Dodgy mortar ?

G

Guju121

Registered User
Messages
25
I am in the process of building a new house by direct labout.
The timber frame is up and the blockwork around it has been completed.
Recently I have noticed and it has been pointed out to me that the mortar between the blockwork was badly mixed, i.e. it is very soft ( you can scrape it away with you nail !! ).
I had to drill some holes through the blocks today but as soon as you touch them with a hammer action drill, the blocks come loose.
Also I've noticed that after some rain the morter seems to soak up the water a lot and looks like wet sand, other parts of the walls seem ok, so you can easily see the difference
Anyone seen this before ??
 
Was the mortar batched and mixed up on site or bought in? There could be a number of reasons for the poor quality- dirty sand (containing soil/ clay), cement was off ("warehouse set"), dirty water, improper use of additives. Where and how was cement stored on site? Frost damage is another possibility, especially given the cold nights in recent weeks.
 
Mortor was mixed on site, cement is stored on the ground on top of a pallet and covered with heavy duty polytine. There was no frost at the time of construction ( 2 months ago now ).
Had the block layer on site to check it, he reckonds it was a bad batch of cement. I'm not convinced, I think washing up liquid was added to the mix as some block layers do to make the mortar more workable.
In any case he is confident the wall is strong enough an shouldn't cause any problems. He also thinks that drilling or nailing a single leaf wall can loosen blocks at the best of times. Again I'm not convinced
 
I would get the supervising engineer\architect to look at it. Sounds too soft, as if theres little or no cement in it.
 

I'm not convinced either- if the cement was off it shouldn't have been used at all (it's easy enough to gauge whether cement is off- it'll be lumpy). Washing up liquid is sometimes used as a "plasticiser" although it is not near as effective as the real thing and wouldn't be recommended by the cement manufacturers. If you have an engineer engaged to supervise and issue certificates you should have this work inspected- regular sand/ cement mortar should not be soft. Traditional lime mortars are soft and designed to be so, OPC mortars are not.
 
If too much plasticiser/washing-up liquid is used, it will take from the strength of the mix. Drilling a single leaf should not cause any problems. Hammering? If it is one of the top layers, then maybe. Why not take a core sample and send it to the lab?
 


sounds like a bad mix to me -too much sand too little cement-,
a careless or new labourer on the mixer and blocklayers who dont care what they lay their block on as long as the wall goes up and they get paid -sure its all plastered up afterwards cant see it from my house point of view,
make him pull it and replace it ,you are paying him to do a professional job so why expect shoddy work?
its nots a bad batch of mortar its the lack of cement in the mix thats the cause of it. builers always blame the cement not the guy on the mixer.
 
Thanks guys, I thinks I'll have to get the engineer out asap. The blocklayer reckons it will pass inspection and he is prepared to stand by his work, so we will see what sparks will fly !!!
One thing is certain, you really need to watch these tradesmen when building a house, I never considered a professional blocklayer to mix his mortar badly, I mean its the easiest think in the world to mix up a batch of mortar. Lesson learned I think ...
 


God bless you-Blocklayers dont mix -they just lay.
 
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