Is 4000 psi strong enough for a fence post?

Yes. 4000 psi exceeds what most fence and mailbox posts need. Dig below the frost line, set the post plumb and brace it for 24 hours.

How many bags do I need?

Each 60 lb bag yields about 0.6 cu ft. A 4-inch slab needs about 0.33 cu ft per sq ft, so roughly one bag covers 1.8 sq ft.

How long before I can walk on it?

Initial set takes at least 24 hours. Wait the full 72 hours before putting heavy loads or vehicles on it.

Can I use it for a structural footing?

Yes. It meets ASTM C 387 strength requirements, which covers structural concrete. Check local code for footing size and depth.

Portland cement, sand and gravel, pre-blended. You add only water, following the ratio on the bag.

Bag prices are fairly stable, so compare per-bag prices across stores and buy when you can pick up locally to avoid delivery fees.

Sakrete

High-Strength Concrete Mix

Last price we saw

$5.45at sbsconcreteproducts.com, last seen Nov 2

Prices change often: ask the agent below to check today's price at every store.

Prices are checked against each store and labelled with when.

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Our take on the High-Strength Concrete Mix

Sakrete High-Strength Concrete Mix is a bagged 4000 psi concrete for structural and load-bearing work such as footings, slabs, steps and posts. It meets ASTM C 387 strength requirements and needs only water. Each 60 lb bag yields about 0.6 cu ft, so a 4-inch slab covers roughly 1.8 sq ft per bag. It is a commodity product, so the best price is usually found by comparing bag prices across stores rather than waiting for a sale.

Best forFence posts and mailbox postsSmall footings and structural repairsSetting anchor bolts and bracketsDIY slabs and steps under 2 cu ft

Pros

4000 psi rating suits load-bearing work
Meets ASTM C 387 strength requirements
Just add water; sand and gravel already blended
Consistent, predictable strength batch to batch
Cures enough to walk on in about 24 hours

Cons

Heavy: a 60 lb bag yields only 0.6 cu ft

High-Strength Concrete Mix prices at every store

sbsconcreteproducts.comCheck price at sbsconcreteproducts.com

High-Strength Concrete Mix price history

Lowest price we've seen: $5.45 on Nov 2 at sbsconcreteproducts.com. Tracked across 1 store since Nov 2.

What reviewers say

Owners of Sakrete high-strength mix generally report it sets hard and holds posts and anchors well when mixed to the right consistency. Complaints center on bags that arrive hardened and on the short working time once water is added.

Pros

Sets hard and holds posts and anchors
Mixes easily with a drill and paddle
Consistent strength for small structural jobs

Cons

Bags sometimes arrive lumpy or hardened
Sets fast, so small batches are needed
Heavy bags are awkward to carry and pour

Specifications

Form: Bagged powder
Cure Time

Questions and answers

Is 4000 psi strong enough for a fence post?: Yes. 4000 psi exceeds what most fence and mailbox posts need. Dig below the frost line, set the post plumb and brace it for 24 hours.
How many bags do I need?: Each 60 lb bag yields about 0.6 cu ft. A 4-inch slab needs about 0.33 cu ft per sq ft, so roughly one bag covers 1.8 sq ft.
How long before I can walk on it?: Initial set takes at least 24 hours. Wait the full 72 hours before putting heavy loads or vehicles on it.
Can I use it for a structural footing?: Yes. It meets ASTM C 387 strength requirements, which covers structural concrete. Check local code for footing size and depth.
What is in the bag?: Portland cement, sand and gravel, pre-blended. You add only water, following the ratio on the bag.
When is it cheapest?: Bag prices are fairly stable, so compare per-bag prices across stores and buy when you can pick up locally to avoid delivery fees.