Mortar Q6

Thomas Sim PEA2066

Q.
a) What is mortar? Explain the following types if mortar:-

  1. Lime Mortar
  2. Cement Mortar
  3. Compo Mortar

(10 marks)

b) Explain how mortar joint may be finished and illustrate five (5) types if mortar finishes. (15 marks)

(25 marks, 2011 Q6)

A.
Part b) click here.

a)
Mortar is a workable paste used to bind building blocks such as stones, bricks, andconcrete masonry units together, fill and seal the irregular gaps between them, and sometimes add decorative colors or patterns in masonry walls. In its broadest sense mortar includes pitch, asphalt, and soft mud or clay, such as used between mud bricks.Mortar comes from Latin mortarium meaning crushed.

1. Lime mortar is a type of mortar composed of lime and an aggregate such as sand, mixed with water. It is one of the oldest known types of mortar, dating back to the 4th century BC and widely used in Ancient Rome and Greece, when it largely replaced the clay and gypsum mortars common to Ancient Egyptian construction.[1]
With the introduction of ordinary portland cement (OPC) during the 19th century the use of lime mortar in new constructions gradually declined, largely due to portland's ease of use, quick setting, and high compressive strength. However the soft, porous properties of lime mortar provide certain advantages when working with softer building materials such as natural stone and terracotta. For this reason, while OPC continues to be commonly used in brick and concrete construction, in the repair and restoration of brick and stone-built structures originally built using lime mortar, the use of OPC has largely been discredited.[2]
Despite its enduring utility over many centuries, lime mortar's effectiveness as a building material has not been well understood; time-honoured practices were based on tradition, folklore and trade knowledge, vindicated by the vast number of old buildings that remain standing. Only during the last few decades has empirical testing provided a scientific understanding of its remarkable durability.[3]
2. Portland cement mortar (often known simply as cement mortar) is created by mixing ordinary Portland cement (OPC), hydrated lime, and aggregate (sand) with water.
It was invented in 1794 by Joseph Aspdin and patented on 18 December 1824, largely as a result of various scientific efforts to develop stronger mortars than existed at the time. It was made popular during the late nineteenth century, and owing to the First World War, it had by 1930 superseded lime mortar for new construction. The main reasons for this were that Portland cement sets hard and quickly, allowing a faster pace of construction, and requires fewer skilled workers. However, as a general rule, Portland cement should not be used for the repair or repointing of older buildings constructed in lime mortar, which require the flexibility, softness and breathability of lime if they are to function correctly.[11][12]

3. Compo mortar is made with cement, lime and sand. In some localities a 50:50 cement-lime mix is sold as mortar cement. The addition of the lime reduces the cost and improves the workability. A 1:2:9, cement-lime-sand mix is suitable for general purposes, while a 1:1:6 is better for exposed surfaces and a 1:3:12 can be used for interior walls or stone walls where the extra plasticity is helpful.

Ref:
http://en.m.wikipedia.org/wiki/Mortar_(masonry)
http://www.fao.org/docrep/s1250e/s1250e09.htm