C80 mean

C refers to the compressive strength of concrete, 80 refers to the compressive strength of pumped concrete design strength C80 pillars, the springback value ( This is one of the root, each pillar area) only one test As follows: 42 42 50 42 42 41 and 42 40 and 42 51 50 42 42 examined six pillars, the remaining 5 root, the data is no different. Calculated according to the standard: 'JGJ/T 23 - 2001 'technical specification for concrete compressive strength of the rebound method, get rid of a maximum of three ( 51, 50, 50) , 3 minimum value ( 40, 41, 41) And the remaining 10 average rebound value is: 72. 8. Play pillar is level rebound, there is no correction. All of the surveyed area number 6, not enough 10, therefore the six area choose the minimum measurement to assess. Carbonation depth without the data, to 0. 5; （ Carbonation depth is greater than 2. 0, need more) Check appendix A 'concrete strength conversion table' part of the surveyed area, 45. 7MPa。 If for pumping concrete, according to appendix B 'pumping concrete concrete strength conversion value of revised' part of the surveyed area. Here set the carbonation depth of 0. 5 mm, then revised to 3. 0MPa。 The ultimate compressive strength as: 45. 7 + 3. 0 = 48. 7MPa（ 97. 4%) The five main factors that affect the strength of the 1: influence the active ingredient in cement concrete, cement strength in the mixture ratio under the same conditions, the higher the grade of cement used, made of concrete strength is higher. 2: the influence of water-binder ratio of water/cement ratio, the greater the strength is lower. 3: the influence of coarse aggregate when rock strength is equal, depending on the aggregate surface roughness. Water-binder ratio equal or mixture phase at the same time, the rubble concrete is better than the pebble. 4: the influence of temperature and humidity temperature, cement hydration speed, concrete strength growth. When the temperature drops below freezing, the strength of the concrete of the growth, water ice expansion ( Water freeze expansion volume class about 9%) , make the damage to the internal structure of concrete, has obtained the intensity of the ( If before freezing, concrete has different degree of hardening) By the loss. High and low temperature repeated freezing and thawing, the micro cracks of concrete internal growth, expanding gradually, make the strength of concrete decreases, skin peeling, even concrete completely collapse. Humidity is appropriate, the cement hydration process smoothly, concrete strength is growing rapidly. If the humidity is not enough, can stop the hydration, make the concrete structure is loose, increase water penetration, or dry crack formation, affect durability. 5: the influence of the age of concrete under normal maintenance condition, its strength will rise with the increase of age, the original 7 - Strength rising rapidly within 14 days, 28 days later growth. C80 mean