Analysis of the function of the bolt body of the oxidized paddle frame

The purpose of adding fillers to epoxy mortar is to enhance its mechanical strength, improve resistance to aging, reduce shrinkage during curing, minimize exothermic reactions, and lower overall costs. Commonly used fillers include medium-sized river sand, diabase powder, and cement, which are readily available. The mix ratio can be adjusted depending on ambient temperature and project urgency. In summer, when temperatures are high, it's advisable to use less ethylenediamine and more sand, while in winter, the opposite applies. It's crucial that the mixture remains workable for at least one hour to ensure proper application. Based on years of practical experience, there are standard mix ratios for both summer and winter conditions. For example, in summer, when temperatures may reach up to 30°C, the epoxy resin (E-44), butyl butyl ether, and ethylenediamine are mixed with medium sand (particle size between 0.25mm and 0.5mm) having a moisture content below 0.2%. The exact weight proportions depend on specific requirements. Several factors influence the strength of epoxy mortar: 1. The quantity and quality of ethylenediamine significantly affect the final strength and adhesion. Epoxy resin alone does not harden; it requires the correct amount of ethylenediamine to initiate the curing process. Too much or too little can lead to problems—especially in warm weather, where even a slight excess can cause rapid reaction and potential explosion within minutes. 2. Moisture content in the sand plays a critical role. If the sand has high moisture, it can form a water film on its surface, reducing adhesion. Therefore, the sand must be thoroughly dried to ensure moisture content stays below 0.2%. 3. Porosity directly affects the strength and cohesion of the mortar. More air bubbles mean lower tensile and compressive strength. At room temperature, epoxy resin often contains many bubbles, which are the primary cause of porosity. To reduce this, the resin should be heated to 80°C before use to remove air bubbles, and care must be taken during mixing to avoid introducing new ones. 4. The surface of the bonded object must be clean and free from oil, rust, or dirt. Epoxy mortar adheres strongly due to the polar attraction between its active groups and the surface molecules of the material (such as steel or concrete). Any contamination will weaken the bond and must be removed before application. 5. Besides river sand, diabase powder and cement can also be used as fillers, provided their particle size and moisture content meet specifications. Although these alternatives may offer slightly higher strength, they are more expensive and rarely used in construction projects. Temperature also has a significant impact on the curing process: higher temperatures speed up strength gain, while lower temperatures slow it down. At temperatures near zero, the strength development becomes even slower. At +20°C, epoxy mortar typically exhibits a tensile strength of 15–20 MPa, a compressive strength of 70–90 MPa, a compression modulus of (0.7–1.5) × 10⁴ MPa, and a bulk density of 1.7–1.8 g/cm³. Construction procedures for bonding anchor bolts with epoxy mortar include: 1. Before pouring concrete, any reinforcing bars located at the bolt positions must be removed by at least 80 mm to prevent difficulties during hole formation. 2. Mark the center position of the bolts according to the design drawings on either a new or existing foundation. 3. When drilling holes in a new foundation, wait until the concrete reaches an appropriate strength before starting. If the strength is too low, the hole walls may crack during drilling, affecting the bond quality. If it’s too high, drilling becomes difficult. Practical experience suggests that the optimal time to drill is when the concrete strength reaches 70–100% of its design strength. This can be estimated based on the type of cement and environmental temperature, using a concrete strength curve or measured with a rebound hammer.

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