mineral / Cementitious / Concrete Masonry Unit

Concrete masonry unit, solid, various sizes (90mm, 140mm, 190mm wall thickness)

Solid CMUs in 90, 140, 190, and 290 mm widths; density 2100–2300 kg/m³; f'uc 10–25 MPa; Rw 50–58 for 190 mm solid; FRL up to 240 min structural adequacy; non-combustible (Group 1). Higher mass and cost per unit than hollow CMU but eliminates core-filling and achieves better inherent fire and acoustic ratings.

Atlas code

MIN-CEM-CMU-002

mineralcementitioussolid-cmuconcrete-masonrystructuralfire-ratednon-combustible

Concrete masonry unit, solid, various sizes (90mm, 140mm, 190mm wall thickness)

At-a-glance signals

Overview

Executive summary

Solid concrete masonry units (CMUs) are dense, fully-filled factory-made blocks for masonry walls. Standard face sizes are 390 x 190 mm (L x H) in wall thicknesses of 90, 140, 190, and 290 mm. Because there are no voids, solid CMUs offer substantially higher thermal mass, superior acoustic attenuation (Rw 50–58 for 190 mm), and excellent fire resistance compared with equivalent hollow units, eliminating the need for core-filling on fire or acoustic projects. Manufactured to AS/NZS 4455.1 and tested to AS/NZS 4456; structural masonry design to AS 3700. Density ranges 2100–2300 kg/m³ and characteristic compressive strength f'uc is typically 10–25 MPa depending on mix and manufacturer.

Best when…

Non-combustible — Group 1 material under NCC; no contribution to fire load, no smoke or toxic gas production.
Superior acoustic performance compared with hollow CMU — solid 190 mm wall achieves Rw 50–52 bare, 54–58 rendered, without core-fill.
Excellent fire resistance — solid section provides better thermal insulation in fire; FRL up to 240/240/240 achievable.
High thermal mass (density 2100–2300 kg/m³) reduces peak indoor temperatures and smooths diurnal temperature swings.
Eliminates core-filling labour and material cost on fire and acoustic walls.
Standard modular sizing (390 x 190 mm face, 90/140/190/290 mm widths) integrates with standard masonry accessories and ties.
Durable — 50–100 year design life; resistant to impact, vermin, and weathering.
Low maintenance — no painting required in many commercial applications; repaintable if desired.
Recyclable as crushed aggregate at end of life.

Top advantages

01 Non-combustible — Group 1 material under NCC; no contribution to fire load, no smoke or toxic gas production.
02 Superior acoustic performance compared with hollow CMU — solid 190 mm wall achieves Rw 50–52 bare, 54–58 rendered, without core-fill.
03 Excellent fire resistance — solid section provides better thermal insulation in fire; FRL up to 240/240/240 achievable.
04 High thermal mass (density 2100–2300 kg/m³) reduces peak indoor temperatures and smooths diurnal temperature swings.
05 Eliminates core-filling labour and material cost on fire and acoustic walls.

Top limitations

01 Significantly heavier than hollow CMUs — 190 mm solid unit weighs 28–32 kg versus 14–18 kg hollow, requiring mechanical handling for upper courses.
02 Higher material cost per unit ($4–10 AUD) and per m² ($50–120 AUD supply only) compared with hollow CMU of equivalent size.
03 Greater dead load on foundations and structure compared with hollow or lightweight alternatives.
04 Limited thermal insulation in the bare wall — R-value ~0.12 m²K/W for 190 mm; insulation must be added to meet NCC energy efficiency requirements.
05 Product data is manufacturer-specific; fire and acoustic ratings must not be applied across brands without independent verification (Island Block manual).

Technical

Physical ·9

Density: 2100–2300 (dense weight solid); 1800–2100 (lightweight solid) kg/m3 Solid CMUs are denser than hollow units due to fully filled cross-section. Standard dense-weight solid CMU 2100–2300 kg/m³; lightweight solid CMU 1800–2100 kg/m³. Island Block manual defines lightweight (<1800 kg/m³) and dense weight (>1800 kg/m³) bands.
Specific gravity: 2.1–2.3 Derived from density. Dense-weight solid CMU specific gravity approximately 2.1–2.3 relative to water.
Porosity: 12–18 % Dense-weight solid CMUs have lower porosity than lightweight or hollow units. Typical total porosity 12–18% by volume for dense concrete mix. Lower porosity improves durability and reduces water absorption.
Water absorption: 5–10 (dense); 10–15 (lightweight) % by mass AS/NZS 4456.14 test method. Dense-weight solid CMU typically 5–10% by mass. Lightweight solid CMU may reach 12–15%. Lower absorption than hollow units of equivalent grade due to denser mix.
Hardness: 4–6 Mohs scale Concrete is predominantly calcite and quartz aggregate binder matrix. Approximate surface hardness 4–6 Mohs equivalent. Not a primary design parameter for CMU.
UV resistance: Excellent — no UV degradation Concrete CMU is inherently UV resistant — mineral binder and aggregate are unaffected by UV radiation. Surface colour may bleach slightly over time but structural and performance properties are unaffected.
Chemical resistance: Good (mild conditions); moderate (sulfate/acid exposure — specify SR cement) Good resistance to mild acids, alkalis, and most salts in service conditions. Susceptible to attack by strong acids (H₂SO₄, HCl) and sulfate-bearing soils/groundwater. Sulfate-resistant cement mix recommended for aggressive ground conditions. Good resistance to seawater splash with appropriate cover.
pH tolerance: Resistant pH 7–14; avoid sustained pH < 5 Concrete is highly alkaline (pH 12–13 initially due to Ca(OH)₂). Solid CMU is suitable for contact with alkaline soils; avoid direct prolonged contact with acidic environments (pH < 5). Carbonation progresses over time reducing surface pH to ~8–9.
Surface roughness: 1–3 (standard cast); 3–10 (split face) mm As-cast face has a medium rough texture from steel mould release. Typical surface roughness Ra 1–3 mm equivalent. Split-face finish gives higher roughness 3–10 mm; ground/honed face reduces to <0.5 mm.

Mechanical ·7

Tensile strength: 1.0–2.5 (unit); masonry not designed for tension MPa Direct tensile strength of concrete CMU approximately 1.0–2.5 MPa (roughly 0.1× compressive strength). Masonry is not designed to carry direct tension; flexural and shear reinforcement provided where tension is expected per AS 3700.
Compressive strength: 10–25 (standard 10–15; structural 15–25) MPa Characteristic unconfined compressive strength f'uc. Standard grade: 10–15 MPa. Structural grade: 15–25 MPa. Island Block manual documents f'uc ≥ 15 MPa for lightweight and dense weight blocks. Higher strengths (20–25 MPa) used for loadbearing structural walls. Tested to AS/NZS 4456.4.
Flexural strength: 0.2–0.4 (masonry assemblage, parallel to bed joints) MPa Characteristic flexural strength of masonry f'mt per AS 3700 for unrendered CMU approximately 0.2–0.4 MPa parallel to bed joints. Masonry flexural tensile strength is low; reinforced masonry or pre-stressed designs used for significant lateral loads.
Shear strength: 0.35–1.0 (masonry assemblage) MPa Shear strength of masonry assemblage per AS 3700. Characteristic shear strength f'ms approximately 0.35–1.0 MPa depending on mortar type, unit strength, and construction quality. Determined from testing or AS 3700 tables.
Poisson's ratio: 0.15–0.25 Poisson's ratio for concrete masonry approximately 0.15–0.25. Used in finite element analysis of masonry structures. Consistent with dense concrete values.
Impact resistance: Good (hard surface, high mass) Solid CMU has good resistance to incidental impact loads due to high mass and compressive strength. Hard face finish resists surface damage from minor impacts. Not suitable as a primary impact-absorbing element. No standard rating for masonry impact; qualitative assessment: good for construction traffic loads.
Creep resistance: 1.5–2.5 (long-term creep coefficient) coefficient Concrete masonry exhibits low creep compared with timber or polymer materials. Long-term creep coefficient for concrete masonry approximately 1.5–2.5 at 50 years under sustained load. Creep is more significant in loaded masonry columns than walls.

Sustainability & Health

Embodied carbon & energy ·7

Embodied carbon: 45 kgCO2e/m2 190 mm solid CMU wall supply and installation. Higher than hollow CMU per m² due to greater material volume and cement content. EPD data from Adbri and Austral Masonry available. Supplementary cementitious materials (fly ash, slag) in mix can reduce embodied carbon 10–30%.
Carbon footprint: 0.137 kgCO2e/kg Carbon footprint per kg of solid CMU. Primary source is Portland cement production. Blended cements with fly ash or GGBFS can reduce to 0.09–0.11 kgCO2e/kg.
Embodied energy: 1.32 MJ/kg Embodied energy per kg of concrete masonry. Solid CMU has higher embodied energy per m² than hollow due to greater mass but similar per-kg value. Cement production accounts for 60–70% of total embodied energy.
Water footprint: 150 L/unit Water used in manufacture per block. Concrete mixing and curing accounts for majority. Solid CMU uses more water per unit than hollow due to greater material volume.
Recycled content: 20 % Recycled aggregate, fly ash, and GGBFS can contribute 10–40% recycled content by mass. Some manufacturers use recycled concrete aggregate. Declared recycled content varies by product and batch.
Renewable content: 0 %
Circular score: 7 /10 At end of life, solid CMU can be crushed and recycled as road base, fill, or coarse aggregate for new concrete. Whole blocks can be salvaged and reused if carefully dismantled. Higher value than hollow CMU for thermal mass reuse applications.

Health & emissions ·1

VOC emissions: Zero (cured product) Zero VOC emissions from cured concrete CMU. No organic binders, solvents, or adhesives in standard product. Safe for occupied spaces immediately after installation.

Compliance & Fire

Fire performance ·5

Combustibility class: Non-combustible — NCC Group 1 Non-combustible. NCC Volume 1 Group 1 material. Passes the requirements of AS 1530.1 for non-combustibility. No fire load contribution. Classified as non-combustible under NCC Spec A6.9.
Fire resistance level: FRL 60/120/120 to FRL 240/240/240 (configuration and thickness dependent) minutes FRL expressed as structural adequacy/integrity/insulation. 90 mm solid: FRL 60/120/120 (non-loadbearing) to FRL 120/120/120 (loadbearing, Srf dependent). 140 mm solid: FRL 120/120/120 to FRL 180/180/180. 190 mm solid: FRL 120/120/120 to FRL 240/240/240 (non-loadbearing). Austral Masonry 90 mm solid lists structural adequacy 60–240 min, integrity 120 min (load-bearing Srf < 16) or 240 min (non-load-bearing Srf < 25.83), insulation 120 min; up to 3 m high restrained top and bottom per AS 3700:2018. Solid section provides better insulation FRL than hollow CMU of equivalent width without grouting.
Flame spread index: 0 FSI Concrete does not support flame spread. Flame Spread Index = 0 per ASTM E84 equivalent. BCA/NCC Group 1 material — flame spread index 0, smoke development index 0.
Smoke dev. index: 0 SDI Smoke development index = 0. No smoke generated. NCC Group 1 material. Preferred in smoke-hazard management zones and enclosed public spaces.
Heat release rate: 0 (non-combustible) kW/m2 Concrete masonry is non-combustible. Heat release rate is zero — the material does not contribute to fire load under any circumstances. Group 1 material per NCC Volume 1 specification A6.9 and CSIRO fire testing.

Cost & Lifecycle

Capex & lead time ·6

Material cost (range): 50 – 120 $/m2 Supply only, AUD. Approximately 8–10 units per m² for 190 mm solid. Lower end for standard grey 190 mm; upper end for 290 mm or coloured/textured units. Solid CMU is more expensive per m² than hollow CMU due to higher mass and cement content.
Material cost (per unit): 4 – 10 $/unit AUD per block. Standard 190 mm solid grey CMU approximately $4–7 each. Larger 290 mm solid or special sizes $7–10. Coloured or split-face solid CMU $7–15. Hollow CMU by comparison $2–5 per unit, but solid eliminates core-fill cost on fire/acoustic walls.
Lead time: 3 days Standard grey solid CMU typically ex-stock from masonry suppliers in metropolitan areas. Coloured, split-face, or non-standard sizes may require 5–14 days. Regional projects may require 7–21 days.
Lifecycle cost: 220 – 450 $/m2 Life cycle cost over 50 years including supply, installation, and periodic maintenance (cleaning, repointing, repainting if painted). Solid CMU life cycle cost higher than hollow due to higher material and handling cost but lower than hollow + core-fill for equivalent fire/acoustic performance.
Annual maintenance: 0.5 – 3 $/m2/year Exposed unpainted CMU: occasional cleaning, mortar joint inspection, repointing every 20–30 years. Painted CMU: repaint every 8–12 years. Interior exposed CMU: minimal maintenance.
Market availability: readily available Adbri Masonry (Besser), Austral Masonry, Boral, Midland Brick, and regional manufacturers supply solid CMU nationally. Metropolitan areas ex-stock; regional areas 5–14 days.

Service life & durability ·3

Expected lifespan: 75 years
Maintenance interval: 10 years
Warranty period: 10 years

Layer D

Where it's used

Loadbearing walls in residential and commercial construction

Fire separation walls and fire compartmentation

Acoustic party walls and sound separation

Retaining walls and basement construction

Industrial and warehouse structural walls

Educational, healthcare, and correctional facility walls

Boundary and site perimeter walls

Lift and stair shaft enclosures

Where it's used

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