Exposed Aggregate Concrete Unit Masonry AHA (Activity Hazard Analysis / Job Hazard Analysis)

Updated 2026-06-23

A Exposed Aggregate Concrete Unit Masonry AHA (Activity Hazard Analysis / Job Hazard Analysis) is the plan that keeps the crew building exposed aggregate concrete unit masonry safe through the heavy block handling and abrasive face, from the masonry-wall stability and collapse, and around the block cutting silica and mortar contact. Exposed aggregate concrete unit masonry lays concrete block with an exposed-aggregate face — combining the heavy-block-handling and abrasive-face hazard, the masonry-wall-stability and collapse hazard, and the block- cutting-silica and mortar-contact hazard. This guide walks through building a Exposed Aggregate Concrete Unit Masonry AHA that names the heavy-block-handling/abrasive-face, masonry-wall-stability/collapse, and block-cutting- silica/mortar-contact hazards and assigns the handling, stability, and silica/contact controls that hold up in the field.

Why exposed aggregate concrete unit masonry needs its own AHA

Exposed aggregate concrete unit masonry is the construction of walls using exposed-aggregate concrete masonry units — architectural block whose finished face has the aggregate exposed (ground, polished, or otherwise revealed to show the decorative aggregate) as the exposed architectural surface. This continues the architectural-CMU cluster. The defining feature is that these are concrete masonry units with an exposed-aggregate face: the standard concrete-block hazards apply (heavy handling, wall stability, silica, mortar), with the added consideration that the exposed-aggregate face is a hard, abrasive, textured surface (a minor abrasion/cut consideration when handling, and the aggregate face relates to the silica content). The hazards combine the heavy-block-handling and abrasive-face (the block is heavy (concrete) with an exposed-aggregate face — the handling/ergonomic hazard (heavy block) and the abrasive-face hazard (the exposed-aggregate face is hard, rough, and abrasive — a minor abrasion/cut consideration when handling)), the masonry-wall-stability and collapse (building up the block wall — the wall-stability/collapse hazard (unbraced fresh masonry walls collapse, especially under wind)), the block-cutting-silica and mortar-contact (cutting concrete block (silica) and the caustic mortar (cement burns)), and the scaffold-access/falling-material. The heavy-block-handling/abrasive-face and the masonry-wall-stability/collapse justify a dedicated AHA.

Breaking exposed aggregate concrete unit masonry into steps

The steps for a Exposed Aggregate Concrete Unit Masonry AHA follow the laying:

• Set up scaffold access and material staging (block within reach)
• Mix and spread the mortar (caustic contact)
• Lay the exposed-aggregate block in courses (handling, abrasive face)
• Brace the wall as it is built (wall stability)
• Cut block as required (silica control)
• Manage the handling, stability, and silica hazards
• Point, clean, and protect the aggregate face
• Complete

Each step carries a hazard, and the heavy-block-handling/abrasive-face, the masonry-wall-stability/collapse, and the block-cutting-silica/mortar-contact are where the most significant risks concentrate.

The hazards step by step

Heavy-block-handling and abrasive-face

The block is heavy (concrete) with an exposed-aggregate face — the handling/ergonomic hazard (heavy block) and the abrasive-face hazard (the exposed-aggregate face is hard, rough, and abrasive — a minor abrasion/cut consideration when handling). The controls are managing the heavy-block handling and ergonomics (heavy concrete block — staging within reach, good work height, mechanical/team lifting, pacing, rotation), hand protection against the abrasive aggregate face (the rough, hard aggregate face can abrade/cut hands when handling — gloves), and the handling/ abrasive controls. The heavy-block-handling/abrasive-face is a defining hazard — the block is heavy and its aggregate face is abrasive. (These follow the manual-handling fundamentals.)

Masonry-wall-stability and collapse

Building up the block wall — the wall-stability/collapse hazard (unbraced fresh masonry walls collapse, especially under wind). The controls are bracing masonry walls during construction (unbraced fresh masonry walls collapse under wind — bracing per the requirements, exclusion zones behind a wall being built), and the wall-stability controls. The masonry-wall-stability/collapse is a defining hazard — unbraced fresh block walls collapse. (These follow the masonry-wall-bracing fundamentals.)

Block-cutting-silica and mortar-contact

Cutting concrete block (silica) and the caustic mortar (cement burns). The controls are silica control for cutting concrete block (concrete block is high in silica — cutting generates respirable silica — wet cutting, dust extraction, respiratory protection), preventing skin contact with the caustic mortar (gloves, skin protection), and the silica/contact controls. The block-cutting-silica/mortar-contact is a defining hazard. (These follow the silica and cement-contact fundamentals.)

Scaffold-access/falling-material

The scaffold access and falling material (building from scaffolds, falling heavy block/tools) carries the access/ falling-object hazard. The controls are safe scaffold access (fall protection), falling-object protection (toe boards, controlled access below), and the access/falling controls. (These follow the scaffold and falling-object fundamentals.)

A simple Exposed Aggregate Concrete Unit Masonry AHA structure

Heavy-block/abrasive handling control and wall-stability/silica safety

A Exposed Aggregate Concrete Unit Masonry AHA centers on heavy-block/abrasive handling control and wall-stability/ silica safety. The heavy-block/abrasive handling control addresses the heavy block with the abrasive face — controlled by managing the heavy-block handling and ergonomics and hand protection against the abrasive aggregate face. The wall-stability/silica safety addresses the wall and the cutting — controlled by bracing masonry walls during construction (unbraced fresh block walls collapse under wind) and block-cutting silica control, plus caustic-mortar contact protection. And the scaffold access and falling material get access and falling-object controls. An AHA built on heavy-block/abrasive handling control and wall-stability/silica safety, with access controls, addresses the hazards that define exposed aggregate concrete unit masonry.

From the field: what actually goes wrong

In fourteen years across federal, heavy civil, and industrial projects, exposed aggregate concrete unit masonry lays concrete block with an exposed-aggregate decorative face, and it continues the architectural-CMU cluster. Its hazards are essentially the concrete-block hazards, with the minor added consideration of the abrasive aggregate face. The heavy-block-handling and abrasive-face hazard is a primary defining concern — like all concrete block, exposed-aggregate block is heavy, so the significant manual-handling and ergonomic hazard applies (repeatedly lifting heavy block is a major injury cause, controlled by staging within reach, good work height, mechanical and team lifting, pacing, and rotation), and the exposed-aggregate face adds a minor abrasion consideration: the face is hard, rough, and abrasive (the aggregate is exposed and textured), so it can abrade or cut the hands when handling the block, controlled by hand protection (gloves). The weight is the significant hazard; the abrasive face is a minor handling consideration.

The masonry-wall-stability/collapse and the block-cutting-silica/mortar-contact are the other defining hazards, and they are the shared unit-masonry themes. On the projects I have run, building up the block wall brings the same defining masonry-construction hazard — a freshly laid, unbraced masonry wall can collapse, especially under wind, so bracing masonry walls during construction (per the requirements, with exclusion zones) is critical. And the block-cutting-silica hazard (concrete block is high in silica — cutting generates respirable silica, controlled by wet cutting, dust extraction, and respiratory protection) and the caustic-mortar contact (cement burns — gloves and skin protection) are the familiar masonry material hazards. The scaffold access and the falling-material hazard round it out. The AHA built on heavy-block/abrasive handling control and wall-stability/ silica safety is the one that protects the exposed-aggregate-block crew.

The bottom line

A Exposed Aggregate Concrete Unit Masonry AHA names the heavy-block-handling/abrasive-face, the masonry-wall- stability/collapse, and the block-cutting-silica/mortar-contact hazards with specific controls — managing the heavy-block handling and ergonomics with hand protection against the abrasive aggregate face, bracing masonry walls during construction (unbraced fresh walls collapse under wind), and block-cutting silica control with caustic-mortar contact protection. The heavy-block/abrasive handling control and the wall-stability/silica safety are the defining concerns. The AHA that manages both is the one that protects the crew.

Frequently asked questions

What handling hazards does the exposed-aggregate face add?

Like all concrete block, exposed-aggregate block is heavy (a significant manual-handling and ergonomic hazard), and the exposed-aggregate face adds a minor abrasion consideration — the face is hard, rough, and abrasive, so it can abrade or cut the hands when handling the block. Controls are managing the heavy-block handling and ergonomics (staging within reach, good work height, mechanical/team lifting, pacing, rotation), hand protection against the abrasive aggregate face (gloves), and the handling/abrasive controls.

Why is masonry-wall stability a defining hazard?

Building up the block wall brings the same defining masonry-construction hazard as all unit masonry — a freshly laid, unbraced masonry wall can collapse, especially under wind. Controls are bracing masonry walls during construction (per the requirements limiting unbraced masonry wall height, exclusion zones behind a wall being built), and the wall-stability controls.

What silica and mortar hazards apply?

Concrete block is high in silica, so cutting it generates respirable silica, and the caustic mortar causes cement burns from skin contact. Controls are silica control for cutting concrete block (wet cutting, dust extraction, respiratory protection), preventing skin contact with the caustic mortar (gloves, skin protection), and the silica/contact controls.

What is exposed aggregate concrete unit masonry?

Exposed aggregate concrete unit masonry is the construction of walls using exposed-aggregate concrete masonry units — architectural block whose finished face has the aggregate exposed (ground, polished, or revealed) as the exposed architectural surface. Because the block is heavy with an abrasive face, unbraced fresh masonry walls can collapse, and cutting block generates silica with caustic mortar, those hazards apply.

Related AHAs and JHAs

• Architectural Concrete Unit Masonry AHA — the architectural-CMU fundamentals
• Split-Faced Concrete Unit Masonry AHA — the split-faced variant
• Concrete Unit Masonry AHA — the standard concrete unit masonry
• Masonry and Block Wall Construction JHA — the block-wall-construction fundamentals

Written by Mustafa Tok, CSP, ASP, CHST — OSHA Authorized Outreach Trainer with 14+ years of international construction safety experience across federal, heavy civil, and industrial projects.