continue work at his own risk, while awaiting the results of the 28 day test. If the 28 day site samples fail to meet the requirements, the Contractor shall take down and rebuild the work affected. b. The required 7 and 28 days mean compressive mortar strength for 7 and 28 days shall not be less than 1.7 and 2.5 M/mm2 respectively. 4. The required 7 day strength shown above is for guidance only and is valid for Portland cement without any additives. 5. Test results shall be submitted to the Consultant for approval. 9.4. Material storage 1. Cement and other cementitious material shall be stored in dry weather tight or completely covered. 2. Blocks should be stockpiled close to the erection area, in order to avoid or minimize cracks and irregularities arising from unnecessary double handling. 3. Sand should be stored in the open however contamination from other impurities like soil etc. should be avoided. 4. All block accessories of metal should be stored in dry store and issued in quantities required for the day’s work. 9.5. Axis and Grid Line References and setting out. 1. Reference axis and grid lines shall be followed as per the block work shop drawing. The layout shall be checked in accordance with the attached Inspection & Test Plan (ITP). 2. The surveyor has to set out the block wall on the substrate as per the approved layout shop drawings and structural as-built drawings. Any discrepancies should be brought into the attention of engineer. 9.6. Damp Proof Course (DPC) 3. DPC shall consist of one layer bituminised fibre felt lapped at corners and joints and bedded in cement mortar pointed at both sides (As shown below in Fig.1 &2). Mortar under the DPC shall be made with SRC. DPC shall be used in all block work starting on top of the raft concrete. DPC shall be used on the ground floor but shall be limited to the block work at the periphery of the buildings. Figure 1: First layer
Figure 2: DPC at corner and lapping’s 9.7. Mortar 1. The mortar shall be 1:5 ratio of cement to sand. All mixing shall be done using mechanical mixer. The mortar and grout for block work shall be as per approved mix design. The mortar shall be volume batched using appropriate sized gauge boxes at site and it shall be mixed by mechanical means. This means that boxes of 1.25 cubic foot (1’ x 1’ x 1’3”) shall be provided to measure out the volume of sand added to the cement. So in the case of one 50kg bag of cement (1.25 cut.) three boxes of sand shall be mixed. 2. The mortar shall be transported to the building floor by either hoist or by crane bucket. A clean watertight bucket or wheelbarrows shall be used for individual transporting of mortar mixture or grout. 3. The mortar shall be laid in a 15mm thick layer on concrete masonry blocks that have had their surfaces wetted. 9.8. Concrete Masonry Blocks 1. Concrete Masonry Units in contact with the ground shall be solid sulphate resisting concrete blocks and sulphate resistant cement shall be used for mortar.
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- Fall '19