DSP with Rutile Substituting for Microsilica
- PDF / 669,394 Bytes
- 6 Pages / 420.48 x 639 pts Page_size
- 107 Downloads / 179 Views
DSP WITH RUTILE SUBSTITUTING FOR MICROSILICA LAURENCE. P. ALDRIDGE, ROSS J. CAMPBELL AND DAVID J. CASSIDY Australian Nuclear Science and Technology Organisation (ANSTO), Private Mail Bag 1, Menai, NSW 2234, AUSTRALIA. ABSTRACT DSP is made from heavily superplasticized cement combined with microsilica and relatively small amounts of water. In this paper it is shown that substitution of fine-grained rutile for microsilica results in a workable DSP mix. A comparison of the TGAs, XRDs, SEMs, mercury intrusion porosimetry, and compressive strengths between the two DSP preparations is reported. The results indicate that the DSP made with rutile has very similar properties to DSP made with microsilica. INTRODUCTION Bache [1] first introduced the novel Densified by Small Particles (DSP) cementitious systems where high compressive strengths were achieved from portland cement mixes containing relatively low water contents[2]. These mixes are workable only because of the presence of microsilica (a by-product of the silicon industry) and high doses of a superplasticizer. In some preliminary work we were unable to make DSP mixes with densified microsilica that was locally available. No matter how long the mixing time the mix remained as a slightly damp powder. We believe that this problem occurred because the densified microsilica would not de-agglomerate from its greater than 100 pm size. It was only possible to make DSP mixes of a water powder ratio' less then 0.20 with densified commercial microsilica obtained from ELKEM in Norway if the microsilica was pre-treated - for example by ball milling for 24 hours. This mix has a high water content for DSP - Hjorth [2] states that DSP mixes generally have water powder ratios between 0.12 and 0.22. Rutile of particle sizes about 0.1 pm is commonly dispersed in water and several trials were carried out to find if rutile could be used as a substitute for microsilica in DSP. In this paper we have used identical mixing procedures to make matched rutile based DSP and microsilica based DSP and compared and contrasted the properties of the mixes. In addition to DSP mixes made with sand additional sand-free mixes were made so that the cement / powder interactions could be more easily examined by Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), mercury intrusion porosimetry, Transmission Electron Microscope (TEM), and Thermal Gravimetric Analysis (TGA). The role of microsilica in DSP is thought to be that of, a micro-filler governing the packing between the cement grains, and also as a chemical reactant forming hydration products similar to those found in ordinary cement paste[2]. It is of some interest to examine the effects of replacir g the microsilica with a less reactive material such as rutile and see how this effects the properties of the DSP.
"the
water/powder ratio is defined to be the ratio of the weight of water to the weight of the cement and microsilica. Mat. Res. Soc. Symp. Proc. Vol. 245. @1992 Materials Research Society
224
EXPERIMENTAL DSP Preparation Four s
Data Loading...
