6.1 Materials for Construction: Concrete, Formwork, Masonry, Steel, and Wood Products

6.1 Materials for Construction: Concrete, Formwork, Masonry, Steel, and Wood Products

The AMSTHC TOS lists five one-item competencies under "Materials for Construction":

1. Review concrete materials and accessories, formwork, scaffolding and concrete reinforcement.
2. Estimate concrete masonry, mortar and grout, and masonry design and erection.
3. Analyze mixing, handling, transporting, placing and consolidating of concrete.
4. Determine properties of iron and steel, and steel erection and construction.
5. Specify lumber, plywood, glulam and other panels.

Testing and mix proportioning, which are structural-design TOS items, are in Section 15.5.

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Concrete Materials and Accessories

Aggregate moisture. Mix designs assume saturated surface-dry (SSD) aggregates. If sand carries 5% free moisture, the batch water is reduced and the sand weight increased by the same amount of water.

Accessories include chairs and bar supports, spacers, tie wire, waterstops, construction-joint keys, inserts and anchor bolts, and curing compounds.

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Formwork, Scaffolding and Reinforcement

Formwork must resist the weight of fresh concrete and the lateral pressure (Section 6.2, ACI 347), plus construction live loads. It must also be tight enough to prevent grout loss. Common materials are plywood or phenolic boards on lumber or steel frames, and reusable steel or aluminum systems.

Scaffolding must have firm base plates and sole boards, diagonal bracing and ties to the structure, full decking with toe boards, and guardrails. It should be erected by trained workers and inspected before use (see Section 6.3).

Reinforcement. Deformed bars to PNS 49 or ASTM A615 are specified by diameter (10, 12, 16, 20, 25, 28, 32 and 36 mm) and grade. The approximate mass per meter is:

$\text{mass (kg/m)} \approx \frac{d^2}{162} \qquad (d \text{ in mm})$

Bars are tied with No. 16 GI tie wire, supported on chairs to keep the specified cover, and lapped or mechanically spliced as the design requires.

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Concrete Masonry, Mortar and Grout

Concrete hollow blocks (CHB) in the Philippines are commonly $400 \times 200\text{ mm}$ in face size, in 100, 150 and 200 mm thicknesses.

Number of blocks. Each block plus its joint covers about $0.40 \times 0.20 = 0.08\text{ m}^2$, so:

$\text{CHB per m}^2 = \frac{1}{0.08} = 12.5$

Example. A wall $8.0\text{ m}$ long and $3.0\text{ m}$ high has a $1.0 \times 1.2\text{ m}$ window.

• Net area: $24.0 - 1.2 = 22.8\text{ m}^2$.
• Blocks: $22.8 \times 12.5 = 285$, plus 5% breakage, about 300 blocks.

Mortar and grout.

• Mortar bonds the blocks; it is typically a cement-sand mix such as 1:3 or 1:4 by volume.
• Grout fills the cells containing reinforcement; it is a fluid cement-sand-fine-gravel mix.
• Plaster finishes the faces.

Quantities are estimated by volume, from joint thickness, cell volume, the fraction of cells grouted and plaster thickness, then converted to cement bags and cubic meters of sand. Estimators often use tabulated factors per square meter for each CHB size.

Masonry erection rules:

• Lay blocks in running bond on a level mortar bed.
• Keep vertical reinforcement aligned in grouted cells.
• Place horizontal joint reinforcement or bond-beam bars at the specified spacing.
• Limit the daily lift height so lower courses are not crushed or displaced.

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Mixing, Handling, Transporting, Placing and Consolidating Concrete

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Iron and Steel: Properties and Erection

Structural steel properties.

• Modulus of elasticity about $200\text{ GPa}$, density about $7{,}850\text{ kg/m}^3$, and thermal coefficient about $12 \times 10^{-6}/^\circ\text{C}$.
• Typical grades include ASTM A36 ($F_y = 248\text{ MPa}$) and A572 Grade 50 ($F_y = 345\text{ MPa}$).
• Steel loses strength rapidly above about 400 °C, so fire protection is needed.

Steel erection sequence:

1. Check anchor-bolt positions and base-plate elevations, and grout under the base plates.
2. Erect columns, then beams.
3. Provide temporary bracing and guys until floors and permanent bracing are complete.
4. Plumb and align the frame before final bolting or welding.
5. Tighten high-strength bolts by an approved method: turn-of-nut, calibrated wrench, or tension-control bolts.
6. Use qualified welders and procedures, and inspect welds visually and, where specified, by nondestructive testing.
7. Apply primer and corrosion protection, and touch up after erection.

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Lumber, Plywood, Glulam and Panels

• Lumber is graded visually or by machine. It is measured in board feet (1 bd ft = 1 in × 12 in × 12 in). A piece measuring 2 in × 4 in × 10 ft contains $(2 \times 4 \times 10)/12 = 6.67$ board feet.
• Lumber should be seasoned (kiln- or air-dried) for framing to limit shrinkage and warping, and treated against termites and decay where exposed.
• Plywood is made of cross-laminated veneers, which gives dimensional stability and resistance to splitting. Marine or exterior grades use waterproof glue. Phenolic-faced plywood is used for repeated formwork.
• Glued-laminated timber (glulam) is made by bonding graded lumber laminations into large straight or curved members. It allows long spans and makes efficient use of smaller pieces.
• Other panels include oriented strand board, fiber-cement board and gypsum board for walls and ceilings, and particleboard for interiors.
• Specify the species or strength group, grade, moisture condition, dimensions (nominal or dressed), treatment and fire rating where required.