Mortars
Mortars
Preparation and Good Practice:
- Cold or wet weather can adversely affect the results by hindering the adhesion and setting of the mortar. Building in such conditions should be avoided.
- Block surfaces should be clean and free of dust, residues and moss like substances.
- For lightweight and dense concrete blocks, the suction of blocks will increase as they dry out. Do not wet the blocks but rather adjust the mortar consistency to suit the suction (i.e. the drier the block, the mortar should be made slightly wetter).
- In the case of Airtec aerated blocks, when the blocks are dry the surfaces accepting the mortar should be lightly brushed with water immediately prior to application of the mortar.
- Always use a full bed of mortar and fully fill the perp ends (vertical joints).
- Protect newly laid blockwork from frost and inclement weather using suitable weatherproof sheeting and stabilise the wall wherever strong winds pose a risk.
Mortar Mixes:
- As a rule of thumb, weaker mixes should be used with Airtec aerated blocks to avoid cracking.
- Stronger mixes which are unable to accommodate differential movements may produce some cracking - weaker mixes are able to accommodate the small movements producing only hair-line cracks in joints, which are less noticeable.
- Grade iii mortar which will assist in accommodating small movements, is suitable for the majority of locations and exposed conditions and may be considered the most generally suitable for concrete blockwork.
- It should be noted that improvements in adhesion and resistance to rain penetration are indicated for lime-based mortar.
- Improvement in resistance to frost attack is indicated for mortars containing a plasticiser.
- Insulating mortars, such as Limelite and Pearlite, may be used to improve the thermal performance of the blockwork.
- For thin-joint masonry (Airtec aerated blocks only) water is added to the bagged powder and simply mixed. Always follow the instructions supplied with the mortar.
|
Mix Proportions (by volume) |
Aggregate Blocks |
Airtec Blocks |
Notes | |
|
Above DPC |
Cement:Lime:Sand Cement: Sand (with plasticizer) Masonry Cement: Sand |
1 : 1 : 5-6 1 : 5-6 1 : 4-5 |
1 : 2 : 9 or 1 : 1 : 6 1 : 6 1 : 5 |
Grade iii mortar or iv mortar as per BS 5628-2 |
|
Below DPC |
Cement:Lime:Sand Cement:Sand |
1 : 1 : 5-6 1 :4-5
|
1 : 1 : 4.5 - 5 1 : 4 |
All blocks and mortars meet class 1 and 2 sulphate soil classification. Class 3 and above, sulphate resisting mortar may be required. |
Enquiries
01900 68211
