string concatenation in AX

AjhTestTextBuffer

static void AjhTestTextBuffer(Args _args)
{
    // ajh 2013-05-24: is the TextBuffer faster than using string concatenation?
    // from http://www.mail-archive.com/axapta-knowledge-village@yahoogroups.com/msg07289.html
    TextBuffer tb;
    str a,b;
    int i,j;
    int ts, te;

    ts = WinAPI::getTickCount();

    tb = new TextBuffer();
    a = '';
    b = 'This will be appended to "a" multiple times. ';

    for (i=0; i<30000; i++)
    {
        //j = xGlobal::randomPositiveInt32();
        //b = int2str(j);

        //a = a + b;              // Finished in 68.02 secs!!??
        //a += b;                 // Finished in 0.52 secs.
        tb.appendText(b);       // Finished in 0.17 secs.
    }
    a = tb.getText();

    te = WinAPI::getTickCount();
    info(strFmt("Finished in %1 secs.", (te-ts)/1000));
}