A heavy coat of neat cement grout vigorously brushed

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Unformatted text preview: om mud, dirt, oil, organic deposits, or other foreign material which may prevent a tight bond between the Seams shall be cleaned to a suitable depth and to firm rock and concrete. rock along the side. Where excavation methods or the natural rock strata do not leave a sufficiently rough surface of contact, the bed shall be roughened by cutting steps. grooves, trenches, or keyways into the solid rock. Scaly coatings, hardened grout or concrete, construction debris, and other objectionable materials shall be removed. Seepage shall be The foundation bed and sides shall be properly controlled and diverted. carefully cleaned with stiff brooms, picks, jets of water and air applied at high velocity or other equally effective means, followed by thorough washing. After washing and before placing any concrete, water shall be removed from del’ressions and the rock surface shall be left uniformly damp. 4.9.3 All flat surfaces shall then be coated with mortar about 1.5 cm ( or 4 in ) thick in the case of concrete surfaces and 2 cm ( or 2 in ) thick on rock surfaces. The water-cement ratio for the mortar layer shall not exceed that for the regular contrite mixture, and the mortar shall be of such consistency that it can be spread evenly without flowing. It shall be 16 IS : 457 - 1957 thoroughly broomed and worked into all irregularities, cracks and crevices. The manner of spreading and working shall be such as not to cause any segregation, and concrete shall be placed immediately upon the fresh mortar before its initial .set. 4.9.4 On very rough or broken surfaces, the first few batches crete may, if so required, contain only about one-half the regular tion of coarse aggregate. of conpropor- 4.9.5 No concrete shall be deposited until the foundation has been inspected and approved. Where the rock is dry enough to absorb water from the mortar layer, it shall be soaked for at least 24 hours prior to placing the concrete. Detailed instructions shall be issued for preparing scaly or cracked foundations requiring special treatment or grouting. 4.9.6 Ear& OY Shale Foundations 4.9.6.1 In the case of earth or shale foundations, all mui and surface debris shall be scraped and removed. The be moistened to a depth of about 15 cm ( or 6 in ) to prevent from absorbing water from the fresh concrete. Just before concrete, the surface of the earth shall be tamped or otherwise sufficiently to prevent contamination of concrete during general, concrete shall be deposited only upon material lying undisturbed state. soft or loose surface shall the subgrade placing the consolidated placing. In in a natural, 4.9.6.2 Foundations of porous or free-draining material shall be thoroughly compacted by flushing and by subsequent tamping or rolling, if necessary. The finished foundation surface shall then be blanketed with a layer of tar paper or closely woven burlap carefully lapped and fastened down along the seams so as to prevent the loss of mortar froni the concrete. 4.9.6.3 all fou...
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