Ecocem - Not a direct replacement for opc

[kwdConstruction]

Never had to go back to a job once in over 10 years as a sole trader, except to adjust a patio where a conservatory had since been built or to to do additional works for a happy customer. That was until my local builders yard switched suppliers and sent out EcoCem instead of their usual brand of ordinary portland cement.

Pretty much every mix I've made for a good few years now (bar mortar for facing bricks) I've added at least a dash of Ever Build 503 Premium SBR to the water, buy it in 25l containers and always have it to hand. Magic stuff, I used it originally for making slurry mixes for welding on step treads and copings, but found it just too tempting not to share the love in haunching mixes, beds and jointing mixes.

Thing is, Oct/Nov last year, I used EcoCem + this premium SBR on 2 jobs within weeks of each other, and on both, the concrete and mortar has gone to powdery shit. In one instance, a 5:1 mortar mix went a very odd orange/yellow colour, powdery and crumbled to dust. Never seen anything like it - it's like someone added an icky buff dye and the temperature dropped to minus 30 like 5 minutes after my trowel left it. In another, three sections of 2:3:1 concrete (20mm limestone, zone 2, ecocem), of these 1 is perfectly fine and as rock-hard as you'd expect, the other 2 (both installed same day) are a little discoloured, crumbly and take little effort to turn back to sand and stone under the sole of my boot. Given the timing of the job after others, it seems likely the good section was where I used up the last of the proper cement I had over from the previous job.

So yeah, mightily pissed off.

Not sure what this stuff is made from, but quickly skimmed a page saying it was some sort of reconstituted waste product that gets bagged up and passed off as cement. WTF?! It might well take 25% less carbon to produce, but if it's not a direct swap-out for OPC, it shouldn't be offered as such. And in fairness, nowhere on the packaging did it claim to from what I remember, but the builders yard shipped it out as such, so that point is moot.

So just saying beware if this stuff lands on your site. Whatever the eff EcoCem is, it ain't OPC (more like PoC!) and I'll not be going anywhere near it in future. If it ballses up so spectacularly with SBR added, who knows what myriad other additives, stabilisers, plasticisers etc. will do when brought into contact with this stuff. My advice is, if you're not using it straight, don't assume it'll act as if it were OPC. Actually, it's just steer well clear full stop and use the same, trusted and tested OPC you always have that you know is good.

Ironically, it might well be that using it straight would have produced the expected results, and if I hadn't poured expensive SBR into the mix it'd have been fine, but whatevs, that's no effing consolation when you've grafted and have to go back do repeat work for no fault of your own.

End of rant.

[Brucieboy]

Hi Kevin – sorry to hear about your recent problems.

For information, Ecocem is a blended cement comprising CEM I (newish name for OPC) and ggbs (ground granulated blastfurnace slag). According to Ecocem’s website it contains greater than 50% ggbs (the maximum permitted by CEM III/A is 65%).

CEM III/A is certainly not a new product having been used by the ready mixed concrete industry for over 40 years. Most concrete plants will stock either ggbs or flyash (pfa) as separate materials to blend with CEM I or stock the composite blended cement itself, eg CEM III/A or CEM II(B-V). When blended at certain proportions it provides sulfate resistance for concrete used in ground containing sulfates and for deep pours (thick slabs etc) where it’s used to minimise the effects of thermal cracking. It is also commonly used for general concreting purposes such as footings, oversites, kerbing etc. If you order concrete from most suppliers it will normally be made with a blended cement (together with a water reducing admixture aka plasticiser) unless you specifically ask for CEM I.

The main point to take into consideration when using CEM III/A is it is slower setting than CEM I (particularly in colder weather with the higher percentages of ggbs ) and may result in a bit more bleed water coming to the surface. Neither is a significant issue as long as you are aware. More care is needed when concreting in cold weather to prevent frost damage.

In your particular case, did you ask your builders merchant for “cement� or specifically OPC? Unless you actually state OPC (as said previously, now known as CEM I – pronounced cem one) you’ll probably get a blended cement in one form or another, e.g. General Purpose Cement, Ecocem etc. Even Mastercrete is a blended cement containing limestone fines defined as CEM II/A-L. However, it’s not as slow setting as CEM III/A.

Unfortunately the European terminology for defining cement, i.e. CEM xxxx confuses most buliders merchants and the big sheds. To many, cement is just cement.

I can’t see any reason why using SBR would significantly affect the hardening properties of Ecocem unless you used a high dosage which could have cut down the added water content too much (although very unlikely) nor why it should have an orange /yellowish tinge. Using ggbs generally produces concrete that is much lighter in colour than using CEM I.

Personally, whilst CEM III/A is OK for general day to day concreting requirements (providing you’re aware of its properties), I wouldn’t use it in mortar. As the joints are relatively small in area / depth relative to a concrete slab or footing, the longer setting time of CEM III/A may allow more water to be sucked out of the mix by absorption into the paving unit, substrate etc, hence there may be insufficient for the full hydration of the cement leading to subsequent degradation and crumbling.

When I laid my own Indian sandstone patio 7 years ago, I used a 3:1 by volume building sand : cement mortar (50% Mastercrete / 50% CEM I white cement) with a good dosh of SBR for the jointing. It’s still bullet hard (power washed at least twice a year).

I hope this helps.

[lutonlagerlout]

thanks for the tip,not seen it but will swerve it
mastercrete is OK,but I prefer CEM 1 for concrete
LLL