Many people use the terms “cement” and “concrete” interchangeably, but they’re not the same. Cement is powdery stuff composed of limestone, gypsum, clay with alumino-silicate, and other ingredients. It’s just one of the raw materials used to make concrete – usually no more than 15 percent of the total mass. The rest is sand, crushed stone and water. It’s a good metaphor to keep in mind. If you want to create a durable thing to last as long as concrete, don’t get overly preoccupied with the “cement” at the expense of the other 85 percent of the stuff you need.