Monday, July 13, 2009

[papercreters] Low cement mix ratios and fire -was-Don's nice new photos

Ron:

One of the biggest reasons many people use more cement is to get their finished cured/dry papercrete to be non-smoldering.

A 30% cement/ 70% paper papercrete mix, (by dry weight), with no other additives, will very likely continue to smolder if exposed to fire. It can gradually smolder like a hot coal for hours and hours and eventually all the papercrete will be consumed. Put a torch to a small sample of COMPLETELY DRY low or no cement content papercrete sometime and watch what happens. You simply cannot blow them out if they catch fire. They will actually get hotter with the wind. You must either completely drench the papercrete with water, or physically chop out all of the hot coals from the sample, if you want to avoid the water damage. Some chemical fire extenguishers can often be particularly ineffective.

The most dangerous aspect of this kind of fire is that it can hide and slowly eat away at a structure without anyone being aware. It may take days or weeks depending upon the size, how the structure is built, and how the papercrete is covered.


The more mineral content you add to a papercrete mix, especially finely ground mineral content, the less flamable and smolderable it becomes.

Also... higher percentage cement mixes are typically stronger than lower percentage cement mixes.

The exact non-smolder ratio point, cement/paper, for papercrete is somewhat inexact. Different paper sources have different amounts of internal mineral content. Some mineral content comes from inks, some papers have minerals already embedded in them. Glossy and color papers, like from magazines or those fancy colorful newspaper advertising inserts have some of the highest mineral contents in them.

As a general rule of thumb, a 2-1 weight ratio of dry cement to dry plain newsprint should be non-flamable and non-smoldering with plenty of margin for safety. Someone can often go a little leaner on the cement, but 2-1 is a good starting reference point for experimentation with plain simple newsprint that should not sustain any fire or smoldering.

It's easy to reduce the amount of cement required to get the same results by substituting fine clay or other mineral fines for some of the cement. Flyash also works well.

Another technique is to add Borax to the mix. It's an excellent fire retardant.


Ron, if you are using only 30% cement by weight in your mix, compared to paper, the only way that your dry papercrete won't burn or at least smolder once exposed to flame is if it has something else in the mix, whether you put it in there intentionally or it found its way in your mix hidden inside one of your ingredients.


I always recommend that people flame test a sample of their preferred papercrete mix. I always recommend that builders use a mix that won't burn or smolder. It's just too easy and inexpensive to get that good level of fire safety. It's a shame to allow even small risk of health/safety/property damage just to save a very few pennies when all the different easy inexpensive options are considered.


Food for thought.


--- In papercreters@yahoogroups.com, Ron Richter <ronerichter@...> wrote:
>
> Don,
> I agree about the card board. Seems as though it is everywhere, and as newspapers start shutting down it is good to concentrate on a source that will stay strong. I mentioned on a previous post that I went to the nearest paper printer (Missoula) and they had roll ends (left over from the printing process). These varied in length and diameter. I drove up there because they said they had a lot, but when I got there they only had about 25 AND they wanted .25 for each one. Well for the $7.25 I gave they barely covered 1/2 the bed of my Ford Ranger.
>
> Since you are having good blocks turn out can you share with us the %'s you are using of ingredients? No sense re-inventing the wheel. (water, paper (cardboard), cement, other).
>
> I was shocked the other day when I watched the towmixer on Youtube someone recently shared and the guy said 60 # of paper and 90# of cement. I am just finishing a shed (not a house of course) and have used the 60# of paper but I only use 30# of cement and the blocks are fine. Take a long time to dry however as we get down to 40 at night frequently and we have yet to have a 90 degree day during the daytime (I live in Alaska 9 months of the year so I am definitely not complaining).
>
> Thanks for sharing!
> Ron
>
>
>

------------------------------------

Yahoo! Groups Links

<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/papercreters/

<*> Your email settings:
Individual Email | Traditional

<*> To change settings online go to:
http://groups.yahoo.com/group/papercreters/join
(Yahoo! ID required)

<*> To change settings via email:
mailto:papercreters-digest@yahoogroups.com
mailto:papercreters-fullfeatured@yahoogroups.com

<*> To unsubscribe from this group, send an email to:
papercreters-unsubscribe@yahoogroups.com

<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/