Effect of mixing methods of nano silica on properties of recycled aggregate concrete

Abstract

The effect of presoaking of recycled coarse aggregate (RCA) in nano silica (NS) solution on the properties of recycled aggregates concrete is compared with the direct mixing of NS in concrete. In this study, four series of concrete are considered. The first and second series are control series containing 100% natural coarse aggregate (NCA) and 100% RCA, respectively. The third and fourth series are similar to the second series in every aspect except that 2 wt% NS is added through direct mixing in concrete and presoaking of RCA in 2 wt% NS solution of 24 hr, respectively. Results show that the measured 28-day compressive strength of recycled aggregate concrete containing presoaked RCA is higher than that containing direct mixing of NS in concrete. The volume of permeable voids, water sorptivity, and chloride ion penetration measured after 28 days curing is also reduced in recycled aggregate concrete containing presoaked RCA in NS solution than that containing direct mixing of NS in concrete. The total porosity of mortar adjacent to presoaked RCA is also found to be significantly lower than the same, where NS is mixed directly. The concentration of pores in the matrix adjacent to presoaked RCA is also shifted to medium capillary pores from the large capillary pores of matrix adjacent to RCA containing no NS. The volume of medium capillary pores reduced significantly in the matrix adjacent to presoaked RCA compared to the same, where NS is mixed directly. The scanning electron microscopic image analysis also supports this observation.

Evaluation of microcracks in the interfacial transition zone of recycled rubber concrete

“…Furthermore, concrete durability is affected by the high water absorption of RAC and the porous mortar adhering to the surface . To determine the advantages of recycled concrete, experts and scholars have enhance the performance of RCA through extensively studied treatment methods, such as CO 2 treatment, improvement of mixing technology and addition of admixtures (fly ash, silica fume, nano silica, and glass powder) …”

Dispersion characteristics of various contents of nano‐TiO2 and its effect on the properties of cement‐based composite

“…The cement paste, mainly the amorphous calcium silicate hydrate (CSH), is the continuous matrix that binds other ingredients together and dominates the properties of concrete . Viewed from the bottom‐up, CSH consists of extremely fine particles in the nanoscale size range, these particles form a poorly ordered structure through weak hydrogen bonding with water and strong siloxane linkage . Hence, using nanotechnology in concrete to manipulate the structure at the nanoscale to get a macroscale superior property is getting increasing attention .…”

“…[4][5][6] Viewed from the bottom-up, C S H consists of extremely fine particles in the nanoscale size range, these particles form a poorly ordered structure through weak hydrogen bonding with water and strong siloxane linkage. [7][8][9] Hence, using nanotechnology in concrete to manipulate the structure at the nanoscale to get a macroscale superior property is getting increasing attention. 8 Remarkable improvement in the comprehensive properties of concrete, involving the mechanical properties and durability, has been realized by incorporating nanomaterials into concrete.…”

“…[7][8][9] Hence, using nanotechnology in concrete to manipulate the structure at the nanoscale to get a macroscale superior property is getting increasing attention. 8 Remarkable improvement in the comprehensive properties of concrete, involving the mechanical properties and durability, has been realized by incorporating nanomaterials into concrete. [10][11][12] One type of the widely used nanomaterials in cementbased composites is nanoscale fibers.…”

Vibration analysis of silica nanoparticle‐reinforced concrete pipes filled with compressible fluid surrounded by soil foundation

“…Moradi‐Dastjerdi reported wave propagation in the nanocomposite cylinders that reinforced by straight, single‐walled, carbon nanotubes based on a mesh‐free method. The effect of pre‐soaking of recycled coarse aggregate in nano silica (NS) solution on the properties of recycled aggregates concrete was compared by Shaikh et al with the direct mixing of NS in concrete.…”