Plasticity,strength,permeability and compressibility characteristics of black cotton soil stabilized with precipitated silica

The suitability of using precipitated silica(PS) from the burning of rice husk was investigated to improve the geotechnical engineering properties of a black cotton soil. A laboratory experimental program consisting of series of specific gravity, Atterberg limits, compaction, California bearing ratio(CBR), unconfined compression and consolidation tests was conducted on the untreated and PS treated soil samples. The application of PS to the soil significantly changed its properties by reducing its plasticity and making it more workable, improving its soaked strength, and increasing its permeability and the rate at which the soil gets consolidated. An optimal PS content of 50%, which provided the highest soaked strength, is recommended for the improvement of the subgrade characteristics of the BC soil for use as a pavement layer material.

A Review on Stabilization of Expansive Soil Using Industrial Solid Wastes

In developing countries like India, Industrialization is rising rapidly, and also?a great paucity of land is there, the demand for exploitation of industrial?wastes?which coming from industries is increasing. From geotechnical perspective,?fly ash, granite and quarry waste, cement kiln dust, silica fume, rice husk etc.?are the waste materials?which?have effectual features requisites by an excellent soil stabilization admixture. Stabilization using solid wastes is one of the different?methods of treatment, to improve the engineering properties and make it?suitable for construction. This paper briefs about the recent trends in stabilization of expansive soil using industrial waste (granite and quarry waste, cement kiln?dust, silica fume, rice husk) as stabilizers for decreasing the environmental?hazards.

水泥-石灰和水泥-稻壳灰稳定土的力学性能和冻融耐久性研究

为研究水泥-石灰和水泥-稻壳灰对土体进行加固良的效果及掺量,利用水泥、石灰和稻壳灰分别以水泥∶石灰=1∶1和水泥∶稻壳灰=1∶1制备两种稳定掺料。按照掺入比分别0%、2.5%、5%、7.5%和10%制备稳定土试样,并通过力学试验以及冻融试验对两种稳定土的三轴力学特性以及抗冻融循环的性能进行研究。结果表明:随着围压、稳定掺料和龄期的增加,稳定土的强度逐渐增加;脆性也明显增强;稳定土在3~7 d的强度增长率明显大于7~28 d的强度增长率,且在相同条件下,水泥-石灰稳定土的强度大于水泥-稻壳灰稳定土的强度。冻融循环后质量损失率和超声波变化规律表明土样的冻融耐久性顺序为:水泥-稻壳灰稳定土>水泥-石灰稳定土>纯土。

稻壳灰-高炉矿渣固化膨胀土工程特性及机理

为了改良膨胀土力学性能,提高其膨胀变形稳定性,通过无侧限抗压、自由膨胀率、扫描电镜和X射线衍射等方法,研究以工业固废稻壳灰-高炉矿渣(RHA-GGBS)为材料环保固化剂的膨胀土固化效果及机理.结果表明:固化剂对膨胀土力学性能有显著提升,当配比超过6∶4或RHA-GGBS质量分数超过10%时,力学性能不升反降.试样养护前后自由膨胀率降低原因不同,养护前为替换作用,养护后为水化反应。养护后的试样自由膨胀率降幅均高于未养护的,养护组较未养护组降幅最高为3.6倍.在10%RHA-GGBS质量分数临界值条件下,试样生成的团聚体、少量针棒状物及大量无定型凝胶均分布在土体的表面及孔隙;RHA-GGBS可提高土体强度,降低土体膨胀,RHA-GGBS质量分数超过临界值时,存在过量SiO_(2)无法反应,生成物总量限制,使得固化反应受到不同程度的抑制作用的影响.

稻壳灰-水泥固化镉污染土性能及影响机制

为实现污染土和稻壳灰资源化利用,解决水泥固化材料高排放问题,采用稻壳灰-水泥为固化剂对重金属镉污染土进行固化处理。开展不同养护龄期、固化剂类型及镉含量下固化镉污染土无侧限抗压强度、毒性浸出、X射线衍射及扫描电镜试验,通过分析抗压强度、浸出质量浓度、破坏形态、微观形貌及矿物组成等宏微观特性,揭示稻壳灰-水泥固化镉污染土微观作用机制。结果表明:稻壳灰可以加速水泥水化过程,提高固化土无侧限抗压强度,低水泥掺量时加入5%~10%稻壳灰改善效果较优;固化土强度随镉含量增加而先升后降,存在临界值100~400 mg/kg;稻壳灰掺入后,土体脆性破坏特征减弱,镉污染下土体裂纹较多且破坏面不规则;固化土浸出质量浓度随龄期增加而降低,在镉含量为100 mg/kg时满足标准限值,稻壳灰部分替代水泥后浸出质量浓度相差不大;稻壳灰-水泥主要以水化硅铝酸钙聚合物凝胶(C-A-S-H)和钙矾石(AFt)共同支撑土体孔隙,不断团聚、胶结形成空间网状结构,形成骨架结构并吸附镉离子。

稻壳灰固化重金属污染土的环境特性

为研究稻壳灰固化重金属污染土的环境特性,对稻壳灰和水泥固化镉污染土开展毒性浸出试验和pH值测试,研究稻壳灰和水泥掺量、养护龄期、镉含量对固化污染土环境特性的影响规律以及探讨参数间关系。结果表明:1)镉浸出浓度随着养护龄期增加而不断降低,稻壳灰掺入使得镉浸出浓度总体上先降低后升高,稻壳灰掺量为5%~10%时固化效果较优;镉含量为100 mg/kg时镉浸出浓度满足标准限值;2)固化污染土pH值随着稻壳灰掺量和养护龄期增加先升后降,不同养护龄期下固化土pH值随着镉含量增加均有所降低;3)浸出液pH值随着稻壳灰掺量增加而先升后降,在5%~10%稻壳灰掺量时达到峰值;浸出液pH值随着养护龄期增加而降低;4)镉浸出浓度随着浸出液pH值增大而减小,与pH值较大时固化污染土固化效果较好的结论相一致。

稻壳灰固化重金属污染土力学性能及微观结构研究

为研究废弃物稻壳灰处理重金属镉污染土的固化/稳定化效果,开展低水泥掺量作用下稻壳灰固化镉污染土无侧限抗压强度及微观试验,研究养护龄期、稻壳灰掺量和镉含量对固化污染土应力-应变特性、抗压强度、破坏应变和变形模量的影响规律以及探讨参数间关系,并分析不同污染条件下固化土微观结构变化。研究结果表明:固化土应力-应变过程分为压密阶段、弹性变形阶段和破坏阶段。随着龄期增加,固化土峰值应力和破坏应变分别增大和减小,应力-应变曲线上升和突降变化明显,固化土脆性增大。峰值应力随稻壳灰掺量和镉含量增加均先增大后减小,稻壳灰掺量和镉含量较高时固化土峰值应力大幅降低。低水泥掺量下,5%~10%稻壳灰掺量有助于提高固化土强度。镉含量对固化土强度存在临界值,随着龄期增加,临界值由1 000 mg/kg转变为100 mg/kg,且高镉含量下土体强度劣化显著。固化土破坏应变和变形模量随抗压强度增加分别减小和增大,破坏应变和变形模量存在线性关系。固化土体在未污染条件下生成大量针棒状和絮凝状产物,形成空间网状结构,共同支撑土体并提高强度。重金属镉作用下反应产物减少,固化作用被抑制。

Evaluation of rice husk ash and Portland cement reinforced clay for use as road subgrade using the CBR test

The amount of rice husk waste generated in Nigeria is posing serious threat to the environment and the ecosystem.Utilizing these wastes for productive purposes has been of interest to government and researchers.This study evaluated rice hush ash(RHA)reinforced clay for use as road subgrade,using the California Bearing Ratio(CBR)as prescribed in ASTM D1883.The clay was mixed with RHA/Portland cement in the ratios of 0%(control),2.5%,5%,7.5%and 10%.Results showed that the physical properties of the soil in its natural form did not meet the FMW&H guideline specification for subgrade road;thus there was a need to stabilize the soil.As the percentage of RHA increased,the strength of the soil increased,with the maximum strength observed at 5%RHA,beyond which there was decrease in the load bearing capacity of the soil.Optimal CBR ratio of 9.35%was obtained at 5%RHA,5%Portland cement and 90%clay soil.Comparing this result with the soil at natural state(CBR=1.55%),it shows that RHA is a good improvement agent for the soil.This research can be beneficial to highway road construction in areas with similar soil conditions.