Wisitsak Tabyang

This research investigated the unit weight and unconfined compressive strength (UCS) of cellular lightweight high-calcium fly ash geopolymer and cement-stabilized soft Bangkok clay (CLFAG-OPC stabilized SC) as potential lightweight embankments and backfill materials. The investigated parameters included the soft clay:fly ash (SC:FA) ratio (50:50 to 90:10), ordinary Portland cement (OPC) content (0%-3%), water content (1.5LL-3.0LL), liquid alkaline content (L) (0.6FA to 1.5FA), NS:NH ratio (0.5-3), NH concentration (8 M), air foam content (Ac) (0%-150% by SC volume), and curing time (7-90 days). The results indicated that the SC:FA ratio, OPC content, water content, NS:NH ratio, L content, and Ac significantly influenced both the unit weight and UCS of samples. Increasing water content, L content, and Ac generally reduced unit weight, except when influenced by FA content, OPC content, and the NS:NH ratio. The optimal composition for maximum UCS was achieved with an SC:FA ratio of 50:50, OPC content of 3%, water content of 2.0LL, NS:NH ratio of 1, L content of 0.6FA, and 0% Ac. A predictive equation for unit weight was proposed using phase diagrams. Additionally, mix design charts were shown to be valuable tools for calculating the unit weight and UCS, demonstrating their effectiveness for lightweight embankment and backfill applications.

This study investigates the durability under wetting and drying conditions of marginal lateritic soil (MLS) stabilized with a one-part high-calcium fly ash geopolymer (OPFAG). The variables include an MLS: fly ash ratio of 70:30, solid sodium hydroxide content ranging from 0 to 40%, and the number of wet-dry cycles. Durability is evaluated by measuring the unconfined compressive strength (UCS) of MLS samples stabilized with OPFAG and MLS samples stabilized with ordinary Portland cement (OPC). The results show that OPFAG improved the engineering properties of MLS. The highest UCS values are achieved at 20% solid sodium hydroxide, achieving a UCS of 1889 kPa for the geopolymer-stabilized MLS and at 5% OPC for OPC-stabilized MLS (1320 kPa). The UCS of both stabilized MLS samples increases with the number of wet-dry cycles up to 6 cycles, after which a decline is observed.

Rubber wood fly ash (RWFA) is one of the main components of biomass ash materials. This research investigates the possibility of using RWFA geopolymer (RWFAG) to stabilize marginal lateritic soil (MLS) as green subbase materials. RWFA was used as a starting material. The studied influence factors included MLS:RWFA ratio, sodium silicate (NS):sodium hydroxide (NH) ratio, soaked and unsoaked conditions, and curing time. The study involved testing the unconfined compressive strength (UCS), indirect tensile strength (ITS), and conducting microstructure. The test results revealed that the optimal liquid content for the MLS-RWFAG specimens ranged between 12–24% for all ingredients. As the RWFA content increased, the maximum dry unit weight of the MLS-RWFAG decreased due to the lower specific gravity of RWFA. The MLS-RWFAG specimen with 30% RWFA content and an NS:NH ratio of 70:30 yielded the maximum UCS and ITS. The SEM-EDS analysis demonstrated the production of C-S-H and N-A-S-H gels, resulting in a dense and homogeneous matrix in the MLS-RWFAG specimens. Considering cost-effectiveness, the optimum ingredients for the MLS-RWFAG specimen were identified at an MLS:RWFA ratio of 70:30 and an NS:NH ratio of 10:90, meeting the 7-day soaked UCS requirement for pavement subbase materials. Moreover, the CO₂-eq emissions from MLS-RWFAG specimens were lower compared to those from 3% cement-stabilized MLS samples. These findings strongly support the use of RWFAG as a viable alternative to Portland cement for stabilizing MLS in subbase materials.

This research investigated high calcium fly ash geopolymer stabilized recycled concrete aggregate (RCA-FAG) as pavement base material. The effect of recycled concrete aggregate (RCA):high calcium fly ash (FA) ratios, sodium silicate (Na₂SiO₃):sodium hydroxide (NaOH) ratio, and curing time on the unconfined compressive strength (UCS) and scanning electron microscope (SEM) properties of RCA-FAG samples were evaluated. The maximum dry unit weight of the RCA-FAG sample was 20.73 kN/m³ at RCA:FA ratio of 80:20 and Na₂SiO₃:NaOH ratio of 60:40. The 7-d UCS of RCA-FAG samples increased as the FA content and Na₂SiO₃:NaOH ratio increased. The 7-d UCS of the RCA-FAG sample was better than that of the RCA with no FA because FA particles filled in RCA particles, resulting in a dense matrix. The 7-d UCS of RCA-FAG samples passed the 7-d UCS requirement for the low-traffic road. All ingredients met the 7-d UCS requirement for the high-traffic road except the sample with RCA:FA of 100:0 and Na₂SiO₃:NaOH of 50:50 and 60:40. The 7-d SEM images indicated that spherical FA and RCA particles are bonded together, resulting in the dense matrix for all Na₂SiO₃:NaOH ratios. The proposed equation for predicting the UCS of RCA-FAG offered a good coefficient of correlation, which is useful in designing pavement base material from RCA-FAG material.

The use of concrete in road construction has grown over the past decade due to the material’s great durability. However, concrete has poor tensile strength, ductility, and energy absorption. This paper aims to investigate the utilization of plastic waste, namely polypropylene (PP), to create a novel fiber to enhance the engineering properties of fiber reinforced concrete (FRC), an eco-friendly concrete that can reduce environmental problems. The 28-day design strengths of 28 and 32 MPa were used in this study because the compressive strength requirements for concrete footpaths and pavement specified by Austroads and the Department of Highways, Thailand, were at least 25 and 32 MPa, respectively. The fiber (F) was a mixture of virgin PP and recycled PP (RPP). The study used F contents of 0.25, 0.50, 0.75, and 1% by weight of cement and PP:RPP ratios of 100:0, 75:25, 50:50, 25:75, and 0:100. The compressive strength, flexural strength, leaching, and CO₂ emissions savings of FRC were evaluated. Improvements in the compressive strength, flexural strength, and toughness of the samples with F were observed in comparison to the control concrete samples for all design strengths. All mixtures met the compressive strength requirements for concrete footpaths, except for F contents of 0.75 and 1% and a PP:RPP ratio of 0:100. By contrast, the 32 MPa FRC samples with F contents of 0.25 and 0.5% and all PP:RPP ratios met the requirements for rigid pavement. From an environmental perspective, the heavy metal contaminants of the 32 MPa FRC sample were within the allowable limits for all mixtures. Regarding incineration disposal, the maximum CO₂ emissions savings of 28 MPa and 32 MPa FRC with an F content of 0.5% and a PP:RPP ratio of 0:100 were 1.0 and 1.11 kg CO₂-e/m³, respectively. This research will enable plastic waste, traditionally destined for incineration and landfill disposal, to be used as a sustainable fiber in the construction industry.