Memory usage of c++ code more and more but not getting less

Maybe someone has an answer to the strange memory usage of the following program:

#include <iostream>
#include <vector>

#define SIZE 25
#define FULL SIZE * SIZE * SIZE * SIZE * SIZE * SIZE

class T {
  public:
    std::vector<char*> test[FULL];
};

int main(int argc, char** argv) {
  std::cout << "creating test object..." << std::endl;
  std::cout.flush();
  T* t = new T();

  std::cout << "creating strings..." << std::endl;
  std::cout.flush();
  for (int i = 0; i < FULL; i++) {
    char* newChar = new char[50];
    t->test[i].push_back(newChar);
  }

  std::cout << "freeing strings..." << std::endl;
  std::cout.flush();
  for (int i = 0; i < FULL; i++) {
    delete[] t->test[i].front();
    t->test[i].pop_back();
  }

  std::cout << "freeing test object..." << std::endl;
  std::cout.flush();
  delete t;
  return 0;
}

Note: This program uses nearly 80 GB ram!

The problem now: the ram usage is getting more and more which is correct. But the memory usage is not getting less when strings are beeing freed or the object t is deleted.