Lime-RHA Binder

Submitted by T_Nhien on Mon, 11/06/2018 - 16:01

Dear Geoffrey,
I am currently experimenting with hydrated lime and raw rice husks to build insulating panels. As a binder I would like to use a mix of lime, pozzolan and a small amount of cement to increase the initial setting and at the same time maintaining the advantage of lime (carbonation effect).

I have a few questions and I hope you can give me some advice on Lime-RHA based binder:
1) According to your experience what would be the most suitable binder mix, i.e. Lime/RHA/OPC and binder/water ratio?
2) can you please provide me your RHA specs as well.

Thank you. I am looking forward to hearing from you.

Best regards,
Nhien

Submitted by geoffrey on Mon, 11/06/2018 - 16:48

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1. We can successfully replace at least 30% of lime or OPC [ordinary portland cement) with RHA (finely ground rice husk ash). The RHA pozzolan tends to drink up more water so it is necessary to use a superplasticizer in order to keep the W/C ratio (water to cement ratio) below .40   In Thailand there are already lime/opc cements available so it is probably not necessary to mix your own although you can.

2. The RHA spec's or properties can mean the percent constituents of various elements and minerals. To determine these some high-tech laboratory analysis is required. This is suitable for scientific research endeavors. If we are working on finding and appropriate mix, especially in a precast concrete product situation, then we cast several trial mixes, cure the products for appropriate lengths of time (3, 7, 28 days) and then test the product strength against an appropriate standard (TIS, ASTM, BS, etc.) and against 100% opc mixes.

I believe that all cement companies in Thailand offer a "mixed" cement such as Siam City Cement Company's Insee Daeng.

I have an inquiry in to see if we can get a lime/OPC ratio for it. Again, it is fairly straight forward to make some sample blocks with various lime/cement ratios and do some compression tests on them. "The proof is in the pudding," as the Yankees say. It is not essential to know the lime/OPC ratio of the cement.