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3 Temperature measurement during concrete curing shall comply with the following regulations:.
Construction Precast Development
Precast News From China
precast-tech
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3 Temperature measurement during concrete curing shall comply with the following regulations:.
Load cracks, also known as stress cracks, are structural cracks that occur under external loads.
This type of crack has a strong regularity, and accurate conclusions can generally be drawn through calculation and analysis.
A typical simply supported beam experiences stress cracks, with a normal section bending crack at the mid span, perpendicular to the beam axis and larger at the bottom and smaller at the top; The end is a diagonal section shear crack, starting from the support and pointing towards the concentrated load at the top of the beam.
Cracks in steel-concrete columns under axial compressive loads are distributed longitudinally along the column axis, with slightly denser cracks in the middle.
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Currently, the construction industry is accelerating its transition towards green and industrial development, with concrete PC components (precast concrete components) becoming a key driving force.
The traditional on-site pouring mode is greatly constrained by natural factors, has a lot of construction waste, and is difficult to control quality.
On the other hand, PC components are precast in factories through standardized processes, covering types such as laminated floor slabs, precast exterior walls, stairs, beams and columns, just like standardized building parts, solving industry pain points.
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Quality of cement substrate: The type and proportion directly determine the compressive strength and chemical resistance of concrete.
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Plastic shrinkage often occurs in the semi fluid or plastic stage of concrete, which is caused by various factors such as settlement motion, capillary tension, early chemical shrinkage, and self shrinkage, resulting in changes in concrete volume.
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However, although polycarboxylate based admixtures have solved the requirements for high-rise pumping and durability of ready mixed concrete, they are highly sensitive to fluctuations in concrete raw materials and environmental conditions, leading to various problems during the construction of ready mixed concrete.
If there is a phenomenon of rebound in the slump of ready mixed concrete, especially in winter, this phenomenon is more common, and the ready mixed concrete mixing plant also solves it vaguely every time.
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According to Chapter 7 of the national standard “Code for Construction and Acceptance of Concrete Structures” (GB50204), based on local temperature data for many years, when the daily average outdoor temperature remains below 5 ℃ for 5 consecutive days, concrete construction should enter the winter season.
At this point, the first day when the temperature remains stable below 5 ℃ for 5 consecutive days is considered the initial day for winter construction.
Similarly, when the temperature rises, the end of winter construction is the day when the temperature remains stable above 5 ℃ for 5 consecutive days.
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This document specifies the test methods for the volumetric density, water absorption rate, compressive strength, axial compressive strength, static compressive modulus, flexural performance (flexural ratio ultimate strength, flexural ultimate strength, and flexural modulus), tensile strength, impact strength, anchor rod pull-out force, embedded bolt sleeve pull-out force, frost resistance, and shrinkage rate of non load bearing components of ultra-high performance concrete.
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For a long time, many scholars have conducted in-depth research on other components of concrete, such as cementitious materials and additives.
Even for fine aggregates, due to the increasing scarcity of natural sand in recent years, research has been strengthened, leading to rapid development in the production and use of mechanism sand.
However, coarse aggregates, which are the largest volume component of concrete, have not received sufficient attention.
With the development of concrete technology, the requirements for concrete performance are also increasing, and the impact of coarse aggregates on concrete performance is becoming increasingly prominent.
A comprehensive and in-depth exploration of the characteristics of coarse aggregates on concrete performance has become an urgent issue for concrete workers.
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Transform thinking and shift the focus of work from post pouring testing and inspection to pre pouring mix design and raw material control, and integrate them throughout the entire construction process.
By optimizing technology and refining management, the pouring of high-quality concrete becomes “simpler and more controllable”, thereby naturally reducing the labor intensity of workers.
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