Problematic soil stabilization processes involve the application of binders to improve the engineering properties of the soil. This is done to change the undesirable properties of these soils to meet basic design standards. However, very little attention has been given to the reactive phase of soil stabilization. This phase is the most important in every stabilization protocol because it embodies the reactions that lead to the bonding of the dispersed particles of clayey soil. Hence, this reactive phase is reviewed. When clayey soils which make up the greatest fraction of expansive soil come in contact with moisture, they experience volume changes due to adsorbed moisture that forms films of double diffused layer on the particles. When this happens, the clayey particles disperse and float, increasing the pore spaces or voids that exist in the soil mass. Stabilizations of these soils are conducted to close the gaps between the dispersed clayey soil particles. This is achieved by mixing additives that will release calcium, aluminum, silicon, etc., in the presence of adsorbed moisture, and a hydration reaction occurs. This is followed by the displacement reaction based on the metallic order in the electrochemical series. This causes a calcination reaction, a process whereby calcium displaces the hydrogen ions of the dipole adsorbed moisture and displaces the sodium ion responsible for the swelling potential of clayey soils. These whole processes lead to a pozzolanic reaction, which finally forms calcium alumina‐silica hydrate. This formation is responsible for soil stabilization.

Gene expression programming has been applied in this work to predict the California bearing ratio (CBR), unconfined compressive strength (UCS), and resistance value (R value or R_value) of expansive soil treated with an improved composites of rice husk ash. Pavement foundations suffer failures due to poor design and construction, poor materials handling and utilization, and management lapses. The evolution of sustainable green materials and optimization and soft computing techniques have been deployed to improve on the deficiencies being suffered in the abovementioned areas of design and construction engineering. In this work, expansive soil classified as A-7-6 group soil was treated with hydrated-lime activated rice husk ash (HARHA) in an incremental proportion to produce 121 datasets, which were used to predict the behavior of the soil’s strength parameters utilizing the mutative and evolutionary algorithms of GEP. The input parameters were HARHA, liquid limit (), (plastic limit , plasticity index , optimum moisture content (), clay activity (A_C), and (maximum dry density (δ_max) while CBR, UCS, and R value were the output parameters. A multiple linear regression (MLR) was also conducted on the datasets in addition to GEP to serve as a check mechanism. At the end of the computing and iterations, MLR and GEP optimization methods proposed three equations corresponding to the output parameters of the work. The responses validation on the predicted models shows a good correlation above 0.9 and a great performance index. The predicted models’ performance has shown that GEP soft computing has predicted models that can be used in the design of CBR, UCS, and R value for soils being used as foundation materials and being treated with admixtures as a binding component.

The major challenge surrounding construction projects are hinged on time, cost and quality, which are all susceptible to uncertainty and have financial implications. As a response to the excessive uncertainty, standard contracts for construction projects demand that contractors indemnify all works associated with a project and the people involved in it through having insurance cover. Even though the consensus that insurance as a primary means of managing risk has expanded significantly, few contractors have adopted it in developing countries. This study set out to evaluate the factors influencing insurance use as a risk response tool for contractors alongside its efficiency in the construction industry. Quantitative research method was adopted to achieve the aim of the study in which a close-ended questionnaire was developed. Respondents were chosen using a purposive sampling technique and they include Architects, Construction Managers, Project Managers, Quantity Surveyors, Engineers and Insurance professionals within Gauteng province. Retrieved data was analysed using descriptive statistics, One-Sample T-test, and exploratory factor analysis. Findings revealed that factors influencing insurance use as risk response tool by contractors can be categorised into project characteristics, financial stability influence, organisational objective influence, insurer’s influence, and insured participants and legal requirement influence. It was also established that insurance is efficient in managing external risks. Based on these findings, it was concluded that project characteristics play a major role in the decision to employ insurance as a tool for managing risk. It was recommended that construction team players and stakeholders should encourage the use of the different insurance covers for construction projects.

Volume change in expansive soils is a problem encountered in earth work around the world. This is prominent with hydraulically bound structures or foundations subjected to prolonged moisture exposure. This behavior of clayey used as subgrade, foundation, landfill, or backfill materials causes undesirable structural functionality and failures. To prevent this happening, clayey soils are studied for possible volume change potential and degree of expansion. Consequently, the problematic soils are stabilized. In this work, the stabilization of clayey highly expansive soil classified as A‐7‐6 soil and highly plastic with high clay content was conducted under laboratory conditions. The treatment exercise was experimented using quicklime‐activated rice husk ash (QARHA), hydrated lime‐activated rice husk ash (HARHA), and calcite‐activated rice husk ash (CARHA) at the rates of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%. Upon treatment with the three calcium compounds to produce three sets of treated experimental specimens, the plasticity index was observed and recorded and swelling potentials were evaluated using the plasticity index method (PIM). The results showed a consistent improvement on the properties of the treated soil with the addition of the different activated admixtures. While the utilization of CARHA and HARHA improved the clayey soil to medium expansive soil, the treated clayey soil substantially improved from highly expansive soil with a potential of 23.35% to less expansive with a final potential of 0.59% upon the addition of 10% QARHA. Finally, QARHA was adjudged as the best binding composite due to the highest rate of reduction recorded with its utilization.