泵送粉煤灰混凝土回弹测强曲线特性

通过对不同强度等级、不同粉煤灰掺量的泵送混凝土标准立方体试块进行抗压、回弹、碳化试验，研究各测试数据随龄期的变化规律，根据常用曲线形式进行测强曲线拟合并分析其与普通混凝土统一测强曲线的区别．试验表明：混凝土各测试数据的发展受粉煤灰影响不同而呈现不同规律，掺量高的低强混凝土抗压强度发展慢，回弹发展快，碳化深度大；而掺量低的高强混凝土抗压强度发展快，回弹发展慢，碳化深度低．该现象的内在原因为掺量低时粉煤灰微集料效应为主，抗压强度提高明显；掺量高时粉煤灰低活性限制抗压强度增长，而回弹值提高明显．各测试数据的发展规律不同造成曲线拟合误差大，分析建议将胶凝材料含量〉400kg／m2、粉煤灰掺量≤20％的高强混凝土的回弹值适当增大后拟合，可得到满足地区曲线的精度要求的统一曲线．

Characteristics of Rebound Strength Detection Curve of Pumping Fly Ash Concrete

The standard cubes of pumping concrete with different strength classes and contents of fly ash are cast for the test of compression, rebound and carbonation for research on the development of different test data, fitting the rebound strength detection curve by curve form commonly used, and analyzing difference between our curve and unified detection curve of ordinary concrete. Test shows a different influence of fly ash on data to have a asynchronous development, high content in low- strength concrete make compressive strength develop slowly, rebound value develop rapidly and carbonation depth great, low content in high-strength concrete have a opposite effect on test data. The underlying reason is micro-aggregate effect of fly ash takes dominant role in low-content concrete and increase compressive strength significantly, while low-activity effect of fly ash in high-content concrete limit the increase of compressive strength whose rebound value still increase because of micro-aggregate effect. The different development law makes fitting error large, suggestion is made to increase rebound value of concrete appropriately whose content of cementing materials is larger than 400 kg/ma and fly ash is less than or equal to 20% to get one measuring curve whose error meet the requirements of technical specification.