【正文】 that loaded with pressing force shall not be shorter than 200mm.(5) Overlapping length of steel bar tied with wire and is in light aggregate shall be longer than that in mon concrete by 5d: for colddrawn steel bar 50mm shall be increased.(6) When strength of concrete is lower than C20, overlapping length of class I and class II steel bars shall be the value of C20 in the table plus 10d.(7) Overlapping length of load bearing steel bars of class I and class II that are required for antiearthquake capability shall be increased by 5d.(8) When two pieces of steel bars with different diameters, overlapping length shall be based on the thinner. Reinforced concrete structure engineering projectConstruction and acceptance specification of concrete structure engineering project GB 5020492 Class, category and diameter of steel bars shall be adopted according to design. When substitution is needed, it should be agreed by the design institute. Shape and size of processing steel bars shall meet requirement of design. Surface of steel bar shall be clean without damage, oil spot, painting dirt and rust. Steel bars with pellet rust or scale are not allowed to use. Thickness concrete protective layer of load bearing steel bar shall meet requirement of design. If design has no significant requirement, it shall be smaller than diameter of load bearing steel bar and meet the regulation in table . Thickness of concrete protection layer of steel bars table environment and conditionname of structure memberclass of concrete strengthlower than C25C25 and C30higher than C30normal indoor ambientboard, wall and shell15beam and column25outdoor or indoor high humid environmentboard, wall and shell352515beam and column453525with paved cushion layerfoundation35without paved cushion layer70Note: (2) For prefabricated structure members in normal factory indoor environment, when the strength is not lower than C20 and if construction work quality is assured, thickness of concrete protection layer may be reduced from the value listed in the table by 5mm, but that of prestressed reinforcing bar shall not be thinner than 15mm. Those at outd。 if there is still one of the samples is unqualified, the batch will be considered as unqualified. 10 batches will be tested at site for inspection, if all the onedirection tests are qualified, quantity of joint for each batch may be increased by twice.Construction and acceptance specification of concrete structure engineering project GB 5020492 Tying steel bars shall meet the following rules:I．Cross points of bars shall be tied firmly.II．For steel bar net of board and wall, in addition to the cross points of the two rows of bars that are at the outside edges shall all be tied firmly, partial crossing points in middle may be tied every other point in a staggering way, but it should be guaranteed that position of steel bars with no deviation。 if the aggregate contains active carbonate, rock column method shall be used.After the above mentioned inspection, if the aggregate is judged as hazard, and is of alkalicarbonate reaction and if the aggregate must be used, it should be finally evaluated with special concrete testing result.If the potential hazard is of alkalisilicon reaction, only when it meets the following regulation can it be used: Use cement that contains alkali less than %, or use blending material that can inhibit reaction between alkaliaggregate. When additives containing potassium or soda ions, special test shall be performed.Construction and acceptance specification of concrete structure engineering project GB 5020492 Seawater is not allowed to blend reinforced concrete and concrete with prestress.Standard for quality control of concrete GB 5016492 When additive is selected, category and amount of additive shall be determined according to requirement of concrete, processing and weather conditions, properties of raw materials, mixing ratio and suitability of cement by means of test. Additives shall have quality certificate, if necessary, its hazard content of chlorides, sulfates shall be inspected. Only after proved that such content is not harmful to concrete can the additive be used. Additives of different category shall be stored separately and marked. Impurities mixing in during transportation and pollution are prohibited.Technical specification for application concrete additives GBJ 11988 Concrete that requires high antfreezingmelting must be mixed with gasinducting agent or gasinducting waterreducing agent, for which the amount shall be in accordance with requirement of gas content requirement of concrete. Toxic antifreezing agent containing chromate with valency of six and nitrite are prohibited to use in city water engineering project and that contacts foods.Construction and acceptance specification of concrete structure engineering project GB 5020492 Mixed materials are allowed to use in portland cement and mon portland cement for preparing concrete. Mixed materials must be qualified and amount for mixing shall be determined by test. The following documents and records shall be provided for acceptance of concrete structure.1．Certificate on change of design and steel material substitution.2．Certificate on qualification of raw materials and other materials.3．Test report of reinforcing bar and welding joint.4．Record of construction of reinforced concrete.5．Test report of samples of concrete.6．Records of assembled structures members and installation and acceptance check.7．Qualification certificate and inspection record of anchoring clamping devices and jointers for prestressing steel bars.8．Record for coldtensile and tensile of prestressing bars.9．Thermotechnical putation and record for construction in winter.10．Record of acceptance of hidden items in construction