Cooling in concrete construction of large transfer beams by circulating cooling method

This article will mention some cooling solutions in the construction of large transfer beams by pumping circulating cooling water in civil construction in Vietnam.
Concrete or reinforced concrete structures are considered as large blocks of sufficient size to cause tensile stresses, arising due to the thermo-hydrogenation effect of cement, exceeding the tensile strength of concrete to cause concrete cracking and due to It is necessary to take measures to prevent cracks. In hot and humid conditions in Vietnam, a structure with the smallest side (a) and height (h) greater than 2m can be considered as a large block.

Large concrete blocks are cracked due to the thermo-hydrogenation effect of cement when there are two factors: The temperature difference between points or areas in the concrete block exceeds 25°C; The temperature difference modulus between points in the concrete block is not less than 50°C/m.

Structures with dimensions exceeding the upper limit need to have solutions to prevent cracking for concrete right from the design and construction stages. The phenomenon of heat-induced cracking in bulk concrete can be controlled by applying effective solutions to reduce the amount of heat generated as well as the degree of temperature change. Commonly used solutions include: pre-cooling, post-application cooling or a combination of both, and one solution is now commonly used by the circulating cooling water pump method and how heat for concrete surfaces exposed to the environment…

The degree of temperature control to prevent cracking varies depending on many factors such as: geographical location, height and thickness of the structure, characteristics of aggregate, properties of concrete…

1. Purpose

The work of monitoring the temperature and cooling of the concrete of the works is carried out for the following purposes:

– Determine the maximum temperature in the concrete of the mass transfer beam at different positions;

– Determination of maximum temperature difference in bulk concrete;

– There is a measure to lower the temperature in large concrete blocks by circulating cooling water injection method.

2. Technical requirements of concrete used

– The temperature of the concrete mix before pouring at the construction site is required not to exceed 32°C;

– The maximum temperature difference of 2 points is 25°C;

– The maximum temperature allowed to appear in the concrete block is 85°C.

3. Construction sequence

3.1. Step 1: Preparatory work

– Personnel

+ All construction workers must wear appropriate labor protection: wear protective hats, shoes, glasses, at work, workers engaged in welding, cutting or other similar activities must be required If you need to wear safety glasses, welding mask or shield, dust-proof items working over 2m high must wear full safety belts, full body…

+ Before construction, workers must have all the documents as prescribed by the Investor / Supervision Consultant and be trained in occupational safety according to current regulations.
– Device

All machines will be tested prior to work. Certificates and technical information will be provided for the Investor/Supervising Consultant to review.

All machines and tools are always in good condition, safe and suitable for the work being carried out.

All machinery and equipment will be monitored and recorded by the safety management department. The machines are tested for electrical safety monthly and stamped with inspection stamps if they are safe.
Some types of machinery used in the construction process:

+ Pipe threading machine

+ Cutter

+ Electric welding machine
+ Heat welding machine

+ Drilling machine

+ Concrete chisel…

– Drawing

+ From the design drawing provided by the Investor, the contractor redraws it into a drawing serving the construction process. This drawing is submitted back to the investor/Consultant for inspection and approval.

+ Attach the drawing of the principle diagram and related technical instructions

+ Only approved construction drawings can be used on the construction site

– Supplies
Only use approved supplies and materials for use in the construction process.

The materials are gathered and preserved in accordance with the regulations of the Investor / Supervision Consultant. The material gathering area is cleaned, covered, and raised warning flags

When the materials are returned to the project, they must report back to the Investor / Supervision Consultant for acceptance of input materials, if they meet the requirements, they will be put into use for construction.

Some supplies and materials used in the construction process:

+ Black steel pipe DN15, DN20, DN40, DN50, DN65, DN80, DN100.

+ Black steel pipe fittings, galvanized threaded steel pipe fittings.

+ PPR pipes and fittings.

+ Water valves and accessories

+ Temperature gauge, pressure gauge

+ Pump

+ Additional materials…

– Construction methods

Construction contractor and submit construction methods to the Investor/Supervising Consultant for approval

Construction in accordance with approved construction methods

3.2. Step 2: Install the cooling pipe parallel to the reinforcement of the structure

– Construction of PPR . pipes
+ The water supply pump pipe system, return water from the supply tank to the floors using PPR DN100 pipe, the water supply and return water collection pipe system on the floors uses PPR DN80 pipe. Connected together by fittings and heat sealers.

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