Physico-mechanical properties of high performance concrete using different aggregates in presence of silica fume

Abstract

Heavy weight high performance concrete (HPC) can be used when particular properties, such as high strength and good radiation shielding are required. Such concrete, using ilmenite and hematite coarse aggregates can significantly have higher specific gravities than those of concrete made with dolomite and air-cooled slag aggregates. Four different concrete mixes with the same cement content and different w/c ratios were designed using normal dolomite aggregate, air-cooled slag by-product and two different types of iron ore aggregates. High performance concrete (grade-M60) can be achieved using superplasticizer to reduce the water/cement ratio; the effect of SF on the performance of concrete was studied by addition of 10% silica fume to the total cement content. The physico-mechanical properties of coarse aggregates and hardened concrete were studied. The results show that, Ilmenite coarse aggregate gives higher physical and mechanical properties than the other aggregates. Also, addition of 10% silica fume developed a stronger and a denser interfacial transition zone (ITZ) between concrete particles and the cement matrix. Crushed air-cooled slag can be used to produce a high-strength concrete with better mechanical properties than corresponding concrete made with crushed hematite and ilmenite. Heavy density concrete made with fine aggregates of ilmenite and air-cooled slag are expected to be suitable as shielding materials to attenuate gamma rays.

Assessment of compacted-cementitious composites as porous restrictors for aerostatic bearings

“…The X-ray diffraction (XRD) patterns of cementitious composites made with silica and silicon carbide are shown in Figure 2. The patterns for all cementitious composites show the presence of hydrated cement products, such as: Portlandite (p, Ca(OH) 2 ) with the main peaks at 2θ 17.97°, 28.75° and 34.13° (PDF #44-1481 and literature 34 ), Calcium silicate hydrate (CSH) peak at 2θ 29.4° (PDF #33-306 and literature 34 ), Calcite (C, CaCO 3 ) with peaks at 2θ 23.07°, 29.43°, 39.44° and 47.15° (PDF #5-586 and 28 34 ). In addition, it can be observed the presence of unhydrated products such as: Alite (a, C 3 S) (PDF #49-442 34 ), Larnite (L, β-C 2 S) (PDF #33-302 34 ).

Figure 2.XRD patterns of cementitious composites reinforced with silica (a) and silicon carbide (b).

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“…. 34 ) is observed for silica cementitious composites (C1 to C4) (see Figure 2(a)), and for silicon carbide (SiC) (main peaks at, PDF #49-1428, #49-1431) cementitious composites (C5 to C8) ( Figure 2(b)). Due to the amorphous morphology of resin-coated CMF (C9 to C12), only sharp Bragg peaks for portlandite are shown, which preclude a more detailed analysis for the others cementitious phases.…”

“…Calcium silicate hydrate (CSH) peak at 2y 29.4 (PDF #33-306 and literature 34 ), . Calcite (C, CaCO 3 ) with peaks at 2y 23.07 , 29.43 , 39.44 and 47.15 (PDF #5-586 and 2834 ). .…”

Influence of Local Sand on the Physicomechanical Comportment and Durability of High Performance Concrete

“…This is due to the difference of the density and the porosity between the different fine aggregates used (angular crushed, round dune sand, and fillers). In fact, the porosity (voids and pores) is influenced by the padding characteristics of the full mixture that includes fine aggregates, cement, and water [31]. 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1Time ( √ h) Figure 7: Absorption coefficients by capillarity of HPC.…”

“…Long ripening (one year) can further split the capillary pore network. We can significantly reduce the diffusion coefficient in maintaining longer favorable curing conditions (effect of water/binder ratio and the ripening on the diffusion coefficient of chlorine ions) [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36].…”