标准编号:	GB 50496-2018
中文名称:	大体积混凝土施工标准
英文名称:	Code for construction of mass concrete
行业分类:	GB    国家标准
发布机构:	住房和城乡建设部
发布日期:	2018-04-25
实施日期:	2018-12-1
标准状态:	现行
替代旧标准:	GB 50496-2009 大体积混凝土施工规范
翻译语言:	英文
文件格式:	PDF
中文字符数:	42000 字
翻译价格(元):	2940.00 元
交付时间:	付款后 1 个工作日

1 General provisions

1.0.1 This standard is formulated with a view to implementing the national technical and economic policies, ensuring the engineering quality, and achieving advanced technology, reasonable process, resource saving and environmental protection in the construction of mass concrete.

1.0.2 This standard is applicable to the construction of mass concrete in concrete structure, but is not applicable to the construction of roller-compacted concrete (RCC) and hydraulic mass concrete engineering, etc.

1.0.3 In addition to this standard, the construction of mass concrete shall also comply with those stipulated in the current relevant standards of the nation.



 

2 Terms and symbols



2.1 Terms

2.1.1 mass concrete

large volume of concrete in concrete structure body with a minimum size of not less than 1m, or concrete expected to have harmful crack due to temperature change and shrinkage caused by hydration of cementitious material in the concrete

2.1.2 cementitious material

a generic term for Portland cement and active mineral admixture for preparation of concrete

2.1.3 alternative bay construction method

a construction method that the ultra-long concrete block is divided into several small blocks, construction of these small blocks is hereby carried out alternatively to allow stress release for a short term, and then they are connected as a whole, and the connected concrete block can resist the temperature shrinkage stress of the next section relying on the tensile strength of concrete

2.1.4 permanent deformation seam

seam reserved permanently to vertically divide the building (structure), including expansion joint and settlement joint

2.1.5 vertical construction seam

seam reserved vertically at appropriate position when concrete cannot be continuously placed and the placing pause time may exceed the initial setting time of concrete

2.1.6 horizontal construction seam

seam reserved horizontally at appropriate position when concrete cannot be continuously placed and the placing pause time is possible to exceed the initial setting time of concrete

2.1.7 thermal stress

stress generated inside the concrete when the temperature deformation of the concrete is constrained

2.1.8 shrinkage stress

stress generated inside the concrete when the shrinkage deformation of the concrete is constrained

2.1.9 peak value of rising temperature

the maximum temperature rise value inside the placed concrete body

2.1.10 temperature difference of core and surface

the difference between the maximum temperature inside the placed concrete body and the temperature at a position 50mm inside its external surface

2.1.11 thickness weighted mean temperature

value obtained by weighted averaging the temperature value of each measuring point according to the weight of the length to thickness of the section represented by each temperature measuring point of the test spot

2.1.12 descending speed of temperature

decrease of the thickness weighted mean temperature within 24h after the internal temperature of placed concrete body reaches the peak value of rising temperature under heat dissipation condition

2.1.13 temperature of mixture placing to mold

temperature at which the concrete mixture is placed to the mold

2.1.14 harmful crack

crack that affects structural safety or use functions

2.1.15 adiabatic temperature rise

temperature rise value at a certain time inside the placed concrete body in an adiabatic state

2.1.16 binder paste content

ratio of the paste amount of cementitious material in the concrete to the total amount of concrete

2.1.17 temperature field

spatial and temporal distribution of concrete temperature



2.2 Symbols

2.2.1 Temperature and material performance



a——the thermal diffusivity of concrete;



C——the specific heat capacity of concrete;



Cx——the horizontal deformation stiffness of external restraint medium (foundation or old concrete);



E0——the elastic modulus of concrete;



E(t)——the elastic modulus of concrete at an age of t;



Ei(t)——the elastic modulus of concrete at an age of t in the ith calculation section;



ftk(t)——the standard value of tensile strength of concrete at an age of t;



Kb, K1, K2——the corrected value of heat transfer coefficient for the surface thermal insulation layer of placed concrete body;



m——the coefficient related to cement type, placing temperature, etc.;



Q——the total hydration heat of cementitious material;



Q0——the total hydration heat of cement;



Qt——the cumulative hydration heat at an age of t;



Rs——the total thermal resistance of thermal insulation layer;



t——the age of concrete;



Ts——the surface temperature of placed concrete body;



Tb(t)——the surface layer temperature in the placed concrete body at an age of t;



Tbm(t), Tdm(t)——respectively the temperature of the upper and lower surface layers of placed concrete body when the maximum temperature occurs at the middle part;



Tmax——the maximum temperature in the placed concrete body;



Tmax(t)——the maximum temperature in the placed concrete body at an age of t;



Tq——the average atmospheric temperature when the concrete reaches the maximum temperature;



T(t)——the adiabatic temperature rise of concrete at an age of t;



Ty(t)——the shrinkage equivalent temperature of concrete at an age of t;



Tw(t)——the expected stable temperature or final stable temperature of placed concrete body at an age of t;



ΔT1(t)——the temperature difference of core and surface of the placed concrete body at an age of t;



ΔT2(t)——the comprehensive temperature drop difference of placed concrete body during temperature descending at an age of t;



ΔT1max(t)——the maximum temperature difference of core and surface that may occur after concrete is placed;



ΔT1i(t)——the increment of the temperature difference of core and surface of placed concrete body at an age of t in the ith calculation section;



ΔT2i(t)——the increment of the comprehensive temperature drop difference of placed concrete body at an age of t in the ith calculation section;



βμ——the heat release coefficient of solids in air;



βs——the total heat release coefficient of the thermal insulation material;



λ0——the thermal conductivity of concrete;



λi——the heat conductivity coefficient of the ith layer of thermal insulation material.

2.2.2 Quantitative and geometric parameters



H——the thickness of the placed concrete body, which is the sum of the actual thickness of the placed body and the virtual thickness of thermal insulation layer converted into concrete;



h——the actual thickness of concrete;



h′——the virtual thickness of concrete;



L——the round-trip distance of concrete truck mixer;



N——the number of concrete truck mixers;



Q1——the actual average output of each concrete pump;



Qmax——the maximum output of each concrete pump;



S——the average driving speed of concrete truck mixer;



Tt——the total stop time of each concrete truck mixer;



V——the capacity of each concrete truck mixer;



W——the consumption of cementitious material per cubic meter of concrete;



α1——the piping condition coefficient;



δ——the thickness of thermal insulation layer on the surface of concrete;



δi————the thickness of the ith layer of thermal insulation material.

2.2.3 Calculation parameters and others



H(t, τ)——the relaxation coefficient of the restraint stress, which is generated at an age of τ, after reaching the age of t;



K——the crack resistance safety coefficient;



k——the hydration heat adjustment coefficient of admixture under different mixing amount;



k1, k2——respectively the hydration heat adjustment coefficient corresponding to the mixing amount of flyash and slag powder;



M1, M2…M11——the correction coefficients of concrete shrinkage deformation under different conditions;



Ri(t)——the restraint coefficient of external restraint in the ith calculation section at an age of t;



n——the constant, depending on factors such as cement type and specific surface area;



——the reciprocal of the hydraulic radius;



α——the coefficient of linear expansion of concrete;



β——the correction coefficient for elastic modulus by the admixture in concrete;



β1, β2——respectively the correction coefficient for elastic modulus corresponding to the mixing amount of flyash and slag powder in concrete;



ρ——the mass density of concrete;



ε_y^0——the relative deformation value of the final shrinkage of concrete under standard test conditions;



εy(t)——the relative deformation value caused by shrinkage of concrete at an age of t;



σx(t)——the tensile stress generated under external restraints due to the comprehensive temperature drop difference at an age of t;



σz(t)——the cumulative value of the self-restraint tensile stress generated due to the temperature difference of core and surface of placed concrete body at an age of t;



η——the operation efficiency;



σzmax——the maximum self-restraint stress.



 

3 Basic requirements

3.0.1 For the construction of mass concrete, construction organization design or construction technical scheme shall be prepared, and technical measures for environmental protection and safe construction shall be provided.

3.0.2 The construction of mass concrete shall meet the following requirements:



1 The design strength grade of mass concrete should be C25~C50, and the strength of concrete at an age of 60d or 90d may be used as the basis for concrete mix proportioning design, concrete strength evaluation and engineering acceptance;



2 The structural reinforcement of mass concrete shall meet the bearing capacity and detailing requirements of the structure, and the constructional steel bar for temperature and shrinkage control shall also be applied in combination with the construction method of mass concrete;



3 When the mass concrete is placed on the rock foundation, a sliding layer should be provided on the concrete cushion;



4 Technical measures shall be taken to reduce the external restraints of mass concrete;



5 The relevant test requirements for temperature field and strain shall be proposed in design according to the engineering conditions.

3.0.3 Before the construction of mass concrete, the temperature, thermal stress and shrinkage stress of the placed concrete body shall be calculated, the control indexes for the peak value of rising temperature, temperature difference of core and surface and descending speed of temperature of the placed concrete body shall be determined, and corresponding temperature control technical measures shall be formulated.

3.0.4 The temperature control index for the construction of mass concrete shall meet the following requirements:



1 The temperature rise value of placed concrete body on the basis of temperature of mixture placing to mold should not be greater than 50℃;



2 The temperature difference of core and surface of the placed concrete body (excluding the shrinkage equivalent temperature of concrete) should not be greater than 25℃;



3 The descending speed of temperature of the placed concrete body should not be greater than 2.0℃/d.



4 When the thermal insulation cladding is removed, the difference between the surface temperature of placed concrete body and atmospheric temperature shall not be greater than 20℃.

3.0.5 Before the construction of mass concrete, construction preparation shall be done, and local meteorological station shall be contacted to grasp the recent meteorological conditions. In the winter construction, the construction of mass concrete shall also comply with the relevant requirements for winter construction of concrete.

3.0.6 The construction of mass concrete shall be provided with the energy-saving, material-saving, water-saving and land-saving and environmental protection measures, and shall meet the relevant requirements of the current national standard GB/T 50905 Code for green construction of building.



 

4 Materials, mix proportioning, production and transportation



4.1 General requirements

4.1.1 In addition to the design requirements such as strength grade, durability, impermeability and volume stability, mix proportioning design of mass concrete shall also meet the construction technology requirements of mass concrete, and it’s also required to use materials reasonably and reduce the adiabatic temperature rise of concrete.

4.1.2 As for preparation and transportation of mass concrete, in addition to meeting the requirements of concrete design strength grade, the relevant parameters of ready-mixed concrete shall be adjusted according to its transportation distance, transportation equipment, supply capacity, material batch No. and ambient temperature.



4.2 Materials

4.2.1 Selection and quality of concrete shall be in accordance with the following requirements:



1 Cement shall conform to the relevant requirements of the current national standard GB 175 Common Portland Cement. When other types of cement are used, the performance indexes shall conform to the relevant current standards of the nation;



2 It is required to use the common Portland cement with low hydration heat; 3d hydration heat should not be greater than 250kJ/kg and 7d hydration heat should not be greater than 280kJ/kg; when the cement of strength grade 52.5 is used, 7d hydration heat should be less than 300kJ/ Kg;



3 The temperature of cement into machine at the mixing plant should not be higher than 60℃.

4.2.2 The type, code, strength grade, packaging or bulking No., ex-factory date, etc. shall be checked when the cement to be used for mass concrete enter the site; the strength, stability, setting time and hydration heat of such cement shall also be inspected, and the inspection results shall meet the relevant requirements of the current national standard GB 175 Common Portland Cement.

4.2.3 In addition to the relevant requirements specified in the current professional standard JGJ 52 Standard for technical requirements and test method of sand and crushed stone (or gravel) for ordinary concrete, the selection of aggregates shall also meet the following requirements:



1 Medium sand should be adopted for fine aggregate whose fineness modulus should be greater than 2.3 and silt content shall not exceed 3%;



2 For coarse aggregate, the particle size should be 5.0mm~31.5mm, it shall be continuously graded, and the silt content shall not exceed 1%;



3 It is required to use non-alkali reactive coarse aggregate;



4 When non-pumping construction is adopted, the particle size of the coarse aggregate may be appropriately increased.

4.2.4 The quality of flyash and ground granulated blast furnace slag shall meet the relevant requirements of the current national standards GB/T 1596 Fly ash used for cement and concrete and GB/T 18046 Ground granulated blast furnace slag used for cement, mortar and concrete.

4.2.5 The quality and application technology of admixture in the concrete shall meet relevant requirements of the current national standards GB 8076 Concrete admixtures and GB 50119 Code for utility technical of concrete admixture.

4.2.6 In addition to the relevant requirements of 4.2.5, the selection of admixture shall also meet the following requirements:



1 The type and mixing amount of admixture shall be determined according to the material test;



2 It is advisable to provide the influence coefficients of admixture on the shrinkage of the hardened concrete;



3 For mass concrete with high durability requirements or in cold areas, air-entraining agent or air-entraining water-reducing agent should be used.

4.2.7 The quality of water for mixing the concrete shall conform to the current professional standard JGJ 63 Standard of water for concrete.



4.3 Mix proportioning design

4.3.1 In addition to the current professional standard JGJ 55 Specification for mix proportion design of ordinary concrete, the mix proportioning design of mass concrete shall also meet the following requirements:



1 When 60d or 90d concrete strength acceptance index are used, it shall be used as the design basis for concrete mix proportioning;



2 The slump of concrete mixture should not be greater than 180mm;



3 The amount of mixing water should not exceed 170kg/m3;



4 The mixing amount of flyash, that of slag powder and the sum of both should not be greater than 50%, 40% and 50% of the consumption of cementitious material respectively;



5 The water-cementitious material ratio should not be greater than 0.45;



6 The sand percentage should be 38%~45%.

4.3.2 Before the preparation of concrete, it is advisable to carry out the tests of technical parameters that affect the crack control of mass concrete, such as adiabatic temperature rise, bleeding rate and pumpability. If necessary, the mix proportioning design shall be verified by trial pumping.

4.3.3 During the determination of the mix proportioning of concrete, the technical measures for coarse/fine aggregates and mixing water as well as control of temperature of mixture placing to mold during concrete preparation should be proposed according to the requirements of construction scheme in terms of concrete adiabatic temperature rise and temperature control.



4.4 Preparation and transportation

4.4.1 The capacities of concrete preparation and transportation shall meet the requirements of concrete placing technology. The quality of ready-mixed concrete shall comply with the relevant requirements of the current national standard GB/T 14902 Ready-mixed concrete, and shall meet the technical requirements of construction process for slump loss and slump of mixture placing to mold, temperature of mixture placing to mold, etc.

4.4.2 For ready-mixed concrete for subitems of the same works, the content of cementitious materials & admixtures and mix proportioning shall be consistent, and the preparation process and quality control level shall be basically the same.

4.4.3 Concrete truck mixer shall be used for transportation of concrete mixture. The trucks shall be provided with sun protection, rain protection and thermal insulation measures according to the actual conditions of the construction site.

4.4.4 The quantity of truck mixers shall meet the requirements of concrete placing technology, and the calculation method may be determined in accordance with Annex A.

4.4.5 The time of transportation by truck mixers shall meet the relevant requirements of the current national standard GB/T 14902 Ready-mixed concrete.

4.4.6 During the adjustment through supplementation with admixtures in the transportation process, the truck mixers shall stir quickly for at least 120s.

4.4.7 During the transportation and placing process, the performance shall be adjusted in methods except for adding water to the mixture.

4.4.8 When the slump loss or segregation is severe during transportation, the concrete mixture shall not be placed into the mold after it fails to restore its working performance using certain measures.

1 General provisions
2 Terms and symbols
2.1 Terms
2.2 Symbols
3 Basic requirements
4 Materials, mix proportioning, production and transportation
4.1 General requirements
4.2 Materials
4.3 Mix proportioning design
4.4 Preparation and transportation
5 Construction
5.1 General requirements
5.2 Technical preparation
5.3 Formwork
5.4 Concrete placing
5.5 Concrete curing
5.6 Construction in special climate
5.7 Site sampling
6 Temperature monitoring and control
Annex A Calculation for output of concrete pump and number of truck mixers
Annex B Calculation for thermal stress and shrinkage stress during construction of placed mass concrete body
Annex C Calculation for the thickness of surface thermal insulation layer of placed mass concrete body
Explanation of wording in this standard
List of quoted standards

1 总 则
1.0.1 为在大体积混凝土施工中贯彻国家技术经济政策，保证工程质量，做到技术先进、工艺合理、节约资源、保护环境，制定本标准。
1.0.2本标准适用于混凝土结构中大体积混凝土施工。不适用于碾压混凝土和水工大体积混凝土等工程施工。
1.0.3大体积混凝土施工除应符合本标准外，尚应符合国家现行有关标准的规定。
2术语和符号
2.1 术 语
2.1.1大体积混凝土mass concrete
混凝土结构物实体最小尺寸不小于1m的大体量混凝土，或预计会因混凝土中胶凝材料水化引起的温度变化和收缩而导致有害裂缝产生的混凝土。
2.1.2胶凝材料 cementitious material
配制混凝土的硅酸盐水泥与活性矿物掺合料的总称。
2.1.3跳仓施工法 alternative bay construction method
将超长的混凝土块体分为若干小块体间隔施工，经过短期的应力释放，再将若干小块体连成整体，依靠混凝土抗拉强度抵抗下段温度收缩应力的施工方法。
2.1.4永久变形缝permanent deformation seam
将建(构)筑物垂直分割开永久留置的预留缝，包括伸缩缝和沉降缝。
2.1.5竖向施工缝vertical construction seam
混凝土不能连续浇筑时，浇筑停顿时间有可能超过混凝土的初凝时间，在适当位置留置的垂直方向的预留缝。
2.1.6水平施工缝horizontal construction seam
混凝土不能连续浇筑时，浇筑停顿时间有可能超过混凝土的初凝时间，在适当位置留置的水平方向的预留缝。
2.1.7温度应力thermal stress
混凝土温度变形受到约束时，在混凝土内部产生的应力。
2.1.8收缩应力 shrinkage stress
混凝土收缩变形受到约束时，在混凝土内部产生的应力。
2.1.9 温升峰值peak value of rising temperature
混凝土浇筑体内部的最高温升值。
2.1.10里表温差temperature difference of core and surface
混凝土浇筑体内最高温度与外表面内50mm处的温度之差。
2.1.11 断面加权平均温度thickness weighted mean tempera-ture
根据测试点位各温度测点代表区段长度占厚度权值，对各测点温度进行加权平均得到的值。
2.1.12 降温速率descending speed of temperature
散热条件下，混凝土浇筑体内部温度达到温升峰值后，24h内断面加权平均温度下降值。
2.1.13入模温度temperature of mixture placing to mold
混凝土拌合物浇筑入模时的温度。
2.1.14有害裂缝harmful crack
影响结构安全或使用功能的裂缝。
2.1.15绝热温升adiabatic temperature rise
混凝土浇筑体处于绝热状态条件下，其内部某一时刻温升值。
2.1.16 胶浆量 binder paste content
混凝土中胶凝材料浆体量占混凝土总量之比。
2.1.17温度场temperature field
混凝土温度在空间和时间上的分布。
2.2 符 号
2.2.1温度及材料性能
a——混凝土热扩散率；
C——混凝土比热容；
Cx——外约束介质(地基或老混凝土)的水平变形刚度；
E0——混凝土弹性模量；
E(t)——混凝土龄期为t时的弹性模量；
Ei(t)——第i计算区段，龄期为t时，混凝土的弹性模量；
ftk(t)——混凝土龄期为t时的抗拉强度标准值；
Kb，K1，K2——混凝土浇筑体表面保温层传热系数修正值；
m——与水泥品种、浇筑温度等有关的系数；
Q——胶凝材料水化热总量；
Q0——水泥水化热总量；
Qt——龄期t时的累积水化热；
Rs——保温层总热阻；
t——混凝土的龄期；
Ts——混凝土浇筑体表面温度；
Tb(t)——龄期为t时，混凝土浇筑体内的表层温度；
Tbm(t)、Tdm(t)——混凝土浇筑体中部达到最高温度时，其块体上、下表层的温度；
Tmax——混凝土浇筑体内的最高温度；
Tmax(t)——龄期为t时，混凝土浇筑体内的最高温度；
Tq——混凝土达到最高温度时的大气平均温度；
T(t)——龄期为t时，混凝土的绝热温升；
Ty(t)——龄期为t时，混凝土收缩当量温度；
Tw(t)——龄期为t时，混凝土浇筑体预计的稳定温度或最终稳定温度；
ΔT1(t)——龄期为t时，混凝土浇筑块体的里表温差；
ΔT2(t)——龄期为t时，混凝土浇筑块体在降温过程中的综合降温差；
ΔT1max(t)——混凝土浇筑后可能出现的最大里表温差；
ΔT1i(t)——龄期为t时，在第i计算区段混凝土浇筑块体里表温差的增量；
ΔT2i(t)——龄期为t时，在第i计算区段内，混凝土浇筑块体综合降温差的增量；
βμ——固体在空气中的放热系数；
βs——保温材料总放热系数；
λ0——混凝土的导热系数；
λi——第i层保温材料的导热系数。
2.2.2数量几何参数
H——混凝土浇筑体的厚度，该厚度为浇筑体实际厚度与保温层换算混凝土虚拟厚度之和；
h——混凝土的实际厚度；
h′——混凝土的虚拟厚度；
L——混凝土搅拌运输车往返距离；
N——混凝土搅拌运输车台数；
Q1——每台混凝土泵的实际平均输出量；
Qmax——每台混凝土泵的最大输出量；
S——混凝土搅拌运输车平均行车速度；
Tt——每台混凝土搅拌运输车总计停歇时间；
V——每台混凝土搅拌运输车的容量；
W——每立方米混凝土的胶凝材料用量；
α1——配管条件系数；
δ——混凝土表面的保温层厚度；
δi——第i层保温材料厚度。
2.2.3计算参数及其他
H(t，τ)——在龄期为τ时产生的约束应力延续至t时的松弛系数；
K——防裂安全系数；
k——不同掺量掺合料水化热调整系数；
k1、k2——粉煤灰、矿渣粉掺量对应的水化热调整系数；
M1、M2……M11——混凝土收缩变形不同条件影响修正系数；
Ri(t)——龄期为t时，在第i计算区段，外约束的约束系数；
n——常数，随水泥品种、比表面积等因素不同而异；
——水力半径的倒数；
α——混凝土的线膨胀系数；
β——混凝土中掺合料对弹性模量的修正系数；
β1、β2——混凝土中粉煤灰、矿渣粉掺量对应的弹性模量修正系数；
ρ——混凝土的质量密度；
εy0——在标准试验状态下混凝土最终收缩的相对变形值；
εy(t)——龄期为t时，混凝土收缩引起的相对变形值；
σx(t)——龄期为t时，因综合降温差，在外约束条件下产生的拉应力；
σz(t)——龄期为t时，因混凝土浇筑块体里表温差产生自约束拉应力的累计值；
η——作业效率；
σzmax——最大自约束应力。
3 基本规定
3.0.1 大体积混凝土施工应编制施工组织设计或施工技术方案，并应有环境保护和安全施工的技术措施。
3.0.2大体积混凝土施工应符合下列规定：
1大体积混凝土的设计强度等级宜为C25～C50，并可采用混凝土60d或90d的强度作为混凝土配合比设计、混凝土强度评定及工程验收的依据；
2大体积混凝土的结构配筋除应满足结构承载力和构造要求外，还应结合大体积混凝土的施工方法配置控制温度和收缩的构造钢筋；
3大体积混凝土置于岩石类地基上时，宜在混凝土垫层上设置滑动层；
4设计中应采取减少大体积混凝土外部约束的技术措施；
5设计中应根据工程情况提出温度场和应变的相关测试要求。
3.0.3大体积混凝土施工前，应对混凝土浇筑体的温度、温度应力及收缩应力进行试算，并确定混凝土浇筑体的温升峰值，里表温差及降温速率的控制指标，制定相应的温控技术措施。
3.0.4大体积混凝土施工温控指标应符合下列规定：
1 混凝土浇筑体在入模温度基础上的温升值不宜大于50℃；
2混凝土浇筑体里表温差(不含混凝土收缩当量温度)不宜大于25℃；
3混凝土浇筑体降温速率不宜大于2.0℃/d；
4拆除保温覆盖时混凝土浇筑体表面与大气温差不应大于20℃。
3.0.5大体积混凝土施工前，应做好施工准备，并应与当地气象台、站联系，掌握近期气象情况。在冬期施工时，尚应符合有关混凝土冬期施工规定。
3.0.6大体积混凝土施工应采取节能、节材、节水、节地和环境保护措施，并应符合现行国家标准《建筑工程绿色施工规范》GB/T 50905的有关规定。
4原材料、配合比、制备及运输
4.1 一般规定
4.1.1大体积混凝土配合比设计除应满足强度等级、耐久性、抗渗性、体积稳定性等设计要求外，尚应满足大体积混凝土施工工艺要求，并应合理使用材料、降低混凝土绝热温升值。
4.1.2大体积混凝土制备及运输，除应满足混凝土设计强度等级要求，还应根据预拌混凝土供应运输距离、运输设备、供应能力、材料批次、环境温度等调整预拌混凝土的有关参数。
4.2原 材 料
4.2.1水泥选择及其质量，应符合下列规定：
1水泥应符合现行国家标准《通用硅酸盐水泥》GB 175的有关规定，当采用其他品种时，其性能指标应符合国家现行有关标准的规定；
2应选用水化热低的通用硅酸盐水泥，3d水化热不宜大于250kJ/kg，7d水化热不宜大于280kJ/kg；当选用52.5强度等级水泥时，7d水化热宜小于300kJ/kg；
3水泥在搅拌站的入机温度不宜高于60℃。
4.2.2 用于大体积混凝土的水泥进场时应检查水泥品种、代号、强度等级、包装或散装编号、出厂日期等，并应对水泥的强度、安定性、凝结时间、水化热进行检验，检验结果应符合现行国家标准《通用硅酸盐水泥》GB 175的相关规定。
4.2.3骨料选择，除应符合现行行业标准《普通混凝土用砂、石质量及检验方法标准》JGJ 52的有关规定外，尚应符合下列规定：
1 细骨料宜采用中砂，细度模数宜大于2.3，含泥量不应大于3％；
2粗骨料粒径宜为5.0mm～31.5mm，并应连续级配，含泥量不应大于1％；
3应选用非碱活性的粗骨料；
4 当采用非泵送施工时，粗骨料的粒径可适当增大。
4.2.4 粉煤灰和粒化高炉矿渣粉，质量应符合现行国家标准《用于水泥和混凝土中的粉煤灰》GB/T 1596和《用于水泥、砂浆和混凝土中的粒化高炉矿渣粉》GB/T 18046的有关规定。
4.2.5外加剂质量及应用技术，应符合现行国家标准《混凝土外加剂》GB 8076和《混凝土外加剂应用技术规范》GB 50119的有关规定。
4.2.6外加剂的选择除应满足本标准第4.2.5条的规定外，尚应符合下列规定：
1外加剂的品种、掺量应根据材料试验确定；
2宜提供外加剂对硬化混凝土收缩等性能的影响系数；
3 耐久性要求较高或寒冷地区的大体积混凝土，宜采用引气剂或引气减水剂。
4.2.7混凝土拌合用水质量应符合现行行业标准《混凝土用水标准》JGJ 63的有关规定。
4.3配合比设计
4.3.1 大体积混凝土配合比设计，除应符合现行行业标准《普通混凝土配合比设计规程》JGJ 55的有关规定外，尚应符合下列规定：
1 当采用混凝土60d或90d强度验收指标时，应将其作为混凝土配合比的设计依据；
2混凝土拌合物的坍落度不宜大于180mm；
3拌合水用量不宜大于170kg/m3；
4粉煤灰掺量不宜大于胶凝材料用量的50％，矿渣粉掺量不宜大于胶凝材料用量的40％；粉煤灰和矿渣粉掺量总和不宜大于胶凝材料用量的50％；
5水胶比不宜大于0.45；
6砂率宜为38％～45％。
4.3.2混凝土制备前，宜进行绝热温升、泌水率、可泵性等对大体积混凝土裂缝控制有影响的技术参数的试验，必要时配合比设计应通过试泵送验证。
4.3.3在确定混凝土配合比时，应根据混凝土绝热温升、温控施工方案的要求，提出混凝土制备时的粗细骨料和拌合用水及入模温度控制的技术措施。
4.4制备及运输
4.4.1混凝土制备与运输能力应满足混凝土浇筑工艺要求，预拌混凝土质量应符合现行国家标准《预拌混凝土》GB/T 14902的有关规定，并应满足施工工艺对坍落度损失、入模坍落度、入模温度等的技术要求。
4.4.2对同时供应同一工程分项的预拌混凝土，胶凝材料和外加剂、配合比应一致，制备工艺和质量控制水平应基本相同。
4.4.3混凝土拌合物运输应采用混凝土搅拌运输车，运输车应根据施工现场实际情况具有防晒、防雨和保温措施。
4.4.4搅拌运输车数量应满足混凝土浇筑工艺要求，计算方法可按本标准附录A确定。
4.4.5搅拌运输车运送时间应符合现行国家标准《预拌混凝土》GB/T 14902的有关规定。
4.4.6运输过程补充外加剂进行调整时，搅拌运输车应快速搅拌，搅拌时间不应小于120s。
4.4.7运输和浇筑过程中，不应通过向拌合物中加水方式调整其性能。
4.4.8运输过程中当坍落度损失或离析严重，经采取措施无法恢复混凝土拌合物工作性能时，不得浇筑入模。
5 施 工
5.1一般规定
5.1.1大体积混凝土施工组织设计，应包括下列主要内容：
1 大体积混凝土浇筑体温度应力和收缩应力计算结果；
2施工阶段主要抗裂构造措施和温控指标的确定；
3原材料优选、配合比设计、制备与运输计划；
4主要施工设备和现场总平面布置；
5温控监测设备和测试布置图；
6浇筑顺序和施工进度计划；
7保温和保湿养护方法；
8应急预案和应急保障措施；
9特殊部位和特殊气候条件下的施工措施。
5.1.2大体积混凝土浇筑体温度应力和收缩应力，可按本标准附录B确定。
5.1.3保温覆盖层的厚度，可根据温控指标的要求按本标准附录C确定。
5.1.4大体积混凝土施工宜采用整体分层或推移式连续浇筑施工。
5.1.5 当大体积混凝土施工设置水平施工缝时，位置及间歇时间应根据设计规定、温度裂缝控制规定、混凝土供应能力、钢筋工程施工、预埋管件安装等因素确定。
5.1.6超长大体积混凝土施工，结构有害裂缝控制应符合下列规定：
1 当采用跳仓法时，跳仓的最大分块单向尺寸不宜大于40m，跳仓间隔施工的时间不宜小于7d，跳仓接缝处应按施工缝的要求设置和处理；
2 当采用变形缝或后浇带时，变形缝或后浇带设置和施工应符合国家现行有关标准的规定。
5.1.7混凝土入模温度宜控制在5℃～30℃。
5.2 技术准备
5.2.1大体积混凝土施工前应进行图纸会审，并应提出施工阶段的综合抗裂措施，制定关键部位的施工作业指导书。
5.2.2 大体积混凝土施工应在混凝土的模板和支架、钢筋工程、预埋管件等工作完成并验收合格的基础上进行。
5.2.3施工现场设施应按施工总平面布置图的要求按时完成，场区内道路应坚实平坦。必要时，应制定场外交通临时疏导方案。
5.2.4施工现场供水、供电应满足混凝土连续施工需要。当有断电可能时，应采取双回路供电或自备电源等措施。
5.2.5大体积混凝土供应能力应满足混凝土连续施工需要，不宜低于单位时间所需量的1.2倍。
5.2.6大体积混凝土施工设备，在浇筑混凝土前应进行检修和试运转，其性能和数量应满足大体积混凝土连续浇筑需要。
5.2.7混凝土测温监控设备的标定调试应正常，保温材料应齐备，并应派专人负责测温作业管理。
5.2.8大体积混凝土施工前，应进行专业培训，并应逐级进行技术交底，同时应建立岗位责任制和交接班制度。
5.3模板工程
5.3.1大体积混凝土模板和支架应进行承载力、刚度和整体稳固性验算，并应根据大体积混凝土采用的养护方法进行保温构造设计。
5.3.2模板和支架系统安装、使用和拆除过程中，必须采取安全稳定措施。
5.3.3对后浇带或跳仓法留置的竖向施工缝，宜采用钢板网、铁丝网或快易收口网等材料支挡；后浇带竖向支架系统宜与其他部位分开。
5.3.4大体积混凝土拆模时间应满足混凝土的强度要求，当模板作为保温养护措施的一部分时，其拆模时间应根据温控要求确定。
5.3.5大体积混凝土宜适当延迟拆模时间。拆模后，应采取预防寒流袭击、突然降温和剧烈干燥等措施。
5.4混凝土浇筑
5.4.1 大体积混凝土浇筑应符合下列规定：
1 混凝土浇筑层厚度应根据所用振捣器作用深度及混凝土的和易性确定，整体连续浇筑时宜为300mm～500mm，振捣时应避免过振和漏振。
2整体分层连续浇筑或推移式连续浇筑，应缩短间歇时间，并应在前层混凝土初凝之前将次层混凝土浇筑完毕。层间间歇时间不应大于混凝土初凝时间。混凝土初凝时间应通过试验确定。当层间间歇时间超过混凝土初凝时间时，层面应按施工缝处理。
3混凝土的浇灌应连续、有序，宜减少施工缝。
4混凝土宜采用泵送方式和二次振捣工艺。
5.4.2当采取分层间歇浇筑混凝土时，水平施工缝的处理应符合下列规定：
1 在已硬化的混凝土表面，应清除表面的浮浆、松动的石子及软弱混凝土层；
2在上层混凝土浇筑前，应采用清水冲洗混凝土表面的污物，并应充分润湿，但不得有积水；
3新浇筑混凝土应振捣密实，并应与先期浇筑的混凝土紧密结合。
5.4.3大体积混凝土底板与侧墙相连接的施工缝，当有防水要求时，宜采取钢板止水带等处理措施。
5.4.4在大体积混凝土浇筑过程中，应采取措施防止受力钢筋、定位筋、预埋件等移位和变形，并应及时清除混凝土表面泌水。
5.4.5应及时对大体积混凝土浇筑面进行多次抹压处理。
5.5混凝土养护
5.5.1大体积混凝土应采取保温保湿养护。在每次混凝土浇筑完毕后，除应按普通混凝土进行常规养护外，保温养护应符合下列规定：
1应专人负责保温养护工作，并应进行测试记录；
2保湿养护持续时间不宜少于14d，应经常检查塑料薄膜或养护剂涂层的完整情况，并应保持混凝土表面湿润；
3保温覆盖层拆除应分层逐步进行，当混凝土表面温度与环境最大温差小于20℃时，可全部拆除。
5.5.2混凝土浇筑完毕后，在初凝前宜立即进行覆盖或喷雾养护工作。
5.5.3混凝土保温材料可采用塑料薄膜、土工布、麻袋、阻燃保温被等，必要时，可搭设挡风保温棚或遮阳降温棚。在保温养护中，应现场监测混凝土浇筑体的里表温差和降温速率，当实测结果不满足温控指标要求时，应及时调整保温养护措施。
5.5.4高层建筑转换层的大体积混凝土施工，应加强养护，侧模和底模的保温构造应在支模设计时综合确定。
5.5.5大体积混凝土拆模后，地下结构应及时回填土；地上结构不宜长期暴露在自然环境中。
5.6特殊气候条件下的施工
5.6.1大体积混凝土施工遇高温、冬期、大风或雨雪天气时，必须采用混凝土浇筑质量保证措施。
5.6.2当高温天气浇筑混凝土时，宜采用遮盖、洒水、拌冰屑等降低混凝土原材料温度的措施。混凝土浇筑后，应及时保湿保温养护；条件许可时，混凝土浇筑应避开高温时段。
5.6.3当冬期浇筑混凝土时，宜采用热水拌合、加热骨料等提高混凝土原材料温度的措施。混凝土浇筑后，应及时进行保温保湿养护。
5.6.4当大风天气浇筑混凝土时，在作业面应采取挡风措施，并应增加混凝土表面的抹压次数，应及时覆盖塑料薄膜和保温材料。
5.6.5雨雪天不宜露天浇筑混凝土，需施工时，应采取混凝土质量保证措施。浇筑过程中突遇大雨或大雪天气时，应及时在结构合理部位留置施工缝，并应中止混凝土浇筑；对已浇筑还未硬化的混凝土应立即覆盖，严禁雨水直接冲刷新浇筑的混凝土。
5.7现场取样
5.7.1 当一次连续浇筑不大于1000m3同配合比的大体积混凝土时，混凝土强度试件现场取样不应少于10组。
5.7.2 当一次连续浇筑1000m3～5000m3同配合比的大体积混凝土时，超出1000m3的混凝土，每增加500m3取样不应少于一组，增加不足500m3时取样一组。
5.7.3 当一次连续浇筑大于5000m3同配合比的大体积混凝土时，超出5000m3的混凝土，每增加1000m3取样不应少于一组，增加不足1000m3时取样一组。
6温度监测与控制
6.0.1 大体积混凝土浇筑体里表温差、降温速率及环境温度的测试，在混凝土浇筑后，每昼夜不应少于4次；入模温度测量，每台班不应少于2次。
6.0.2大体积混凝土浇筑体内监测点布置，应反映混凝土浇筑体内最高温升、里表温差、降温速率及环境温度，可采用下列布置方式：
1测试区可选混凝土浇筑体平面对称轴线的半条轴线，测试区内监测点应按平面分层布置；
2测试区内，监测点的位置与数量可根据混凝土浇筑体内温度场的分布情况及温控的规定确定；
3在每条测试轴线上，监测点位不宜少于4处，应根据结构的平面尺寸布置；
4沿混凝土浇筑体厚度方向，应至少布置表层、底层和中心温度测点，测点间距不宜大于500mm；
5保温养护效果及环境温度监测点数量应根据具体需要确定；
6 混凝土浇筑体表层温度，宜为混凝土浇筑体表面以内50mm处的温度；
7 混凝土浇筑体底层温度，宜为混凝土浇筑体底面以上50mm处的温度。
6.0.3应变测试宜根据工程需要进行。
6.0.4测试元件的选择应符合下列规定：
1 25℃环境下，测温误差不应大于0.3℃；
2温度测试范围应为-30℃～120℃；
3应变测试元件测试分辨率不应大于5με；
4应变测试范围应满足-1000με～1000με要求；
5测试元件绝缘电阻应大于500MΩ。
6.0.5温度测试元件的安装及保护，应符合下列规定：
1测试元件安装前，应在水下1m处经过浸泡24h不损坏；
2测试元件固定应牢固，并应与结构钢筋及固定架金属体隔离；
3测试元件引出线宜集中布置，沿走线方向予以标识并加以保护；
4测试元件周围应采取保护措施，下料和振捣时不得直接冲击和触及温度测试元件及其引出线。
6.0.6测试过程中宜描绘各点温度变化曲线和断面温度分布曲线。
6.0.7 发现监测结果异常时应及时报警，并应采取相应的措施。
6.0.8 温控措施可根据下列原则或方法，结合监测数据实时调控：
1控制混凝土出机温度，调控入模温度在合适区间；
2升温阶段可适当散热，降低温升峰值，当升温速率减缓时，应及时增加保温措施，避免表面温度快速下降；
3在降温阶段，根据温度监测结果调整保温层厚度，但应避免表面温度快速下降；
4在采用保温棚措施的工程中，当降温速率过慢时，可通过局部掀开保温棚调整环境温度。