ACT Grouts cheat sheet

Water-to-cementitious ratio by weight governs strength and permeability; typical structural grout mixes fall between 0.40 and 0.50.

Neat cement grout = cement plus water only; sand is added to form sanded grout, and coarse aggregate produces concrete.

Bentonite or attapulgite clay increases cohesion and reduces bleed in water-rich grout used for void filling.

Superplasticizers raise flowability at fixed water content; adding water instead lowers strength roughly in proportion to the w/c increase.

Expansive or non-shrink grout uses gas-generating or crystalline additives to offset drying shrinkage after set.

Grout yield in cubic feet per bag = bag weight divided by (27 times the mix density in lb per cubic foot).

Set time shortens as temperature rises; accelerators cut set time, retarders extend it for long placements or hot weather.

Pre-bagged grouts must be mixed at the manufacturer's stated water volume; exceeding it voids the stated compressive strength.

Concrete surfaces receiving grout must be sound, clean, and free of laitance, curing compound, oil, and dust; bond depends on open aggregate pores.

Acid etching or mechanical scarification opens the substrate; surfaces are then flushed and brought to a saturated-surface-dry condition.

Saturated-surface-dry means the pores are full of water but no free water film remains on the surface.

Concrete substrate temperature below about 40 F slows hydration and risks freezing; above about 90 F accelerates set and increases plastic shrinkage.

Formed surfaces and keyways increase mechanical interlock; smooth, polished, or sealed surfaces should be roughened before grouting.

Water stops, backer rod, and joint sealant placement must precede grouting where movement joints are specified.

Substrate moisture migration through slabs-on-grade can be checked with a plastic sheet test or calcium chloride test.

Placement methods include gravity or pour, pressure injection, tremie, and preplaced-aggregate (grout-intrusion) methods.

Pressure injection uses low flow rates and rising pressure to fill cracks; stop injection when grout appears at the next vent.

Tremie placement keeps the discharge end submerged in fresh grout to prevent segregation and water washout.

Preplaced-aggregate method fills a coarse-aggregate bed by pumping grout from the bottom up so it displaces air and water.

Positive displacement pumps with progressive cavity or piston design handle sanded grout; centrifugal pumps risk segregation.

Grout must be placed continuously to avoid cold joints; where interruption is unavoidable, form a deliberate construction joint.

Vibration or rodding consolidates grout and releases entrapped air; over-vibration causes segregation of sand and bleed.

Curing keeps moisture in the grout; methods include wet burlap, curing compound, plastic sheeting, and water ponding.

Curing compound forms a membrane that blocks moisture loss but may interfere with later bond of sealants or toppings.

Cold weather protection maintains grout above about 40 F until it reaches adequate strength; blankets and heaters are common.

Hot weather controls include pre-cooling water or aggregate, shading, and working at night to limit plastic shrinkage cracking.

Sealers applied after full cure protect grout from water, stains, and freeze-thaw; penetrating sealers leave the surface breathable.

Evaporation rate depends on air temperature, grout temperature, humidity, and wind; high rates cause plastic shrinkage cracks.

Grout should not be exposed to traffic or loading until it reaches the specified strength, often 7 days for full design strength.

Compressive strength is checked on cube or cylinder specimens cast from the same batch and cured under standard conditions.

Flowability is measured with a flow cone or flow table; efflux time in seconds indicates grout consistency.

Bleeding test measures water separation at the top of a grout column; excessive bleed causes voids under plates.

Expansion of non-shrink grout is verified with a restrained expansion test or height-change measurement.

Field inspection includes verifying mix proportions, water addition, placement continuity, and curing method.

Grout samples should be taken at the point of placement, not from the mixer, to reflect actual installed material.

Acceptance criteria come from the project specification; testing frequency is set by the spec or the engineer of record.

Silica exposure from mixing or cutting sanded grout requires respiratory protection and dust controls under OSHA 29 CFR 1926.1153.

Cement is alkaline and can cause chemical burns; gloves, eye protection, and prompt washing are required.

Confined-space grouting requires atmospheric testing, ventilation, and an attendant per OSHA 29 CFR 1910.146.

ASTM C1107 covers non-shrink grout; ASTM C476 covers grout for masonry; ASTM C939 covers flow of grout for preplaced aggregate.

ACI 351 provides guidance for grouting of equipment and structural foundations.

Material Safety Data Sheets (SDS) must be available on site for all grout components and admixtures.

Waste grout and wash water must be contained and disposed of per local environmental regulations, not discharged to storm drains.