Construction World October 2018

READYMIX

SELF-COMPACTING CONCRETE'S RELIABLE PARTNER Readymix concrete applications have been considerably enhanced since the introduction of self compacting concrete (SCC) technology to South Africa in the early 2000s, with its remarkable ability to flow into complex shapes and penetrate inaccessible spots – while still achieving high strengths and superior surface finishes.

S CC can flow under its own weight and completely fill space within formwork. It achieves this without any vibration, while retaining its homogeneity. This makes is particularly useful where there is highly congested reinforcement, narrower concrete sections complex geometrical shapes or where it is not possible to gain access with a vibrator. It is also a good option wherever low noise levels are imposed on a project. Making this all possible are the new generation CHRYSO ® Superplasticisers, which are formulated for use in both the readymix and precast industries. Geared specifically for SCC applications in readymix is the CHRYSO ® Fluid Optima range of super- plasticers, designed through a unique and patented phosphonate technology. This range assists in producing cohe- sive/mobile concrete, with the correct blend of fill free and thixotropic properties and is compatible with the majority of cement types. This ensures a mix design that is robust, non-sensitive and easily implement- ed. CHRYSO ® Fluid Optima 100 is a good example of a robust admixture, in terms of a wide range of dosage being possible,

allowing the production of SCC which is not water-sensitive. As a world leader in concrete admixtures and solutions, CHRYSO is well equipped and experienced in matching superplasticers with cement chemistry. After evaluating the cement, CHRYSO will choose the correct superplasticers within the CHRYSO ® Fluid Optima/Premia range. By finding the best cement-admixture compatibility, CHRYSO can optimise the dosage of the superplas- ticers for cost purposes. CHRYSO can also help customers to address a challenge with regard to SCC, in that South Africa typically uses dry batch plants. This provides little room for error as the mix design must be correct the first time around, making it vital to receive the correct technical advice. With its extensive technical skills, knowledge and experience, CHRYSO can evaluate a customer’s raw materials, select the appropriate admixtures and optimise the mix design to meet specific requirements. So successful have CHRYSO’s solutions with SCC been, that they have been used in landmark projects both locally and abroad.

Testing CHRYSO's Fill Free technology at CHRYO's Sermaises Research Centre in France.

Here in South Africa, they have been applied in the Soccer City Stadium, the Nelson Man- dela Bridge and N14 Bridge in Muldersdrift. Among the international sites where CHRY- SO has been involved, are three important French projects: the CMA-CGM Towers in Marseilles, a waste water treatment plant in Le Havre and at the famous Roland Garros tennis stadium. Other products from CHRYSO that are applied in SCC applications are CHRYSO ® Quad 20, a viscosity modifying enhancer that promotes robustness and cohesion and prevents bleed and segregation. Due to the high fines contents of many SCC’s, it is important to reduce stickiness, CHRYSO’s fill free technology present in many of its admixtures, assists in achieving this. Pro- tection of an SCC during the plastic phase is vitally important, in terms of reducing shrinkage cracking potential. CHRYSO ® Profilm 19, an evaporation retarder, achieves this goal. The CHRYSO ® Cure range assists with the vitally important curing process, carried out after final surface finishing, ensuring adequate protection of SCC during the hardening stage. The CHRYSO ® Fluid Premia range of superplasticers is also available for the application of SCC in the precast industry, offering workability retention between 30 and 45 minutes. It assists in enabling a comparatively early stripping time and creat- ing a high quality finish – reducing surface defects and the need for concrete repairs.  FAR LEFT: Testing underway on self-compacting concrete which contains CHRYSO admixtures. LEFT TOP: Testing is used to demonstrate the difference between SCC containing CHRYSO's Fill Free technology and one which does not. LEFT BOTTOM: Precast culverts manufactured using CHRYSO admixtures.

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CONSTRUCTION WORLD OCTOBER 2018