Study On The Performance And Micro-structure Of The Low Clinker Cementious Materials Used In Shaft Ling Concrete

The shaft lining concrete owned high strength and large volume. The cementitious materials used in the shaft ling concrete are made of high strength grade cement?52.5cement or above? and special additive for mine. The dosage of the cement is high?more than 400kg/m3 in per cubic concrete?. In recent years, the particles of cement is more finer and the surface area is more larger in grinding. It lead the higher hydration speed, the huger hydration heat, the higher rise temperature and larger temperature stress in the process of concrete casting.The shaft lining concrete owned higher early age strength contrast to the lower later age strength. The volume stability become poor and easy to crack which seriously affected the durability of the mine wall concrete and the normal use of the wall construction.In this paper, it monitored the temperature of the shaft lining concrete in the process of construction of the Mongolia mine and analyzed the failure mechanism of the shaft lining concrete in Huanghuai district. On the basis of the characteristics of the shaft lining concrete and the cementitious materials used, it put forward the technical route of "low specific surface area,low dosage of cement clinker, high specific surface area, high mineral mixture rate, the optimized content of SO₃ and integration of super plasticizer " to prepare the low clinker cementitious materials used in the shaft lining concrete. It studied the development of the mechanical properties and volume stability of the low clinker cementitious materials and the hardening body. The characteristics of hydration heat release, the adiabatic temperature rise and the relations of thermal—stress were studied. It optimized and established the calculation method of hydration heat quantity of the low clinker cementitious materials. It got the mathematical calculation results of the adiabatic temperature rise and the thermal stress of the shaft lining concrete combined with the test data based on the composition and the hydration heat release characteristics of the low clinker cementitious materials. The erosion resistance of the shaft lining concrete made by low clinker cementitious materials in the erosion environment were studied. It studied the microscopic pore structure characteristics and development by the mercury intrusion method and the low-temperature nitrogen adsorption method. It observed and analyzed the hydration morphology and products with XRD, TG-DTA and SEM.The main conclusions as flows:?1?It can get that the temperature high to 80? after the high strength and large volume shaft lining concrete pouring into mould in 24 hours. Too high temperature can produce great stress and impact the concrete volume stability severely. The shaft lining wall concrete was destroyed seriously in Huanghuai district of 30 years old. It suffered solubility corrosion and crystallization corrosion. The CH and AFt were depleted and C-S-H were broken down. The Glauber's slat and rock salt were generated. And the silicone without gel and CaCO₃ of poor crystallization were shaped on the surface of the concrete.?2?It prepared the low clinker cementitious materials by the technical route of "low specific surface area, low dosage of cement clinker, high specific surface area, high mineral mixture rate, the optimized content of SO₃ and integration of super plasticizer". The 90th minimum compressive strength can get 46MPa, the flexural strength get 7.6MPa of 40%clinker?specific surface area 310m²/kg?, 20% fly ash,20%slag power,20% limestone power and 1.3% super plastcizer. The 90th maximum compressive strength can get 63MPa, the flexural strength get 9.2MPa of 70% clinker,10% fly ash,20% slag power and 0.7% super plastcizer. The C30?C70 concrete of low clinker cementitious materials long term minimum compressive strength can get 36.9MPa,57.3MPa and 78.5MPa is superior to the traditional cement concrete. The strength of low clinker cementitious harden body can continued growing as the development of the age. The 180^th shrinkage rate low clinker cementitious materials mortar specimen is between 0.06?0.09%. The 3^nd non-contact shrinkage rate of the concrete is among 0.008?0.024% and the contact shrinkage rate is among 0.039?0.071%. It owned lower shrinkage rate. The cracking time and width were both later and smaller of the shaft lining concrete made of low clinker cementitious materials contrast to the same grade common cement concrete. The low clinker cementitious materials owned the more better volume stability.?3?The 72h fastest hydration heat release rapid was 5.07,4.77,3.80J/gh and the biggest amount hydration heat release was 210,181,155J/g of different kinds of low clinker cementitious materials which lower than the traditional shaft lining concrete cementitious materials which fastest hydration heat 10.04,7.82,9.70J/gh and hydration heat amount 293,256,259J/g. The 144h adiabatic temperature of the C30?C70 low clinker cementitious materials concrete were 46,51,58? which lower 1?6? than the traditional cement concrete. The relations of the thermal—stress showed that the C30?C70 low clinker cementitious materials concrete were 0.7?1.2MPa. It calculated the adiabatic rise temperature and the cracked thermal stress based on the method of the low clinker cementitious materials hydration heat calculation method. The results showed a good correlation with the experiment results.?4?The shaft ling concrete made of low clinker cementitious materials owned the better sulfate attack resistance, carbonation resistance and resistance to chloride ion permeability in the erosion environment.?5?The pore proportion of the pore diameter more than 200nm reduced significantly which decrease from 75% of 3^nd to 16% of 180^th and the pore proportion of pore diameter below 20nm increased greatly which grow from 8% of 3^nd to 25% of 180^th of the 180^th low clinker cementitious materials mortar. The average pore diameter reduced gradually as the growth of the age. It decreased from 18nm to 7?9nm from 3^nd to 180^th. The pore morphology is the kind of typical partition slot wool stoma. The porosity of the low clinker cementitious materials concrete was smaller and the pore size distribution more reasonable. The cumulative pore volume and pore area and average pore diameter were lower than the traditional cement concrete. The hydration products' interface structure were more compact and the C₂S?C₃S can be found in. The hydration was still ongoing. The C-S-H in the hydration products was ? type C-S-H and the Ca?OH?₂ decreased significantly.