Polycarboxylate Superplasticizer For example, self-consolidated concrete and slump retention beyond two hours without significant set time extension have been made possible with PCEs. I was fortunate to be on the R&D/marketing team for a major chemical admixture company that launched the first group of polycarboxylate-based admixtures in the 1990s. Like all new technologies introduced into the building industry, there has been a long learning curve which underscores the highly diverse set of materials and applications with concrete construction. This article summarizes a few key performance attributes which have been learned from both commercial concrete applications and the research laboratory. Some of the benefits provided by polycarboxylate superplasticizers have been discussed and previously published in The Concrete Producer. The term “polycarboxylate” actually applies to a very large family of polymers, which chemists can design to impart a special performance to concrete mixtures. Subsequent to the introduction of so-called general purpose PCE superplasticizers, new PCE products have been developed especially designed to provide high early strength and different levels of slump retention, as well as provide different capabilities to manage air contents in concrete. One such class of polycarboxylates has little impact on initial slump, but because of a time-release function built into the PCE polymer, concrete slump increases generally in a predictive manner as a function of mixing time (see Figure 1). Thus, such a product can be added at various dosages to an already admixed concrete to dial in slump retention as a function of job conditions (haul time, temperature, delay before discharge, etc). Very often, a superplasticizer will be formulated with a blend of two or more PCEs to achieve a combined performance of both early strength and long slump life. Researchers will continue to actively manipulate PCE polymer structure to meet the ever changing material and construction requirements. This remarkable strength difference, obtained by merely changing the superplasticizer type from a PNS to a polycarboxylate, was verified from a scientific study, and can be useful in reducing cement contents while still meeting strength specifications. Interestingly, the strength difference does not seem to be associated with increased heat of hydration, but rather is related to a denser microstructure produced by the combination of a calcium-based accelerating or corrosion-inhibiting admixture and polycarboxylate-based admixture. The PCE superplasticizer replaced both the PNS/lignin and Type A water-reducing products at about one-third the dosage rate. Also, note the 50% drop in AEA dosage rate with the PCE admixed concrete to obtain the same air content. To summarize, though the concrete industry has learned much about harnessing the versatility and understanding the limitations of PCE-based superplasticizers, chemists, working with concrete technologists, will continue to modify the polymer structure to achieve new capabilities for the production, placement and service life of concrete mixtures. by-Ara PCE based plasticizer Shanghai Hongyun New Construction Materials Co., Ltd , https://www.hongyunpce.com
When comparing MIFARE Classic cards with CPU cards, it's clear that the latter addresses many of the security and functional limitations of the former. But what exactly makes a CPU card different, and what are its advantages? Here’s a detailed comparison:
(1) **Storage Capacity and Organization**
MIFARE Classic cards have very limited memory and use a fixed sector and block structure, which restricts flexibility. In contrast, CPU cards offer significantly more storage space—often several times larger than MIFARE Classic. They also support a file-based system similar to an operating system, allowing for much more flexible and efficient data management.
(b) **Key Length and Security Management**
MIFARE Classic uses a 6-byte password per sector, which is vulnerable to attacks. CPU cards, on the other hand, support 16-byte keys and can be partitioned into multiple levels, enabling multi-layered key control. This enhances security and allows for more complex access control scenarios.
(c) **Encryption and Authentication Algorithms**
MIFARE Classic relies on a proprietary and undisclosed encryption algorithm, which has been successfully cracked in the past. CPU cards use industry-standard, open algorithms (either software or hardware-accelerated), making them more secure and customizable. These algorithms often meet financial and government security standards.
(IV) **Read-Write Security Mechanism**
MIFARE Classic uses a built-in key delivery mechanism and authenticates with a base station chip, a method that has been compromised. CPU cards employ a universal read-write module that communicates securely through SAM (Security Access Module) keys. The authentication process involves both cards, and encrypted random numbers are used during transmission, greatly enhancing the security of read/write operations.
(E) **Transaction Process**
The transaction process in MIFARE Classic is simple and non-standard, requiring custom security measures. CPU cards follow standardized financial protocols, allowing for both compliance and user-defined flexibility in application design.
(6) **Access Control**
MIFARE Classic supports basic access modes like read-only, write-only, read-write, and increment/decrement. CPU cards, however, allow for highly customizable access control, where different authentication methods can be applied to various files, offering greater control over data access.
(VII) **Advantages of CPU Cards**
From a security standpoint, CPU cards represent a significant advancement. They support multiple security mechanisms and can even protect the embedded software system. This makes them ideal for applications requiring high security, such as banking, transportation, and identity verification. Additionally, CPU cards can run multiple applications simultaneously, including virtual MIFARE Classic card emulation, effectively turning one card into many. Combined with the COS (Chip Operating System) and custom software, they provide unmatched flexibility and scalability in real-world deployments.The Polycarboxylate Family
Comparison of MIFARE1 Card and CPU Card Features
MIFARE Classic Card vs. CPU Card: Key Differences and Advantages
Some 20 years ago, a new type of Superplasticizer based on polycarboxylate polymers (PCE) was commercially introduced to the North American concrete construction industry. Just as the application of naphthalene-based admixtures starting in the 1970s enabled significant improvements in the numerous engineering properties of plastic and hardened concrete, polycarboxylates have further extended the performance of concrete mixtures.