IMPROVEMENT OF CONCRETE DURABILITY BY COMPLEX MINERAL SUPER-FINE POWDER

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Introduction
Coal gangue is a rock included in the coal bed and a waste discharged during coal
mining and transportation as well as the most industrial waste discharged in China. It
is estimated [1, 2], that the amount of gangue calculated as 15% of the coal output,
there would be 100 million ton increment annually. Most of the coal gangue is a clay
rock; its main mineral composition consists of clay mineral, followed by primary
mineral quartz, feldspar, mica and pyrite, carbonate. After calcination under high
temperature of 700-900°, the clay mineral is dewatered and disintegrated, the carbon

Raw materials
2.1.1 Cement
In the tests the PO425 cement manufactured by Chongqing Tenghui Diwei Cement
Plant was applied with specific surface 3300 cm2/g.

2.1.2 Coal gangue
The coal gangue is from the Huaying Mountain mine and treated by calcinations and
grinding;



2.1.4 Fly ash
The fly ash is a dry one from the Chongqing Jiulongpo Electric Power Plant; its
properties conform to the Chinese Standard GB1596-91, “Fly ash for cement and
concrete,” as standard class II.

2.1.5 Fine aggregate
Medium size sand from Sichuan Jianyang with a modulus of fineness Mx = 2.32;
normal grading with the silt content 0.8%.

2.1.6 Coarse aggregate
Crushed limestone is from Xiaoquan, Chongqing City with a size of 5-20 mm and
normal continuous grading. The content of flaky and elongated particles is <3% and
the crushing index ≤6%.

2.1.7 Admixture
A complex retarding super-plasticizer FDN with slight air entraining, water reduction
rate 23% and other properties conforming to the requirements for first class one in
Chinese standard “Admixtures for concrete” (GB8076-2000), the dosage of the
admixture is 1.2%.