Oct 2018 WHY IS THE SOUNDNESS OF CEMENT IMPORTANT?
A critical consideration when selecting good quality cement for any construction project, Sephaku Cement explains the “Soundness of Cement” and why it’s so important to review before building commences.
A primary ingredient used to mix mortar, concrete, plaster and other construction constituents, cement is an essential part of building, regardless of whether cement is used in a do-it-yourself project, home or business architecture or if it’s utilised on a more significant scale such as civil buildings, the quality of Portland Cement selected in any construction project is a critical consideration.
The Soundness of Cement used in concrete is a term used when assessing the quality of Portland Cement and should not be taken lightly if you intend for the structure to remain steadfast, load bearing and safe for occupancy.
Cement “Soundness” is an indication of the cement’s ability to harden and retain a constant volume after it has been mixed in concrete and cured. To clarify, as concrete cures and particularly in the presence of free lime (CaO) and/or magnesia (MgO) the curing cement in concrete undergoes a significant change in volume either by way of expansion or contraction. Destructive expansion is caused by an excess of free lime (CaO) or magnesia (MgO) which will almost always cause cracks and fissures in set concrete and thus making it become “Unsound”. Unsound concrete presents with questionable durability and an unstable construct making occupancy and use of the structure unsafe.
In converse to this, sound cement does not experience this change in volume and if it does the effect is only very slight and does not compromise the quality of the construct or the concrete’s soundness of strength.
Determining the soundness of cement is done by the “Le chatelier method” or by performing an ‘Autoclave’ test.
- The Le Chatelier Method
Placing hardened cement specimens in moulds inside a Le Chatelier water bath, the cement is boiled for a fixed period of approximately 3 hours speeding up the cements propensity to expand through this boiling process. Measuring two control indicators and the degree at which the cement has expanded will determine the soundness of the cement.
- The Autoclave Test
An ‘Autoclave’ test measures the expansion of cement by making use of a neat or “fresh” cement specimen. Placed in moulds with reference points indicating the specimen’s original size, the cement is placed in an autoclave exposing the sample to extremely high pressure and temperatures. After around 24 hours the cement is removed and measured whereby the change in size will indicate the change in volume and thus be an indicator of the “Soundness” of the cement hence the soundness of concrete made using this cement.
Adhering to only the highest quality standards as set out by the South African National Standard SANS 50197-1:2013 Sephaku Cement fully complies with the requirements for each strength class across all our products. Based on outcomes by tests conducted in accordance with SANS 50197-1 test methods at a SANAS accredited laboratory, Sephaku Cement prides itself on producing quality Portland Cement / Portland Blended cements. Suited to general purpose applications, a wide range of general civil, building and concrete industry applications as well as offering a high performance professional strength product