排序方式: 共有81条查询结果,搜索用时 15 毫秒
21.
22.
杨英姿 《武汉理工大学学报(材料科学英文版)》2010,(2)
The effects of water/binder ratio (w/b) on the toughness behavior, compressive strength and flexural strength of engineered cementitious composites (ECC) were investigated. The w/b ratios of 0.25, 0.31, 0.33 and 0.37 were selected and the specimens were tested at the ages of 7 d and 28 d. The experimental results showed that there was a corresponding increase in first cracking strength, modulus of rupture, compressive strength and flexural strength with the decrease of w/b. Within the w/b range of 0.25-0.37... 相似文献
23.
Fly ash used as the main raw materials,incorporated with sintering expansion additive and fluxing additive in different ratio,was sintered high-strength lightweight aggregates of fly ash (ceramsite) in the laboratory-controlled electric furnace.The results show that the optimal sintering system is the sintering temperature range of 1250 ℃ to 1280 ℃ and retaining time of 5 min-10 min.The bulk density,the apparent density and 24 h water absorption of ceramsites decrease with the increase of sintering additive and the decrease of the amount of fly ash.The addition of fluxing additive can significantly enhance the compressive strength of ceramsite pellets,reduce its water absorption at 24 h and improve pore-shape ofinner structure.The firing coefficient (Pk) changed within 7.8-8.1 of raw materials can prepare high strength and low water absorption ceramsites.Pk kept a good linear relationship with porosity and strength of ceramsite particles. 相似文献
24.
In order to improve the mechanical properties and Greenness of engineered cementitious composites (ECC),four-point bending test,compressive strength and flexural strength test were employed to analyze the effects of fly ash content on the mechanical properties of.ECC.The replacement ratio of cement with fly ash was 50%,60%,70% and 80%,respectively.The experimental results indicate that ECCs with high volume fly ash still remained the characteristic of pseudo-strain hardening and the mid-span deflection in four-point bending test increase remarkably by adding more fly ash.The observations of ECCs indicate that the multiple cracks are saturated and the crack width is relatively smaller for higher volume fly ash ECC,owing to the lower strength of matrix and the improvement ofinterface bonding.Fly ash reduces the compressive strength and flexural strength of ECC at all ages.Therefore,as the compressive strength could meet the requirement of practical engineering,employing the higher volume fly ash ECCs would benefit to obtain relatively high ductility. 相似文献
25.
工作性对负温防冻剂混凝土性能的影响 总被引:1,自引:0,他引:1
在混凝土冬季施工中,防冻剂通常被加到混凝土以保证低温下强度的持续发展.JC475-92防冻剂标准中规定基准混凝土的坍落度通常控制在(30±10)mm.然而,越来越多的大坍落度的混凝土或自密实混凝土被广泛应用于冬季混凝土施工.因此,探讨了掺与未掺防冻剂的不同坍落度混凝土强度的变化规律.当水灰比固定而用高效减水剂提高坍落度时,减水刺对常温下混凝土的影响可以忽略,但对负温度下混凝土强度的影响明显.负温度混凝土强度随着坍落度的增加而降低,其原因是高效减水剂延长了水泥的凝结时间,并易造成混凝土早期的冻害. 相似文献
26.
高强粉煤灰烧胀陶粒制备的影响因素研究 总被引:2,自引:0,他引:2
采用粉煤灰为主要原材料,掺入不同比例的助胀剂和助熔剂,在实验室利用可控式电热炉,进行了高强粉煤灰烧胀陶粒的试验研究.结果表明:煅烧温度高于1200 ℃时,粉煤灰陶粒膨胀性能随着煅烧温度的提高明显改善.煅烧温度固定为1250 ℃、煅烧时间为8 min时,粉煤灰陶粒的膨胀性能最佳.在烧制粉煤灰陶粒过程中,焙烧温度1250~1280 ℃、焙烧时间5~10 min时,随着助胀剂掺量的增加,粉煤灰烧胀陶粒的体积密度、表观密度和24 h吸水率逐渐减小;助熔剂掺入后可显著提高陶粒的颗粒强度,降低其吸水率. 相似文献
27.
28.
矿物掺和料对混凝土早期开裂的影响 总被引:8,自引:0,他引:8
针对高性能混凝土普遍存在的早期开裂问题,采用板式混凝土开裂架研究了掺硅灰、粉煤灰、矿渣粉对混凝土早期开裂的影响规律,同时测量了混凝土早期自收缩及在干燥条件下的总收缩。试验结果表明:掺硅灰对混凝土在干燥条件下的早期总收缩影响不大,但使混凝土早期开裂加重;掺粉煤灰使混凝土早期自收缩明显减小,而总收缩并不降低;掺矿渣粉使混凝土早期自收缩和总收缩都增大,而掺粉煤灰和矿渣粉均使混凝土早期抗裂性改善,且掺粉煤灰抗裂性优于矿渣粉。掺硅灰混凝土早期抗裂性差的主要原因是混凝土早期弹性模量增大,徐变和应力松弛能力降低;而掺矿渣粉或粉煤灰混凝土早期抗裂性改善的主要原因在于混凝土早期弹性模量减小、徐变和松弛能力提高。 相似文献
29.
30.