GB 50496-2018Code for construction of mass concrete (English PDF)

1.0.1 This standard is formulated in order to implement national technical and economic

policies in mass concrete construction, ensure project quality, achieve advanced technology, reasonable process, resource saving, environment protection.

1.0.2 This standard applies to mass concrete construction in concrete structures. It is

not applicable to the construction of roller compacted concrete and hydraulic mass concrete.

1.0.3 In addition to complying with this standard, mass concrete construction shall also

comply with the relevant current national standards.

2.1 Terms

2.1.1 Mass concrete

A large volume concrete which has a minimum physical dimension of not less than 1 m, OR concrete which is expected to cause harmful cracks due to temperature changes and shrinkage caused by hydration of the cementitious materials in the concrete.

2.1.2 Cementitious material

A general term for Portland cement and active mineral admixtures used to prepare concrete.

2.1.5 Vertical construction seam

The vertical reserved joint which is left in appropriate positions, when the pouring pause time may exceed the initial setting time of concrete, during the noncontinuous placing of concrete.

2.1.6 Horizontal construction seam

The horizontal reserved joint which is left in appropriate positions, when the pouring pause time may exceed the initial setting time of concrete, during the noncontinuous placing of concrete.

2.1.7 Thermal stress

The stress generated inside the concrete, when the temperature deformation of the concrete is restrained.

2.1.8 Shrinkage stress

The stress generated inside the concrete, when the shrinkage deformation of the concrete is restrained.

2.1.9 Peak value of rising temperature

The maximum temperature rise inside the concrete cast block.

2.1.10 Temperature difference of core and surface

The difference -- between the maximum temperature inside the concrete block and the temperature 50 mm inside the outer surface.

2.2 Symbol

2.2.1 Temperature and material properties

a - Thermal diffusivity of concrete;

C - Specific heat capacity of concrete;

3.0.1 Mass concrete construction shall prepare a construction program or construction

technical plan, which shall include technical measures for environmental protection and safe construction.

3.0.4 The temperature control indicators for mass concrete construction shall comply

with the following requirements.

3.0.6 Mass concrete construction shall adopt energy-saving, material-saving, water-

saving, land-saving, environmental protection measures. It shall comply with the relevant provisions of the current national standard "Code for green construction of building" GB/T 50905.

4.1 General requirements

4.1.1 In addition to meeting the design requirements for strength grade, durability, impermeability, volume stability, the mass concrete's mix proportion design shall also meet the requirements for mass concrete construction technology; it shall use materials rationally and reduce the adiabatic temperature rise of concrete.

4.2 Materials

4.2.1 The selection and quality of cement shall comply with the following requirements.

4.2.2 When cement used for mass concrete enters the site, it shall check the cement

variety, code, strength grade, packaging or bulk number, date of exit-factory, etc.;

it shall inspect the strength, stability, setting time, heat of hydration of the cement.

The inspection results shall comply with the relevant provisions of the current national standard "Common Portland cement" GB 175.

4.3.2 Before preparing concrete, it should conduct tests on technical parameters such as

adiabatic temperature rise, bleeding rate, pumpability, etc. that have an impact on the control of cracks in mass concrete. If necessary, the mix proportioning design shall be verified through trial pumping.

4.3.3 When determining the concrete mix proportioning, it shall propose the technical

measures for coarse and fine aggregate and mixing water during concrete preparation and control of temperature of mixture placing to mold, based on the requirements of the concrete adiabatic temperature rise and temperature control construction plan.

4.4 Production and transportation

4.4.4 The number of mixer trucks shall meet the requirements of concrete pouring

technology; the calculation method can be determined according to Appendix A of this standard.

5.1 General requirements

5.1.1 The construction program of mass concrete construction shall include the

following main contents.

5.1.3 The thickness of the thermal insulation covering layer can be determined based

on Appendix C of this standard, according to the requirements of the temperature control indicators.

5.1.4 Mass concrete construction should adopt overall layered or push-type continuous

pouring construction.

5.2 Technology preparation

5.2.1 Before the construction of mass concrete, it shall carry out joint review of the

drawings; propose comprehensive anti-cracking measures during the construction stage;

formulate the construction work instructions for key locations.

5.2.2 Mass concrete construction shall be carried out on the basis that the concrete

formwork and brackets, steel bar engineering, embedded pipe fittings and other work have been completed and accepted.

5.3 Formwork

5.3.1 It shall check the bearing capacity, stiffness, overall stability of mass concrete

formwork and brackets; it shall design the thermal insulation structure based on the maintenance methods used for mass concrete.

5.3.2 Safety and stability measures must be taken, during the installation, use, removal

of formwork and support systems.

5.5 Curing

5.5.1 Mass concrete shall be cured with thermal insulation and moisturizing. After each

concrete placing, in addition to regular curing as ordinary concrete, thermal insulation curing shall comply with the following requirements.

5.6 Construction in special climate

5.6.1 When mass concrete construction encounters high temperatures, winter, strong

winds or rain or snow, measures must be taken to ensure the quality of concrete pouring.

6.0.1 The temperature difference of core and surface of the mass concrete, the

descending speed of temperature, the ambient temperature shall be tested not less than

4 times every day and night after the concrete is placed; the temperature of mixture placing to mold shall be measured not less than 2 times per shift.

6.0.3 Strain test should be carried out according to project needs.

6.0.4 The selection of test components shall comply with the following requirements.

6.0.6 During the test process, the temperature change curve of each point and the cross-

section temperature distribution curve shall be drawn.

6.0.7 When abnormal monitoring results are found, it shall sound the alarm immediately

and take corresponding measures.

6.0.8 Temperature control measures can be adjusted in real time based on the following

principles or methods and combined with monitoring data.