Influence of Asphalt Emulsion Inclusion on Fly Ash/Hydrated Lime Alkali-Activated Material

Supplementary cementitious materials have been widely used to reduce the greenhouse gas emissions caused by ordinary Portland cement (OPC), including in the construction of road bases. In addition, the use of OPC in road base stabilization is inefficient due to its moisture sensitivity and lack of flexibility. Therefore, this study investigates the effect of hybrid alkali-activated materials (H-AAM) on flexibility and water prevention when used as binders while proposing a new and sustainable material. A cationic asphalt emulsion (CAE) was applied to increase this cementless material’s resistance to moisture damage and flexibility. The physical properties and structural formation of this H-AAM, consisting of fly ash, hydrated lime, and sodium hydroxide, were examined. The results revealed that the addition of CAE decreased the material’s mechanical strength due to its hindrance of pozzolanic reactions and alkali activations. This study revealed decreases in the cementitious product’s peak in the x-ray diffraction analysis (XRD) tests and the number of tetrahedrons detected in the Fourier transform infrared spectroscopy analysis (FTIR) tests. The scanning electron microscope (SEM) images showed some signs of asphalt films surrounding hybrid alkali-activated particles and even some unreacted FA particles, indicating incomplete chemical reactions in the study material’s matrix. However, the H-AAM was still able to meet the minimum road base strength requirement of 1.72 MPa. Furthermore, the toughness and flexibility of the H-AAM were enhanced by CAE. Notably, adding 10% and 20% CAE by weight to the hybrid alkali-activated binder produced a significant advantage in terms of water absorption, which can be explained by its influence on the material’s consolidation of its matrices, resulting in significant void reductions. Hence, the outcomes of this study might reveal an opportunity for developing a new stabilizing agent for road bases with water-prevention properties and flexibility that remains faithful to the green construction material concept.

Ferrochrome slag aggregate: physical-chemical characteristics and potential use in lightly cemented road bases

Purpose Most developing countries simply dump ferrochrome slag as waste which occupies huge areas of useful land. The purpose of this study is to underscore the significance of reusing ferrochrome slag as a sustainable and eco-friendly road aggregate material, with the added benefits of preventing possible environmental pollution and promoting sustainable mining of non-renewable construction materials. Design/methodology/approach Physical-mechanical characteristics were investigated using various South African National Standards test procedures. Chemical and mineralogical characteristics were evaluated using the X-ray fluorescence and the X-ray diffraction techniques, respectively. The toxicity characteristic leaching procedure test was used to evaluate the slag’s environmental suitability. Using two cement types, cement proportions of 1%, 2% and 3% of the slag aggregate weight mixed with optimum moisture content of the non-treated compacted slag were used to make lightly cemented ferrochrome slag aggregate (LCFSA) composites, subsequently tested for compressive strength. Findings Ferrochrome slag aggregates have excellent physical-mechanical characteristics that conform to international specifications for use in road base construction. The slag can be classified as non-hazardous solid waste. However, in acidic environments, some toxic elements may leach from the slag and pollute the environment. Optimum cement contents of 2.3% (CEM II) and 2.6% (CEM VB) can be mixed with the slag to produce LCFSA for road bases. Originality/value No research was found in literature on the use of LCFSA in road bases. This research, therefore, presents new data on mix design and strength properties of LCFSA as well as some physical-chemical characteristics of coarse ferrochrome slag aggregate.

Prediction Model of Elastic Modulus for Granular Road Bases

The estimation of elastic modulus for road bases is the primary objective of this research which is implemented a significant role in transmitting the vertical loading to the pavement foundation layers. In this study, the effect of weathering conditions on the stiffness of base course is investigated and implied the durability test by subjecting the prepared samples to a different numbers of wet-dry cycles (0,2, 4, 6, 8 and 10). A conventional base materials of local natural gravel aggregate and treated base materials with recycled concrete aggregate RCA at different percentages (0%, 25%, 50% 75% and 100%) is adopted in this research. The elastic characteristics are estimated in terms of elastic modulus. Elastic modulus are estimated by passing the ultrasonic pulse velocity through the untreated and treated base materials laboratory specimens. This test can be used to study the elastic modulus properties of base materials. A multiple linear regression analysis is used for prediction the elastic modulus using the SPSS (software ver.21). Elastic Modulus (kPa) is the dependent variable whereas the independent variable are; No. of wet- dry cycle and Percent (%) of RCA stabilizer. The obtained results for elastic modulus (Es) of granular base material layer showed increasing in elastic modulus with percentage of RCA%., results revealed that the (Es) values reached a maximum value of (6927kPa) for 100%. For the OMC’s values increases due to the percentage increment of RCA in granular base material mixture, this increment in water contents is refer to high absorption capacity of the paste clinging to the RCA. On other side the dry density decrease gradually with adding percentage of (RCA) in granular base material mixture.