Abstract
The present work was accomplished to investigate silica fume (SF) and nano silica (NS) effects on the compressive strength (fcu28) of concrete made by cement contents (CC) of 300, 400, 500 and 600 kg/m3. Two NS types having purity of 89% (Type I) and 99% (Type II) were partially replaced CC by the percentages of 1.5% and 3%. The influence of replacing cement by 5% and 10% SF was also studied. Nano silica was mixed by two techniques, mechanically and by ultrasonic device. The influence of SF, NS and CC on fcu28 and water absorption (WA) was found. The obtained results indicated that fcu28 increased and WA% reduced by replacing part of CC by either NS or SF. For both of NS types, the enhancement ratio in fcu28 was higher when replacing cement by 1.5% NS compared to replacement ratio of 3% and both ratios recorded greater values of compressive strength when compared to that without NS. At 1.5% NS ratio, fcu28 increased by about 14.81% for type I and by 41.33 for type II while at 3% NS, the enhancement ratios were 5.86% for type I and 35.46 for type II respectively. Mixing Type I NS by ultrasonic mixing method recorded higher values for fcu28 as compared to those recorded by the mechanical method.
Highlights
Concrete is considered the most familiar construction materials around the world
The legend of specimen refers to content of CM (3 for 300 kg/m3 and 4 for 400 kg/m3 and so) followed by nano silica (NS) percent (N-%) silica fume (SF) percent (S-%) and in ultrasonic method the samples names tailed by letter (U)
As NS percentage increases, the superplasticizer dosage was increased to regulate the slump of mixture
Summary
Concrete is considered the most familiar construction materials around the world. The recent advance in concrete industry is to reduce cement content by using supplementary cementitious materials (SCMs). The obtained results indicated that, for basalt fiber specimens containing 0%, 1%, 1.5%, adding 5% SF leads to increase the compressive strength up to 23%, 37% and 12%, respectively. The test results reported in [15] indicated that the replacement of cement by 0.5% NS and 0.75% NS increased the compressive strength by 14.2% and 20.5% for 7 days, 8.7% and 24.4% for 28 days and 8% and 18.1% for 90 days respectively over that of the control mix. The influence of NS on the concrete strengths tested at 7, 28 and 90 days was discussed [17, 18] In these works, cement content was partially substituted with 0%, 0.5%, 1%, 1.5% and 2% NS. In This paper is aimed to evaluate the concrete properties casted with different cement contents incorporating SCMs in micro scale and nano-scale. The influence of SF, NS and CC on water absorption (WA) was found
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