ORACIONES PROFÉTICAS

5.1 MATERIALS

5.1.1 Concrete Bricks and Blocks

Concrete bricks and blocks shall be constructed from Class B (sulphate resisting Portland Cement) concrete but the coarse aggregate shall be 10 mm to 5 mm. The blocks shall be cast in clean oiled moulds.

They shall be free from cracks, uniform in size, true to shape, free from deleterious matter, clean, hard, impervious with smooth faces in appearance similar to normal Class B concrete and with well defined arises.

Bricks and blocks shall not be incorporated into the Works until they have matured under suitable conditions for 28 days.

5.1.2 Bricks

Engineering bricks and special purpose bricks such as radial bricks, weir bricks, copings and bull nosed bricks shall have an average compressive strength of at least 69 N/mm2 and an average absorption not exceeding 4.5 percent by weight measured by a standard boiling or vacuum method. Faces of engineering bricks to be exposed to the weather or liquids shall not be wire cut.

Bricks for arches and circular work of 1.5 metres and less in diameter shall be purpose made radial bricks.

5.1.3 Sand for Mortar

Sand for mortar shall comply with the following table:- Table 5-1. Sand for Mortar

Percentage by mass passing sieve

Sieve Size Rendering Brickwork/General Purposes

5.00 mm 100 100 2.36 mm 90 - 100 90 - 100 1.18 mm 70 - 100 70 - 100 600 microns 40 - 80 40 - 100 300 microns 5 - 40 5 - 70 150 microns 0 - 10 0 - 15

SECTION 5 BRICKWORK AND BLOCKWORK

5/2 5.1.4 Lime for Mortar

Lime for cement-lime and lime-sand mortar shall be the hydrated type to the approved standard.

5.2 CONSTRUCTION 5.2.1 General

Bricks and blocks shall be properly stacked on level hardstanding. Broken blocks shall be removed from the site.

Bricks shall be adequately protected from inclement weather.

During hot and dry weather bricks and blocks shall be wetted as necessary and the tops of walls shall be wetted before a course is laid

All faces of brickwork or blockwork will be kept clean and no rubbing down of exposed faces will be permitted.

Vertical faces of all bricks shall be well buttered before being laid and the whole well grouted at each course.

Brickwork and blockwork should be built in a uniform manner. Corners and other advanced work should be raked back and not raised above the general level more than 1.0 m at one lift.

All blocks shall be laid on even full beds of mortar; vertical faces of all blocks shall be well buttered before being laid and the whole well grouted at each course.

The overall dimensions of four blocks laid in mortar shall not exceed by more than 25 mm the overall dimensions of the same blocks laid dry.

5.2.2 Engineering Brickwork

Unless otherwise specified or ordered all engineering brickwork shall be built in English bond.

In all engineering brickwork the overall dimensions of four bricks laid in mortar shall not exceed by more than 25 mm the overall dimensions of the same bricks laid dry.

SECTION 5 BRICKWORK AND BLOCKWORK

5/3

When concrete is to be faced with brickwork, header bricks shall be built into every fourth course and at intervals of 2 bricks horizontally so as to project 1/2 brick into the concrete. Headers in successive courses shall be staggered.

5.2.3 Blockwork

All blockwork shall be built level, plumb and true to line with all perpends in line vertically. Blockwork shall be built in stretcher bond and alternate courses shall be bonded in at all junctions. All blockwork shall be set in gauged mortar as described to the lengths, heights and thicknesses shown on the drawings. Fair and fair-faced work shall be kept perfectly clean and no rubbing down of blockwork will be allowed. Blockwork to be plastered shall have joints struck off flush and left rough.

5.2.4 Cement Mortar

Mortar for precast concrete units, brickwork and blockwork shall be gauged in the proportions of one part of cement to three parts of sand. Lime shall only be added if specifically ordered.

Cement mortar shall be mixed on a clean surface in small quantities sufficient only for 30 minutes work and shall not be remixed or worked up again after setting or hardening; any mortar that has become set or hard shall be rejected and removed from the site.

Ingredients shall be measured in proper boxes and shall be turned over and thoroughly mixed on a wooden platform.

5.2.5 Cement Lime Mortar

Cement lime (gauged) mortar shall consist of one part Portland Cement, one part of lime and six parts of sand by volume (1:1:6). All materials shall be accurately gauged using gauge boxes and shall be thoroughly mechanically mixed. Mortar that has begun to set shall not be revived or re-used.

5.2.6 Cement Mortar Rendering

Cement mortar rendering shall consist of two or more coats; the undercoat shall be 13 mm thickness and scored to form a key for the final coat which shall be not less than 6 mm in thickness. The finished coat shall be worked with proper metal floats, and the face left with an even and polished surface. The mortar for the undercoat of the rendering shall be gauged in the

SECTION 5 BRICKWORK AND BLOCKWORK

5/4

proportion of one part of cement to three parts of sand, and the finished coat shall be in the proportion of one part of cement to two parts of sand.

For at least 24 hours before rendering is applied the concrete or brickwork face or previous coat of rendering shall be thoroughly soaked with water, and the finished rendering shall be watered at least four times a day and kept damp for a period of a least fourteen days after completion. Not more than three days shall elapse between the application of one coat and its being covered up with a second or finishing coat. All arises shall be sharp and linear.

When rendering is to be applied to brickwork, the joints shall be raked and cleaned out to a depth of 13 mm.

SECTION 6