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CQJSJ

Introduction
 CQJSJ, a powder material, is a strength-enhancing shrinkage-reducing additive for Portland cement mortar and concrete, particularly precast concrete. CQJSJ contains calcium sulfoaluminate as main component and other activating minerals. CQJSJ accelerates the hydration of Portland cement and alters the morphology and microstructure of hydration products, resulting in the following improved properties of mortar and concrete:
• High early age strength, reduce curing duration and/or lower curing temperature
• High final strength, 28d compressive strength enhanced by 5%-30%
• Low shrinkage and reduced cracking
• Low permeability
• Good sulfate resistance
Properties
Physical properties
 
Fineness (Blaine) 5000‒5500cm2/g
Specific density 2.90‒2.95g/cm3

Shrinkage

Mixtue Shrinkage ratio
100%OPC 100%
85%OPC+15%CQJSJ 86.7%
80%OPC+20%CQJSJ 65.3%
 
 
Strength at room temperature (w/b ratio of 0.5)
 
Mixture Compressive strength ratio
1d 28d
100%OPC 100% 100%
85%OPC+15%CQJSJ 115.2% 108.7%
80%OPC+20%CQJSJ 121.8% 117.3%

 

Strength after steam curing (w/b ratio of 0.5)

Mixture Flex./compr. strength (MPa)
Curing 1# Curing 2# Curing 3#
100%OPC 0.1/0.8 1.4/5.1 2.7/6.9
85%OPC+15%CQJSJ 0.5/2.6 2.5/8.8 4.0/14.2
80%OPC+20%CQJSJ 1.5/5.3 2.7/9.3 4.2/16.2
#Steam curing scheme 1 (4h40min): i) 20°C for 40min, ii) 55°C for 2.5h, iii) within 1.5h from 55°C to 20°C;
#Steam curing scheme 2 (5h40min): i) 20°C for 40min, ii) 55°C for 3.5h, iii) within 1.5h from 55°C to 20°C;
#Steam curing scheme 3 (6h40min): i) 20°C for 40min, ii) 55°C for 4.5h, iii) within 1.5h from 55°C to 20°C.
 

 
  • Application
    Steam curing free for precast concrete
    Reference mix proportion (kg/m3)
    OPC CQJSJ Sand Gravel w/b SP
    360 60 823 974 0.33 7

    Compressive strength (MPa) cured under 20°C

    8h 7d 28d
    25.3 46.2 50.4
     
    Reduced steam curing time
    Reference mix proportion (kg/m3)
    OPC Fly ash GGBFS CQJSJ Sand Gravel w/b SP
    300 47 40 73 662 1183 0.3 6.9

    Compressive strength (MPa) cured under the following scheme: i) 20°C for 40min, ii) within 1h from 20°C to 55°C, iii) 55°C for 2h30min, iv) within 1h from 55°C to 20°C.

    4h10min 7d 28d
    24.3 54.2
    58.4
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