Single 12-ft Grout Pour: Cleanouts, Slump, and Consolidation
A warehouse wall 20 ft long and 12 ft tall is built of 8-in. nominal concrete masonry, fully grouted, with no. 5 vertical bars at 32 in. on center and a no. 5 bond beam at the top. The specified grout is ASTM C476 coarse grout with f'g of 2,000 psi. Masonry was laid on Tuesday; the contractor plans to grout Thursday in a single continuous pour pumped from the top of the wall through a 2-in. line, dropping the full 12 ft. The inspector finds no cleanout openings at the base. At 8:00 a.m. the slump measured at the pump hopper is 7 in. The foreman says the mix sets up in the line and proposes adding water at the pump until the slump reaches 9 in. A pencil vibrator is on site, and the crew says they will use it at the top of the pour to settle everything. The cells look clean and the bed joint is full.
1. May the contractor grout this wall in one continuous 12-ft pour as planned? Identify what must be in place before grouting and how the permitted pour height is determined.
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The pour height itself is not automatically a rejection. TMS 602 caps grout pour height at 12 ft 8 in. for coarse grout and 5 ft 4 in. for fine grout (confirm the edition adopted by the project), so a 12-ft coarse-grout pour falls inside the limit. What fails here is the supporting setup. A pour that exceeds 5 ft is high-lift grouting and requires cleanout openings at the bottom of the pour so the grout space can be inspected, debris and mortar droppings flushed, and the first grout verified. The inspector has found no cleanouts, which means the bottom of the pour cannot be examined and the pour height cannot be reliably measured from a cleanout sill.
Before grouting I would require: cleanouts installed and accessible; verification that cells and grout spaces are free of mortar fins, blocking, and trash; written confirmation that the specification and mix design permit high-lift placement; and a consolidation plan with the vibrator available before the first grout enters the wall. If cleanouts cannot be provided, the work must be grouted in lifts within the low-lift provisions instead. Grouting should not start until the pre-grout inspection is signed off.
2. How should the inspector respond to the 7-in. slump and to the proposal to add water at the pump?
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Grout is required to have a slump at the point of placement within the range the standard sets, commonly 8 to 11 in. A 7-in. reading is below that range, so the grout as delivered does not conform and should not be placed. The reason the range exists is workability without segregation: grout that is too stiff bridges, voids, and blocks the pump line, while grout that is too wet bleeds, segregates, and loses strength and bond.
Adding water at the pump is not an acceptable correction. The approved mix design fixes the water content and water/cementitious ratio; water added in the field is unmeasured, changes that ratio, lowers f'g, increases shrinkage and bleeding, and is precisely the kind of uncontrolled adjustment that slump testing is meant to catch. If the grout has begun to stiffen, retempering with water is not permitted and the batch should be discarded.
The correct path is to reject the load, notify the contractor and the engineer of record, and require the producer to supply grout that meets the approved mix design and the specified slump at placement, using an approved water-reducing admixture if the mix must be made more fluid. I would record the time, location, slump, and disposition in the daily report.
3. Evaluate the crew's plan to vibrate only at the top of the pour. What should the inspector require, and what should be documented if the contractor proceeds?
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Vibrating only at the top consolidates nothing below the vibrator tip; the lower portion of a 12-ft pour would be left with entrapped air, voids under bond beam bars, and cold joints between grout that stiffened before the next grout arrived. Grout must be mechanically consolidated throughout the pour: the vibrator is lowered quickly and withdrawn slowly, inserted at intervals close enough that the zones of influence overlap, and each insertion penetrates into the lift below so the lifts knit together. The vibrator should not be used to push grout laterally over long distances, which causes segregation.
I would require a written consolidation procedure before the pour, a working vibrator plus a standby, and continuous observation during grouting rather than spot checks. During the pour I would watch for grout loss or leakage at the base, for the grout level dropping in cells after consolidation (a sign of voids), and for any interruption long enough to create a cold joint.
If the contractor proceeds with top-only vibration, I would document the pour sequence, the vibrator use actually observed, and the locations, notify the contractor in writing, and refer the element to the engineer of record for evaluation, with cores or removal of a unit as possible follow-up.