FAQ's - frequently asked questions

QUESTION	ANSWER
CONCRETE MIX What volume does 20kg make? What volume does 40kg make? What is the strength of the mix?	CONCRETE MIX 0.01 of a cubic metre 0.02 of a cubic metre There is no requirement for 28 days, 7days is minimum 12MPa.
QUICK SET CONCRETE What volume does the bag make? What is the use? What is the strength? Can it be used with Aluminum products?	QUICK SET CONCRETE The same volume as the Concrete Mix. NON structual use. Due to the quick setting nature of product, early strength is not guaranteed, 7 day strength are over 15MPa. Not to be used with Aluminum products.
MORTAR MIX Where can this be used? Can it be used for roof tiles?	MORTAR MIX For use in general mortar applications. No, the mix for roof tiles is 1 cement to 4 sand.
QUICK SET MORTAR Where is this used? Can it be used on roof tiles?	QUICK SET MORTAR Patching around clay pipes (Plumbing). No, the mix for roof tiles is 1 cement to 4 sand.
ACRYLIC DRY RENDER Where can this be used? Where can't it be used? Can we colour the render? Do I have to add a bonding agent? How long before it is dry? Can I paint the render?	ACRYLIC DRY RENDER On all clean bricks, blocks & concrete panels. Blueboard (special render), painted surfaces, inside fire places. Yes, coloured oxides are available. No, this is already in the render mix. This depends upon the weather conditions. Tape a piece of plastic over a small area and if there is no moisture under the plastic after 24 hours the render is dry. Yes, wait until it is dry and then paint.
COLOURED OXIDES How much do I need? I want a lighter shade? Why can't I match the colour I have seen else where?	COLOURED OXIDES 8% by weight of the cement content will give maximum colour. For lighter shades, reduce the oxide weight by experimentation & make a record of it for future reference. This will depend upon the kind of cement & sand or lime used, the amount and type of oxide used in the mix and the drying conditions. It is always recommended to purchase enough materials to finish the entire job at the start of project.

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Cold Weather Concreting

Helpful information:

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Bulk Density of
Cement Products

Is your Mortar up to scratch?

Australian Standard AS 3700 table 10.1 sets out the requirements for mortar
compositions which are deemed - to - satisfy.

General Mortar:

For fired clay bricks and concrete brick, the mix is as follows:

M3 Mortar: 1 Cement Type GB or GP. 1 Lime Hydrated (Building lime) 6 Sand
(free from deleterious materials, no more than 10% passing a 75 micron sieve).
NOTE: Mix proportions are to be volume batched.
For other mortars: i.e. in severe marine environments and saline wetting etc.
refer to AS 3700 Masonry structures Standard and amendment No 1.

Mixing of Mortar:

Only mix the amount of mortar that can be used immediately.
The mix should be workable i.e. not too wet.
Use water which is free from harmful quantities of material deleterious to
masonry reinforcement and any embedded items.

Mortar Joints:

Mortar joints which are tooled are more durable than joints which are struck off
flush with brick work or are raked out.

Cleaning Brick Work:

Masonry should be cleaned and stains removed as necessary in such a
manner that the mortar is not damaged.
Remove all lumps of mortar from brick work with a scraping or wire brushing.
Drench brick work with clean water to wash off loose dirt and reduce absorption.
If required a solution of 1 Hydrochloric acid to 20 parts of water may be used on
stubborn stains and washed off immediately with water.

Problems with mortar:

There have been a number of occasions where mortar on houses
tested had not been up to scratch. This may have occurred due to:
Insufficient cement contents - Shovels used to batch cement will give
an inconsistent proportion of cement per mix.
Over-sanded Mixes - Shovels used to batch sand will give an
inconsistent proportion of sand per mix.
Sand should be clean - The more clay the lower the strength and durability.
Additional water added to mortar mix -
The more water added to the mortar mix the lower the mortar strength.
Additions of Detergents - These are not to be used and are detrimental to good
mortar strength and durability.
Flush or raked joints - Will leave a porous surface on the mortar and may
be less durable.
Cleaning brick work too early - Will wash out the surface of the mortar.
Using a too high concentration of acid - Acid reacts with cement and the high
concentration of acid will remove the cement surface of mortar
and leave a sandy finish.
High pressure water jets - High pressure water jets can wash out mortar,
reducing the durability.

Safety:

Ensure that you read the safety instructions prior to mixing mortar and
cleaning of brick work.

These tips are supplied by: Building Products Supplies Pty. Ltd.
suppliers to the industry of Australian Builders Cement, Eureka Cement,
Australian Builders Mortar Mix and other pre-packaged handyman products.