Product Overview

MC-Crete 720 is a pre-dispersed silica fume (microsilica / condensed silica fume / CSF) slurry admixture from MC-Bauchemie supplied as a stable aqueous suspension of amorphous silicon dioxide particles with median particle diameter of approximately 0.1 to 0.15 microns — approximately 100 times finer than ordinary Portland cement (OPC) particles. The ultra-fine amorphous silica particles react with the calcium hydroxide (portlandite, Ca(OH)2) released during cement hydration through the pozzolanic reaction — SiO2 + Ca(OH)2 → C-S-H gel — converting the relatively soluble, weak portlandite crystals present in the concrete paste into additional calcium silicate hydrate (C-S-H) gel, which is the principal strength-giving and low-permeability phase in cement paste. This secondary pozzolanic C-S-H formation: (i) significantly refines the pore structure of the hardened concrete paste, producing a finer, more tortuous pore network that dramatically reduces water permeability and chloride diffusion coefficient; (ii) improves compressive strength by 15 to 30 percent compared to plain OPC concrete at equivalent water/cement ratio; (iii) eliminates the high-pH leachable Ca(OH)2 that is the primary phase attacked by sulphates (ettringite formation), soft water, and acid solutions — significantly improving chemical resistance; and (iv) reduces alkali-silica reaction (ASR) expansion by consuming the available alkalis in the pore solution before they can react with reactive silica aggregates. The slurry form of MC-Crete 720 is preferred over powder silica fume for concrete admixture use because it disperses uniformly in the mix water without the agglomeration and operator exposure (fine dust hazard) associated with powder silica fume addition — the slurry is added directly to the ready-mix truck or batching plant liquid admixture system without any dust generation or dispersion concerns. Space Arc Engineering supplies MC-Crete 720 for high-performance concrete production in metro rail, highway, marine, and industrial construction projects in Delhi NCR and Uttar Pradesh.

Applications

• Marine and coastal structures — bridge piers, jetties, seawalls, and port structures in high-chloride environments where the dramatically reduced chloride diffusion coefficient of silica fume concrete extends reinforcement protection life from 25 to 50 years or more versus normal concrete
• Bridge decks and piers in de-icing salt environments — NHAI and PWD bridges on mountain highways (Uttarakhand, Himachal Pradesh) where salt is used in winter and high-chloride environments accelerate reinforcement corrosion
• Parking structure decks and ramps — multi-storey parking structures in urban Delhi NCR where chloride-contaminated water runoff from vehicles causes aggressive deterioration of deck and ramp concrete
• Industrial chemical plant foundations and floor slabs — concrete foundations and slabs in contact with sulphate-rich soils (common in certain UP districts), acidic effluents, or industrial chemical environments
• High-rise and super-high-rise column concrete — using microsilica to achieve C60 to C80 grade concrete for slender high-rise columns where the reduced column cross-section demands maximum concrete strength
• Sewage treatment plant structures — concrete in contact with biogenic sulphuric acid (H2S oxidised by bacteria in sewers) where standard concrete deteriorates rapidly and microsilica-modified concrete has demonstrated a 5 to 10-fold improvement in acid resistance

Key Advantages

• Dramatic permeability reduction — chloride diffusion coefficient of silica fume concrete is 3 to 10 times lower than plain OPC concrete, fundamentally extending the chloride-induced corrosion initiation period in aggressive marine and chloride-rich environments
• Compressive strength enhancement — 15 to 30 percent increase in 28-day and 90-day compressive strength allows higher grade concrete at the same cement content, or equivalent strength at reduced cement content with cost savings
• Slurry form for uniform dispersion — pre-dispersed silica fume slurry eliminates agglomeration and dust hazards, ensuring uniform distribution through the concrete mix without dry-powder addition problems
• Sulphate and chemical resistance — pozzolanic consumption of Ca(OH)2 removes the primary phase attacked by sulphate, soft water, and mild acid solutions, extending service life of concrete in aggressive ground and chemical environments
• Alkali-silica reaction mitigation — silica fume is one of the most effective supplementary cementitious materials for controlling ASR expansion in concrete containing reactive aggregates
• Compatible with superplasticisers — MC-Crete 720 is used in combination with MC-Bauchemie PCE superplasticisers (Centrament Nano 500 or Centrament Flow 500) to achieve the required workability at the low water/binder ratio needed for high-performance concrete