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本研究的目的在于开发高膨胀水泥混凝土在钻孔灌注桩中的应用技术,使桩混凝土与桩周土之间产生更强的结合力,从而进一步提高体系的承栽力。膨胀水泥采用高铝水泥(HAC)作为铝质材料来源,测试了膨胀水泥的膨胀、强度和凝结时间。除了无法接受的快凝特性外,该水泥的其他性能都很好。为了克服HAC膨胀水泥混凝土坍落度快速损失问题,建议采用掺外加剂的两步搅拌方法。尽管该方法仅在一定条件下适用,但在质量控制缺乏或对膨胀要求延迟的现场则无法使用。该问题的有效解决方案是用预水化的HAC(H-HAC)替代HAC制备膨胀水泥。H-HAC膨胀水泥混凝土凝结前后的性能均较好。本文介绍了掺掺HAC和H-HAC膨胀水泥的水泥净浆和混凝土的性能,包括坍落度损失、抗压强度、自由膨胀和二维约束膨胀、膨胀力和经特定方法测得的摩擦应力。制备的膨胀混凝土抗压强度达到70MPa,自应力大于8MPa。
The purpose of this study is to develop the application technology of high expansive cement concrete in bored piles so as to make stronger binding force between pile concrete and surrounding soil of piles so as to further improve the bearing capacity of the system. Expansive cement was tested using high-alumina cement (HAC) as an aluminum source for expansion, strength and setting times for expanded cements. In addition to the unacceptable fast setting properties, other properties of the cement are good. In order to overcome the rapid loss of slump of HAC expanded cement concrete, two-step mixing method with admixture is suggested. Although this method is only applicable under certain conditions, it can not be used on sites where there is a lack of quality control or a delay in expansion requirements. An effective solution to this problem is to replace the HAC with pre-hydrated HAC (H-HAC) to produce expanded cement. The performance of H-HAC expanded cement concrete before and after coagulation is better. This paper presents the properties of cement paste and concrete, including slump loss, compressive strength, free expansion and two-dimensional constrained expansion, expansive force, and frictional stress determined by a specific method . The compressive strength of the prepared expansive concrete reaches 70MPa, self-stress is greater than 8MPa.