Difference between medium heat cement and ordinary cement

Performance comparison of ordinary cement, medium heat cement and low heat cement (1) Comparison of hydration heat and low adiabatic temperature rise (measured) From the data in the table, it can be seen that the hydration heat of low heat cement is the lowest, but there is little difference between medium heat cement and ordinary cement. The adiabatic temperature rise of low-heat cement dam concrete is much lower than that of medium-heat cement dam concrete and ordinary cement dam concrete, and the reduction range is 5 ~ 10℃, which is very beneficial to reduce the temperature stress and temperature crack of mass concrete. The average adiabatic temperature rise of low-heat cement concrete poured by the company in Xiangjiaba and Xiluodu is 7℃ lower than that of medium-heat cement concrete. (2) Anti-drying shrinkage: The hydration slurry of low-heat cement has fewer pores that affect the drying shrinkage, and its internal structure is compact, so it has good anti-drying shrinkage performance of concrete, and the drying shrinkage rate of each age is 50-70% of that of ordinary portland cement. (3) Super Sulfate Corrosion Resistance According to the test of China Institute of Building Materials, the corrosion resistance coefficient of low-heat cement after being cured in 3% Na2SO4 solution for 6 months is as high as 0.97, which is nearly twice that of ordinary portland cement. This shows that high belite cementitious materials have better corrosion resistance than portland cement, especially sulfate corrosion resistance. (4) Excellent impact resistance and wear resistance Under the same concrete mix ratio, the wear test results of low-heat cement, ordinary cement and medium-heat cement are shown in the table. Different cement wear test results 1/Page 4 (5) The actual strength is high, the later strength is high, and the strength continues to increase1. Under standard conditions, the 28d strength of low-heat cement is the same as that of medium-heat cement and ordinary cement, but it continues to increase in the later period, reaching 1 24% of that of medium-heat cement and ordinary cement after1year; Test results of several cement mortar strengths (flexural/compressive strength Mpa) 2. When the curing temperature is close to the real internal temperature of dam concrete of 38℃, the strength of low-heat concrete at 7d is about 20% higher than that of standard curing, and the strength at 28d is higher than that of medium-heat concrete. (6) Comparison of water demand and physical properties of several cements As can be seen from the physical properties in Table 3, the water demand of low-heat cement is lower than that of ordinary cement and medium-heat cement, which can reduce shrinkage cracks and enhance durability, so it is more conducive to the preparation of high-performance concrete and 2/4 pages of on-site construction. From the performance comparison of the above cement, low-heat cement has obvious performance advantages and is the first choice to ensure the construction quality of hydraulic concrete. Economic Advantages of Low-heat Portland Cement Due to production costs and other reasons, the price of low-heat Portland cement is usually about 30 yuan/ton higher than that of medium-heat Portland cement, but in fact, using low-heat Portland cement can further save engineering costs than medium-heat Portland cement. 1) Save the investment cost 2) Save the construction period 3) The concrete cost will not increase. 1) can reduce the investment in ice-making equipment, thus saving the investment cost. Take 400,000 m3 RCC dam as an example: in order to meet the requirements of outlet temperature 15℃, aggregate precooling and a large amount of ice making are needed, and a total of about 36,000 tons of cold water and 1 10,000 tons of ice are needed. In order to meet the above refrigeration requirements, about 6 ammonia pump screw refrigeration units and a 240,000 kcal/hour water chiller are needed for cold water, air cooling and ice making equipment. It is estimated that the equipment investment is nearly 10 million yuan, and the equipment electricity consumption is about 3 million kWh. According to the calculation of 0.5 yuan/kWh, the electricity consumption is only about 6.5438+0.5 million yuan, and the cost of each concrete increases by 3.75 yuan. According to the production time of five months, the depreciation investment of ice machine equipment, ice warehouse, personnel and auxiliary equipment is about 6,543,800 yuan, with an increase of about 2.5 yuan per square meter of concrete. The comprehensive ice-making cost increases by about 6.25 yuan /m3 per square concrete. Take Angu Power Station supplied by our company as an example. The main dam adopts low-heat cement, and no ice-making equipment is used. The direct engineering investment of 10 million yuan was saved, and the ice making cost and temperature control cost were reduced during the construction process, which achieved good economic benefits. 2) It can increase the construction warehouse surface and save the construction period. Take 400,000 m3 RCC dam as an example: according to the five-month construction period, 80,000 m3 needs to be built every month. The design of single warehouse is about 2000m3, with 40 warehouses/month. Since the concrete temperature between warehouses can only be lowered below 20℃, the interval between warehouses is about 8- 10d. If low-heat pouring is adopted, the adiabatic temperature rise will be reduced by nearly 7℃, the warehouse surface will be increased by more than half, the interval between warehouses will be increased to 6-8d, and the concrete temperature rise will be low, which can quickly meet the construction temperature requirements between warehouses. The combination of the two aspects can save more than a quarter of the construction period, nearly 65430. Other advantages of warehouse surface can be increased: 1, and the inter-warehouse processing procedures can be reduced; 2. Integrity of high dam; 3. Reduce management and production costs. 3/4 Page 3) The cost of concrete will not increase because of the small amount of low-grade cement in the concrete mixture ratio. If low-grade cement is used, it can reach 125% of that of medium-grade cement due to the advantage of its later strength improvement rate, so it can still meet the design requirements under the condition of using less 15kg concrete per square meter, and the strength guarantee rate is high.