WJEC Vocational Award Constructing the Built Environment Level 1/2

KNOWLEDGE Ratios Materials such as plaster, mortar, concrete, resins and many other construction products rely upon being mixed both off site and on site. These production processes should be subject to codes of practice to ensure all the correct methods, equipment, materials and ratios are used during this vital period in the lifespan of the relative product. Failure to adequately blend, mix or apply materials together under these strict conditions can easily result in compromising materials such as mortar for bonding masonry, structural concrete for load bearing or adhesion of plaster/render products on walls, to name but a few. When some materials such as mortar or plaster are mixed, strict ratios associated with the production process must be followed to prevent such compromise. What is a ratio? In construction terms, a ratio is a like-for-like quantity of two or more materials that are intended to be mixed together. Ratios should be referred to by a like-for-like number, volume or weight to ensure the intended portions are all of the same quantity. UNDERSTANDING The ratio of aggregates for a specified bricklaying mortar could be as follows: • Mortar for a moderate mortar mix will be: Cement : Lime : Sand = 1:1:5 C CEMENT L lime s Sand The amount of water will be set at a maximum amount (to prevent the material failing once set) and a minimum amount to promote workability . KEY TERM Workability: The capability of a product when it is worked. ‘The Plasterer/Dryliner/Taper/ Jointer’, https://www.youtube.com/ watch?v=lg53v-8l7zI. ‘Lime Production – Why Learn Heritage Skills?’, https://www. youtube.com/watch?v=Ve-m6gP3pZ8. 78 Unit 2 Developing Construction Projects