Effect of Temperature Changes on the Unconfined Compressive Strength of OPC Stabilized Engineering Soil with Palm Bunch Ash, PBA as Admixture

Nowadays, waste product such as Palm Bunch Ash (PBA) is produced in large quantities from the agriculture industry on a daily basis. Improper disposal of the agricultural wastes at landfills contribute to environmental pollution. The cost of construction material increases when the demand is high. Therefore, reutilization of these waste products not only reduces the cost of construction material but also minimizes waste disposal problem. In this research, ''The Effect of Temperature on Ordinary Portland Cement Stabilization of Engineering Soil using Palm Bunch Ash as Admixture'', The compressive strength of the (Laterite + cement + palm bunch ash ) specimen cured for 14 days was studied and found to have more strength than that of the 7 days curing period. The addition of palm bunch ash from 0% to 10 % was found to have increase in strength from 23oC to 60oC and records its maximum strength at 60oC which later reduces slightly from 80oC to 100oC, hence its maximum strength was acquired at 60oC. It was observed that the specimen placed at room temperature has a higher strength than that of 100oC. The specimen subjected to 100oC was observed to have the lowest strength for both 7 and 14 days cured specimen. From the compaction test, the optimum moisture content increased from 11.7% to 17.6% considering 0% to 10% addition of Palm Bunch Ash while the Maximum Dry Density decreases from 1860kg/m3to 1730kg/m3for 0% to 10% addition of PBA admixture and  the CBR increased from 82% to 93% with the increase in Palm Bunch Ash addition. Keywords: Temperature changes, unconfined compressive strength, palm bunch ash, ordinary Portland cement, admixture

Effect of Coconut Shell Husk Ash and Palm Kernel Shell Husk Ash on the Grading and Consistency Behaviour of Pozzolan Stabilized Oboro Lateritic Soil

The effect of Coconut shell husk ash and palm kernel shell husk ash on the grading and consistency of oboro lateritic soil stabilized with pozzolan has been studied in this research. Results of the grading analysis have shown that the natural soil was classified as A-7-6 soil according to the AASHTO classification system and CH- inorganic sandy fat clay according to USCS. The consistency result of the natural soil showed that the soil is highly plastic with a plasticity index of 54.4% ˃ 17. The admixtures were used in the proportions of 2%, 4%, 6%, 8% and 10% and their proportional effect on the grading behaviour of the pozzolan stabilized soil showed that the uniformity and curvature of the soil improved with increased admixtures. CSHA recorded a better improvement with the uniformity of the soil while PKSHA recorded better improvement with the curvature of the soil. The consistency limits results showed that the plasticity of the stabilized soil decreased with increase in percentage of admixtures making the mixture less plastic. Finally it has been established that CSHA and PKSHA are good admixtures in the stabilization of weak and highly plastic engineering soil and are recommended for use. Keywords: Coconut shell husk ash, palm kernel shell husk ash, grading and consistency behaviour, oboro lateritic soil, stabilized

Nanostructured Clay (NC) and the Stabilization of Lateritic Soil for Construction Purposes

The use of Nanostructured Clay additive in lateritic soil stabilization and their effect at different percentages on the natural soil was investigated. The preliminary tests on the soil showed it was an A-2-7 soil, according to AASHTO classification. The soil sample was also observed to be silty clayey sand and the general rating as a sub-grade material was ‘GOOD’. The consistency limits result shows that the value of the LL for the natural soil is 47% and 25.15% was recorded for the plastic limit (PL) and finally the PI was 21.85% i.e. highly plastic soil. Further, the effect of the addition of NC in the proportions of 3%, 6%, 9%, 12% and 15% by weight of the stabilized Umuntu Olokoro lateritic soil was investigated. The consistency limits results showed that the addition of variable proportions of NC considerably improved the plasticity of the stabilized soil which gave 13.8%; a medium plastic material at 15% NC addition, compared to the preliminary result of 0% by weight additive which gave 21.85%; a highly plastic material. The strength properties’ test showed significant improvements with the addition of NC; CBR test result recorded 29% at 15% by weight proportion of NC which satisfies the material condition for use as sub-base material and the UCS test results similarly improved consistently and recorded a maximum UCS of 340.18kN/m2 at 15% by weight proportion of NC addition which satisfies “very stiff” material consistency for use as sub-base material. With the foregoing, the addition of various proportions of NC to the stabilized lateritic soil has presented to be a Geotechnical solution to the varied environmental failures on the road pavements. Hence NC satisfies all the material conditions for use as a sub-base material for the stabilization and improvement of the strength characteristics of lateritic soils. Finally, we call on the relevant agencies to use NC as an additive in stabilizing weak lateritic soils for use as either sub-grade or sub-base materials to save both cost and the structural failures on the roads in south eastern Nigeria. Keywords: Environmental Geotechnics; Pavement Geotechnics; Soil Stabilization; Weak Lateritic Soil; South Eastern Nigeria

Characterization of net-zero pozzolanic potential of thermally-derived metakaolin samples for sustainable carbon neutrality construction

Abstract Metakaolin (MK) is one of the most sustainable cementitious construction materials, which is derived through a direct heating procedure known as calcination. Calcination process takes place substantially lower temperatures than that required for Portland cement, making it a more environmentally sustainable alternative to traditional cement. This procedure causes the removal of hydroxyl water from the naturally occurring kaolin clay (Al2Si2O5(OH)4 with MK (Al2O3·2SiO2) as its product. Kaolin naturally exists in large amount within 5°29′N–5°35′N and 7°21′E–7°3′E geographical coordinates surrounding Umuoke, Obowo, Nigeria. Alumina and silica are the predominant compounds in MK, which provide it with the pozzolanic ability, known as the 3-chemical pozzolanic potential (3CPP), with high potential as a cementitious material in concrete production and soil stabilization. Over the years, researchers have suggested the best temperature at which MK is derived to have the highest pozzolanic ability. Prominent among these temperature suggestions were 800 °C (3CPP of 94.45%) and 750 °C (3CPP of 94.76%) for 2 h and 5 h’ calcination periods, respectively. In this research paper, 11 different specimens of Kaolin clay obtained from Umuoke, Nigeria, were subjected to a calcination process at oven temperatures from 350 to 850 °C in an increment of 50 °C for 1 h each to derive 11 samples of MK. The MK samples and Kaolin were further subjected to X-ray fluorescence), scanning electron microscopy (SEM) and X-ray diffraction (XRD) Brunauer–Emmett–Teller (BET) tests to determine the microstructural behaviour and the pozzolanic properties via the 3CPP as to exploit the best MK with the highest cementing potential as a construction material. The results show that the MK heated at 550 °C and 800 °C produced the highest pozzolanic potentials of 96.26% and 96.28%, respectively. The enhancement in pozzolanic potential at optimum calcination temperature is attributed to an increase in the specific surface area upon calcination of kaolinite confirmed by BET results. The SEM and XRD results further supported the above result with the strengthened crystal structure of the MK at these preferred temperatures. Generally, 550 °C is more preferred due to the less heat energy needed for its formulation during 1 h of calcination, which outperforms the previous results, that suggested 750 °C and 800 °C in addition to longer hours of heat exposure

Comparative modelling of strength properties of hydrated-lime activated rice husk-ash (HARHA) modified soft soil for pavement construction purposes by artificial neural network (ANN) and fuzzy logic (FL)

Artificial neural network and fuzzy logic based model soft-computing techniques were adapted in the research study for the evaluation of the expansive clay soil-HARHA mixture’s consistency limit, compressibility and mechanical strength properties. The problematic clay soil was stabilized with varying proportions of HARHA (stabilizing agent) which is an agricultural waste derivative from the milling of rice ranging from 0% to 12%; the utilization of the alkaline activated wastes encourages its recycling and re-use to obtain sustainable, eco-efficient and eco-friendly engineered infrastructure for use in the construction industry with economic benefits also. The obtained laboratory and experimental responses were taken as the system database for the ANN and fuzzy logic model development; the soil-HARHA proportions with their corresponding compaction and consistency limit characteristics were feed to the network as the model input variables while the mechanical strength (California-bearing-ratio (CBR), unconfined-compressive-strength (UCS) and Resistance value (R-values)) responses of the blended soil mixture were the model target variables. For the ANN model, feed forward back propagation and Levernberg Marquardt training algorithm were utilized for the model development with the optimized network architecture of 8-6-3 derived based on MSE performance criteria; while for the fuzzy logic model, the mamdani FIS with both triangular and trapezoidal membership function with both models formulated, simulated and computed using MATLAB toolbox. The models were compared in terms of accuracy of prediction using MAE, RMSE and coefficient of determination and from the computed results, 0.2750, 0.4154 and 0.9983 respectively for ANN model while 0.3737, 0.6654 and 0.9894 respectively was obtained for fuzzy logic model. The two models displayed robust characteristics and performed satisfactorily enabling the optimization of the solid waste derivatives utilization for soil mechanical properties improvement for engineering purposes