不同种类轻骨料混凝土的耐久性能比较

COMPARISON OF DURABILITY OF DIFFERENT KINDS OF LIGHTWEIGHT AGGREGATE CONCRETES

为探讨轻骨料混凝土强度指标与耐久性能指标的影响因素相互关系,以全轻混凝土为基准,通过单掺石灰石粉和短切玄武岩纤维的方法,以及通过适量取代陶砂、陶粒的方法,形成相应的砂轻、石轻和混轻混凝土及其对应的自密实混凝土,并进行抗压强度试验和碳化、氯离子渗透和硫酸盐侵蚀试验。结果表明:不同轻骨料混凝土的耐久性能指标与混凝土种类和强度等级密切相关,但强度与耐久性能指标不同步,其中,石灰石粉、纤维和普通骨料均能有效提高混凝土的抗碳化性能,并以自密实混凝土为更好;同时,改进的普通混凝土碳化预测模型适于轻骨料混凝土;28 d龄期试件的电荷通过量表现出极大差异性,56 d龄期试件的电荷通过量接近,大幅度降低,并以纤维和砂轻自密实混凝土的抗氯离子性能为最好;在相同干湿循环次数条件下,不同混凝土抗压强度损失率和耐蚀系数均分别相近并具有同步性和强相关性,只有自密实混凝土随干湿循环次数增大呈先提高后降低的变化趋势。

To study the correlations of influence factors between strength and durability for lightweight aggregate concrete(LWAC),a serial of tests on compressive strength,carbonization depth,chloride ion penetration and sulfate attack were carried out. Where the tested concretes include all-lightweight shale ceramsite concrete(ALWSCC),ALWSCC replaced part of fly ash with limestone powder(LSP) in equal mass,chopped basalt fibers(CBF) reinforced ALWSCC,the LWCSFA,LWCSCA and HLWC made from ALWSCC replaced shale pottery and shale ceramsite with river sand and normal coarse aggregates in equal volume and in single or double methods accordingly,respectively,and the corresponding self-compacting LWACs(SCLWCSFA,SCLWCSCA and SCHLWC). The results showed that the durability indexes of different kinds of LWACs were closely related to concrete type and strength grade,but the strength indexes were out of step with the durability indexes. The LSP,CBF and normal weight aggregates could effectively improve the carbonation resistance of LWACs,and the self-compacting LWACs were better. The modified carbonization model of normal weight concrete(NWC) was suitable for LWAC. The quantity of electric charge through LWACs showed a great differences at 28 d,but it was significantly reduced and approached at 56 d,and the resistance chloride ion permeability of CBF reinforced ALWSCC and SCLWCSFA were better. The loss rates of compressive strength(k)and corrosion resistance coefficients(Kf) of different kinds of LWACs were similar,respectively,and which exhibited synchronism and strong correlation under the same dry-wet cycle times. However,only the k and Kfof self-compacting LWACs increased first and then decreased with the increase of dry-wet cycle times.