About your question are you interested at UHPC , with mechanical strength very high (more than 120 MPa) , with fine granulometry (maximum size under 1 mm) , extremely high amount of superplasticizer (till 6-7% on the recipe) and w/c ratio between 0,19 and 0,23 , with fluid consistency like Ductal from Lafarge or Smart from Vicat ? Or are you meaning only high performance concrete so with strength over 75 MPa but under 110-115 MPa?

I’m asking this because granulometry of aggregates , amount of Portland cement type 1 (52,5 R only) and amount of Microsilica and superplasticizer or even fibers if necessary are very different. All mix design is really different.

Let me know, please.

Best regards

Alex Reggiani

Max 5 %

For high performance concrete water cement ratio should be in the range of 0.3-0.35 or less and superplasticizer needed is about 2%

Your superplasticizer dosage will also vary depending on which superplasticizer you use and with which cement/SCM you use. Regardless of UHPC or HPC, aggregates (lithology, shape and gradation) and overall mix gradation (granulometry) will also be a factor. There needs to be some direction on what type of mix is needed.

Alex Reggiani

Can you please tell me the name of that super plasticizer , As we are working on a project self compacting light weight concrete and only light weight concrete by using expanded clay with OPC 42.5 but the main problem of expanded clay is it gives very low compressive strength.

How i can increase the compressive strength of my concrete?? Can i increase the compressive strength by using that superplastisizer ??

Waiting for you kind response.

Thanks

Alex Reggiani

Dear Muhammad,

if you use expanded clay, like Leca products, you can’t use OPC 42,5 because is too weak for your goal. I suggest to use for sure Portland cement type I so 52,5 R (faster setting than N type) and at least 15-20% of microsilica that have to stabilize hydrolysis lime from Portland hydration . Let me know about the size of expanded clay , because to have higher strength you must use more pozzolanic effect possible also from clay.

With superplasticizer from BASF or other suppliers (are more cheap the liquid version so Glenium 44 type or similars) is possibile to reduce the water ratio, but not at best because clay absorbs more water than traditional silica sand aggregate . I don’t know what is your target of mechanical resistance after 28days , but with expanded clay I don’t think you may reach very high results (reasonably about 20-25 MPa should be the maximum you can obtain).

Superplasticizer is possible to use also in powder form as BASF Melflux line or similar polycarboxilates polymers. But they are very expensive (more than 12 €/kg in Italy).

Lightweight concrete can’t be compared with high performance concrete, because all systems are quite different .

In any case I suggest to try reducing water with polycarboxilates and thanks microsilica and reactive fillers parts of clay , mechanical properties will increase. If you may use even some sand the aggregate curve will be more strong .

All the best

Alex Reggiani

Alex Reggiani

Yes, you are right, i need to read some articles to know more about this, the information you shared its really very useful.

Dear Prof. Alex can you please provide me your email so I can contact you if i need some help.

I will be very thankful to you.

Dear Mohammad, I’m not a professor , but I work in this field from more than 15 years.

My email is [email protected] , when possible I’ll try to answer you. I must respect NDA with my companies GeoMITS and Renca Rus.

Best regards

Alex Reggiani

I agree with Alex Reggiani. Not all lightweight is created equal. Sometimes expanded shale or slate performs better. What design density of concrete are you trying to meet? All lightweight has inherently reduced strength so good luck. Blending a good normal weight sand will help as Mr. Reggiani stated. Lightweight concrete is sometimes difficult in SCC applications. If the spread/flow is too high the lightweight aggregates can float. Smaller stone sizes than that used in typical lightweight will likely be required. Your admixture supplier should be able to help you with the approximate proportions of materials and especially cementitious/binder for paste content.

Alex Reggiani

Thank you so much...

Dear Alex i read all the comments of different researcher but the information you provided is really valuable and authentic.

You are more than a professor.

I will contact you when i need some help.

Thanks

Dear Muhammad, thanks for your kind words ,my goal is to have from this and other platforms good science and well done scientific papers. So have a nice work .

All the best

Alex Reggiani

Thank you Alex Reggiani

Hello, it will depend on the slump values. If you want to take 50-100 mm slump, then it will be near 1%. Then the more slump you use you need more admixture. But it will not be more than 2%.

Md. Shahrior Alam

you said 1% form what cement or water

Hamad, it is from the Cement content

Another thing one has to keep in mind is what water content/slump you are starting with. For high strength concrete, you may be starting with much less than a 0 slump. How much less will determine the admixture dosage.