Mississippi Marine Construction

Key Concepts

Fall Protection (29 CFR 1926 Subpart M)

• 6-foot threshold: Employers must provide fall protection when workers are exposed to falls of 6 feet or more in construction. This is the critical trigger point.
• Three accepted systems: guardrail systems, safety nets, and personal fall arrest systems (PFAS)
• PFAS components: harness, lanyard, and anchorage point rated to 5,000 lbs minimum per worker
• Guardrail top rail height: 42 inches (±3 inches); mid-rail at approximately 21 inches

Excavation Safety (29 CFR 1926 Subpart P)

• Cave-in protection required in excavations 5 feet or deeper (or shallower if soil is unstable)
• Three protection methods: sloping, shoring, and trench shields (boxes)
• Soil is classified as Type A (most stable), Type B, or Type C (least stable — running soil)
• Type C soil maximum slope: 1½:1 (horizontal:vertical); Type A: ¾:1
• A competent person must classify soil and inspect excavations daily and after rain events
• Employees must not work in excavations where water is accumulating unless controlled

Crane and Derrick Safety (29 CFR 1926 Subpart CC)

• Load charts must be on the crane and used — never exceed rated capacity
• Ground conditions must be assessed; outrigger pads/mats required on soft or unstable ground
• Power line clearance: Minimum 10 feet from energized lines up to 50kV; greater distances for higher voltages
• Assembly/disassembly must be directed by a qualified person
• A Qualified Rigger and Certified Crane Operator are required for lifts

Confined Spaces (29 CFR 1926 Subpart AA)

• A permit-required confined space has: limited entry/exit, not designed for continuous occupancy, AND contains or has potential for a serious hazard
• Atmospheric testing order: oxygen first, then flammable gases, then toxic contaminants
• Acceptable oxygen range: 19.5%–23.5%; lower explosive limit (LEL) must be below 10% before entry
• An attendant must remain outside; an entry supervisor authorizes entry; a rescue plan must be in place before entry begins

Miscellaneous Engineering: Pile Driving (18 questions, 45% of exam)

Key Concepts

Pile Types & Classifications

• Timber piles: Oldest type; driven butt-end down; must be cut off below permanent water table to prevent decay; treated with preservatives (creosote) for marine use
• Concrete piles: Precast or cast-in-place; require cushioning during driving to prevent cracking; prestressed concrete piles are most common in marine construction
• Steel piles: H-piles (end-bearing) and pipe piles (open or closed end); highly resistant to driving stress; can be spliced easily
• Sheet piles: Interlocking sections (steel most common in marine work); used for bulkheads, cofferdams, and retaining walls; installed in sequences to maintain interlock
• Composite piles: Combine two materials (e.g., concrete upper section + timber lower section); used when different soil conditions exist along pile length

Load-Bearing Mechanisms

• Friction piles: Derive capacity from skin friction along the pile shaft; used in soft soils where no firm bearing stratum exists; capacity = unit skin friction × surface area
• End-bearing piles: Transfer load through soft material to a firm stratum (rock or dense gravel) at the tip; capacity determined by tip resistance
• Most marine piles rely on combined friction and end bearing; design specifies which dominates

Pile-Driving Hammers

• Drop hammer: Simple, slow; gravity falls weight; energy = weight × drop height
• Single-acting air/steam hammer: Ram raised by air/steam, falls by gravity; energy = ram weight × stroke
• Double-acting air/steam hammer: Air/steam raises AND accelerates ram downward; higher blow rate; energy calculation requires accounting for downward pressure
• Diesel hammer: Self-contained; open-end (single-acting) or closed-end (double-acting); requires no external power source — preferred for remote marine sites
• Vibratory driver: Uses oscillating eccentric weights to liquefy soil friction; not suitable for end-bearing piles; ideal for sheet pile installation and granular soils; no impact stress on pile

Key Concepts

Cement Types - Portland cement (ASTM C150): The standard hydraulic binder; gains strength through hydration. Named for resemblance to Isle of Portland limestone. - Blended cements (ASTM C595): Portland cement combined with supplementary cementitious materials (fly ash, slag, silica fume, natural pozzolans). Improve durability and reduce permeability — critical in marine exposure. - Hydraulic cements (ASTM C1157): Set and harden by reacting with water; remain stable underwater. Essential knowledge for marine construction context.

Water-Cementitious Materials Ratio (w/cm) - Lower w/cm = higher strength and durability. Typical paste: w/cm between 0.4 and 0.6 by weight. - Higher water content (not w/cm) = higher slump, but does NOT improve strength. - For marine/sulfate/chloride environments, maximum w/cm is tightly restricted.

Aggregates - Fine aggregate: passes No. 4 sieve, retained on No. 200 sieve. Fine aggregate + cement paste = mortar. - Coarse aggregate: larger than No. 4 sieve, up to 3 in. max. Adding coarse aggregate to mortar = concrete. - Normal concrete is approximately ¾ aggregate, ¼ paste by volume. - Larger maximum aggregate size = less cement paste needed = lower cost. - Surface abrasion resistance is almost entirely a function of fine aggregate properties. - Moisture content of aggregates must be measured and accounted for in batching — surface moisture on aggregates counts toward the mix water.

Durability and Exposure Categories - Freeze-thaw resistance: Requires air entrainment; air content varies by aggregate size and exposure severity. - Sulfate attack: Requires low w/cm, sulfate-resistant cement (Type V Portland or blended equivalents), and low permeability. - Chloride/corrosion resistance: Critical in marine environments — use low w/cm, supplementary cementitious materials (silica fume, slag), and adequate cover over reinforcement. - Permeability: Directly controlled by w/cm and degree of hydration. Lower w/cm = denser paste = lower permeability.

Mississippi Marine Construction Licensing Exam Study Brief

Key Concepts

Why Steel Reinforces Concrete Concrete is strong in compression but weak in tension — tensile capacity is only about 1/10 of compressive strength. Steel reinforcing bars (rebar) offset this by carrying tension, resisting shear (via stirrups, ties, hoops, spirals), reducing crack widths, and assisting in compression (columns). The bond between concrete and steel enables composite action; both materials share nearly identical thermal expansion rates.

ASTM Specifications - ASTM A615: Deformed and plain carbon-steel bars — most common spec; covers Grades 40, 60, 75, 80 - ASTM A706: Low-alloy steel bars — specified when weldability is required; Grade 60 is the standard welding-grade bar; all welding must conform to AWS D1.4 - Grade 60 is the most common: minimum yield strength 60,000 psi (420 MPa), minimum tensile strength 90,000 psi (620 MPa) - Grade 80 and Grade 100 are available for high-load or seismic applications

Bar Sizes Rebar is designated by number (e.g., #3 through #18). The bar number corresponds to the bar diameter in eighths of an inch — e.g., a #4 bar = 4/8 = ½ inch diameter.

Identification Markings on Deformed Bars Rolled-in markings identify: 1. Producer's mill mark (letter or symbol) 2. Bar size number (#3–#18) 3. Steel type: S = carbon steel (A615), W = low-alloy (A706), A = axle steel, R = rail steel 4. Grade: Grade 60 bars show either one continuous line or the number 4 (in line spacing); Grade 40/50 bars have no grade mark

Concrete Cover Requirements Concrete cover protects steel from corrosion and fire. Cover is measured from the outer face of concrete to the outside of the reinforcement (including ties and stirrups). Permissible deviations from specified cover are governed by ACI 117. Marine and exposed environments require greater cover than interior members — confirm project specifications for minimum values.

Bar Supports Supports hold rebar in position during concrete placement. Types include: - Wire bar chairs (individual or continuous) - Precast concrete blocks/bricks - Plastic chairs/clips