Basics in Building Construction

Building Components And Types

Lesson 17 and 18 : Arches

Classification Based On Material And Workmanship

Concrete Arches

Concrete arches are of two types.

1. Precast Concrete Block Arches



The kind of arch is made from precast concrete blocks, each block being cast in the mould to the exact shape and size of voussoirs. Special moulds are prepared for voussoirs, key block and skewbacks. Because of exact shape and size of blocks, good appearance of the arch is achieved. Also, joints, made of cement mortar, are quite thin. However, casting of blocks is costly, and such work is economical only when the number of arches is quite large. Cement concrete of 1:2:4 mix is usually used.

2. Monolithic Concrete Arch



Monolithic concrete arch is constructed from cast-in-situ concrete, either plain or reinforced, depending upon the span and magnitude of loading. This arch is quite suitable for larger span. The arch thickness is 15 cm for arches upto 3 meter span. Form work is used for casting the arch, and is removed only when the concrete has sufficiently hardened and gained strength. The curing is done for 2 to 4 weeks.