Bootstrap - animação de botões de carregamento (loading) com CSS

index.html

<!-- Code snippet -->
<div class="form-group">
    <div class="col-md-12 text-center">
        <span class="glyphicon glyphicon-refresh glyphicon-refresh-animate"></span>
    </div>
</div>

site.css

/*
    Original version: http://www.bootply.com/128062
    
    This version adds support for IE 10+ and Firefox.
*/

.glyphicon-refresh-animate {
    -animation: spin .7s infinite linear;
    -ms-animation: spin .7s infinite linear;
    -webkit-animation: spinw .7s infinite linear;
    -moz-animation: spinm .7s infinite linear;
}

@keyframes spin {
    from { transform: scale(1) rotate(0deg);}
    to { transform: scale(1) rotate(360deg);}
}
  
@-webkit-keyframes spinw {
    from { -webkit-transform: rotate(0deg);}
    to { -webkit-transform: rotate(360deg);}
}

@-moz-keyframes spinm {
    from { -moz-transform: rotate(0deg);}
    to { -moz-transform: rotate(360deg);}
}