Found out my mortar mix was off by 15% for the last 3 years

I was reading through an old trade manual from the 80s I found at a garage sale last weekend. Turns out the standard mix ratio I've been using for load bearing walls is way off from what the modern codes call for. I've been doing 1:3 cement to sand when it should be 1:2.5 for structural stuff. That 15% difference is HUGE for strength over time. No wonder a few of my older retaining walls have hairline cracks. Has anyone else caught a mistake in their mix ratios from just assuming they were right?

3 comments

3 Comments

aaron8803d ago

Buddy of mine was building a backyard firepit and kept wondering why his bricks kept crumbling after a few months. Turns out he was using the same mix his grandpa taught him from the 60s. One concrete calculator app later and he realized he was basically building with wet sand.

jenny_lane123d ago

Funny you mention that, I had basically the same problem with a retaining wall last year. Turns out the mix ratios on that old bag of Portland cement were way off for what I was trying to do, so I just started using a basic online calculator to get the water to cement ratio dialed in. Saved me a ton of headache and actually having the wall hold up longer than a season or two.

henryt183d ago

Wish I'd known about those calculators before my first patio cracked to hell.