Concrete Driveway Repair and Replacement in the Syracuse Area

There is a published line and it is about the surface, not the age. NRMCA states that light to moderately scaled surfaces can be repaired, that the unsound surface has to be removed first by hammer and chisel, sandblasting, high-pressure washing or jack hammer, that the surface receiving the repair must be sound, and that the repaired surface will only be as strong as the base it has to bond to. It then says that repairing slabs with excessive and progressing scaling may not be feasible at all. So the questions are how deep the damage goes, whether sound concrete is left underneath, and whether the slab is still level. A driveway that is peeling but level and solid is usually a repair. One losing aggregate over most of its area, or one that has moved, usually is not.

Usually one of four things, and all four are documented rather than mysterious. First, a repair is only ever as strong as the base surface it has to bond to, so new material laid over concrete that was already unsound fails at the bond. Second, NRMCA lists application of excessive de-icing chemicals, especially on newly installed concrete that tends to be saturated and of lower strength, among the causes of most scaling, and new work salted in its first winter is the classic case. Third, excessive finishing reduces the entrained air in the surface layer, so the top skin of a beautifully troweled patch can be the least durable concrete on the property. Fourth, the pour may have happened outside a window it could be protected through. A repair that ignores all four does fail again, which is why the diagnosis is worth more than the discount.

It is a protection question rather than a calendar question. ACI 306R-16 defines cold weather concreting as air temperature having fallen to, or being expected to fall below, 40F during the protection period, and sets that period at 2, 3 or 6 days depending on load and exposure. Syracuse averages 13.9 nights at or below 40F in October, 24.2 in November and 30.3 in December, and the median date of the first fall night at or below 32F is October 14. So an October pour will very likely sit through cold nights and has to be protected accordingly. Fresh concrete freezes below about 25F and can lose more than half its potential strength if it does. What is less well known is that NRMCA also notes cold weather concreting offers the opportunity for better quality, because a cooler initial concrete temperature typically results in higher ultimate strength and improved durability. Late season is not automatically wrong. Unprotected late season is.

Three respectable sources give three different numbers, and the disagreement is worth knowing rather than hiding. NRMCA, consistent with ACI 332, the code for residential concrete, says order exterior slabs at 4,000 psi with about 6 percent air at 3/4 or 1 inch aggregate and a 3 to 5 inch slump. ACI 318's severest freezing and thawing class, which is the condition of concrete that is frequently wetted, freezes and has de-icing chemicals applied to it, sets a 0.40 maximum water to cementitious ratio and 5,000 psi for reinforced members, and 0.45 and 4,500 psi for plain concrete. The Residential Code of New York State, Table R402.2, asks 3,500 psi with air of not less than 5 and not more than 7 percent by volume in its severe weathering column. A driveway here is wetted, frozen and salted by the cars that use it, which is that severe condition by description, so the upper end of the range is the sensible read rather than the code floor.

It depends which road it meets. The part on your own land is a building department question for the city, town or village the house stands in. The strip inside the road right of way is different: Onondaga County requires a Work in the Right of Way permit for all work in the right of way including modifications to existing driveways such as widening and repaving, and New York Highway Law section 136 makes constructing or improving an entrance or connection within a county road right of way without a county work permit a violation carrying a fine of not less than twenty-five and not more than one thousand dollars for each day of violation. Because it accrues for every day the violation continues, it is not a one-off ticket. New York State's highway mileage report puts 790.4 of the county's 3,144.0 centerline miles under county jurisdiction and 1,896.4 under a town, village or city, so it is worth ten minutes to establish which one you are on before ordering anything.

Not in the first winter. NRMCA's stated rule is to avoid de-icing chemicals in the first winter and to use them in moderate amounts after that, with clean sand for traction in the meantime. It also names calcium chloride and sodium chloride, which is rock salt, as acceptable on concrete, and says ammonium sulfate, ammonium nitrate and magnesium-based salts should never be used as a de-icer because they are chemically aggressive and destroy concrete surfaces. On sealing, NRMCA recommends a commercially available silane or siloxane based breathable concrete sealer or water repellent designed for concrete slabs, applied per the manufacturer's instructions with the concrete reasonably dry, and it names late summer with a few dry days beforehand as the ideal time. Sand and a hose are the two cheapest things you can do for a new slab.