Cementitious binders, activators and methods for making concrete
A cementitious binder comprises at least 90% by weight of a hydraulically-active material comprising ground granulated blast furnace slag (GGBS) and/or pulverised fuel ash (PFA), and at least 0.1% by weight of CaO in an activator composition for the hydraulically-active material. The cementitious binder does not comprise any Portland cement and is, therefore, more environmentally friendly. The binder further comprises a superplasticiser such as a polycarboxylate ether (PCE). A concrete, mortar, grout, screed or render may be formed from a mixture of the cementitious binder, aggregate particles, water and superplasticiser.
1. A cementitious binder consisting of at least 90% by weight of a non-Ordinary Portland Cement (non-OPC) pozzolanic hydraulically-active material comprising ground granulated blast furnace slag (GGBS), pulverised fuel ash (PFA) or a mixture of GGBS and PFA, at least 0.1% and less than 9.5% by weight of an activator, which is CaO or lime, and a superplasticiser.
2. A cementitious binder according to claim 1 , in which the superplasticiser is a polycarboxylate-ether-based (PCE) superplasticiser.
3. A cementitious binder according to claim 1 , which consists of GGBS, PFA or the mixture of GGBS and PFA, the CaO or lime and the superplasticiser.
4. A cementitious binder according to claim 1 , comprising at least 1 wt % CaO or lime.
5. A cementitious binder according to claim 1 , comprising greater than 93% by weight hydraulically-active material.
6. A cementitious binder according to claim 1 , comprising between 0.2% and 2% by weight superplasticiser.
7. A cementitious binder according to claim 1 , in which the superplasticiser is in powder form and the binder comprises more than 0.3% by weight and 1.2% by weight superplasticiser.
8. A cementitious binder according to claim 1 , in which the superplasticiser is in liquid form and the binder comprises more than 0.2% by weight and less than 2% by weight superplasticiser.
9. A concrete, mortar, grout or render comprising a cementitious binder as defined in claim 1 .
10. A concrete, mortar, grout, or render according to claim 9 , in which the weight ratio of water to binder is between 0.2:1 and 0.4:1.
11. A concrete, mortar, grout or render according to claim 9 , which has a compressive strength of greater than 15 MPa after 7 days, and greater than 20 MPa after 14 days, and greater than 30 MPa after 28 days.
12. A cementitious binder comprising;
between 94 and 97% by weight of a hydraulically-active material comprising ground granulated blast furnace slag (GGBS), pulverised fuel ash (PFA), or a mixture of GGBS and PFA;
between 1.5% and 3.5% by weight CaO or lime; and
between 0.2% and 2% by weight superplasticiser.
13. A cementitious binder according to claim 12 , comprising between 1-2.5 wt % microsilica and/or PFA.
14. A concrete, mortar, grout or render comprising a cementitious binder according to claim 12 .
15. A cementitious binder according to claim 12 , in which the superplasticiser is a polycarboxylate-ether-based (PCE) superplasticiser.