Crushed Concrete Calculator — Florida

Crushed concrete is recycled concrete aggregate, or RCA. Crews take old concrete from torn-up driveways, sidewalks, foundations, and road slabs, then crush and screen it back into a graded aggregate. Suppliers sell it as crushed concrete, recycled concrete aggregate, recycled base, or crushed recycled aggregate. It is not virgin stone pulled from a quarry. It is a construction material given a second life.

That recycled origin is the whole identity of the product, and it sets crushed concrete apart from a quarried stone like road base. The source rock was already concrete: cement paste, sand, and the original stone aggregate, all bonded together. When it is crushed, you get angular pieces coated in old cement, mixed with a fine cement-rich dust. Those cement fines are what make this material behave in its own way, which the next section covers.

Use crushed concrete where a quarried crushed stone would go: a driveway sub-base, a compacted base under a slab, a working pad, or structural fill. It packs into a firm, load-bearing layer much like a dense-graded stone base. Size it in the calculator the same way, by the area and the finished compacted depth.

Know what you are not getting. Crushed concrete is a reused, variable material, so one load can differ from the next in color, fines content, and the odd bit of brick or asphalt mixed in. A quarried stone is more uniform. You trade that consistency for a lower price and a reused product, which is the trade most sub-base jobs are glad to make.

Here is the trait that makes crushed concrete different from every quarried stone. The old cement in the material is still reactive. When you crush concrete, the fine dust carries unhydrated cement and lime from the original mix. Add water and compaction, and those fines can hydrate again and bind the layer. The base can set up and stiffen over the weeks after you place it, almost like a weak concrete.

This re-cementing is the upside and the catch in one. On the upside, a crushed concrete base can lock into a very stiff, hard platform that holds its shape well under load. Many crews like it under a driveway for exactly this reason. The layer firms up and stays put.

The catch is that the setting is uneven and hard to predict. The amount of live cement varies from load to load, so one batch sets up harder than another. A pile left damp can start to cement in storage and arrive with stiff clumps. Once the layer sets in the ground, it does not rework easily, so you grade and compact it right the first time.

Plan around the trait rather than fight it. Place the base at the correct depth, shape your grade and slope before it stiffens, and compact while the material is workable. If you need to cut or regrade a crushed concrete base later, expect it to be harder than a loose stone base, because the fines may have bound it. Treat the re-cementing as a feature you time, not a surprise you discover.

Crushed concrete earns its place mostly on cost and reuse. It usually sells for less per ton than a quarried crushed stone, because the raw material is demolition waste rather than freshly mined rock. For a large sub-base or a deep fill, that price gap adds up fast. When a job needs volume under the surface and not a finished look, the savings are real.

The green case is just as plain. Every ton of crushed concrete used as base is a ton of old concrete kept out of a landfill and a ton of virgin stone left in the ground. Concrete is heavy and bulky, so diverting it from disposal matters. Reusing it close to where it was crushed also cuts the hauling that new stone would need.

The trade is consistency and finish, not strength. A sub-base of crushed concrete carries load as well as a dense-graded stone for most residential work. What you give up is the clean, uniform look and the predictable gradation of a quarried product. Under a driveway or a slab, where no one sees the base, that trade favors the recycled material.

Match the choice to the role in the job. Reach for crushed concrete on the hidden, load-bearing layers where price and volume rule. Reach for a quarried stone or a decorative aggregate where looks, uniformity, or a spec sheet demand it. The calculator sizes either one the same way, so the choice is about cost and fit, not about the math.

Crushed concrete does its best work in a short list of roles and falls down in a few others. It belongs under things. Use it as a driveway sub-base, a compacted base beneath a slab or pavers, a base for a shed or a pad, and as structural or grading fill. In each of these, it packs into a firm layer and nobody sees it.

It is a poor pick for a visible, decorative surface. The color is a washed-out grey, the texture is rough and dusty, and the odd fleck of rebar rust or brick shows up in the mix. If you want a stone people look at, choose a decorative aggregate instead. Crushed concrete is a base material, not a finish.

Watch for the contaminants that ride along in a recycled product. Reputable suppliers screen out the steel, but stray bits of rebar, wire, brick, wood, or asphalt can slip through. Wear gloves when you handle it and keep it away from bare feet and tires that a sharp shard could cut. Ask your supplier how they process and screen their material before you order.

Two more limits matter. Crushed concrete is alkaline, and water moving through a fresh layer can carry a high-pH, lime-rich runoff, so keep a thick, fresh placement away from ponds, young plantings, and sensitive drainage. And it is not meant to be the aggregate you drop into a batch of new concrete you pour yourself, since reused aggregate needs testing and processing that a bulk base product has not had. Keep it in its lane as a base and fill material.

Crushed concrete comes in a few gradations, and the name shifts by supplier. A dense-graded blend, often a 3/4-inch minus with fines, is the one you want for a compacted base, because the fines let it lock and the cement dust lets it set. A larger, coarser crushed concrete, with bigger chunks and fewer fines, suits deep fill where you only need bulk and some drainage, not a smooth top. Ask your yard which gradations they stock, because the recycled feed varies.

Depth drives the order more than any other input, so set the finished compacted depth before you calculate. Enter that compacted number in the calculator, not the loose pile, and let the tool add the allowance for the loose material you buy.

Match the depth to the load, the same way you would for any base. A patio or walkway sub-base often runs about 4 inches of compacted material. A residential driveway that carries cars and light trucks usually calls for 4 to 6 inches. A driveway that takes heavy trucks or equipment, or a base over soft ground, wants more. Soft or wet subgrade pushes the depth deeper still.

Place the material in lifts, not one deep dump, so it packs all the way through and sets evenly. If the depth changes across the site, run the calculator for each zone and add the totals. Always feed the tool the compacted depth you want to end up with, because the depth you pick sets the whole order.

Once you know your compacted depth, the calculator turns it into both cubic yards and tons. It works out the volume from area and depth, divides cubic feet by 27 to get cubic yards, and multiplies by a density near 1.35 tons per cubic yard to reach tons. Crushed concrete sits a little lighter than a solid natural stone base, because the old cement paste and the pores in the recycled pieces weigh less than dense rock.

Density is not fixed. Moisture, gradation, and the share of fines all shift the weight. Wet material weighs more than dry, and a blend heavy with cement fines packs denser than a coarse, chunky fill. Treat the 1.35 figure as a solid planning number and ask your supplier for the weight of the product they carry.

Order the loose volume, not the finished volume. Crushed concrete arrives loose and full of air, then packs down as you compact it, and the re-cementing fines drive the layer even tighter. The calculator adds a compaction allowance, set to 10 percent by default, so the loose material you buy packs down to the depth you planned. Raise it on a deep base, on soft ground, or when you place thick lifts.

Suppliers quote in different units, so match the number to the yard. Some price bulk crushed concrete by the cubic yard, and some weigh the loaded truck and bill by the ton. Reporting both lets you order either way and check your estimate against the weight ticket. If you hold one number and need the other, multiply cubic yards by about 1.35 for tons, or divide tons by 1.35 for yards.

Bulk crushed concrete comes by dump truck, and one truck holds roughly 10 to 14 tons. Divide your total by that range to see how many loads to expect. A small pad may fit in part of one load, while a long driveway or a wide fill can run past a single truck. Ask your pit what their trucks carry, because it varies by yard.

Name the product when you order, and be specific. Ask for crushed concrete or recycled concrete aggregate, state whether you want a dense-graded base with fines or a coarse fill, and confirm the top size. Ask how the supplier screens the feed, since good screening is what keeps the rebar and the trash out of your load.

Prepare the drop before the truck arrives. Pick a firm, level spot close to the work but clear of the area you must grade, and confirm a loaded truck can reach it. Lay a tarp under the pile to keep the fines and the grey dust off a lawn or a finished drive. Move and spread the material soon after it lands, because a damp pile of crushed concrete can start to cement and stiffen if it sits.

Handle the recycled material with care. Wear gloves, because crushed concrete is rough and can hide a sharp shard of steel or a jagged chunk. Watch for stray rebar as you spread, and pull any you find. A reputable supplier will have screened most of it out, but a recycled product is never as clean as quarried stone.

Most crushed concrete shortfalls trace to a short list of errors. The first is ordering for the finished depth and forgetting that loose material packs down. Crushed concrete shrinks as you compact it, and the cement fines pull it tighter still, so the loose tonnage you buy must beat the finished volume. Keep the compaction allowance on, and raise it on a deep base or soft ground.

The second mistake is treating the density as exact. A recycled product swings more than a quarried one, because the feed and the fines content change from load to load. Use the 1.35 figure to plan, then confirm the weight with your supplier and leave a little room in the order for the swing.

The third is dumping the full depth in one thick layer. The bottom of a thick lift never reaches density, and once the top sets up you cannot easily rework the loose zone below. Build in lifts and compact each one, and shape your grade before the fines cement the layer.

The fourth is using crushed concrete in the wrong place, such as a decorative surface, a drainage bed near sensitive plantings, or a batch of new concrete. Keep it as a hidden base or fill. The last is measuring a curved drive or an odd pad as one clean rectangle. Break an odd shape into simple rectangles, size each in the calculator, add them, and round the order up so a little margin covers the uneven ground and the stiff clumps you may have to discard.