Chemical modified sand soil using polyurethane (PU) for foundation improvement / Norbaya Hj. Sidek

Roads are important assets to a country and need a maintenance programme to ensure that the longest life is achieved. Roads have to be cared for and without any maintenances they will lose their intrinsic value. Construction of road pavement generates instability to the naturally subsoil which encounters numerous engineering problems such as settlement, depression, sinkhole and faulting of subsoil. Conventional method of soil remediation work in subsoil such as crack sealing, patching potholes, overlays and grouting technique provide short term solutions to address those symptoms, but not underlying problem. This study permits a novel technique to solve the subsoil foundation problem precisely in sand that exists in the current pavement designs using Polyurethane (PU) grout. PU is a chemical substance that normally used in polymer industries for instance resilience foam seating, rigid foam insulation panels and microcellular foam seals. The study includes four main parts: the first part aims to optimize the composition of PU by varying the mixture of polyol and isocynate under Unconfined Compression Test (UCT). Two hundred fifty two (252) PU samples with different ratio of PU are tested using UCT and the ideal composition of polyurethane foam with 1:1 ratio is obtained. In addition, an empirical model is derived through the compressive strength of PU foam using numerical analysis (ABAQUS). Based on numerical analysis, the average difference between experimental and numerical results ranging between 3 to 5 % which is satisfactorily. The second part addresses the physical and mechanical properties of treated sand with different percentages of PU. The compressive strength of treated sands are determined by conducting the UCT in accordance with BS 1377: 1990: Methods of Test for Soils for Civil Engineering Purposes: Part 7-Shear Strength Test. The stress-strain relationship of the treated sand is presented. The third phase is to conduct a field evaluation on plate bearing test and mackintosh probe to evaluate the bearing pressure in treated soil. It is found that the performance of the bearing pressure in treated soil has improved almost twice as compared to natural soil. In addition, a great reduction in void ratio and swelling index are found in the treated soil as compared to the natural soil. The last part focuses on a laboratory sample sand model to determine and evaluate the performance of polyurethane in treated sand. Conclusively, this study has presented the reliable results and predictions on behavior of treated sand with PU. This study able to address as alternative remediation method whereby its shorten the time of implementation and eliminate the excavation works. In conclusion, this study is proven beneficial for a better environment and can be used as benchmark of ground improvement technique. This study can contribute to the improvement of pavement rehabilitation and ground modification works in Malaysia

Chemical modified sand soil using polyurethane (PU) for foundation improvement / Norbaya Haji Sidek

Roads are important assets to a country and need a maintenance programme to ensure that the longest life is achieved. Roads have to be cared for and without any maintenances they will lose their intrinsic value. Construction of road pavement generates instability to the naturally subsoil which encounters numerous engineering problems such as settlement, depression, sinkhole and faulting of subsoil. Conventional method of soil remediation work in subsoil such as crack sealing, patching potholes, overlays and grouting technique provide short term solutions to address those symptoms, but not underlying problem. This study permits a novel technique to solve the subsoil foundation problem precisely in sand that exists in the current pavement designs using Polyurethane (PU) grout. PU is a chemical substance that normally used in polymer industries for instance resilience foam seating, rigid foam insulation panels and microcellular foam seals. The study includes four main parts: the first part aims to optimize the composition of PU by varying the mixture of polyol and isocynate under Unconfined Compression Test (UCT). Two hundred fifty two (252) PU samples with different ratio of PU are tested using UCT and the ideal composition of polyurethane foam with 1:1 ratio is obtained. In addition, an empirical model is derived through the compressive strength of PU foam using numerical analysis (ABAQUS). Based on numerical analysis, the average difference between experimental and numerical results ranging between 3 to 5 % which is satisfactorily. The second part addresses the physical and mechanical properties of treated sand with different percentages of PU. The compressive strength of treated sands are determined by conducting the UCT in accordance with BS 1377: 1990: Methods of Test for Soils for Civil Engineering Purposes: Part 7-Shear Strength Test. The stress-strain relationship of the treated sand is presented. The third phase is to conduct a field evaluation on plate bearing test and mackintosh probe to evaluate the bearing pressure in treated soil. It is found that the performance of the bearing pressure in treated soil has improved almost twice as compared to natural soil. In addition, a great reduction in void ratio and swelling index are found in the treated soil as compared to the natural soil. The last part focuses on a laboratory sample sand model to determine and evaluate the performance of polyurethane in treated sand. Conclusively, this study has presented the reliable results and predictions on behavior of treated sand with PU. This study able to address as alternative remediation method whereby its shorten the time of implementation and eliminate the excavation works. In conclusion, this study is proven beneficial for a better environment and can be used as benchmark of ground improvement technique. This study can contribute to the improvement of pavement rehabilitation and ground modification works in Malaysia

Droplet-like bent multimode fiber sensor for temperature and refractive index measurement

This work proposes and demonstrates a bent multimode interference (MMI) sensor for refractive index and temperature measurement. The MMI structure was fabricated by successive splicing between single-mode-multimodesingle- mode (SMS) fibers. A droplet-like bent was introduced in the multimode fiber section for excitation of modes into the acrylate coating. The excitation of higher modes into the acrylate coating is particularly interesting due high thermooptic coefficient of acrylate which could improve temperature sensitivity, while evanescent field interaction of modes at the acrylate surface with surrounding material could be used for refractive index sensing. These modes experienced phase changes due to temperature and/or refractive index changes, consequently shift the spectra of the sensor. The sensor structure was simulated using BeamProp software to determine the required bending to excite light into acrylate coating for sensing. In experiment, a 3.5 mm bent sensor demonstrated refractive index sensitivity of 42.41 nm/RIU tested with refractive index between 1.30-1.395. Meanwhile, temperature sensitivity of 1.317nm/°C was attained using 5 mm bent sensor between 25 °C to 35 °C. The low cost and simple sensor structure is desirable in many applications including for detection, diagnosis, and determine of health, safety, environmental, liquid food, and water quality control

Investigation on Soil Strength and Microstructure of Palm Oil Boiler Ash with Sodium Hydroxide and Sodium Silicate as Alkaline Solution

Palm oil boiler ash is a type of industrial waste from palm oil production, which abundantly disposed on landfill, and contaminate the soil and environment. Recently, boiler ash as a by-product is introduced as an additive in chemical stabilization, known as geopolymer. An alkaline solution functions to activate the silica-alumina structure bonding to replace the Ordinary Portland Cement in concrete application but few in soil stabilization study. This study investigates the strength of laterite with a geopolymer.  Boiler ash was chosen as source material, with sodium hydroxide and sodium silicate mixed at a ratio of 1:2. Unconfined compressive test (UCT) and SEM were conducted for laterite soil with different geopolymer percentages. The test was conducted by adding a different geopolymer percentage at 0%, 5%,10%,15%, and 20% mixed with laterite soil. The soil sample was cured for seven days for an unconfined compression test (UCT). The result shows that the highest compressive strength was obtained at 15% of geopolymer in laterite soil at 340kPa. SEM tests show that the increased compressive strength was attributable to the 15% of the geopolymer, which had a compact and dense structure and less unreacted raw materials. In conclusion, the results indicated that 15% of geopolymer gives optimum value in enhancing laterite properties' strength. The ï¬ndings support boiler ash usage as by-products in geopolymers' production for potential use in soil strength stabilization