- 1. Introduction
- 2. Types and uses
- 3. Properties and tests
- 4. Mixing and batching
- 5. Execution and troubleshooting
- 6. QA and QC
- 7. Specification snippet
- Disclaimer
Purpose: consultant-ready guide to mortars and thin-bed adhesives. Use the TOC to jump to types and uses, properties and tests, mixing and batching, execution and troubleshooting, QA, and specification.
1. Introduction
Mortar binds masonry units, transfers load, seals joints, and provides a finish base. Systems range from cement-sand mortars to polymer-modified mortars and factory-blended thin-bed adhesives. Correct selection drives durability, adhesion, and moisture control.
2. Types and uses
- Cement-sand mortar (CM): Common 1:4 to 1:6 for bricks and blocks. Suited for structural and weather-exposed work.
- Lime-cement-sand mortar: Improved workability and breathability; heritage works.
- Polymer-modified mortar (PMM): SBR/latex modified for higher adhesion, flexibility, and water resistance. Pointing and repairs.
- Thin-bed adhesive: Factory-blended polymer-modified adhesive for AAC/porous blocks, 3–4 mm bed. Per manufacturer TDS (EN 998-1 guidance).
- Special repair mortars: Epoxy mortars, micro-concrete, polymer repair mortars for structural repairs.
3. Properties and tests
Property | Significance | Typical acceptance |
Compressive strength (28-day mortar cubes) | Bond and load transfer | CM 1:6 typically 3–7 MPa (project-specific) |
Adhesion / pull-off (plaster/mortar) | Bond to substrate | ≥ 0.5 N/mm² for good performance |
Water retention | Workability and curing | > 75% recommended for plaster mortars |
Pot life / workable time | On-site usability | Typically 30–60 minutes (varies by PMM/adhesive) |
4. Mixing and batching
- Prefer weighed batching for consistency.
- Convert nominal volume ratios (e.g., 1:6) to weight-based for accuracy. Reference 50 kg per cement bag for calculations.
- Use mechanical mixers; limit hand mixing to small patches.
5. Execution and troubleshooting
Failure | Cause | Prevention |
Weak bond | Improper mix or wet substrates | Control w/c ratio; pre-wet bricks uniformly |
Cracking | Rapid drying or poor curing | Keep moist for at least 7 days |
Efflorescence | Salts in sand or water | Use clean sand and potable water |
Segregation | Over-mixing or extended pot life | Mix small batches; discard expired mixes |
- High w/c ratio lowers strength and increases shrinkage; reduce water or use plasticizer.
- Poor adhesion: dirty or smooth substrate; apply bonding slurry or PMM primer.
- Hot/dry conditions: use shade, fogging, or retarders to prevent flash set.
6. QA and QC
- Mortar cubes: for critical work, cast 3 cubes per batch for 7- and 28-day tests.
- Adhesion tests for plaster: 1 per 200 m².
- Visual checks: bond coverage, porosity, and color uniformity (for pointing).
- Prefer ready-mix mortars where quality control is critical.
- Use SBR-modified mortars in damp-prone zones.
7. Specification snippet
Mortar: Cement-sand mortar 1:6 by weight for brickwork; polymer-modified mortar for external pointing and repairs; thin-bed adhesive for AAC as per manufacturer TDS.
Disclaimer
Conix is an industry initiative & a neutral resource, compiled from industry references and best practices. It is not brand-specific. Always cross-check with project requirements and local codes before finalizing specifications.