Rock salt rubbish - ...fast becoming an urban myth

[Tony McC]

Since Easter, I've heard about or seen at least a dozen decorative concrete driveways that have gone bad. From the sealant going milky white, to chipping and spalling, loss of colour, crumbling and even a case of pretty bad cracking, there has been the usual horror stories that I get every year, and normally I wouldn't think it anything out of the ordinary. After all, I've heard or looked at as many iffy blacktop jobs, and maybe twice as many rum block paving jobs. Nothing unusual in that.

However, a common thread has developed since the spring: on eight jobs, the various contractors have all claimed that the problem has been caused by Rock Salt, carried on to the driveway by cars during the past bad winter.

I have looked at a driveway in S. Yorkshire that is at least 500m from the nearest surfaced roadway, which the client claims was left unsalted over the winter much to the annoyance of local drivers, yet the spalling on his driveway is due to rock salt, according to the contractor - even the spalling in areas where the car could not possibly go! There's a lady in Scotland with a sealant gone milky that is due to rock salt, allegedly. Cracks running the full width of a driveway in Oldham are a result of rock salt, or so says the contractor. And I could go on...

The 'rock salt' excuse is being used widely by some PIC contractors as an excuse for every possible fault, and I think that in many cases, it's a con.

Word seems to have gone around the industry that, because of the winter we had, many concrete drives have been contaminated by Rock Salt which has subsequently damaged the surfacing, and as everyone knows that salt is extremely deleterious to concrete, the contractors cannot be held responsible, or so they claim.

Two problems with that excuse:

1 - if you recall, last winter there were horror stories regarding the shortage of salt and how many roads had NOT been treated

2 - amazingly, driveways constructed from concrete block paving, concrete flags, and plain concrete don’t seem to be affected - just decorative concrete.

Smell a rat? I think I do!

[Pablo]

Could the cracking be caused by the sub bases heaving due to freezing. Driveways are quite thin and the cold lasted for so long it could easily penetrate that depth.



Edited By Pablo on 1280669470

[Tony McC]

The cracking is probably movement of the sub-grade, as there is no sub-base. One thing is for certain though: it wasn't caused by Rock Salt as the pillock contractor is claiming.

[lutonlagerlout]

in a previous thread i mentioned a concrete base we had done for a factory (to an engineers spec) had effectively lost the first 2-3 mm of fines
it looked like someone had shotblasted it or it was exposed aggregate
although the maintenance manager is fine with it ,i was aghast to see the sate of it after 9 months
i wondered if it was abrasion as its a turning circle for artic and fork trucks?
maybe it was the severe cold?
I have seen a fair bit of muckwork on roofs etc fail this year due to the winter we had
maybe it has had an adverse effect on concrete?
LLL

[mickg]

I don't know the spec for patterned concrete as that would be the last surface finish I would consider on any job but anytime I have laid concrete externally what is exposed I have always ordered it with air entrainment added to the mix and its been batch from a concrete plant

Air entrainment in concrete

was the concrete batched from a plant Tony or ordered from a barrow service and mixed on site ?

a lot of these barrow service guy are using reclaimed crushed aggregates and cheap sand rather than new from the quarry but using these products also reflects in the price too, if you bought the stone sand and cement and mixed your own it is more expensive and it won't be a C30 or C40 mix either

[lutonlagerlout]

it was barrowmix but the guys we use are top notch,their lorry carries the stone and grit sand separately so every mix is correct
I am wondering now if I over tamped it and pushed the aggregate too far down
its playing on my mind as we had a stiffish slump to avoid anything like this,
back to the OP i have always been told that rocksalt bleaches the colour from CBP?
is that BS as well?
LLL

[digerjones]

i had i barrow mix for a slab recently, day or two later i was tidying around slab and noticed that when you broke a peice in 2 there was white bits in it. turns out it was reclaimed materials. not a problem on this exstention slab but i am about to concrete my own shed base and i dont think i would use it. i will use the other barrow mix contractor in my area.

[digerjones]

heres one from last winter in the cold spell taking a few inches off a garden, turned out about 10 12 inches with the frost in the ground.

[I-w]

i know to several driveways(pic) where the surface has failed,its not rocksalt it could be lack of aea, lignite and poorly manufactured csh.lafarge have now stopped manufacturing these products up in sheffield.

[Tony McC]

Lignite was definitely implicated in at least one driveway in Yorkshire, where the concrete had been supplied by Lafarge, who subsequently used an army of lawyers to browbeat the client into believing they had no responsibility for what could only be considered 'sub-standard' concrete.

[lutonlagerlout]

welcome to the brew cabin IW
interesting stuff there dude?
pointless trivia ==> i get my bacon rolls from kevin foley's mum's cafe in luton :;):
LLL

[haggistini]

i tend to think that cbp small imperfections allow freeze thaw action which crumbles some blocks and not others which is exagerated by the use of grit salt???