掺花岗岩石粉的管桩高强混凝土微结构和力学性能研究

本文采用蒸压养护方式制备管桩高强混凝土,以相同配合比的标准养护混凝土为对比组,分别研究磨细砂和石粉双掺时石粉取代率(花岗岩石粉/(花岗岩石粉+磨细砂),质量比)和石粉单掺时石粉掺量(花岗岩石粉/(花岗岩石粉+水泥),质量比)对管桩高强混凝土强度的影响,并通过XRD、ESEM等方法研究掺花岗岩石粉的管桩高强混凝土水化产物的种类及形貌特征。结果表明:蒸压养护下,混凝土强度随石粉取代率和石粉掺量的增加均先增大后减小, 石粉取代率为25%和石粉掺量为20%时混凝土强度分别达到最大值。由于花岗岩石粉中的SiO₂在蒸压条件下会与水泥水化产物Ca(OH)₂发生火山灰反应并生成托勃莫来石,使混凝土更为密实,因此相同配合比条件下蒸压养护3 d的混凝土强度高于标准养护28 d的混凝土强度。

Microstructure and Mechanical Properties of Pile High-Strength Concrete Incorporating Granite Powder

This paper intended to prepare high-strength pipe concrete using autoclaved curing,while the concrete with standard curing was used as control sample.The influences of the stone powder replacement rate(granite stone powder/(granite stone powder+ground)sand,by mass),and the stone powder content(granite stone powder/(granite stone powder+cement),by mass)without adding ground sand on the strength of the pipe high-strength concrete were conducted,respectively.The types and morphological characteristics of hydration products of pipe high-strength concrete with granite powder were investigated by XRD and ESEM.The results show that under autoclaved curing,the concrete strength increases first,and then decreases with the increase of stone powder replacement rate and stone powder content.The strengths of the concretes are highest when the stone powder replacement rate is 25%and the stone powder content is 20%,respectively.The SiO₂in the granite powder has a pozzolanic reaction with Ca(OH)₂(cement hydration product)and produce tobermorite under autoclaved condition,and consequently the concrete become more compact.Therefore,the strength of concrete under autoclave curing at 3 d is higher than that of the concrete under standard curing at 28 d in the same mix ratio.