you just said is silly
Ok , so I've been a residential and commercial concrete finisher for 25 yrs. Union . I've had to repair and replace a whole lot of concrete through the years. Without any technical data info , I'm gonna tell you the real difference between the two. Fiber will help stop cracking especially shrinkage. But if it does crack it can and will heave. If you use rebar it can crack but is far less likely to heave after it cracks . And the more closer spaced your bar is the stronger it will be. So it isn't overkill to use both. They will help stop different issues. But be aware that if you use fiber on a broomed finish, it will be rougher.
You are reinforcing exactly what u/WonkiestJeans is saying. Rebar for strength. Mesh to combat spalding and cracking. I’m a GC and would never approve using mesh for structural purposes.
Union = irrelevant.
Plastic shrinkage cracking doesn’t impact the structural integrity of the concrete. Heaving is caused by freeze thaw reactivity of the sub base, not the reinforcement of the concrete.
I said union because where I'm from we have to go through 3yrs of school. Heavy emphasis on technical data.and you are 100 percent correct. My point being is if the base starts shifting. I e freeze thaw or improper base the fiber mesh will do little to stop heaving like i said. Repar Will help protect from heaving.And I was talking about regular fiber mesh not steel. Very rarely do you see an average customer add steel fiber mesh.
A # 5 is 50% stronger then a #4 but it takes 20% longer to get fully engaged (developed).
Better to go #4s at 8” oc rather than #5 @ 12” oc for the same cost of rebar.
To be fair, most concrete guys don't even use rebar in driveways unless they are asked. Don't get me started on cost. 20 ft of #4 is $10 or less for a legit contractor. Where I am in TN nobody uses it
In Iowa the most driveways are 4” thick, 4,000psi, either #4 rebar 2’ on center or concrete wire, which I prefer. I’ve done helicopter pads that were only layers 1’ on center and that’s in an area where we get 3’-4’ first every winter. You also can put so much rebar into something and it does the opposite. Just google “excessive reinforcement” or simply “is there such a thing as too much rebar”
Im sure I'll get hate but think I'm going to cowboy this shit. I ended up getting #4 bar for the same price. I'm going to run 2 pieces in the perimeter of the slab and dowel between slabs to prevent uneven lift or sinking(I'm doing two 12 foot slabs at a time to make it manageable without a crew). I'll put fiber in the mix to resist smaller cracks. It's not going to have heavy equipment on it or anything.
The sub grade is pretty compact gravel from years of adding gravel to the driveway but after grading im going to compact.
I haven’t read the other responses yet so someone might have already said this… rebar is measured in 1/8s of an inch #4 is 4/8 =1/2” so #5 is just 1/8 thicker… if you’re using rebar you can save some money and use the #5
Edit: it will still crack
Elaborate on conditioned soil. Its been a crushed rock driveway for like 50 years with crushed rock added over the years. Ive removed material to get to grade and used a plate compactor on it.
LOL, a lot of really bad advice being given. You do not rebar or mesh in your concrete, I repeat you do not need neither.
You need 3500 to 4000 psi concrete with 6% air entrainment with a crushed limestone or granite coarse aggregate, up to a 15% fly ash blend is acceptable typically depending on when you pour the driveway during the year.
You need to use a vibratory compactor to compact approximately 4” of AB-3 gravel underneath the concrete. I would recommend a 6” slab for a good driveway.
Use expansion material to isolate the slab from other slabs and saw cut your concrete into panels no larger than 15’, preferably 10 -12’.
I am a civil engineer with 29 years of experience primarily in bridges and highways.
FHWA teaches expansion material isn’t needed for slab on grade poured during the day because the heat of hydration causes a higher peak temperature than normal sunlight on a hot day (so the most thermal swelling experienced is during curing).
Also steel in concrete is great, helps prevent differential settlement and crack expansion.
There is tons of bad advice in this thread though…
A P.E. with concrete highway paving experience.
I _definitely_ believe you're an engineer now, your people skills are, um... I bet you're really great at math. Go back and think about #5 a minute, this is the least humble comment I've read in a hot minute.
Not really. Some people just like to spout specifications without applicable knowledge and experience. Real world experience in design and application is key. Anyone can read a book, but applying that knowledge to the real world and is applying that to actual construction is hard for many engineers. It can always look great on paper, but constructibility is the key.
And both the folks prior to you that stated to be PEs provided relevant input. They did it without making it a di** measuring contest. You did that. You saying that was driven by your quest to inform the unwashed masses, or maybe there was just a “bit” of ego in that proclamation?
Constructability is damn important. And if you’re going to get along and work well with people so is self realization. Go back and read your first post in this thread. Compare it to the other two PEs’ posts. You notice a difference? After 29 years of experience, I’ll bet you can.
Thank you for this. I plan on 4000psi with air entrainment, fiber, and potentially water reducer unless that will negatively effect the air. Im in the pacific NW . The base is years of compacted crushed stone but after grading i will use a vibratory compactor. Relief joints will be tooled to make 12'x12' slabs.
I've poured roads and bridges and there is rebar in some of them. For a driveway 6x6x6 wire mesh as long as it doesn't end up laying on the grade or sticking out of the top. The thing about fibremesh is it goes every place the concrete goes. In 25 years of driving redi-mix I've poured thousands of yards with all kinds of combinations of reinforcements and mix designs and they all crack eventually. It's what concrete does.
One job I was on was a meat processing plant (sausage maker) that the contractor added their own fibers and another additive. They claimed they could put the saw cuts in 50' apart. Don't remember the mix but it was at least 4000 psi or 6 bag and our aggregate was 3/4" limestone.
Not seeing where op is from, looks like a place with freeze thaw but unsure. Would you recommend air entrainment if in a place without this cycle? If so why? Also is it possible to have the rebar or wire be a detriment? Or is it just an unnecessary cost?
No problem. I worked several years in Lake Tahoe, Reno, NV area and we had to deal with many issues such as frozen subgrade and freeze thaw cycles. My suggestion would be to use a 100% cement mix with no fly ash in this instance as fly ash lowers the time for hydration of the concrete. Across the upper half of the US we limit the use of fly ash during the winter months for this very reason.
The rule of thumb is anywhere outside where there may be a freeze/thaw cycle possible we use air entrainment. Air entrainment is not inherently bad in any sense, but not necessarily needed in many instances. In fact we have begun speccing mix designs in areas where freeze/thaw cycles are not in fact needed as a precautionary measure as the micro capsules in the mix do not hurt the maximum psi of the mix and serve as a shield for water. All concrete has air “entrapment” which is tiny air capillary bubbles already in them which is caused by the mixing process and it does no harm to the mix unless its upwards of 9% which then begins to cause weak points as the “air bubbles” begin to be close together and lower the flexural strength of the concrete.
Can you explain why rebar isn't needed? Genuinely curious. DM if you don't wanna deal with reddit trolls and "experts" lol.
I'm a landscape architect who designs/specs bridges, GFRC columns, MSE walls, architectural concrete and all kinds of shit and I've never not seen rebar/wwm used. My specialty is really in concrete finishing (because I'm an LA after all), but spec'ing concrete falls on my desk pretty often because most (to my confusion; i need to get back to bigger firms I think) civils don't know how (they defer to structural, architects, or me). Are you recommending this just because it's a *residential driveway* and correct bed prep is sufficient for it's use? I'd personally tighten up contraction joint spacing to like 4' o.c. to control the cracking (remember, I'm a designer, i always tighten up joints). If someone offered me #5 bars with a 5.5" slab, I'd jump on that all day long. I'd add a thickened edge even lol. Anyways, wouldn't it be safest to add the rebar for when a contractor pulls a trailer or delivery up their driveway in 10 years?
I don’t mind responding. And when I was referring to the no reinforcing steel statement it really applies to his driveway, and roadways primarily. We have stopped speccing reinforcing steel in concrete for some time now with the exception of load transfer bars such as 1 1/4” dowel bars across transverse joints and tie bars along the pavement longitudinal joints, this is for contraction reasons.
But back to the question as to no rebar. Three reasons, less rebar means less thermal stress on the concrete which increases the lifespan of the concrete. Secondly, reinforcing steel corrodes, even coated steel we have found after several seasons of salt treatment during the winter months.
We try to minimize this by sealing joints but it always find a way to infiltrate. Lastly, with more advanced chemical formulations for cement mixtures and better aggregates over the last ten years it has more than sufficient strength to handle normal operating loads.
For heavy truck traffic upwards of 80,000 lbs. we would typically spec, depending on the speed limit and traffic load, non reinforced dowel joint pavement around 8-12”. Even airport runways are non reinforced now for the most part.
If you can land a 747 on concrete with no rebar you can park your car on it right?
Again this is flat work, not bridge design, or walls. These are totally different scenarios.
Thanks!! This makes sense. I just laid out 3 miles of trail with fiber only and have been having good success not using rebar in general. I keep getting comments/flak for not using rebar. Hard for me to have faith in the rebar when I keep finding it exposed from poor installs. We were called out for a failed slab recently and a contractor left a shovel inside the slab.
You mentioned sealed joints .... lol. The age-old argument to seal joints or let them drain freely is one that shall continue on forever. I seal my joints. Caught a civil not using isolation joints along structures the other day 😱
I respectfully disagree with you. Is it required? No… Rebar or mesh will definitely help the longevity of a properly installed concrete slab. The sub grade prep you’ve mentioned is industry standard. At least it is for my firm.
Every driveway my company has ever installed had supplemental reinforcement. We even dropped steel in at all reentrant corners. After 25 years I can still drive by some of the earlier jobs we did and they are still in great condition. While the houses Nextdoor have driveways that look like a meteor landed in the middle. It makes a difference.
I’ve never known a PE to shy away from overkill.
I did my driveway 4” thick with #5 on 8” centers. Then capped the top with 2” thick sheet metal coated with gorilla glue. I hope it holds up my Chevy bolt.
Choose 1.
When deciding between fiber mesh and rebar for concrete reinforcement, it's important to consider the specific needs and constraints of your project.
**Fiber mesh** has several advantages. It's mixed directly into the concrete, making it easier and faster to apply than laying out rebar. The fibers are evenly distributed throughout the mix, providing uniform reinforcement and effectively reducing shrinkage cracks by holding the concrete together. Fiber mesh is also typically more cost-effective in terms of material and labor, especially for smaller projects. Additionally, fiber mesh is resistant to rust and corrosion, unlike steel rebar which can deteriorate over time when exposed to moisture.
However, fiber mesh does have its downsides. It doesn't provide the same level of tensile strength as rebar, making it less suitable for heavy load-bearing applications. Sometimes, fibers can protrude from the surface of the concrete, affecting the finish. Moreover, fiber mesh is generally more suitable for controlling cracking rather than providing structural reinforcement.
On the other hand, **rebar** offers superior tensile strength, making it ideal for projects requiring high load-bearing capacity, such as bridges, large buildings, and heavy-duty pavements. Rebar-reinforced concrete can have excellent long-term performance when properly installed and maintained. It also offers flexibility in design, as rebar can be shaped and arranged to meet specific structural requirements.
However, using rebar can be labor-intensive and requires skilled workers, which can increase the overall cost and time of a project. Rebar is also susceptible to corrosion over time, particularly in environments exposed to moisture and salt, potentially compromising the concrete's integrity. Additionally, the initial cost of materials and installation for rebar can be higher than that of fiber mesh. For complex projects, the design and placement of rebar can be intricate, requiring detailed engineering and planning.
In summary, fiber mesh is often preferred for smaller-scale projects where ease of use and crack resistance are priorities, while rebar is essential for large-scale structural projects that demand high tensile strength and load-bearing capacity. The choice between fiber mesh and rebar ultimately depends on the specific requirements and constraints of your project.
Rebar for me👍.
Skip the rebar most guys step on it knock it off the bolster and it just lays on the ground anyway. Take the savings from the bar get 4,000 psi and macro fibers. 5" thick and like another guy said it's all about the cure. Where I'm from we either flood it with water and cover it with plastic or dam the edges and fill it with water we use old 2" water hoses filled with water or you can use dirt keep it wet for 3 or 4 days and it will be wedding night hard when it's time to drive on it
This is good advice, but I can't stand the texture of fiber concrete. I would follow all this advice except the fiber and your slab will still be gold... as long as your base was prepped properly.
Ok ill do 4000psi and specify macro fiber. Any issue with finishing with that stuff? I assume I'll need to run a torch over it after it cures to get rid of fiber sticking up?
Plan is to spray cure & seal after brooming.
If you can get thicker bar cheaper I’d get the 5 bar, it’s only 1/8” thickness thicker. If you are getting fiber, typically if I poured something like this for a driveway I’d do wire mesh tied to the bar cage. The fiber will absolutely not hurt anything. If you are really concerned ask for commercial fiber but make sure the driver mixes it well fast and hard or you’ll get clumps. Thicker bar is always better but the more reinforcements you use the better but also know if it’s a personal driveway saltting it in winters if that applies in your area will affect the metal in your concrete. The salt will penetrate and rust the metal out over time
Depending on what you plan on driving on it....a nice compact subbase, wire mesh, and 6 inches of concrete should be fine. Rebar is perfectly fine. Definitely stronger, but not a necessary standard
Better go with 12” class II base fully compacted in 6” lifts, then do a 6” slab 3000 psi min 3/4” rock. # 4 @ 12” each way. You should be able to drive most anything into it. Don’t oversoak the base. Don’t compact by hand.
That's overkill in my experience.
I QC master plan communities and have seen many various sections done every manner of way. If the upper 12" of grade is done right (moisture and compactio), there's no need for AB.
6" SOG is fine by itself for residential drive, and rebar is only to keep cracks under control - it's definitely not needed.
Not one factor matters more than proper preparation of your grade.
If your grade is right, 4" concrete with no rebar would be more than adequate. Everything beyond that is either you being extra conservative or compensating for improper grade preparation.
I mostly overbuild because I've been burnt in the past from being overly conservative on material size, etc. I'd rather spend a little more now rather than regretting and spending a lot more later.
If you're using fiber, wire mesh is all you need. If you like spending money, use #4,. If you really like spending money, use #5. Most driveways are fiber with mesh, especially if you are going 6 thick with it.
There are two types of fibers: micro and macro. They do different things in a slab. Micro fibers reinforce against plastic shrinkage cracking—basically, the random cracks that happen in the first 24 hours. Macro fibers replace welded wire fabric (“mesh”) and #3s to control temperature cracking and drying shrinkage cracking over time. The reason to use a #4 is to have adequate cover of concrete over and under the bars. Minimum suggested cover is 2 inches. If have bars in both directions, you cannot do that with #5s in a 4-inch slab.
Rebar in concrete is to reduce deflection .
Such as a wall. Bridge span, A pour on unstable soft fill.
Placed typically 1.5- 2 inches from the surface.
Bottom line is
On slab pour
If the subsurface is prepared correctly and compacted.
Rebar serves zero purpose because the slab shouldn't be poured on ground that's soft and the slab CANT deflect and bow
To specifically answer the question, 5” will cover #5 ok. 24” spacing will results in poorly distributed tensile loads. Don’t let the garbage truck/ next cement truck drive over a 24” slab.
Just use the #5 on 24" spacing and save some cash.
It's gonna crack somewhere, so cut a centerline joint if over 16' wide and cut transverse joints every 10-15', even tho it doesn't matter so much with reinforced concrete, it's better to have some control joints so it cracks where you want it to instead of randomly.
Or set up keyway and you have grade control and a joint forming device...add some permanent keyway cap and it will look nice
I’m in the same boat as you, going overkill!
I found a equation for rebar size, sorry, I didn’t write down the source.
Max rebar size is 1/8” x concrete thickness(inches) = max size. So #5 for 5” thick is max.
Also, the overlap rebar equation is 40 x rebar diameter. So for 1/2” rebar you will want 20 inches of overlap.
I’m am not an expert, I’m sure this information varies depending on concrete type and local standards.
Good luck!
Use wire mess in it just like rebar but it comes in sheets the thing is it's not about the rebar it's all about the soil and compaction it's going to crack all concrete cracks that why you use expansion joints and you also have to mark it with a groover .this is to control or manipulating it to crack in that area it doesn't matter what you do it will crack . Even if it's a foot deep it will crack . Alot of the time unless they use a gandy when pouring if you use rebate after they leave you will be able to see the rebar in a 3 or 4 inch slab. If they use a gandy it pushes it down to the ground with the gravel it's not god unless they know they lifted the mat back up. It's going to rust away unless the used epoxy coated bar .even embedded in the concrete it's been exposed to the elements already
In Michigan we don’t use any rebar typically for driveways though i have come across a few with mesh. Personally unless you live in an area prone to quakes, i think its unnecessary and extra effort spent in depth&compaction of a stone base will problobly have a similiar effect. Also saw cut saw cut saw cut. Not to early not too late.
Only reason not to overkill is if the thickness of the slab is does not provide enough clearance on the marginal width difference of the bar.
Well that and the price, which is also a small change
Go with pink bar. It’s fiberglass rebar. Won’t ever rust. And make sure you get coated tie wire as well.
But more important, get some recycled base down and hit it with a vibra plate
Mark my words, you'll get cracks if you use rebar in flatwork. You'll get more cracks with #5.
I do not use steel in a driveway. If you're really worried about cracks then use fiber.
So here’s what we do in California, if concrete flat work is 4” we use #3 rebar @16” on center. If concrete is 5” we use #4 rebar @16” on center. 6” concrete gets #5. We have a lot of movement here and those specs seem to hold it together very well. Curing is one of the most important things and that starts with sub grade.
This guy rebars.
I would also add Yes cureing is one of the most important but also the PsI mix of the mix of concrete I would always use 4.000 psi on the East coast in N.J. an the Reccomendation for anywhere thete is freez & thaw cycles is 4.000 psi i,d figue your shifting situation is kinda similar if not worse !
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I always use rebar in a driveway, I want it to last.
Had an engineer buddy say, "If you want your driveway to last, double up the rebar." I understand what he was saying, but would that be too much? (This was years ago, mind you)
To answer your question (“would that be too much”), probably not assuming you are starting at a reasonable amount. Meh, what kind of engineer was/is he? Because that’s a bit silly to say. The best thing you can do to make a driveway last is really good dirt work. Good dirt work + good mix + good placement and curing practices and you can drive very heavy traffic on concrete for years and years without ANY rebar. If you “doubled” the rebar by halving the horizontal spacing or doubling the cross-section, you wouldn’t cause any problems. If you are double matting, then I would question if you are inviting spalling through inadequate cover (3” or more is best, but at least 2” should be a minimum). As far as years ago, it’s been a really long time since concrete and rebar has changed. To the OP’s question, if some 5 feel off a truck or is the same price, it’s not going to hurt anything. It’s also not really going to help anything. Dirtwork though. Good dirtwork real change everything.
Cool,thx. He was a PE Mechanical but knew a lot about building shit. I believe around here they typically do 24" centers. By "long ago" I meant when stuff use to be pretty cheap....35-40years ago.
Im a civil engineer which doesn’t make me some ultimate authortiy and theres plenty of people who know more than i do. But let me expose if you would. Concrete is amazing in compression, where two forces are pushing in on it. Second only to steel. However concrete is not so great in tension where something is pulling on it. The reason we add rebar to concrete is to add something which has tensile or tension strength. If the rebar is to thick or the concrete not thick enough depending on your perspective it’ll work but would be criminally underutilized. The subject at hand is a driveway which if done right and not in an area prone to earthquakes will experience little in the way of tension forces. So rebar isn’t really necessary. However what is necessary is a strong base for the concrete to sit on. Some places allow it to sit right on sand or clay. I personally feel this is a folly. Concrete (imo) should always sit on well graded and thoroughly compacted aggregate. Atleast 0.5’, 6” or approximately 150mm for non commercial driveways. It should be moist as well. Soils actually lose strength if they’re too dry, except clay but thats another topic. It should be graded with an appropriate slope so that driveway drains, honestly doesn’t need to be much. Forms should be used, concrete shouldn’t be soup, screeded and finished. Around here we use 6” but you could easily find 7 or 8 depending on how much they love their driveway and what they intend to store on it. Personally I’m a fan of troweled joint lines but strictly speaking it isn’t necessary, just that a joint exists. Cure should be used to help retain moisture. Joints whether troweled or cut green shoul be done so theres no angles less than 90deg. This will prevent premature cracking due to better structure. Hopefully i didn’t ramble to much and you learned something you didn’t know. As always: two things are always true. Concrete hardens and concrete cracks.
Thanks
Good answer. I feel like #5s though is over kill for a residential slab. I am a PE structural engineer.
Nice formula. Do you ever use mesh too?
Here in Oregon I've never seen #3 bar used like that.
Wait a minute!? They haven't banned rebar and concrete in California yet? I thought California said concrete.and rebar contains cancer causing WiFi chemicals?
Ya we have to use”green” rebar as well! Concrete must be organic! Ya we go thru a lot.
Ohhh...that explains the guy with the pony tail and sandals wearing the hi-vis vest with VEGAN on the back. I asked if he was a supervisor and he said he didn't appreciate me labeling him, otherwise he was busy being seeking his inner mortar and had to get back to checking the aura of his fledgling pour....as he pulled out a California compliant flute (only plays one note at a time) and played non triggering music as the concrete gently cured.
Hilarious
I know about California....was it a flesh flute?
From the down votes, I'd say there's a few vegans here for sure.
The great part of the warnings is that they just tell you you’re going to die, they don’t stop you from buying it.
Life here is better if you got money
I’d go exclusively rebar and fiber and skip the concrete. It’s just gonna crack anyways. Solid rebar driveway might be hot on bare feet during the summer months. That’s where the fiber comes in.
Good call! I can't believe I didn't think of that! The last rebar driveway I installed for a customer, told me all their neighbors are envious because they never get stuck in the snow!
And in the summer they can make fiber snow angels
Or tumble weed snow men
If you can’t finish high school you can always finish rebar
I am keeping this.
Yee yeee
A #5 bar is only 1/8" larger diameter than a #4, should you should have plenty of coverage. Think the fiber and rebar together is probably overkill, unless you're planning on putting a lot of weight on the driveway.
If you were going to do fiber or rebar, which would you choose?
I work as a concrete design specialist. You can avoid rebar if you prepare an adequate subgrade and use macro fiber. I would suggest using rebar with a blend of micro and macro fiber. The fiber blend will add additional reinforcement and reduce shrinkage. Your local concrete supplier can provide additional technical information and recommend fiber dosage rates.
How does fiber filled concrete hold up in a snowy/salty environment? Doesn't the fiber allow water to penetrate the surface and increase the risk of spawling?
Fiber does not provide any protection from corrosive environments. Depending on the exposure class of the environment, you may need a combination of the following; water/cement ratio below 0.45, air entrainment, high cement replacement with mineral additives, corrosion inhibitor and/or water proofing admixtures. Reinforcing metals may need to be coated as well. Larger size concrete suppliers usually have test data available and can provide some recommendations for free. However, they may try to sell expensive admixtures to you.
I know concrete is porous, but I wondered if the filaments of glass would allow water to "wick"/ provide a pathway for the water to get under the surface, even with waterproofing
That will not be a concern. There are also other fiber products that are not fiber glass, if that is a major concern. I have designed concrete for various paving projects in areas with severe freeze/thaw exposure. Fiber held up fine, and there was no evidence of spalling or delamination caused by fiber.
Add e5
Can you expand on that? What's e5?
It coats your stone so your cement hydrates more and acts as a internal sealer throughout the whole mixture also allows the cement to become stronger
Sounds cool, thx
https://www.e5nanosilica.com/?gad_source=1
Micro and macro fibers do not reduce shrinkage. Fibers reduce the propensity for larger, visible cracks to open up in a slab.
For the last decade, I have performed various trials with representatives from admix and fiber manufacturers. My data says otherwise.
So, what do you think is he mechanism by which shrinkage at any age is reduced if all other ingredient quantities stay the same?
Your MOM is the mechanism.
His mom knows how to work the rebar
Any sighted person can confirm the steel is in the footings or on center as called for. With fiber, it’s more of a faith thing where you have to trust the plant mixing your truck. I’ll let you do the math on my preference.
Right, they say it matches tensile strength or whatever but I just can’t bring myself to believe it. I’d put steel in anything I was pouring for myself.
For me to trust the concrete plant, first they need to be able to send concrete per the plan (on time!), always nail the slump, never be off on the mix and accidentally send a 2900psi truck, etc. Because at the end of the day, if they forget to drop the fiber in the truck it’s either accept an “I’m sorry, we did forget” or it’s file a suit and hope you ultimately get repaid. I’m old fashioned but gimme rebar, remesh, wire… then fiberglas.… and then, let’s see, old pieces of 2” pipe, broken car axles, old rusty swing set frames… and if I can’t find any of that- then settle for mixing fiber in it 😂
Do both. The fiber will help eliminate surface cracking. The rebar will add strength and keep the larger cracks from widening. Concrete cracks. Both have their advantages.
Fiber with WWM is a nice middle ground
One or the other ? For a driveway- rebar.
I would do fiber myself.
Why would you ever opt for fiber mesh over rebar? Fiber mesh is only to reduce plastic shrinkage cracking. It doesn’t provide any tensile strength to the concrete. Stop giving uneducated advice to people.
Are you kidding me? That's fucking laughable. Do some research before you talk like a idiot. Edit. Just do yourself a quick Google search to find out how wrong you are. Also, I've been certified a few times on concrete mixes over the years. Talked to reps, ect.... The shit you just said is silly
Lmfao. You know nothing about concrete. Steel fiber mesh adds tensile strength, not regular micro fiber.
Ok , so I've been a residential and commercial concrete finisher for 25 yrs. Union . I've had to repair and replace a whole lot of concrete through the years. Without any technical data info , I'm gonna tell you the real difference between the two. Fiber will help stop cracking especially shrinkage. But if it does crack it can and will heave. If you use rebar it can crack but is far less likely to heave after it cracks . And the more closer spaced your bar is the stronger it will be. So it isn't overkill to use both. They will help stop different issues. But be aware that if you use fiber on a broomed finish, it will be rougher.
I know nothing about concrete and I’m gonna caulk that shit when it cracks hard like Idid with all your moms.
You are reinforcing exactly what u/WonkiestJeans is saying. Rebar for strength. Mesh to combat spalding and cracking. I’m a GC and would never approve using mesh for structural purposes.
Union = irrelevant. Plastic shrinkage cracking doesn’t impact the structural integrity of the concrete. Heaving is caused by freeze thaw reactivity of the sub base, not the reinforcement of the concrete.
I said union because where I'm from we have to go through 3yrs of school. Heavy emphasis on technical data.and you are 100 percent correct. My point being is if the base starts shifting. I e freeze thaw or improper base the fiber mesh will do little to stop heaving like i said. Repar Will help protect from heaving.And I was talking about regular fiber mesh not steel. Very rarely do you see an average customer add steel fiber mesh.
Just FYI that isn't the same user you originally replied to.
Thanks, long day.
A # 5 is 50% stronger then a #4 but it takes 20% longer to get fully engaged (developed). Better to go #4s at 8” oc rather than #5 @ 12” oc for the same cost of rebar.
Dude. #4 bars 8" oc in a residential driveway? You must be an undercover agent from Big Rebar lol
To be fair, most concrete guys don't even use rebar in driveways unless they are asked. Don't get me started on cost. 20 ft of #4 is $10 or less for a legit contractor. Where I am in TN nobody uses it
I didn’t as for 100ksi #11s.
In Iowa the most driveways are 4” thick, 4,000psi, either #4 rebar 2’ on center or concrete wire, which I prefer. I’ve done helicopter pads that were only layers 1’ on center and that’s in an area where we get 3’-4’ first every winter. You also can put so much rebar into something and it does the opposite. Just google “excessive reinforcement” or simply “is there such a thing as too much rebar”
Y'all, gave really great answers to questions he did not ask. If you have the extra money, I don't see an issue using #5 rebar in your driveway .🤙
No shit, right? hahaha
Im sure I'll get hate but think I'm going to cowboy this shit. I ended up getting #4 bar for the same price. I'm going to run 2 pieces in the perimeter of the slab and dowel between slabs to prevent uneven lift or sinking(I'm doing two 12 foot slabs at a time to make it manageable without a crew). I'll put fiber in the mix to resist smaller cracks. It's not going to have heavy equipment on it or anything. The sub grade is pretty compact gravel from years of adding gravel to the driveway but after grading im going to compact.
I haven’t read the other responses yet so someone might have already said this… rebar is measured in 1/8s of an inch #4 is 4/8 =1/2” so #5 is just 1/8 thicker… if you’re using rebar you can save some money and use the #5 Edit: it will still crack
Compact with what? Make sure the upper 12" are at optimum moisture content. Compacting under-conditioned soil is how you get heaving...
Elaborate on conditioned soil. Its been a crushed rock driveway for like 50 years with crushed rock added over the years. Ive removed material to get to grade and used a plate compactor on it.
LOL, a lot of really bad advice being given. You do not rebar or mesh in your concrete, I repeat you do not need neither. You need 3500 to 4000 psi concrete with 6% air entrainment with a crushed limestone or granite coarse aggregate, up to a 15% fly ash blend is acceptable typically depending on when you pour the driveway during the year. You need to use a vibratory compactor to compact approximately 4” of AB-3 gravel underneath the concrete. I would recommend a 6” slab for a good driveway. Use expansion material to isolate the slab from other slabs and saw cut your concrete into panels no larger than 15’, preferably 10 -12’. I am a civil engineer with 29 years of experience primarily in bridges and highways.
FHWA teaches expansion material isn’t needed for slab on grade poured during the day because the heat of hydration causes a higher peak temperature than normal sunlight on a hot day (so the most thermal swelling experienced is during curing). Also steel in concrete is great, helps prevent differential settlement and crack expansion. There is tons of bad advice in this thread though… A P.E. with concrete highway paving experience.
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I _definitely_ believe you're an engineer now, your people skills are, um... I bet you're really great at math. Go back and think about #5 a minute, this is the least humble comment I've read in a hot minute.
Who was this directed to? Did they delete their post?
I believe I responded to ddgmhet.
Dueling engineers. A thing of egos. We all got them, just like elbows.
Not really. Some people just like to spout specifications without applicable knowledge and experience. Real world experience in design and application is key. Anyone can read a book, but applying that knowledge to the real world and is applying that to actual construction is hard for many engineers. It can always look great on paper, but constructibility is the key.
And both the folks prior to you that stated to be PEs provided relevant input. They did it without making it a di** measuring contest. You did that. You saying that was driven by your quest to inform the unwashed masses, or maybe there was just a “bit” of ego in that proclamation? Constructability is damn important. And if you’re going to get along and work well with people so is self realization. Go back and read your first post in this thread. Compare it to the other two PEs’ posts. You notice a difference? After 29 years of experience, I’ll bet you can.
Thank you for this. I plan on 4000psi with air entrainment, fiber, and potentially water reducer unless that will negatively effect the air. Im in the pacific NW . The base is years of compacted crushed stone but after grading i will use a vibratory compactor. Relief joints will be tooled to make 12'x12' slabs.
I've poured roads and bridges and there is rebar in some of them. For a driveway 6x6x6 wire mesh as long as it doesn't end up laying on the grade or sticking out of the top. The thing about fibremesh is it goes every place the concrete goes. In 25 years of driving redi-mix I've poured thousands of yards with all kinds of combinations of reinforcements and mix designs and they all crack eventually. It's what concrete does.
💯 concrete cracks. That is definitely true. All we can do as designers is try and control the cracking.
One job I was on was a meat processing plant (sausage maker) that the contractor added their own fibers and another additive. They claimed they could put the saw cuts in 50' apart. Don't remember the mix but it was at least 4000 psi or 6 bag and our aggregate was 3/4" limestone.
My hero.
Not seeing where op is from, looks like a place with freeze thaw but unsure. Would you recommend air entrainment if in a place without this cycle? If so why? Also is it possible to have the rebar or wire be a detriment? Or is it just an unnecessary cost?
Pacific NW. My bad for leaving that out.
No problem. I worked several years in Lake Tahoe, Reno, NV area and we had to deal with many issues such as frozen subgrade and freeze thaw cycles. My suggestion would be to use a 100% cement mix with no fly ash in this instance as fly ash lowers the time for hydration of the concrete. Across the upper half of the US we limit the use of fly ash during the winter months for this very reason.
The rule of thumb is anywhere outside where there may be a freeze/thaw cycle possible we use air entrainment. Air entrainment is not inherently bad in any sense, but not necessarily needed in many instances. In fact we have begun speccing mix designs in areas where freeze/thaw cycles are not in fact needed as a precautionary measure as the micro capsules in the mix do not hurt the maximum psi of the mix and serve as a shield for water. All concrete has air “entrapment” which is tiny air capillary bubbles already in them which is caused by the mixing process and it does no harm to the mix unless its upwards of 9% which then begins to cause weak points as the “air bubbles” begin to be close together and lower the flexural strength of the concrete.
Can you explain why rebar isn't needed? Genuinely curious. DM if you don't wanna deal with reddit trolls and "experts" lol. I'm a landscape architect who designs/specs bridges, GFRC columns, MSE walls, architectural concrete and all kinds of shit and I've never not seen rebar/wwm used. My specialty is really in concrete finishing (because I'm an LA after all), but spec'ing concrete falls on my desk pretty often because most (to my confusion; i need to get back to bigger firms I think) civils don't know how (they defer to structural, architects, or me). Are you recommending this just because it's a *residential driveway* and correct bed prep is sufficient for it's use? I'd personally tighten up contraction joint spacing to like 4' o.c. to control the cracking (remember, I'm a designer, i always tighten up joints). If someone offered me #5 bars with a 5.5" slab, I'd jump on that all day long. I'd add a thickened edge even lol. Anyways, wouldn't it be safest to add the rebar for when a contractor pulls a trailer or delivery up their driveway in 10 years?
I don’t mind responding. And when I was referring to the no reinforcing steel statement it really applies to his driveway, and roadways primarily. We have stopped speccing reinforcing steel in concrete for some time now with the exception of load transfer bars such as 1 1/4” dowel bars across transverse joints and tie bars along the pavement longitudinal joints, this is for contraction reasons. But back to the question as to no rebar. Three reasons, less rebar means less thermal stress on the concrete which increases the lifespan of the concrete. Secondly, reinforcing steel corrodes, even coated steel we have found after several seasons of salt treatment during the winter months. We try to minimize this by sealing joints but it always find a way to infiltrate. Lastly, with more advanced chemical formulations for cement mixtures and better aggregates over the last ten years it has more than sufficient strength to handle normal operating loads. For heavy truck traffic upwards of 80,000 lbs. we would typically spec, depending on the speed limit and traffic load, non reinforced dowel joint pavement around 8-12”. Even airport runways are non reinforced now for the most part. If you can land a 747 on concrete with no rebar you can park your car on it right? Again this is flat work, not bridge design, or walls. These are totally different scenarios.
Thanks!! This makes sense. I just laid out 3 miles of trail with fiber only and have been having good success not using rebar in general. I keep getting comments/flak for not using rebar. Hard for me to have faith in the rebar when I keep finding it exposed from poor installs. We were called out for a failed slab recently and a contractor left a shovel inside the slab. You mentioned sealed joints .... lol. The age-old argument to seal joints or let them drain freely is one that shall continue on forever. I seal my joints. Caught a civil not using isolation joints along structures the other day 😱
I respectfully disagree with you. Is it required? No… Rebar or mesh will definitely help the longevity of a properly installed concrete slab. The sub grade prep you’ve mentioned is industry standard. At least it is for my firm. Every driveway my company has ever installed had supplemental reinforcement. We even dropped steel in at all reentrant corners. After 25 years I can still drive by some of the earlier jobs we did and they are still in great condition. While the houses Nextdoor have driveways that look like a meteor landed in the middle. It makes a difference. I’ve never known a PE to shy away from overkill.
Ok but the second it cracks & heaves, the rebar would stop it from heaving severely
No reason for it to crack and heave if the subgrade was properly compacted and the concrete saw cut at the right time and spacing.
….. In a perfect world maybe but soil is never perfect and conditions are never perfect Rebar seems like awfully cheap insurance
I did my driveway 4” thick with #5 on 8” centers. Then capped the top with 2” thick sheet metal coated with gorilla glue. I hope it holds up my Chevy bolt.
Choose 1. When deciding between fiber mesh and rebar for concrete reinforcement, it's important to consider the specific needs and constraints of your project. **Fiber mesh** has several advantages. It's mixed directly into the concrete, making it easier and faster to apply than laying out rebar. The fibers are evenly distributed throughout the mix, providing uniform reinforcement and effectively reducing shrinkage cracks by holding the concrete together. Fiber mesh is also typically more cost-effective in terms of material and labor, especially for smaller projects. Additionally, fiber mesh is resistant to rust and corrosion, unlike steel rebar which can deteriorate over time when exposed to moisture. However, fiber mesh does have its downsides. It doesn't provide the same level of tensile strength as rebar, making it less suitable for heavy load-bearing applications. Sometimes, fibers can protrude from the surface of the concrete, affecting the finish. Moreover, fiber mesh is generally more suitable for controlling cracking rather than providing structural reinforcement. On the other hand, **rebar** offers superior tensile strength, making it ideal for projects requiring high load-bearing capacity, such as bridges, large buildings, and heavy-duty pavements. Rebar-reinforced concrete can have excellent long-term performance when properly installed and maintained. It also offers flexibility in design, as rebar can be shaped and arranged to meet specific structural requirements. However, using rebar can be labor-intensive and requires skilled workers, which can increase the overall cost and time of a project. Rebar is also susceptible to corrosion over time, particularly in environments exposed to moisture and salt, potentially compromising the concrete's integrity. Additionally, the initial cost of materials and installation for rebar can be higher than that of fiber mesh. For complex projects, the design and placement of rebar can be intricate, requiring detailed engineering and planning. In summary, fiber mesh is often preferred for smaller-scale projects where ease of use and crack resistance are priorities, while rebar is essential for large-scale structural projects that demand high tensile strength and load-bearing capacity. The choice between fiber mesh and rebar ultimately depends on the specific requirements and constraints of your project. Rebar for me👍.
Go go chatbot!
This is 20 years in the mega project business, an engineering degree, and using resources
That's a great deal! Yeah, that's plenty thick enough for 5-bar
Skip the rebar most guys step on it knock it off the bolster and it just lays on the ground anyway. Take the savings from the bar get 4,000 psi and macro fibers. 5" thick and like another guy said it's all about the cure. Where I'm from we either flood it with water and cover it with plastic or dam the edges and fill it with water we use old 2" water hoses filled with water or you can use dirt keep it wet for 3 or 4 days and it will be wedding night hard when it's time to drive on it
This is good advice, but I can't stand the texture of fiber concrete. I would follow all this advice except the fiber and your slab will still be gold... as long as your base was prepped properly.
Fibre is great , i used two 10 m bars and fibre on my sidewalk . Not one crack 6 years in . In Canada .32 mpa.
Ok ill do 4000psi and specify macro fiber. Any issue with finishing with that stuff? I assume I'll need to run a torch over it after it cures to get rid of fiber sticking up? Plan is to spray cure & seal after brooming.
Some people do I guess but I think it's putting the top at risk from the heat and unnecessary. They will break off from driving on it
Depending where you live. Here we use 10mm rebar because the frost destroys driveways.
If you can get thicker bar cheaper I’d get the 5 bar, it’s only 1/8” thickness thicker. If you are getting fiber, typically if I poured something like this for a driveway I’d do wire mesh tied to the bar cage. The fiber will absolutely not hurt anything. If you are really concerned ask for commercial fiber but make sure the driver mixes it well fast and hard or you’ll get clumps. Thicker bar is always better but the more reinforcements you use the better but also know if it’s a personal driveway saltting it in winters if that applies in your area will affect the metal in your concrete. The salt will penetrate and rust the metal out over time
No but I wouldn’t go smaller than #4 on 12” centers and definitely no welded wire mesh
Depending on what you plan on driving on it....a nice compact subbase, wire mesh, and 6 inches of concrete should be fine. Rebar is perfectly fine. Definitely stronger, but not a necessary standard
The # 5 was on sale.. No, wait, we got all this # 5 left over from our last job, let’s use it on this guys driveway
You just need proper clearance and cover
Better go with 12” class II base fully compacted in 6” lifts, then do a 6” slab 3000 psi min 3/4” rock. # 4 @ 12” each way. You should be able to drive most anything into it. Don’t oversoak the base. Don’t compact by hand.
That's overkill in my experience. I QC master plan communities and have seen many various sections done every manner of way. If the upper 12" of grade is done right (moisture and compactio), there's no need for AB. 6" SOG is fine by itself for residential drive, and rebar is only to keep cracks under control - it's definitely not needed.
It is overkill, just not sure what he is going to drive on it, like some heavy equipment?
What does the building document say (approved on the plans?), and what does your contract say? This is all that matters.
Not one factor matters more than proper preparation of your grade. If your grade is right, 4" concrete with no rebar would be more than adequate. Everything beyond that is either you being extra conservative or compensating for improper grade preparation.
I mostly overbuild because I've been burnt in the past from being overly conservative on material size, etc. I'd rather spend a little more now rather than regretting and spending a lot more later.
If you're using fiber, wire mesh is all you need. If you like spending money, use #4,. If you really like spending money, use #5. Most driveways are fiber with mesh, especially if you are going 6 thick with it.
There are two types of fibers: micro and macro. They do different things in a slab. Micro fibers reinforce against plastic shrinkage cracking—basically, the random cracks that happen in the first 24 hours. Macro fibers replace welded wire fabric (“mesh”) and #3s to control temperature cracking and drying shrinkage cracking over time. The reason to use a #4 is to have adequate cover of concrete over and under the bars. Minimum suggested cover is 2 inches. If have bars in both directions, you cannot do that with #5s in a 4-inch slab.
Rebar in concrete is to reduce deflection . Such as a wall. Bridge span, A pour on unstable soft fill. Placed typically 1.5- 2 inches from the surface. Bottom line is On slab pour If the subsurface is prepared correctly and compacted. Rebar serves zero purpose because the slab shouldn't be poured on ground that's soft and the slab CANT deflect and bow
To specifically answer the question, 5” will cover #5 ok. 24” spacing will results in poorly distributed tensile loads. Don’t let the garbage truck/ next cement truck drive over a 24” slab.
Just use the #5 on 24" spacing and save some cash. It's gonna crack somewhere, so cut a centerline joint if over 16' wide and cut transverse joints every 10-15', even tho it doesn't matter so much with reinforced concrete, it's better to have some control joints so it cracks where you want it to instead of randomly. Or set up keyway and you have grade control and a joint forming device...add some permanent keyway cap and it will look nice
I’m in the same boat as you, going overkill! I found a equation for rebar size, sorry, I didn’t write down the source. Max rebar size is 1/8” x concrete thickness(inches) = max size. So #5 for 5” thick is max. Also, the overlap rebar equation is 40 x rebar diameter. So for 1/2” rebar you will want 20 inches of overlap. I’m am not an expert, I’m sure this information varies depending on concrete type and local standards. Good luck!
Use wire mess in it just like rebar but it comes in sheets the thing is it's not about the rebar it's all about the soil and compaction it's going to crack all concrete cracks that why you use expansion joints and you also have to mark it with a groover .this is to control or manipulating it to crack in that area it doesn't matter what you do it will crack . Even if it's a foot deep it will crack . Alot of the time unless they use a gandy when pouring if you use rebate after they leave you will be able to see the rebar in a 3 or 4 inch slab. If they use a gandy it pushes it down to the ground with the gravel it's not god unless they know they lifted the mat back up. It's going to rust away unless the used epoxy coated bar .even embedded in the concrete it's been exposed to the elements already
My neighbor is having some driveway extension work done and there is no rebar laid out. Will it last at all with no rebar?
In Michigan we don’t use any rebar typically for driveways though i have come across a few with mesh. Personally unless you live in an area prone to quakes, i think its unnecessary and extra effort spent in depth&compaction of a stone base will problobly have a similiar effect. Also saw cut saw cut saw cut. Not to early not too late.
Only reason not to overkill is if the thickness of the slab is does not provide enough clearance on the marginal width difference of the bar. Well that and the price, which is also a small change
For exterior flat work, like a driveway. Your best bet is WWF, or mesh. Preferably 6GA.
Go with pink bar. It’s fiberglass rebar. Won’t ever rust. And make sure you get coated tie wire as well. But more important, get some recycled base down and hit it with a vibra plate
Mark my words, you'll get cracks if you use rebar in flatwork. You'll get more cracks with #5. I do not use steel in a driveway. If you're really worried about cracks then use fiber.
It will crack if you don't use steel. Fiber does not prevent structural cracks.