Construction Precast Development
Precast News From China
The three types of concrete cube plastic test molds and test block sizes are relatively close, and the test mold sizes meet the requirements of the national JG237-2008 concrete test mold standard.
There are no abnormalities in the size and flatness of the test blocks.
.
The concept of lean production originated from the Toyota Production System and was created by engineer Naiichi Nono.
Lean theory divides all activities in production systems into two categories: transformation activities and flow activities.
Transforming activities into products or processes adds value, while mobile activities (i.
e.
NVA activities) consume time, costs, and resources without adding value.
Previous studies have shown that lean concepts can effectively improve environmental benefits, such as reducing inventory waste, equipment waste, and material waste (Luo et al.
, 2005).
In precast concrete factories, the implicit carbon of precast concrete columns can be reduced by 8% (Wu and Low, 2011a).
.
The carbon emissions from cement production account for 5% -8% of the global total emissions, and the corrosion of steel bars caused by chloride ion erosion in the marine environment is the core issue of the durability of concrete structures.
Alkali activated materials (AAM) using industrial solid waste as precursors are an important way to achieve low-carbon cement production.
Granulated blast furnace slag (GGBS) is currently the most widely studied alkali activated system, and limestone powder (LS) can partially replace GGBS as an auxiliary cementitious material.
However, the chloride ion transport mechanism and microstructural evolution of the AAS-LS composite system in different exposed areas of the ocean are still unclear.
.
Against the backdrop of rapid urbanization and industrialization, the demand for concrete in China continues to grow, and the carbon emissions from ordinary cement production are severe.
The large-scale storage of phosphogypsum poses environmental risks.
Industrial solid wastes such as phosphogypsum, slag, and fly ash can be used as auxiliary cementitious materials to replace some cement, and recycled aggregates can replace natural aggregates to reduce resource consumption.
However, the micro damage mechanism of low-carbon concrete still lacks in-depth research, and the combination of CT and DVC technology provides a new approach to solve this problem.
.
3D printed concrete faces challenges such as material proportioning, rheological properties, and difficulty in coordinating printing parameters.
Traditional trial and error designs are unable to cope with complex nonlinear relationships, resulting in unstable quality, high costs, and carbon emissions amplification.
The combination of machine learning and multi-objective optimization provides a new approach to solving this problem.
.
The mechanism diagram explains the most complex scientific story with the lowest communication cost.
It is not only an illustration, but also a core tool for efficiently conveying complex scientific problems to readers.
.
In the 21st century, with the rapid development of science and technology, applied science continues to lead society, and construction has undergone significant changes.
New materials, new technologies, and new processes are constantly being applied in practical construction, especially the extensive use of pumped concrete.
As industrial waste or industrial by-products (fly ash and slag powder) with cementitious properties, they gradually play a dominant role in the development and utilization of concrete mixtures.
Previously, concrete was mainly characterized by low plasticity or plasticity, and the sand ratio was mainly considered based on its filling effect.
The selected sand ratio was generally smaller.
Nowadays, the determination of sand ratio for highly mobile concrete is mainly based on the principles of fluidity and pumpability, which has increased significantly compared to before.
All of these have caused significant changes to the surface of concrete structures.
.
Reinforced concrete structures are continuously exposed to the atmospheric environment during service, and carbon dioxide in the air diffuses into the interior through the pores on the concrete surface and undergoes neutralization reactions with alkaline hydration products.
The carbonization front gradually advances deeper into the structure over time.
When the carbonization depth reaches the surface position of the steel reinforcement, the passive film of the steel reinforcement, which was originally in a highly alkaline environment, will lose stability due to the decrease in pH value and undergo electrochemical corrosion in the presence of moisture and oxygen.
Concrete structures such as industrial buildings, underground garages, tunnels, and coastal structures that are exposed to high concentrations of carbon dioxide or high humidity are facing a more severe threat of carbonation.
Due to historical reasons such as low design standards and extensive construction management, some early construction projects have a common phenomenon of carbon degradation, which poses a significant burden on the owner units in terms of structural safety hazards and maintenance and reinforcement costs.
.
During the hot summer season, the production and construction of concrete projects in summer is a difficult point in engineering construction.
At high temperatures, the evaporation rate of water in concrete is fast, the hydration rate of cement increases, and the slump loss is too fast, which has a negative impact on the physical quality of concrete.
This article discusses the control measures for the production and construction of concrete under high temperature weather.
.
The rationality of mix design is based on a certain quality of raw materials, theoretical calculations, and multiple trial mixes to meet the process of strength, construction performance, workability, durability, and economic performance.
This also requires concrete designers to fully understand the factors that affect strength, the conditions that affect construction and work performance, the weight of durability and cost, and to choose raw materials reasonably and selectively.
But often the mixing plant needs to meet the performance requirements of the concrete based on the materials used, without any selectivity, which forces the design to meet the requirements but is difficult to achieve.
.