Concrete

Mixing one's own concrete instead of having truck delivery is like tackling Godzilla instead of petting one's dog.  But that's what one gets working solitarily on the mountain playing trial and error with one's dedication.

I hope the abaquas model is easily amenable to different strengths of concrete.  New vistas have opened, mainly concrete mix design options.  The first is exactly what I gave you.  The second was trying to get that mix down to a 0.4 water cement ratio.  In order to do that, I had to cut way back on the crusher fines and end up with only a 60% yield, and that's using maximum dosage of super plasticizer.  I haven't tested any of those yet but I know they'll be substantially stronger.    Here there's a standard concrete mix known as Qwikcrete that the home improvement stores sell.  I figured that would be a known uniform standard but forced into using that mix design.  So I mixed a batch with that, again trying for a minimum w/c ratio with plasticizer.  And now I'm realizing a universal standard of the 3/8" pea gravel and alas, using official "concrete sand" that should be a universal specification world wide.  I don't know that for sure but most likely it's true.  I think that will help me increase the pea gravel content for less surface area and still get a good 0.33 w/c ratio.  So all these mixes I can do the crushing and pull out tests on.  I'm wondering what you think and hopefully not getting turned into the weeds.

My 280 mix design to use a Ryobi 5 cubic foot mixer to its maximum.

46 Pounds portland cement (I pound leaks out during handling)

0.32  water cement ratio = 14.72 pounds of water, 8.3 pounds with 4 ounces Akton air entrainment, then gradually 6.2 pounds water with 3.3 ounces Plastol 6400

110 pounds 3/8" pea gravel

109 pounds cement sand

3 cups packed PVA fiber

Self Consolidating Concrete (Plastol 6400 and Xantham Gum)

Using Xantham gum to be avoided when possible.

How to adjust the water-to-cement ratio when using both admixtures?

Adjusting the water-to-cement (w/c) ratio when using both xanthan gum (VMA) and polycarboxylate ether (PCE) superplasticizers requires a "water-reduction-first" approach. Instead of adding more water to fix the stiffness caused by xanthan gum, you must leverage the water-reducing power of the PCE to maintain a low w/c ratio, which preserves concrete strength. [1, 2, 3]

The step-by-step optimization process relies on strict control over water content: [1]

1. Establish the Target Low Water-Cement Ratio

Because PCE can reduce mixing water requirements by 25% to 40%, target a structurally ideal, low baseline w/c ratio (typically between 0.30 and 0.40 for high-performance or self-compacting concrete). Do not increase this baseline ratio to compensate for the thickening effect of the xanthan gum. [1, 2, 3, 4, 5]

2. Include Liquid Admixture Volumetrics

If your PCE or xanthan gum is introduced in a liquid or pre-dissolved format, the water content within those liquid chemical doses must be subtracted from your mixing water calculation. For example, if your liquid PCE dosage introduces 2 liters of fluid per cubic meter of concrete, you must remove exactly 2 liters from your batch water to keep the true w/c ratio accurate. [1, 2, 3]

3. Stepwise Adjustment Protocol (The "Two-Knob" Method)

When fine-tuning the concrete consistency during trial batches, treat water as a fixed value and use the two admixtures as your adjustable knobs: [1, 2]

• If the mix is too stiff or lacks flow: Do not add water. Instead, incrementally increase the PCE dosage (usually by 0.05% to 0.1% of cement weight) to disperse the particles and free up trapped water. [1, 2, 3, 4, 5]

• If the mix bleeds, separates, or segregates: Do not reduce water. Instead, incrementally increase the xanthan gum dosage (by 0.02% to 0.05%) to physically bind the free water into a cohesive gel matrix. [1, 2, 3, 4, 5]

• If the mix is too sticky but has the right flow: Lower the xanthan gum dosage slightly, or reduce the overall volume of cement paste while keeping the w/c ratio identical. [1]

4. Account for Aggregate Moisture

Because this dual-admixture system is highly sensitive to free water, you must measure the moisture content of your sand and gravel before mixing. Any surface moisture present on the aggregates must be deducted from the batch water calculation. Failing to do so will result in an accidentally high w/c ratio, which will trigger massive fluidity over-dosage when the PCE activates. [1, 2, 3, 4]

5. Standard Sequential Mixing Procedure

To ensure the water interacts correctly with both polymers without clumping, follow this sequence: [1, 2]

1. Mix the aggregates and cement dry. [1]

2. Add 70% to 80% of the total calculated batch water. [1, 2]

3. Introduce the xanthan gum (either dry-blended with the cement or pre-dissolved in that initial water) and mix thoroughly until the paste thickens. [1, 2]

4. Blend the PCE superplasticizer into the remaining 20% to 30% of the water and pour it into the mixer. This delayed addition allows the PCE to liquefy the stabilized gel efficiently without competitive blockages. [1, 2, 3, 4]