2.12 MORTARS AND GROUTS

1. 2.12 MORTARS AND GROUTS • 2.12.1 Definitions • 2.12.2 Masonry mortars • 2.12.3 Rendering

2. Definitions • CEMENTITIOUS MATERIAL : Cement or cement replacement • CONCRETE : Cementitious + Water + Fine aggregate + Coarse aggregate • MORTAR (OR SANDED GROUT) : Cementitious + Water + Fine aggregate • PASTE (OR UNSANDED GROUT) : Cementitious + Water

3. Typical application of mortar

4. Application for grout Column Bolt Grout Concrete

5. Small grouting contracts …

6. Mixes without coarse aggregate will: • Generally have lower strengths • Generally have lower w/c ratios • Have high shrinkage, this makes them unsuitable for use in thick sections • Often require high shear mixing

7. 2.12 MORTARS AND GROUTS • 2.12.1 Definitions • 2.12.2 Masonry mortars • 2.12.3 Rendering

8. The requirements of mortar when it is wet • It should be sufficiently workable to spread easily. • It should be sufficiently cohesive to stay on a trowel and then adhere to a masonry unit (brick or block) during laying. • It should remain useable for two hours after mixing (note that, unlike most concrete, mixing is not continued until use). • It should set fast enough to permit walls to be raised 1m each day and to give some resistance to overnight frost (although protection should be used). Accelerators rarely work due to the thin sections. Do NOT use calcium chloride, it leaches as well as causing corrosion. Work must stop below 3oC.

9. The requirements of mortar after it has set (1) • It should be strong enough to carry the loads which are applied on it by the masonry units. Apart from the w/c ratio the sand grading has a substantial effect. Note that a 10m high masonry wall with a density of 2000kg/m3 only requires a strength of 0.2 MPa to support its weight. • It should be flexible enough to take up movement in the structure. All movement caused by thermal effects and moisture movement etc. (often high in new bricks) should be taken up in the mortar, not the masonry units. Therefore, as a working rule, the mortar must not be stronger than the units that it is bonding. • It should resist water penetration. Note that some water penetration into a wall cavity is harmless due to tray dpc's and weep holes.

10. Brick wall detail rain Brick cavity wall Weep holes Damp Proof Course (dpc) Concrete Footing

11. The requirements of mortar after it has set (2) • It should have an attractive uniform appearance. Uniformity requires accurate proportioning for mixing. Adding water makes a mortar whiter. • It should be durable. The main durability considerations are: i. Frost resistance. This is easily achieved with air entrainment and, if it fails, requires re-pointing. ii. Sulphate resistance. Some bricks leach sulphates, if SRPC is not used the consequences are almost impossible to rectify. Below dpc sulphates in groundwater may be a problem. iii.Protection of embedded steel, i.e. reinforcement (mesh) and wall ties. This requires resistance to carbonation.

12. Mortar mixes

13. 2.12 MORTARS AND GROUTS • 2.12.1 Definitions • 2.12.2 Masonry mortars • 2.12.3 Rendering

14. Rendering This has two main functions: • To improve appearance (often on block walls). • To resist water penetration (often on solid walls).

15. Rendering is normally applied in two layers: • The first layer seals the surface so the second layer can cure without losing all its water by capillary suction into the substrate. • The second layer provides the durability.