click below
click below
Normal Size Small Size show me how
Engin. Analysis 2
Lime and cement Block 1
Question | Answer |
---|---|
What is Lime and Mortar? | Lime and mortar is a type of mortar composed of :Lime, an aggregate (e.g. sand), & water. |
What is Hydraulic Lime? | Hydraulic limes set (hardens) under water. To produce hydraulic lime mortars, the lime is derived from limestone containing impurities. |
What is Non-Hydraulic Lime? | Non hydraulic lime needs air (doesn't harden underwater) to carbonate and therefore set. it can be produced from high purity calcium limestones. |
How is Dolomite formed? | Dolomite is formed when water containing dissolved magnesium seeps into sediments that are largely calcium carbonate. the magnesium then replaces some of the calcium. |
How is Non Hydraulic Lime produced? | Non-Hydraulic lime is produced by firt heating of sufficiently pure limestone, driving off CO2 to produce quicklime (CaO). |
What is Calcination? | Process of heating limestone so that it decomposes to lime and CO2. done in a lime kiln. |
What is Slaking? | Slaking is the action of combining moisture with the quicklime. |
once the quicklime has been taken out of the kiln it must be slaked. When quicklime and water are combined an exothermic reaction takes place as the quicklime begins to swell and crumble away, it produces calcium hydroxide. | |
Lime slaking continued? | if quicklime is slaked with minimum amount of water, it breaks down to a powder or a hydrated lime (Ca(OH2). if it is done with excess water, it can be worked down to form milk and over time this milk will settle out and LIME PUTTY will be formed. |
What is Lime Putty? | Milk of lime form when excess water is added to quicklime during slaking, it does not carbonating as much, because it is wet. |
What is Carbonation? | It is a reaction with atmospheric CO2. |
How does Hydraulic Lime set? | After the lime mortar has been applied, Co2 dissolves in the water to form carbonic acid (H2CO3) which combines with the dissolved Ca(OH)2 to form CaCo3. - Ca(OH)2+CO2=CaCO3+H2O |
What are the properties of Lime Mortar? | Lime mortar is not as strong in compression as OPC mortar. (Ordinary Portlanr Cement). it does not adhere as strongly to O.P.C. Lime mortar is self healing due to re-crystallising micro-cracks. Lime mortar is relatively simple to repair. |
What are the properties of Lime Mortar 2 ? | Lime mortar is more porous than cement mortars.Using lime mortar for repointing will allow the bricks to dry out. |
Pointing is the name given to the sacrificial mortar that fills the first 20mm of the vertical and horizontal gap around the bricks. |