Abstract
This paper systematically studied the modification of cement-based materials by nano-SiO2 particles with an average diameter of about 20 nm. In order to obtain the effect of nano-SiO2 particles on the mechanical properties, hydration, and pore structure of cement-based materials, adding 1%, 3%, and 5% content of nano-SiO2 in cement paste, respectively. The results showed that the reaction of nano-SiO2 particles with Ca(OH)2 (crystal powder) started within 1 h, and formed C–S–H gel. The reaction speed was faster after aging for three days. The mechanical properties of cement-based materials were improved with the addition of 3% nano-SiO2, and the early strength enhancement of test pieces was obvious. Three-day compressive strength increased 33.2%, and 28-day compressive strength increased 18.5%. The exothermic peak of hydration heat of cement increased significantly after the addition of nano-SiO2. Appearance time of the exothermic peak was advanced and the total heat release increased. Thermogravimetric-differential scanning calorimetry (TG-DSC) analysis showed that nano-SiO2 promoted the formation of C–S–H gel. The results of mercury intrusion porosimetry (MIP) showed that the total porosity of cement paste with 3% nano-SiO2 was reduced by 5.51% and 5.4% at three days and 28 days, respectively, compared with the pure cement paste. At the same time, the pore structure of cement paste was optimized, and much-detrimental pores and detrimental pores decreased, while less harmful pores and innocuous pores increased.
Highlights
Cement-based materials are widely used as building materials around the world
It was reported that nano-SiO2 can promote the hydration of cement and generated more C–S–H gel [16,17]
In order to define the microstructure of the reaction product produced by nano-SiO2 and Ca(OH)[2], the corresponding scanning electron microscopic (SEM) images of the products were investigated
Summary
Cement-based materials are widely used as building materials around the world. With the development of cement-based materials, its performance is becoming more and more important in modern construction. Nanomaterials are functional materials with many excellent properties, such as size effects, quantum effects, surface effects, and interfacial effects [3]. These properties can enhance the physical and chemical properties of cement, and open up new areas for cement research. Some researchers used nanomaterial as an additive added into cement-based materials, and have obtained some remarkable results. Many nanomaterials, such as nano-TiO2 [4–8], nano-CaCO3 [9,10], nano-Al2O3 [11–13], and carbon nano-tubes [14] have been added in cement-based materials to improve various properties of cement. Researchers have done much work on the influence of nano-SiO2 on the hydration and mechanical properties of cement. Particle Size nm 15 nm 15 nm 15 + 5 nm 30 nm 50 nm 80 nm 30–100 nm 120 nm Concentration
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