Study on the ability of nano-dispersion of Silica in superplasticizer and water additive system

Currently, the mineral silica fume admixture is commonly used in concrete to improve the properties of concrete and cured concrete mixes. With the development of technology, nano Silica (nS) is researched, fabricated and applied. In fact, several studies have shown a marked improvement in the properties of concrete using nS. However, the efficiency of using nS depends greatly on the dispersion of nS because the ultrafine nS particles have a large surface energy and it is easy to agglomerate to create particles with larger sizes. reduces the beneficial effects of using nS. To overcome this phenomenon, it is possible to study the dispersion of nS in the water system and superplasticizer (PGSD).
1. Introduction

Nano silica (nS) are amorphous SiO2 particles with porous structure with specific surface area of ​​about 283mg and mean capillary radius of 50 A° (MCM-41 form). Nano silica is widely used in practice as adsorbents, catalyst carriers and catalysts. nS can be prepared by different methods such as reaction between alkali silicates with acids or acidic salts. nS is usually prepared from liquid glass and sulfuric acid. The silicon oxide used as the substrate is amorphous SiO2 synthesized by the Sol-Gel method, so it has a relatively large surface area. This is a simple and economical method [1,2,7].

Currently SiO2 is used in industries to improve the surface and other mechanical properties of materials. It is used as a filler, additive, and viscosity modifier of products such as paints and coatings, plastics, neoprene, adhesives, waterproofing agents, or insulation materials. Specifically, amorphous silicon dioxide (smoke silica) at microscopic size (such as silica fume with an average particle size of about 0.15 m) has been used as a mineral additive to improve the properties of concrete mixes. and cured concrete [3].

With the development of technology, nano Silica has been researched, manufactured and applied. In fact, some studies have shown a marked improvement in the properties of concrete when using nS [4-6]. However, the efficiency of using nS depends greatly on the dispersion of nS, because the ultrafine nS particles have a large surface energy, so it is easy to agglomerate to create larger particles with larger sizes. , thereby reducing the beneficial interactions of nS particles in concrete.

To overcome this phenomenon, it is possible to study to improve the dispersion of nS in the superplasticizer system (PGSD) and water. There are actually many types of PGSD, usually polymers with high molecular weight that can be synthesized or are available in nature, such as superplasticizers Melamine Formaldehyde Sulfonate, Naphthalene Formaldehyde Sulfonate, Polycarboxylate (PC) based superplasticizers. . New generation superplasticizers based on Polycarboxylate containing negatively charged COO functional group. Thus, it is possible to create a good dispersion for positively charged nS particles with electrostatic interaction mechanism. This is also the goal of the article.
The research results on the dispersion ability of nS presented in the article are based on the conductivity, viscosity and images observed under the transmission electron microscope TEM for PGSD and water systems with the participation. nS’s family.

2. Materials, equipment and research methods

2.1 Research materials and equipment

a) Research materials: Some materials used for research include superplasticizer (PGSD) ACE 388 SureTec (based on Polycarboxylate Ether- PCE with 60% dry content), Silica nanomaterial with size 15 nm with an area ratio of about 170mg.

b) Research equipment: The equipment used in the research includes: Mechanical stirrer, conductivity meter, OAKTON CON 510; Viscometer, SV 10:0.3 mPa.s-10,000 mPa.s; Microscope, MOTIC B1-220; Analytical balance, JJ300; Transmission electron microscopy; Drying cabinet and some tools and some other equipment.

2.2 Research Methods

In the study, non-standard physico-chemical analysis methods were used to measure conductivity, viscosity… combined with modern analytical methods such as observation by optical microscope, electric microscope. transmission electron (TEM)… Based on the results of the study, the interaction mechanism of nS particles in the PGSD system and water has been proposed.
2.3 Experimental procedure
The experimental procedure is shown in Figure 1. The amount of PGSD and water are calculated according to the given ratios (by mass) with a total mass kept constant of 200g, then stirred at a speed of 6000 rpm/ min and slowly add a predetermined amount of nS to the system. Continue stirring until the dispersion is uniform, then measure the conductivity, viscosity and microscope of the product sample.

3. Results and discussion

3.1 Effect of nS on conductivity of PGSD and Water (N) systems

The author has investigated the dispersion of nS in the system containing PGSD and N with the ratio PGSD/N (calculated by mass) varying by the ratios of 1/1; 1/3; 1/5; 1/8; 1/10; 1/12; 1/15; 1/17. The effect of nS with different concentrations on the conductivity of the system (PGSD + N) with different PGSD/N (PGSD/N) ratios is shown in Fig.

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