To promote the utilization of fly-ash, based on the orthogonal experiment method, wet density and unconfined compressive strength of Foamed Mixture Lightweight Soil mixed with fly-ash and quicklime (FMLSF) are studied. It is shown that the wet density and unconfined compressive strength of FMLSF increase with the increase of cement content, while decreasing with the increase of foam content. With the mixing content of fly-ash increase, the wet density and unconfined compressive strength of FMLSF increase firstly and then decrease. Scanning Electron Microscope (SEM) tests show that ball effect or microaggregate effect of fly-ash improves the wet density and unconfined compressive strength of FMLSF. With the mixing content of quicklime increase, the wet density and unconfined compressive strength of FMLSF increase firstly within a narrow range and then decrease. In addition, the primary and secondary influence order on wet density and 28-day compressive strength of FMLSF are obtained, as well as the optimal mixture combination. Finally, based on two abutments in China, behind which they are filled with FMLSF and Foamed Mixture Lightweight Soil (FMLS), the construction techniques and key points of quality control behind abutment are compared and discussed in detail, and the feasibility of utilization fly-ash as FMLSF is verified by the experimental results.
The durability of lightweight cellular concrete (LCC) and the corresponding assessment method are studied in this paper to improve the utilization of LCC in subgrade construction engineering. The durability assessment method is established by combining the analytic hierarchy process (AHP) with fuzzy comprehensive evaluation (FCE). The main assessment processes are as follows. Firstly, based on the physical and mechanical properties of LCC, the influencing factors are selected in terms of preliminary design, construction technology, and operation and management after completion of construction. The grading standard of influencing factors is established as well. Secondly, a multilevel assessment model with targets level, criteria level, and indexes level is established. AHP determines the effective weight of the lower level relative to the upper level. The consistency check of the judgment matrix is conducted to prove the rationality of the distribution of influencing factors’ effect weight. Thirdly, the membership function which is suitable for each influencing factor is built to calculate the membership degree. Besides, the practicality and reliability of AHP combined with FCE are demonstrated through a practical engineering case, which is the third section of a highway in Guangdong Province, China.
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