Compilation ideas

1. Taking the design work experience as the basic requirement for engineering waterproofing

The general waterproof specification specifies the basic requirements for waterproof performance for all buildings and municipal engineering projects that require waterproof protection through top-level design. Starting from functional requirements, the waterproof design service life of various types of buildings and municipal engineering has been clarified, which means the service life that can be used for the intended purpose without major repairs. The working years of engineering waterproofing design are determined based on factors such as the importance of the project, economic losses caused by damage or performance reduction, the possibility and time cycle of maintenance, existing materials, and structural performance. The basic requirements for engineering waterproofing proposed from the perspective of basic functional requirements of the project are important parameters and performance goals of engineering waterproofing design. The design and material selection of engineering waterproofing should meet the requirements of the working years of waterproofing design.

2. Determine the engineering waterproofing level from two dimensions: "engineering waterproofing category" and "engineering waterproofing usage environment category"

3. Comprehensive improvement of defense standards

In response to the high leakage rate and the high proportion of leakage in construction quality complaints, in order to standardize the waterproof performance of buildings and municipal engineering, and ensure the basic waterproof functional requirements of buildings and municipal engineering, the general waterproof specification has comprehensively improved the waterproof fortification standards.

The improvement of waterproofing standards for roof engineering is reflected in two aspects. Firstly, waterproofing requirements. According to the "Technical Code for Roof Engineering" GB50345-2012, Grade II adopts one layer of waterproofing, while Grade I adopts two layers of waterproofing. The general waterproof specifications stipulate that level three is one waterproof barrier, level two is two waterproof barriers, and level one is three waterproof barriers. The requirements for first level waterproofing have increased, and an additional layer of waterproofing has been added to the original foundation. This not only improves the reliability of roof waterproofing, reduces the possibility of leakage, but also enhances the durability of the roof waterproofing system. This has a significant impact on the service life and maintenance costs of buildings. The second is that the general waterproof specification stipulates that the design service life of roof engineering waterproofing should not be less than 20 years. Even if only one waterproof layer is set for the third level waterproofing, the design service life of 20 years must be achieved. This is a great challenge and requires comprehensive coordination from multiple aspects such as construction, material selection, node construction, protective layer setting, operation and maintenance to achieve the predetermined goals.

In the waterproofing design of underground engineering, the current "Technical Specification for Waterproofing of Underground Engineering" GB50108-2008 stipulates that the bottom plate and side walls constructed by external waterproofing and internal pasting method of underground engineering can meet the first level waterproofing requirements with a single layer of polymer self-adhesive film waterproofing membrane. The general waterproof specifications stipulate that for underground engineering using the open cut method with first level waterproof protection, waterproof concrete should be used as one waterproof layer, and two external waterproof layers should be set up. The general waterproof specifications do not allow the use of single-layer pre laid anti adhesive waterproof rolls for first level waterproof protection. Therefore, when using pre laid anti adhesive waterproof rolls, two external waterproof layers should also be set up.

There has always been no mandatory waterproofing requirement for building exterior walls. The "Technical Specification for Building Exterior Wall Waterproofing Engineering" JGJ/T 235-2011 is a recommended standard that does not classify exterior wall waterproofing, but requires areas with high rainfall and basic wind pressure to adopt overall exterior wall waterproofing, while other areas should take measures to prevent node structure waterproofing. However, as it is a recommended standard, it has not been widely implemented, and external wall leakage is still very common. The general waterproof specifications have stricter requirements for exterior wall waterproofing and have more specific requirements. For frame infill walls or masonry structure exterior walls with a waterproof grade of level one, two or more waterproof layers should be set up, at least one of which should be waterproof mortar, and the other can be waterproof coating or other waterproof materials. The frame infill wall or masonry structure exterior wall with secondary waterproof protection, or the cast-in-place concrete exterior wall and prefabricated concrete exterior wall panel with primary waterproof protection should be equipped with one or more waterproof layers.

The "Technical Code for Indoor Waterproofing Engineering of Residential Buildings" JGJ 298-2013 and the "Technical Specification for Indoor Waterproofing Engineering of Buildings" CECS 196:2006 both have requirements for indoor waterproofing, generally focusing on one layer of waterproofing. The general waterproof standards have put forward higher requirements for indoor waterproofing. In frequent water situations, the first level waterproof protection should be set up with no less than 2 layers of waterproof protection, including at least 1 layer of waterproof coating or waterproof roll, and the other layer can be waterproof mortar, waterproof coating or waterproof roll, etc.

4. Propose performance requirements for waterproof materials from an engineering perspective

Waterproof materials are the core element of ensuring the quality of engineering waterproofing. The design of engineering waterproofing structures, methods, node defenses, and related engineering application standards are all based on materials, so waterproofing engineering is constrained by waterproofing materials. The general specification for waterproofing puts forward requirements for the performance of waterproofing materials from the perspective of engineering requirements. Material production enterprises should conduct corresponding material research and development and improvement according to these requirements to meet engineering needs.

(1) Emphasize the durability of waterproof materials

The general waterproof specifications require that waterproof materials used in engineering should meet durability requirements. The durability of waterproof materials should be compatible with the design service life of engineering waterproofing, and the material performance should be compatible with the environmental conditions of engineering use. Performance index requirements for water resistance, thermal aging, and artificial climate aging of waterproof rolls and waterproof coatings have been proposed. The durability of waterproofing membranes and coatings in corrosive environments, as well as the engineering requirements for root puncture resistance of planting roofs and underground engineering planting roofs, have been proposed.

(2) The requirements for the peeling strength and impermeability of waterproofing membrane joints were first proposed

One of the main reasons for the failure of the waterproof layer of the waterproofing membrane is the defects such as warping, misalignment, wrinkles, delamination, and virtual adhesion caused by the weak bonding of the lap joint during use. In response to this engineering defect, the general waterproof specification proposes different lap joint techniques such as hot melt bonding, self-adhesive bonding, adhesive bonding, tape bonding, and welding for waterproofing membranes, including no treatment, heat aging treatment, and immersion treatment for joint peeling strength and joint impermeability. This provides a reliable guarantee for the waterproof performance and long-term working performance of the lap joint.

5. Add a chapter on operation and maintenance

The service life of waterproofing engineering is closely related to the operation and maintenance of the project. After the completion of waterproofing engineering, departments and individuals often neglect the maintenance work of waterproofing engineering. If the usage function is changed arbitrarily during use, drilling holes or installing equipment on the waterproof layer, it may cause damage to the waterproof layer. Lack of daily inspection and maintenance, clogging of the drain outlet and floor drain, and formation of ponding, even backflow in rainstorm. Therefore, the general specification for waterproofing has added a chapter on operation and maintenance, which stipulates the warranty responsibility, scope, and period of waterproofing engineering, proposes the establishment of a waterproofing engineering maintenance management system, regular inspections and maintenance requirements, and puts forward principled requirements for defect repair.

Author Zhang Wenhua

Professor, School of civil engineering, Zhejiang University of Technology