AAC block adhesive is a polymer-based versatile jointing material specially designed to provide high bonding, durability and speed up the build process of AAC blocks, fly ash bricks, concrete blocks, etc.

It is a pre-mixed, easy to apply high-quality mortar comprising of cement, graded sand and admixtures which replaces conventional jointing mortar of 12-18 mm thickness with highly versatile 3-5 mm thickness.

In this article we discuss, jointing procedure, functions, technical specification and advantages of AAC block Adhesive.

Procedure of Jointing

1. Surface Preparation

  1. The surface of application must be properly cleaned for loose particles, dust, dirt, oil, and grease.
  2. The base on which the adhesive is applied must be cured.
  3. The surface defects such as cracks, holes or voids should be repaired prior to application.

2. Mixing of Adhesive

  1. The mixing of adhesive must be done properly and thoroughly with water.
  2. The ratio of adhesive and water is approximately 25-30% of the weight of the adhesive.
  3. Clean potable water is recommended to be used for mixing.
  4. The bucket used to mix the adhesive is cleaned and add water to it and put the required quantity of adhesive in it.
  5. It is advisable to use a mechanical stirrer for uniform and thorough mixing to save time, labor and for maximum workability.
  6. Depending on the nature of use, the thickness and consistency of the mix are decided.

3. Application of Adhesive

  1. Apply a thin layer of mixed adhesive on the AAC blocks in the thickness of 3 to 5mm by using a proper trowel on which the block work is to be carried out.
  2. After placing the first block apply the AAC Block Adhesive of the same thickness on both the sides of the block continuously keeping a check on the line and level.
  3. The excess adhesive coming out of the block is cleaned immediately and the procedure is carried out for entire blockwork.
AAC Block Adhesive
Fig 1: AAC Block Adhesive

Features of AAC Block Adhesive

  1. High adhesive strength with a thin jointing layer.
  2. The adhesive is pre-mixed, thus the mixing and jointing become easy.
  3. As the thickness is very thin (3 to 5mm), the cost of adhesive when compared to the cement mortar is too less. Thus, economical.
  4. No curing is required neither for AAC blocks or adhesive.
  5. High tensile strength is achieved in less time.
  6. As the thickness of the adhesive is very thin, it eliminates the shrinkage cracks in joints.
  7. As the adhesive is polymer-based, it has low VOC and suitable for green buildings.

Techincal Specification of Adhesive

PropertySpecification
Bulk Density1550-1650 kg/ cum
Water powder ratio25 % by weight
Pot life1 hour @ 27 C
Usable time post application24 hours
Tensile Adhesion (N) IS:15477 -2004
Dry Condition750N
Wet Condition450N
Shear Adhesion (kN) IS:15477 -2004
Dry Condition @ 24hrs2.5 kN
Dry Condition @ 14 days8 kN
Wet Condition4 kN
Heat Ageing4 kN
Splitting tensile strength @ 28 days
– ASTM C 1660-09
0.50 N/ sq mm
Compressive strength @ 28 days
– ASTM C 1660-09
6-7 N/ sq mm

Advantages of AAC Block Adhesive

1. Thin Joints and Less Material

As the thickness of 3-4 mm of adhesive is sufficient to join AAC blocks as compared to cement sand mortar, which takes 8-12 mm thick mortar joints. Thus, the amount of jointing material is reduced by up to 75%.

2. Speedy Construction

AAC block adhesive is a ready-mix material and only water is to be added in it for application. While in the case of cement sand mortar, the raw materials are to be correctly proportioned and then mixed carefully to obtain the paste, which is time-consuming.

3. No Curing

The water added while mixing is enough for the adhesive to achieve the required strength without the additional water. Thus, the curing process is completely eliminated.

4. Site Cleanliness

As the process of mixing, transporting and application is very well defined and hassle-free, the site environment can be easily kept clean.

5. Minimum Process Time

As no curing is required, the masonry wall is ready for further works such as plastering in just 24 hours. While in the case of cement sand mortar, curing is done for 7 days.

6. Less Wastage

Cement mortar accounts for 20-30% of wastage during its use. While there is negligible or no waste of AAC block adhesive.

7. Thermal Insulation

The AAC block adhesive is specially formulated to match the thermal insulation property of AAC blocks. Hence, the whole masonry acts as a thermal barrier which is not the case of cement mortar.

Read More: Autoclaved Aerated Cement Blocks (AAC Blocks)-Properties and Advantages