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Microsilica for mortar additive

Updated: 2026-07-24

Overview

Microsilica for mortar, commonly referred to as silica fume, is a byproduct of silicon and ferrosilicon alloy production. It consists of ultrafine particles of amorphous silicon dioxide (SiO2) and is widely used in construction materials due to its high reactivity and pozzolanic properties. When added to mortar or concrete, microsilica fills the voids between cement particles, resulting in a denser and more durable matrix. This material is particularly valued in high-performance concrete applications where enhanced strength and reduced permeability are critical.

Physical and Chemical Properties

Microsilica is characterized by its extremely fine particle size, typically less than 1 micron, and a high surface area ranging from 15,000 to 30,000 m²/kg. Its amorphous structure contributes to its high reactivity with calcium hydroxide in cement, forming additional calcium silicate hydrate (C-S-H) gel. The material is chemically stable but can pose health risks if inhaled due to its fine particulate nature. It is insoluble in water and has a low bulk density, often requiring densification for efficient handling and transportation.

Main Applications

The primary use of microsilica is in the construction industry, where it serves as a supplementary cementitious material (SCM) in high-strength concrete, shotcrete, and precast products. It significantly improves compressive strength, abrasion resistance, and chloride penetration resistance. Beyond construction, microsilica finds applications in refractory materials, oil well cementing, and even as a filler in polymers and ceramics. Its ability to enhance material properties makes it a versatile additive in various industrial processes.

Safety and Storage

Proper handling of microsilica is essential due to its fine particulate nature, which can cause respiratory irritation if inhaled. Workers should use NIOSH-approved dust masks, gloves, and eye protection when handling the material. Storage should be in sealed containers or bags in a dry, well-ventilated area to prevent moisture absorption, which can reduce its effectiveness. The material is non-combustible but may generate dust clouds that could pose explosion hazards in confined spaces.

B2B Procurement Guide

When procuring microsilica for mortar applications, buyers should prioritize suppliers who can provide consistent quality with SiO2 content typically exceeding 85%. Particle size distribution and loss on ignition (LOI) are critical quality indicators that should be verified through certificates of analysis. Bulk purchasing often provides cost advantages, but transportation logistics should be considered due to the material's low bulk density. Establishing long-term relationships with reliable suppliers can ensure stable pricing and consistent quality for ongoing construction projects.

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