The Effect of Slag and Limestone Filler on Resistivity, Sorptivity, and Permeability of Concrete with Low Paste Content
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The Effect of Slag and Limestone Filler on Resistivity, Sorptivity, and Permeability of Concrete with Low Paste Content Yury A. Villagrán Zaccardi1, Ángel A. Di Maio1, Roberto Romagnoli2 1 LEMIT and CONICET, 52 entre 121 y 122, 1900 La Plata, Argentina 2 CIDEPINT and CONICET, 52 entre 121 y 122, 1900 La Plata, Argentina ABSTRACT This paper deals with several concrete properties and to what extent they are influenced by slag and limestone filler, either one or both of them are included. Concrete was designed for low paste content, this is, a water reducing admixture (WR) was used to limit mixing water content. The results are compared with concrete made with commercial composite cement, blended during milling. Concrete was tested for compressive strength, sorptivity, resistivity, and water penetration under pressure. The volume of paste in all concrete mixes was the same. Results showed the effect of slag on concrete transport properties. The effect of limestone filler was minimal either admixed solely or in conjunction with slag. On the other hand, blended cement appeared to be less effective on improving concrete transport properties. Compressive strength was less affected than transport properties by slag inclusion.
INTRODUCTION Transport properties of concrete are usually related to the water/binder ratio (w/b). However, paste content may be reduced by lowering mixing water content with the use of water reducers (WRs). Transport properties are thus diminished, as paste is usually more porous than aggregate. Different supplementary cementitious materials (SCM) affect transport properties differently. Slag (E) reacts with calcium hydroxide and forms CSH, but limestone filler (F) offers mostly physical action. Though SCMs may be included directly to the concrete mix, commercial blended Portland cement (BPC) includes specific additives that affect the action of SCMs. The inclusion mode may lead to some disparities on their effect. When finely ground slag (E) is added to Portland cement, the influence on concrete strength is minimal, medium, and evident, at ages of 0-3days, 3-14d, and >14d, respectively [1]. E Slag is a pozzolanic latent hydraulic SCM, and time evolution of concrete properties is more evident if concrete contains E slag than if it is made only with Ordinary Portland Cement (OPC) [2]. In contrast, high percentage replacement of clinker by limestone filler (F) may result in reduction of strength and durability properties [1], since it is an SCM that does not produce significant extra hydration products. Though, early strength is generally increased because of interaction between F and clinker. A main effect of F is the supplement in the granulometry of cement. It increases the finer fraction without increments in the water demand. Other simultaneous effects include calcium carboaluminate formation, accelerated C3S hydration, and modifications in the Ca/Si relationship in CSH gel. Another effect associated with the use of F is the attenuation of the sensibility of cement to curing treatment, due to a hi
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