Effect of sodium compounds additives on the strength of cement-stabilized soils

摘要

Chemical stabilisation using cement is a common method of improving the weak properties of soft soils. This study presents the results of experimental tests on the effects of three sodium additive solutions, sodium hydroxide (NaOH), sodium carbonate (Na2CO3) and sodium chloride (NaCl), on the strength of clayey (CS) and non-plastic/low plasticity property (NPS) soil-cement mixtures. Both soils condition, CS and NPS, represent the predominant soils in Mosul city, Iraq. The physical properties of these natural soils were obtained. X-ray diffractometry (XRD), X-ray fluorescence spectrometry (XRFS), and mercury intrusion porosimetry (MIP) tests were performed to further examine the microstructural characteristics of the soil samples. Furthermore, various concentrations of sodium additive solutions (0.5, 1, 1.5, 2, 2.5 and 3%? by dry soil weight) were added to the soils to study the effect of these solutions on the unconfined compressive strength (UCS), California bearing ratio (CBR), and swelling potential characteristics of the soils. Variables such as cement content, curing period and concentration of chemical additives were considered. The results show an increase in the UCS of soil-cement mixtures corresponding to the incremental increases in the cement content and curing period of the samples. Also, the addition of NaOH and Na2CO3 increased the strength of soil-cement mixtures, with a limited effect in the case of NaCl addition. The results indicate that 1% and 1.5% of sodium additives were optimal additive contents for maximal UCS and CBR values, respectively. The results also confirm the decreased swelling potential of CS-cement mixtures with the addition of sodium additives and demonstrates the superiority of NaOH over Na2CO3 as an additive for soil stabilization.