The "Research and Application of Key Technologies for the Design of Rigid Self-waterproof Functions of Modern Concrete" of China Construction West Construction Southwest Co., Ltd. won the third prize of the 2022 China Concrete and Cement Products Association Concrete Science and Technology Award • Science and Technology Progress Category, which solves a major problem in the construction industry: the leakage problem of concrete engineering structures.
When there is leakage in the concrete structure, water and harmful substances dissolved in water enter the concrete, which is easy to corrode the steel bars inside the concrete, thereby reducing the durability of the concrete structure and shortening the service life of the building. "Research and Application of Key Technologies for Rigid Self-waterproof Functional Design of Modern Concrete" carried out systematic research from four aspects: concrete low-heat cementitious materials, concrete crack and seepage resistance improvement technology, rigid self-waterproof concrete preparation, and concrete construction-monitoring-maintenance measures optimization.
Scientific and technological achievements and engineering applications
In the past three years, the project technology has been transformed to produce large-volume concrete covering C30-C60 strength grades, which has improved the crack resistance of concrete, optimized cost and quality control, and has been successfully used in Chengdu BOE Hospital, Chengdu Metro Line 19 Phase II and other concrete projects with high impermeability and crack prevention requirements have ensured the construction quality and progress, and achieved direct transformation benefits of more than 7,320 yuan, with significant economic benefits. This project has been approved 3 national invention patents and published 5 papers.
BOE Hospital linear acceleration of the distribution and pouring effect of steel bars in the computer room
Chengdu Metro Line 19 Changshun Village parking lot side wall steel bar distribution and pouring effect
The main innovations
1. Key technologies for the design and evaluation of low-heat cementitious systems
Based on the hydration differences of different mineral admixtures, the hydration exothermic law and the differences of hydration products of the cementitious system were investigated through microcalorimetric quantitative analysis, microscopic and thermogravimetric analysis, and the hydration process model of different cementitious systems was established. Combined with the strength differences of different cementitious systems, an evaluation system of low-heat cementitious systems was established with the hydration heat and strength of cementitious materials as the comprehensive performance objectives, and the comparative study of the adiabatic temperature rise of different cementitious systems was carried out, so as to provide a basis for the selection of cementitious systems for the study of low-heat and low-shrinkage concrete.
Hydration model of a cementitious system
2. Research on key technologies for comprehensive improvement of concrete crack and seepage resistance
Hydration temperature rise inhibitors were developed to accurately control the hydration rate of concrete at different stages through gradient release, and there was no negative impact on the strength of concrete in the later stage. The influence of expansion agent and curing conditions on the efficiency of expansion agent in micro-expanded concrete was investigated, and combined with fiber and water evaporation inhibitors, a composite concrete anti-cracking technology was formed, which delayed the cement hydration reaction and established internal micro-expansion through "wrapping-dissolving", "filling-refinement" and "anti-capillary effect", and at the same time reducing the water evaporation rate on the concrete surface, which significantly improved the crack resistance of concrete and achieved the purpose of self-waterproofing.
The principle of hydration temperature rise inhibitor and its effect on the heat of hydration of cement
3. Key technologies for the design and preparation of rigid self-waterproof concrete mixture
The low-heat cementitious system was optimized, combined with the comprehensive improvement technology of anti-cracking and anti-seepage performance, and the concrete mix ratio was optimized based on the three functional criteria of hydration heat of cementitious material, concrete insulation temperature rise and compressive strength, so as to realize the optimal design of the mix ratio with the goal of concrete temperature rise and strength control, and form the key technology of self-waterproof concrete preparation.
Technology roadmap for the formulation of rigid self-waterproofing concrete
China Construction West Construction Southwest Co., Ltd. was formally established in 2008 and is dedicated to commercial concrete and related businesses. The parent company, China Construction West Construction Co., Ltd., is the first independently listed professional company under China State Construction Group Co., Ltd. and the only development platform for concrete business. The business of Southwest Company covers 5 regions in China and 2 countries overseas. With an annual output of more than 15 million square meters of concrete, an annual output value of more than 7 billion yuan and an annual tax payment of more than 300 million yuan, it is a leading enterprise in the concrete industry in southwest China and a vice president unit of Sichuan Concrete Association.
The "Waterproof General Regulations" guide the development of rigid waterproofing
Article 2.0.2 of the "Waterproof General Regulations" stipulates that "the working life of waterproof design of underground engineering shall not be less than the working life of engineering structure design". The reason for this regulation is mainly because the peripheral waterproof layer of underground engineering is a non-replaceable component, and the maintenance of the peripheral waterproof layer is extremely difficult and the cost is relatively high. The characteristics of such engineering structure determine that the working life of its waterproof design should not be lower than that of engineering structure design.
At present, only structural materials can have the same life as engineering structures, so self-waterproofing of concrete structures is the ultimate waterproofing measure for underground engineering.
Article 3.1.1 of the "Waterproof General Regulations" stipulates that "the durability of waterproof materials shall be compatible with the working life of the engineering waterproof design". The durability of waterproof materials is the basis for realizing the working life of engineering waterproof design, so doing a good job of waterproof concrete is the basis for realizing the same life of waterproofing and structure.
In addition to good impermeability, waterproof concrete should also have good crack resistance. Article 3.2.2 of the "Waterproof General Regulations" stipulates that "technical measures to reduce cracking shall be taken for waterproof concrete. At the same time, the article lists anti-crack technology and material measures.
In addition, Article 3.2.3 of the Waterproof General Regulations stipulates that "in addition to meeting the requirements of compression, impermeability and cracking, waterproof concrete shall also meet the durability requirements of the environment and working conditions in which the project is located." "The provisions on the durability of concrete in the "Waterproof General Regulations" have promoted the implementation of concrete durability standards such as the recommended standard "Design Standard for the Durability of Concrete Structures" (GB/T 50476-2019).
Therefore, one of the general directions of the "waterproof general regulations" is that we should pay attention to and do a good job in the self-waterproofing of concrete structures, clarify the target direction for the development and application of waterproof concrete, encourage and support the application and development of waterproofing and anti-cracking technology and material measures in waterproof concrete, and provide a standard basis for increasing the cost investment in waterproof concrete in actual projects. This is a great opportunity for the development of rigid waterproofing.
From 丨China Concrete and Cement Products Association