With construction becoming increasingly competitive, ambitious and having to build in ever more aggressive conditions, for example in the Gulf states and the Middle/Far East countries, it is not surprising that design engineers are specifying higher performance concrete (HPC), particularly in term of workability, strength and/or durability. Indeed, the National and International Standards and Codes of Practice worldwide, reflect this, with their acceptance of a very big range of constituent materials for making structural concrete. Dirk India, which have successfully, and were the first to do so in India, developed a range of Pozzocrete products, such as P40, P60, P63, P83, for use, as a cement component, in normal concrete, have been developing Pozzocrete 100 (P 100), much finer than the other Pozzocrete products, with the aim to facilitate significant improvements in both the microstructure and binding capacity of concrete
The main mechanism in producing HPC, having high strength (HSC) or high durability (HDC) is through improving its;
1. Microstructure, to increase tortousity and thus reducing permeation. [minimising porosity]
2. Binding capacity, to reduce ingress of aggressive agents. [immobilising harmful species]
Amongst the materials considered for use in achieving HPC;
(i) Silica fume (SF), which, due to its ultra-fineness, is most effective in improving the
microstructure of concrete and thereby resulting in high strength and high durability concrete.
(ii) Processed Fly Ash (FA), such as Pozzocrete 60, which, due to its chemical composition, is
primarily most effective in improving the binding capacity of concrete for aggressive agents,
with some supplementary improvement, due to its pozzolanic nature, to the microstructure of
concrete.
The POZZOCRETE 100 product details can be downloaded using this link
Recently, P100 has been tested in two trials using Grade 70 concrete, produced at a building site. The reference mix contained 10% SF by mass of Portland cement (PC) and 27% of Pozzocrete 60. Two test mixes were prepared with Pozzocrete 100 (Mix 1 and 2). The first mix (Mix 1), with PC content increased by the amount that of SF in the reference mix, which was omitted from the Mix 1, and P60 replaced by P100 in exactly the same amount. In Mix 2, however, PC content was kept the same as in the SF concrete mix, but the aggregate grading was modified to maximise water reduction in the mix, at nearly 20%. The results showed that the performance of Pozzocrete 100 concrete, in terms of strength and durability, was significantly improved and for Mix 2 was similar to that of SF concrete, implying that P100 has potential for producing HPC concrete.
The main observations made during the trial and testing period were that, with the same superplastiser dosage used, Pozzocrete 100 concrete mixes, in comparison with Silica Fume concrete, were easier to work with in the fresh state, they developed higher (Mix 1, same total cement content) or similar (Mix 2, nearly 7 % less total cement content) strength at 1, 3, 7 and 28 days and that the Mix 2 had a similar resistance to chloride penetration. Additionally, P100 concrete can be up to 20% cheaper than SF concrete.
In conclusion, Pozzocrete 100 is proving to have potential for producing high performance concrete, similar to or better than Silica Fume concrete.