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One of the most frightening scenes when pouring concrete on a construction site is when the pump truck is still pouring materials, the sky suddenly darkens, the wind changes, and raindrops begin to fall on the freshly spread concrete surface.
Outsiders may think that concrete already needs to be filled with water, how big a deal could it be with a little rain? Anyway, it will be hard in a few days.
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On July 2nd, the national cement market experienced a small-scale decline, involving Wuxi, Changzhou, Changsha, Changchun and other places.
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The main raw material for high flow concrete is cement, which is an inorganic, powdery material that, when mixed with aggregates and appropriate water, undergoes a series of physical and chemical reactions and gradually hardens into hard stone through flow dynamics.
The experiment uses P • O42.
5 ordinary Portland cement with a density of 3100kg/m3.
The physical properties and mineral composition were determined through experiments and are shown in Tables 1 and 2.
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Once the impermeability performance is compromised, water and harmful chemicals from the external environment will enter the interior of the concrete, causing further corrosion of the concrete matrix and leading to steel corrosion, significantly reducing durability.
With the continuous accumulation and expansion of rust products, micro cracks and surface peeling will appear in the internal structure of concrete, causing structural damage and severe damage to the overall stability of the building system.
In chloride environments, the service life of concrete structures is generally 30-40 years, with the shortest being less than 10 years.
Even worse, in environments with high salt concentrations, some concrete structures that have been in use for less than a year have to be repaired.
Therefore, in order to extend the service life of buildings, research on the impermeability performance of concrete cannot be ignored.
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Starting from January 1, 2026, according to Announcement No.
10 of 2026 issued by the Ministry of Finance and the State Administration of Taxation, the simple 3% tax calculation policy for commercial concrete that has been in use for more than ten years will be officially abolished, and all self-produced ready mixed concrete will be uniformly subject to a general tax rate of 13%.
Recently, countless general contractors and cost colleagues have sent private messages asking: Is the increase in the mixed use tax rate from 3% to 13 points a direct increase in procurement costs for construction units? Should the bidding price be increased? Can we make up for the tax difference in the settlement of old projects?.
（1） Raw material issues: 1.
Low cement grade/insufficient amount.
Priority should be given to C25/C30 for the ground.
If low-grade cement is used or the cement content in the mortar layer is too low, the hydration strength will be insufficient, and the surface will become loose and powdery.
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The sand content exceeds the standard, and there are many impurities in yellow soil and silt, which wrap around cement particles and cannot form effective bonding.
After completion, it will start to dust as soon as it is rubbed; The standard requires sand to have a mud content of ≤ 3%.
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If the water cement ratio is too high (the most common), water can be added randomly during construction .
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Early damage to municipal concrete pavement is mostly caused by rough construction and improper maintenance, rather than material issues.
Below is a brief summary of the top 5 common quality issues at the construction site, with straightforward reasons and practical measures, suitable for on-site construction and quality inspection disclosure reference.
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According to the “Technical Specification for Construction of Highway Cement Concrete Pavement” JTG/T F30 and the “Code for Construction and Quality Acceptance of Urban Road Engineering” CJJ1, after the commercial concrete/on-site mixed concrete is transported to the paving site, except for the admixture dilution allowed by the laboratory, it is not allowed to add water arbitrarily; Only when the slump loss exceeds the standard and is confirmed by the supervisor and laboratory, can cement, water, and additives be added synchronously according to the mix proportion.
Simply adding water is a serious violation of regulations.
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With the rapid development of self-healing technology, the comprehensive performance of microcapsule self-healing cement-based materials has been significantly improved.
This study provides a systematic review of the current research status of microcapsule self-healing concrete.
Based on bibliometric methods, the research progress and hotspot evolution in this field were evaluated from multiple dimensions such as publication time distribution, research institutions, countries (regions), and citation networks.
Based on this, the latest improvement achievements in performance optimization of microcapsule self-healing cement-based composite materials were summarized.
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The damp corners of the basement walls, dripping water from the garage roof, and peeling of the roof during the rainy season can easily lead people to think: Is concrete inherently prone to leakage? Even though they are made of concrete, water tanks, subway side walls, and underground garage exterior walls can also provide long-term water retention.
The difference lies not only in the waterproofing membrane, but also in whether the concrete itself has sufficient impermeability.
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