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Question 1

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What is the primary PTI standard governing the design and analysis of post-tensioned slabs-on-ground on expansive soils?

PTI DC10.1

PTI DC10.5

ACI 318

ASTM C94

to track

2026 Statistics

Key Facts: PTI Slab-on-Ground PT Exam

~50

Exam Questions

PTI

70/80%

L1/L2 Passing Score

PTI

2 days

Workshop Length

PTI

$800-$1.2K

Workshop + Exam Fee

PTI

4 years

Certification Validity

PTI

Closed

Book Policy

PTI

The PTI SOG exam is a closed-book test at the end of a 2-day workshop. Score 70% for Level 1 or 80% for Level 2. Key domains: SOG Design (25%), Tendon Installation (20%), Stressing (15%), Soil & Foundation (15%), Concrete Placement (10%), Inspection & QC (10%), and Codes (5%). No prerequisites beyond workshop attendance.

Sample PTI Slab-on-Ground PT Practice Questions

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1What is the primary PTI standard governing the design and analysis of post-tensioned slabs-on-ground on expansive soils?

A.PTI DC10.1

B.PTI DC10.5

C.ACI 318

D.ASTM C94

Explanation: PTI DC10.5 is the standard specifically addressing the design and analysis of shallow post-tensioned concrete foundations on expansive soils. It is directly referenced by the International Residential Code (IRC) and International Building Code (IBC) for PT slab-on-ground design. Exam Tip: PTI DC10.5 is code-referenced and mandatory — know its scope, applicability, and relationship to the model building codes.

2What is the purpose of a geotechnical investigation before designing a post-tensioned slab-on-ground?

A.To determine the color of the soil

B.To characterize the soil type, expansive properties, moisture conditions, and bearing capacity for foundation design

C.To locate underground utilities only

D.To test the air quality at the site

Explanation: A geotechnical investigation provides essential data including soil classification, plasticity index, Atterberg limits, moisture content, swell potential, edge moisture variation distance (em), and allowable bearing pressure. This information directly influences the slab design, including beam depth, tendon spacing, and slab thickness. Exam Tip: The geotechnical report is the starting point for all PT slab-on-ground design — never begin design without one, and verify that it addresses site-specific expansive soil conditions.

3What is an 'edge lift' condition in post-tensioned slab-on-ground design?

A.The slab is physically lifted at the edges by a crane

B.Soil at the slab perimeter swells due to moisture increase, causing upward movement at the edges relative to the center

C.The edges of the slab are raised during construction

D.Wind causes the slab edges to lift

Explanation: Edge lift occurs when the soil at the perimeter of the slab absorbs moisture and swells, causing the edges to move upward while the interior remains at a lower elevation. This creates bending moments that stress the slab in a dish-shaped deformation. Edge lift is typically the controlling design condition in wetter climates. Exam Tip: Edge lift is associated with wet climates or heavy irrigation near the foundation perimeter — the slab must be designed with sufficient stiffening beams to resist this upward bending.

4What is a 'center lift' condition in post-tensioned slab-on-ground design?

A.A hydraulic jack lifts the center of the slab

B.Soil beneath the center of the slab swells due to moisture increase, causing the center to rise relative to the edges

C.The center of the slab is thicker than the edges

D.A column supports the center of the slab

Explanation: Center lift occurs when the soil beneath the interior of the slab absorbs moisture and swells while the perimeter soil dries out, causing the center to rise relative to the edges. This creates a dome-shaped deformation. Center lift is typically the controlling design condition in drier climates where edge drying occurs. Exam Tip: Center lift is the more common controlling condition — it occurs when perimeter soils dry and shrink while interior soils remain moist under the insulating slab.

5What is the function of stiffening beams (ribs) in a post-tensioned slab-on-ground?

A.To provide a decorative pattern on the slab bottom

B.To increase the slab's flexural stiffness and resistance to differential soil movement

C.To serve as plumbing chases

D.To reduce the amount of concrete used

Explanation: Stiffening beams are deepened sections of the slab that extend below the slab bottom, running in two directions to create a grid pattern. They increase the slab's moment of inertia and flexural capacity, enabling it to resist the bending forces caused by differential soil movement (edge lift and center lift conditions). Exam Tip: Stiffening beam depth is one of the primary design outputs — deeper beams resist larger differential soil movements but require deeper excavation and more concrete.

6What is the typical tendon spacing range for residential post-tensioned slabs-on-ground?

A.12 to 18 inches on center

B.36 to 60 inches on center

C.72 to 96 inches on center

D.120 to 144 inches on center

Explanation: Residential PT slabs-on-ground typically have tendons spaced at 36 to 60 inches (3 to 5 feet) on center in each direction. The exact spacing is determined by the engineer based on the required average precompression, slab thickness, and loading conditions. Closer spacing provides higher precompression. Exam Tip: Tendon spacing must be uniform and match the approved shop drawings — uneven spacing causes non-uniform precompression and potential cracking in under-stressed areas.

7What is the minimum average precompression stress typically required for PT slabs-on-ground per PTI standards?

A.25 psi

B.50 psi

C.100 psi

D.200 psi

Explanation: PTI standards typically require a minimum average precompression of 50 psi in each direction for post-tensioned slabs-on-ground. This minimum ensures adequate residual compression under service loads to control cracking and maintain structural integrity. Some designs may specify higher precompression. Exam Tip: The 50 psi minimum precompression is a fundamental design requirement — verify that the tendon count and spacing deliver at least this value in both directions across the entire slab.

8What is the purpose of a moisture barrier (vapor retarder) beneath a post-tensioned slab-on-ground?

A.To increase the soil bearing capacity

B.To prevent moisture migration from the subgrade up through the slab, protecting interior finishes and reducing slab curl

C.To serve as a bond breaker for the tendons

D.To increase the concrete strength

Explanation: A moisture barrier (typically 10-mil or 15-mil polyethylene sheeting or a Class A vapor retarder) is placed beneath the slab to prevent moisture from the subgrade from migrating upward through the concrete. This protects floor coverings, prevents mold growth, and reduces differential moisture conditions that can cause slab curling. Exam Tip: Ensure the moisture barrier is continuous with sealed laps and extends up the edge forms — any gap or tear creates a path for moisture to reach the slab bottom.

9What type of soil is most problematic for post-tensioned slab-on-ground foundations?

A.Sandy soils with low plasticity

B.Expansive clay soils with high plasticity index

C.Gravel soils

D.Rock substrates

Explanation: Expansive clay soils with a high plasticity index (PI) are the most problematic because they undergo significant volume changes with moisture variations — swelling when wet and shrinking when dry. These volume changes create the differential soil movements (edge lift and center lift) that PT slabs must be designed to resist. Exam Tip: Higher PI values indicate more expansive soil — PI above 30 generally indicates highly expansive conditions requiring deeper stiffening beams and closer tendon spacing.

10What is the 'edge moisture variation distance' (em) and why is it important in PT slab-on-ground design?

A.The distance water can travel across the slab surface

B.The horizontal distance from the slab edge over which the soil moisture content changes, affecting the extent of edge lift or center lift

C.The distance between the slab edge and the nearest water source

D.The thickness of the moisture barrier

Explanation: The edge moisture variation distance (em) is the horizontal distance from the perimeter of the slab over which the soil moisture content transitions from the equilibrium condition beneath the slab interior to the changed condition at the slab edge. A larger em value means a greater area of soil is affected by moisture changes, requiring a stiffer slab design. Exam Tip: em values are provided by the geotechnical engineer and vary by climate, soil type, and drainage conditions — they directly affect the design moments and beam depths in the PTI design method.

About the PTI Slab-on-Ground PT Exam

The PTI Slab-on-Ground PT certification validates competency in the installation and inspection of single-strand unbonded post-tensioning systems for residential and light commercial slabs-on-ground. The exam covers SOG design basics, tendon installation, stressing procedures, soil and foundation fundamentals, concrete placement, and inspection practices. This specialized credential is essential for PT professionals working on foundation slabs.

Questions

50 scored questions

Time Limit

End of 2-day workshop

Passing Score

70% (Level 1) / 80% (Level 2)

Exam Fee

$800-$1,200 (workshop + exam) (Post-Tensioning Institute (PTI))

PTI Slab-on-Ground PT Exam Content Outline

25%

Slab-on-Ground Design Basics

PT slab design concepts, tendon layout, edge distances, slab thickness, reinforcement

20%

Tendon Installation for SOG

Tendon placement, profile control, chair layout, edge anchorage placement, pocket formers

15%

Stressing and Lock-Off

Stressing procedures specific to SOG, elongation measurements, lock-off, tail cutting

15%

Soil and Foundation Basics

Expansive soils, soil reports, moisture barriers, edge moisture variation, slab performance

10%

Concrete Placement for SOG

Concrete placement, finishing, curing, minimum strength before stressing, cold/hot weather

10%

Inspection and Quality Control

Pre-pour inspection, tendon count verification, profile checks, stressing records

Codes and Standards

PTI DC10.5, ACI 318, ACI 360, local building code requirements for PT slabs

How to Pass the PTI Slab-on-Ground PT Exam

What You Need to Know

Passing score: 70% (Level 1) / 80% (Level 2)
Exam length: 50 questions
Time limit: End of 2-day workshop
Exam fee: $800-$1,200 (workshop + exam)

Keys to Passing

Complete 500+ practice questions
Score 80%+ consistently before scheduling
Focus on highest-weighted sections
Use our AI tutor for tough concepts

PTI Slab-on-Ground PT Study Tips from Top Performers

1Understand expansive soil behavior and how post-tensioning counteracts soil movement

2Know the minimum prestress requirements for SOG slabs per PTI DC10.5

3Study tendon layout patterns: uniform vs banded, edge distances, and anchorage zones

4Memorize minimum concrete strength before stressing and typical wait times

5Review moisture barrier placement and edge moisture variation distance concepts

Frequently Asked Questions

What is the PTI Slab-on-Ground PT certification?

The PTI SOG certification validates knowledge of installing and inspecting unbonded post-tensioning in residential and light commercial foundation slabs. It covers tendon layout, stressing, soil fundamentals, concrete placement, and inspection procedures.

How does the SOG certification differ from the general unbonded PT certification?

The SOG workshop focuses specifically on foundation slabs, including soil mechanics, expansive soil behavior, moisture barriers, and slab-on-ground-specific design concepts. The general unbonded PT certification focuses on elevated structures like building floors and beams.

Why are expansive soils important for SOG PT?

Expansive soils swell when wet and shrink when dry, causing differential movement that can crack slabs. Post-tensioning counteracts this by compressing the slab, which is why PT slabs are standard in expansive soil regions like Texas and California.

What is PTI DC10.5?

PTI DC10.5 is the standard for design of post-tensioned slabs-on-ground. It provides design procedures for PT residential and light commercial foundation slabs, including tendon layout, edge distances, and minimum prestress requirements.

When can you stress SOG tendons after concrete placement?

Tendons in SOG slabs typically cannot be stressed until the concrete reaches a minimum compressive strength, usually 2,000-3,000 psi. The exact requirement depends on the project specifications and anchorage system used.

Is the SOG certification valid for elevated structures?

No. The PTI SOG certification is specifically for slab-on-ground applications. For elevated structures, you need the PTI Level 1 or Level 2 Unbonded PT Installation certification.