水稳碎石基层取芯临界强度与整体性质量评价时机

Coring critical strength and integrity quality evaluation time of cement⁃treated aggregate base layers

为了确定水稳碎石基层合理的整体性质量评价时机,消除养生条件、级配类型和设计强度(水泥剂量)的影响,弥补采用固定龄期法则评价施工质量的局限性,采用振动成型方法成型3种类型级配、3种水泥剂量的大型试件,并采用3种养生路径养生后进行钻芯和劈裂强度试验,建立成熟度与劈裂强度的关系.结果表明:水泥剂量(质量分数)对取出完整芯样的龄期有很大的影响,5.5%水泥剂量的试样,3种级配在7 d龄期均能取出完整的芯样,而水泥剂量为4.5%时,悬浮-密实级配在14 d才能取出完整芯样,当水泥剂量为3.5%时,3种级配类型的水泥稳定碎石均不能在7 d取出完整致密芯样;级配越趋于悬浮-密实,芯样侧壁越不致密,悬浮-密实级配水泥剂量必须达到5.5%以上,才能在7 d龄期取出致密芯样,否则需增加养生龄期;水泥稳定碎石能否取出完整致密芯样与其劈裂强度密切相关,当劈裂强度达到取芯临界劈裂强度时,则能取出完整致密芯样;不同养生路径下的水稳碎石劈裂强度与成熟度曲线有较好的双曲线关系.基于取芯临界劈裂强度及劈裂强度与成熟度的关系曲线,提出了取芯临界成熟度标准.采用取芯临界成熟度科学地确定水泥稳定碎石基层的整体性评价时机是可行的.

To determine the reasonable integrity quality evaluation time of cement⁃treated aggregate base(CTAB)layers,eliminate the influences of curing conditions,gradation types,and design strengths(cement dosage),and make up the limitations of using fixed age to evaluate CTAB construction quality,large specimens with three types of gradations and three kinds of cement dosages were molded by vibration method for experiment.After using three kinds of curing paths to preserve,the coring and splitting strength tests were carried out,and the relationship between maturity and splitting strength was established.Experiment results show that cement dosage(mass fraction)had a great influence on the age at which an intact core could be taken out.When the cement dosage was 5.5%,intact cores could be taken out from specimens of all three gradation types in seven days;when the cement dosage was 4.5%,intact cores could be taken out from specimens with suspend⁃dense structure grading until 14 days;as the cement dosage dropped to 3.5%,intact cores were failed to be taken out under the three gradation types in seven days.When the gradation tended to suspend⁃dense structure,the side walls of cores were less dense.Intact dense cores could be taken out in seven days,only when the cement dosage was above 5.5%under suspend⁃dense structure grading,otherwise the curing age must be increased.Whether the intact cores of CTAB could be taken out was closely related to splitting strength,when the splitting strength reached the coring critical strength,intact dense cores could be taken out.There was a hyperbolic relationship between the splitting strength of CTAB and the maturity curve under different curing paths.Based on the coring critical splitting strength and the relationship between splitting strength and maturity,the critical maturity standard of coring was put forward.It is feasible to use coring critical maturity to scientifically determine the integrity quality evaluation time of CTAB.