Aggregate Moisture Corrections pt. 1

[@steveallphin9631]

First, I have to say that I'm addicted to your channel. Huge Fan! I'm a concrete countertop manufacturer and we found that what people normally call false set is just the aggregate absorbing water from the mix as you talk about. We use this to our advantage. We mix our concrete and then turn off the mixer letting it sit for 5 to 10 minutes, then restart the mixer and add water to bring us back to the consistency we want. You could continue to mix while this is happening, but we found that doing that adds heat to the mix, decreasing our set time. Water content is very important to us as our formula yields 16K PSI at a .2 W/C ratio, so we are very precise with how much water we add. We weigh out our water and initially only add about 80%. Then after the false set wait, we add what is needed to get the mix back to the right consistency. This generally keeps us between .19 and .2 W/C ratio. One other tip we found was that switching to Silica Sand as opposed to sedimentary sand, we decreased the amount of water being absorbed. Silica sand has very low water absorption. I love watching your videos and learning the science behind the things I've learned through trial and error.

[@mikeymo4]

Thank you for explaining it to me like I'm a child. I needed that, seriously, haha. Cleared everything up for me. Appreciate your video and I'll be checking out your other stuff.

[@MrPJBarney]

Hi, Mr. Ley. I am taking Civil Engineering Materials right now at UNLV, and the main subject of the course is concrete mixture proportion and design. Therefore, I find your videos very helpful. At 5:55, I believe you misspoke, "In these situations where we are above SSD, we are actually going to be adding more water to the concrete. In these situations where we are above SSD, we are actually going to be taking a water out of the concrete mixture." Based on the remainder of your video and Pt. 2 of this video series, I believe you meant to say 1.) If aggregate moisture condition > SSD, remove water. 2.) If aggregate moisture condition < SSD, add water. Thank you for producing your videos, Mr. Ley. I sincerely appreciate them and benefit from them.

[@MrPJBarney]

Take care. God bless. John 3:16. John 14:6.

[@SpaceCrete]

All totally correct information, very clearly presented as usual! For much of the US, concrete is still batched only by slump, because they don't know what the MC is (I never know). A big problem can arise where you have a porous aggregate below SSD - with then possible extreme slump loss in transit, and blockage of the pump lines. Ask me how I know this! A most sensitive issue with volumetric mixers. My hard lesson learned is to be at least SSD at least overnight. Thanks!

[@TylerLey]

Thanks! for the comment and keep up the awesome work.

[@ralphaldridge1049]

Would you not Calculate the Spec gravity when adding aggregates due to moisture? 2.63 spec gravity would not equal a 1 to one 1 adjustment i don't think

[@amolingale5851]

May I know how much time is needed for aggregates to make them ovendry. Most of them say that keep the aggregates in oven for a night. So should I keep it for 8hrs or 10hrs? Please help me out.

[@imranramuthy7856]

Can i know which standard did you follow?

[@simppin3160]

What if i use oven dried aggregates on my sample, will i use just the water calculated or should i add the absorption of the aggregates? (No moisture content) based on ACI

[@buchweiz]

So I was browsing around internet searching for things to learn (as you do). And you're videos are wonderful! Thank you! But I have a layman's question: why does the moisture content in aggregate matter, if it's literally only a fraction of percent of the whole mix? Would this really affect the finished product?

[@TylerLey]

Thanks for the question. Aggregates make up 70% of the volume of a concrete mixture. If these aggregates can absorb 2% moisture and you don't account for it then you will have a very different water content in your mixture. This changes the water to cement ratio and will change the strength and durability of the material. For some concrete it doesn't matter but for the material that we want to be long lasting then these details are important.