REINFORCED BRICKWORK (R.B. WORK)

MATERIALS

Brick should be strict of first-class quality and mortar shall be of fresh Portland cement. Fine aggregate should be clean and free from foreign matter. Steel reinforcement shall be of standard specification as described in items.

CENTERING AND SHUTTERING

The centering and shuttering shall be fabricated with planking or sheeting of bamboos packed together at the particular level supported on runners of beams and covered with a thin layer of about 2.5 cm thick of earth finished off with a light sprinkle of fine aggregate. The centering shall be simple in making so that it could be conveniently removed without disturbing the structure. The planking shall remain clear of the bearing of the slab and will rest on cross beams only. Planks shall not be put too close as to render them liable to jam. Crossbeam shall be carried on the walls braced at intervals by ballies or temporary dry brick pillars. The top surface of centering shall be given a camber of 2 mm for every 30 cm of span up to a maximum of 4 cm for lintels.

MIXING OF MORTAR

Mortar of cement and fine aggregate shall be thoroughly mixed in the proportion of 1:3. First, we have to mix it dry and then by adding water slowly and gradually and mixing by turning at least three times to get a uniform plastic mix of workable consistency so that the mortar can be packed around the reinforcement. The quantity of water shall not exceed 25 ltr/bag of cement. Mortar shall be mixed just before it is actually required to be put in use and shall be used within 30 minutes. Stale or hardened mortar shall never be used.

LAYING

All bricks must have to be thoroughly soaked with water for not less than six hours before use. Brick shall be laid with frogs portion downward over the centering in a straight line parallel to the direction of the reinforcement bars leaving the required gap for the mortar joint. It should be kept in mind that no vertical joint should come along the inner edge of the wall. The gap provided for the mortar joint in which reinforcement has to be placed shall not be less than four times the diameter of the bar, so as to provide a cover of 12 mm on all sides of the provided steel bars. Generally mortar joint shall be 32 mm to 40 mm. Other joints where there will not be any bar should be of 6 mm to 10 mm thick. The reinforced brick slab shall have a bearing equivalent to its thickness with a minimum of 12 cm.

After the bricks have been laid and arranged to center in a straight line over the whole area fresh mixed mortar shall be placed into the gaps in between the bricks to a thickness of 2.5 mm. Reinforcing rods already cut to the correct length and bent and hooked as per design shall be placed exactly at the center of the joint and pressed down into the mortar to leave 12 mm clear mortar below the bar. The joints shall then be filled in entirely with fresh mortar. A newly laid portion shall not be troubled or disturbed or walked over. Each slab must be laid in one operation. Necessary care should be taken that the reinforcement at all points is completely surrounded by mortar.

Centering and shuttering shall be stripped slowly and carefully without any shock not earlier than 10 days. After stripping off the centering if the work is found defective and steel is exposed and visible to a sufficient extent the work shall be dismantled and reconstructed. If the steel is exposed at few places only, then they should be covered with rich cement mortar of 1:2 proportion by putting the mortar into the gaps immediately after the removal of the centering while the laid work is green in state.

For double layers, the upper layer should be laid with joints of 10 mm thickness with 1:3 proportions cement and coarse sand mortar immediately after laying the bottom layer. If there are any top bars provided in the upper layer, the joints shall be thicker as for the bottom layer.

2.5 cm to 4 cm thick cement concrete of 1:2:4 proportion may be provided over one layer of R.B. work if specified to have substantial compressive strength.

CURING

After about two hours laying when mortar and concrete has begun to harden, it shall be kept damp by covering with wet gunny bags or wet sand for 24 hours, and then cured by flooding with water making mud walls 7.5 cm high or by covering with wet sand or earth and kept damp continuously for 15 days.

MEASUREMENT

Measurement shall be taken in cum (cu ft) for the finished work and no deduction shall be made for the volume of steel provided. Steel reinforcement shall be measured under a separate item in quintal as a unit. Plastering if any shall not be included in the measurement. The rate for R.C.C. work shall be for the complete work as specified excluding steel but including centering and shuttering and all tools and plants.

PLASTERING

The joint of the brickwork shall be raked out to a depth of 18 mm and the surface of the wall shall be washed and kept wet for at least two days before plastering.

The materials of mortar, cement, and sand or lime and surkhi or sand, or kankar lime as specified should be of standard specification as given in the Indian Standards Code or if any mentioned. The materials or mortar shall be first dry mixed properly, by measuring with boxes having defined volume to have the required proportion and then water added slowly and gradually and mixed thoroughly.

The thickness of plasters shall be as specified usually 12 mm in thickness and applied in two or three coats. To ensure uniform thickness of plaster, patches of 15 cm X 15 cm strips 1 m apart and 10 cm wide plasters shall be applied first at about 2 m apart to act as a guide for maintaining the level. First mortar shall be dashed and pressed over the surface to be plastered and then brought to a truly smooth and uniform surface by means of float and trowel. External plastering shall be started from top portion and worked down towards the floor. Internal plastering shall be started when the building frame is ready and the centering of the roof slabs has been stripped. Ceiling plastering must be completed before starting of the wall plaster. The plastered surface shall be kept wet for 10 days for gaining proper strength. The surface should be protected from heavy rain, sun, frost, etc., and cured properly.

Curing shall be started as soon as the plaster has hardened sufficiently not to be damaged during watering. The plastered surface shall be kept wet for at least 10 days. Any defective in the plastered surface shall be cut in rectangular shape and replace.

POINTING

The joint of the brickwork shall be raked out to a depth of 20 mm and the surface of the wall should be washed and cleaned and kept wet for two days before pointing.

The material of mortar shall be first dry mixed properly by measuring with boxes to have the required proportion as specified (1:2 or 1:3 for cement and sand mortar, 1:1 for lime surkhi mortar or kankar lime mortar), and then thoroughly mixed by adding water slowly and gradually.

Mortar shall then be applied in the joints a bit in excess and pressed by a proper tool of the required shape and size. Extra mortar if any is removed and the surface is finished smoothly. Mortar shall not spread over the face of bricks, and the edges of bricks shall be clearly defined to give a neat and aesthetic appearance. After pointing the surface shall be kept wet for at least seven days.

REINFORCED BRICKWORK (R.B. WORK)