CSLB C-8 Concrete (Trade Exam) — All Questions
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17 questions
Wall forms that needed finishing were stripped early. What must follow right away?
- a.Curing the exposed faces✓
- b.A coat of form oil
- c.Nothing until day 7
- d.Sandblasting of the wall
If forms are removed before the end of the curing period, curing and protection must be provided for the rest of it; form oil is not a curing method.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
How stiff should dry-pack mortar be?
- a.Pourable like grout
- b.Completely dry powder
- c.Stiff; balls when squeezed✓
- d.Wet enough to self-level
Dry pack is mixed with just enough water to form a ball when squeezed gently by hand, then rammed into place; wetter mixes shrink and bond poorly.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5
A patch on a visible gray wall looks darker than the wall. How is color usually matched?
- a.Add some white cement✓
- b.Use form oil on the patch.
- c.Paint the patch gray.
- d.Add extra water to lighten it.
Caltrans notes color matching can be achieved by adding a small amount of white cement, testing sample patches in inconspicuous locations. Extra water weakens the patch.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5
Small surface holes appear on a wall cast against steel forms. What most likely caused them?
- a.Too much reinforcing steel
- b.Trapped air bubbles✓
- c.Late sawing of joints
- d.Excess curing compound
Bug holes come from air bubbles trapped against forms, especially impervious forms such as steel or plastic liners; proper vibration or revibration helps prevent them.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5
How is epoxy injection of a dormant crack done?
- a.Pour epoxy into the open crack
- b.Seal it, then inject via ports✓
- c.Rout it and fill with sealant
- d.Spray epoxy over the whole wall
NPS describes sealing the crack surface on both sides and injecting epoxy through small holes or ports; routing and sealing is the method for moving cracks.National Park Service Preservation Brief 15
What must an owner know before a clear penetrating sealer is applied?
- a.It fills cracks permanently.
- b.It can't be removed once applied.✓
- c.It lasts the life of the slab.
- d.It forms a peelable film.
NPS notes penetrating sealers cannot be effectively removed (irreversible), do not bridge or fill cracks, and require periodic reapplication.National Park Service Preservation Brief 15
Why must joint sealants be inspected and replaced over time?
- a.They are only temporary fillers.
- b.They turn into mortar.
- c.They harden the concrete edges.
- d.They wear out before concrete.✓
NPS notes sealants deteriorate faster than their substrates and must be replaced periodically as part of cyclical maintenance.National Park Service Preservation Brief 15
What does a penetrating sealer do for fine cracks and pores in concrete?
- a.It fills and bridges cracks up to 1/4 inch wide
- b.It dissolves salts and carries them out of the slab
- c.It repels water without bridging cracks✓
- d.It seals them beneath a hard, glossy surface film
Penetrating sealers make fine cracks and pores water-repellent (hydrophobic) but do not bridge or fill cracks. They do not fill cracks, they are not film-forming, and they do not remove salts.National Park Service Preservation Brief 15
What must a Caltrans contractor submit before staining concrete?
- a.A tint order signed by the paint supplier
- b.Cylinder results from the 28-day breaks
- c.A written weather forecast for the whole week
- d.A staining plan and stain test panels✓
The contractor submits a staining work plan and test panels for staff review and authorization before staining. A tint order, cylinder results, and a forecast do not show how the stain will look.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5
Where do the surface-preparation requirements for staining concrete come from?
- a.Whatever the foreman's usual practice has been on past jobs
- b.Manufacturer instructions and contract specifications✓
- c.The ready-mix supplier's delivery ticket notes
- d.The weather service's forecast for the week
Surface preparation follows the manufacturer's instructions and the contract specifications. A foreman's habit, a delivery ticket, and a weather report are not the source of those requirements.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5
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Before a full-scale cleaning of concrete begins, what does NPS guidance call for?
- a.Trial samples of the cleaning process✓
- b.A fresh coat of curing compound
- c.Strong muriatic acid on a small corner
- d.A pressure wash of the whole wall
For any cleaning process, trial samples should be done before full-scale work. A full wash skips the test, strong acids such as muriatic acid should not be used on concrete, and curing compound has nothing to do with cleaning.National Park Service Preservation Brief 15
Under the federal guide specification, what must happen before materials that adsorb VOCs are installed over a sealed slab?
- a.Wash the slab down with clean water
- b.Let the compound or sealer cure first✓
- c.Apply a second coat of compound first
- d.Cover the surface with plastic sheeting
Curing compound or sealer installations must cure before materials that adsorb VOCs go in. A second coat, plastic cover, and washing do not address the off-gassing.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
What mortar proportion does Caltrans cite from its contract specification for the dry-pack mortar used in a simple patch?
- a.1 part cement to 3 parts sand
- b.1 part cement to 2 parts sand✓
- c.1 part cement to 4 parts sand
- d.1 part cement to 1 part sand
The mortar is made by mixing 1 part cement with 2 parts sand and only enough water to moisten it. 1:1 is richer than specified, and 1:3 and 1:4 are leaner.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5
In the simple dry-pack patch procedure, how is the finished mortar patch cured?
- a.With the water method for 12 hours
- b.With the water method for 72 hours✓
- c.With curing compound for 3 hours only
- d.Left dry for 72 hours
The patch is cured with the water method for 72 hours. Leaving it dry skips curing, 12 hours and 3 hours are too short.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5
Which ASTM standard does the federal guide specification cite for nonshrink grout?
- a.ASTM C143
- b.ASTM C172
- c.ASTM C1107✓
- d.ASTM C1074
Nonshrink grout is specified under ASTM C1107. C1074 is the maturity method, C143 is slump, and C172 is sampling fresh concrete.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
When a groove is filled with joint sealing compound, how full should it be?
- a.Slightly underfilled, so it cannot squeeze out✓
- b.Filled with sand and topped off with a layer of grout
- c.Left empty until the compound skins over
- d.Overfilled to leave a raised bead on top
The groove is slightly underfilled so the compound cannot squeeze out as the joint moves. A raised bead would be pushed out, sand and grout make a rigid plug, and an empty groove is not sealed.UFGS 03 30 00 Cast-in-Place Concrete (Chg 10, Aug 2025)
Right after forms come off, how can suspect locations be checked for voids?
- a.Weigh each suspect section on a hand-held scale
- b.Tap with a hammer or drag a chain over them✓
- c.Spray them with water and look for small bubbles
- d.Compare the surface color against a paint chip
Tapping with a light hammer or dragging a chain gives a dull or hollow sound over voids. Water bubbles, weighing a section, and color comparison do not find voids behind the surface.Caltrans Reinforced Concrete Construction Manual (June 2025), ch. 5