Standard Specifications and Code of Practice for Road Bridges, Section IV (Brick, Stone and Cement Concrete Block Masonry) (Second Revision)
2002 Edition

For masonry in bridges, only solid concrete blocks complying with IS:2185 Part-I are acceptable, requiring a minimum compressive strength of 10.5 MPa as specified in Clauses 404.4.1 and 402.5.1. Hollow or lightweight blocks are disallowed per Clause 402.5.2. These blocks must satisfy dimensional, material composition, curing, and physical property criteria outlined in IS:2185 Part-I, including a minimum size of 200 mm thickness and width, and a density not less than 2.2 metric tons per cubic meter.

Masonry arches are to be constructed by first laying out a full-scale arch shape on a level platform near the work site, marking the exact sizes and mortar thickness for each stone or block (Clause 404.5.1). Voussoirs must be shaped to fit radial planes with joints parallel to the arch's transverse axis. The intrados faces should be dressed for solid seating on centering. Stones are laid symmetrically about the crown in full mortar beds, with dry fitting performed prior to final mortar setting (Clause 404.5.2). Pinning with spalls is prohibited. Robust scaffolding must support all loads securely, and holes left for scaffolding must be filled after removal (Clause 404.5.3). Centering structures must be designed and installed according to IRC:87, and removed only after adequate curing, typically 2 to 4 weeks after construction, by gradually stripping from the crown outward without sudden shocks (Clauses 404.5.4 and 404.5.5). For multiple spans, centering removal must be coordinated to maintain stability.

Brick masonry curing involves maintaining continuous moisture on all faces for seven days, with the top surface flooded at the end of each workday to preserve green mortar integrity and prevent washout (Clauses 404.2.7.1 and 404.2.7.2). For composite mortars, curing begins two days after laying and continues for seven days. In hot climates, walls should be covered and kept wet to avoid rapid drying. Stone masonry requires stones to be sufficiently wetted prior to laying to prevent water absorption from mortar (Clause 404.3.4.2). Pointing and plastering finishes should be cured as soon as they harden enough not to be damaged and kept moist for at least seven days (Clauses 404.2.7.3 and 404.2.7.4). Throughout curing, protection against damage and drying out is essential.

According to Clause 405.1, expansion joints in extended masonry walls should be provided at intervals of 30 meters, consisting of a 40 mm wide gap to accommodate thermal expansion and contraction. This gap should be filled with premoulded bituminous sheeting or another suitable flexible material to allow movement while maintaining continuity. Additionally, when abutments and return walls have foundations at differing levels, a minimum 40 mm separation gap must be maintained (Clause 405.2). These provisions help prevent cracking and structural damage from differential movement.

For piers and abutments located in rivers with velocities exceeding 4.5 meters per second carrying abrasive sediments, IRC 40 Clause 403.11.5 prescribes specific protective measures: an additional 100 mm sacrificial thickness should be provided up to 0.5 meters above the High Flood Level (H.F.L.); stone masonry courses must have a minimum height of 250 mm; and bricks used must have a crushing strength of at least 10 MPa. Furthermore, weep holes must be installed at horizontal intervals not exceeding 2 meters and vertical intervals not exceeding 1 meter, staggered appropriately, with the lowest row positioned 150 mm above the low water or ground level. These weep holes should utilize 100 mm diameter asbestos cement pipes sloped at 1:20 towards the draining face, accompanied by a suitable filter layer to prevent hydrostatic pressure buildup (Clause 403.11.6). These measures safeguard the masonry against abrasion, water pressure, and ensure adequate drainage.