泵送山砂混凝土配制技术研究

Study of the preparation of pump concrete with pit sand

贵州地区由于缺乏可以利用的河砂,长期以来因地制宜发展山砂混凝土。山砂混凝土与河砂混凝土虽然配制机理大致相同,但由于贵州地区生产山砂规格不一、砂两头粗、中间级配少、表面粗糙、石粉含量偏高、需水量较大,对混凝土的和易性影响较大。由于砂石原材料供不应求,山砂的超粒径、石粉含量偏多、颗粒级配差等问题更加明显。随着泵送混凝土的广泛应用,山砂混凝土坍损快,导致堵泵、爆管事故频发的难题一直未得到解决。笔者根据长期从事山砂混凝土配制技术的研究,通过增加粉煤灰用量弥补山砂的缺陷,控制单位立方米用水量调整其拌合物的黏稠度,调整砂率等技术手段,有效解决了上述难题。另外,山砂中适量的石粉对于山砂混凝土是有利的。

Due to poor supply of natural river sand,machine-crushed pit sand has been substituted for commonly used river sand to make concrete in Guizhou province for a long time.The quality of the pit sand in Guizhou is not well controlled that the grading of the sand usually exhibits lacking of moderate particles and that much limestone powder is usually present,which induces a higher water demand and a poor workability of concrete. These problems become more serious owing to the high local demand of aggregate resources.With the extended application of pump concrete,the fast slump loss of pit sand concrete leads to frequent pumping problems that hasn＇t been well solved.The dosage of fly ash was increased to improve the defacts of the pit sand.Moreover,by virtue of water demand control and adjustment of sand to aggregate ratio,the problem described above was effectively worked out.In addition, moderate limestone powder was proved to be beneficial to the property of the concrete.