Portland cement porous concrete (PCPC) has received immense interest recently due to its environmental aids. Its porous structure helps to reduce the water runoff amount while improving the recharge of groundwater. Earlier studies have concentrated on illustrating and knowing the functional as well as structural properties of PCPC. However, very few studies are available on PCPC in combination with natural silica sources as supplementary cementitious materials (SCMs). Most SCMs are by-products of industrial manufacturing processes and cause some environmental concerns, but with their pozzolanic effect, they could be utilized as partial substitute materials for ordinary Portland cement (OPC) to enhance the strength as well as durability performance. The aim of this study is to evaluate the effects of diatomaceous earth (DE) as a supplementary cementitious material for partial substitution of OPC for Portland cement porous concrete application. Compression strength, split tensile strength, and flexural strength tests were performed to determine the effect of partial replacement. To investigate the impact of test variables, basic tests, including void content and water permeability, were also performed. Compared to the control concrete, the results show that a 15% replacement of cement with DE significantly increased the compressive strength (by 53%) while also providing adequate porosity and better water permeability. Statistical analysis (ANOVA) and regression analysis showed that there is a significant (p < 0.05) growth within the physical characteristics of concrete upon the replacement of cement by 15% DE. Collectively, the replacement of cement with DE could not only improve the concrete strength but also reduce the consumption of cement, thereby lessening the cost of construction as well as indirectly reducing the carbon footprint.

Stabilizing sand with cement is considered to be one of the most cost-effective and useful methods of in-situ soil improvement, and the effectiveness is often assessed using unconfined compressive tests. In certain cases, zeolite and cement blends have been used; however, even though this is a fundamental issue that affects the settlement response of a soil, very few attempts have been made to assess the stress-strain behaviour of the improved soil. Also, the majority of previous studies that predicted the unconfined compressive strength (UCS) of zeolite cemented sand did not examine the effect of the soil improvement variables and strain concurrently. Therefore, in this paper, an initiative is taken to predict the relationships for the stress-strain behaviour of cemented and zeolite-cemented sand. The analysis is based on using the unconfined compression test results and Group Method of Data Handling (GMDH) type Neural Network (NN). To achieve this end, 216 stress-strain diagrams resulting from unconfined compression tests for different cement and zeolite contents, relative densities, and curing times are collected and modelled via GMDH type NN. In order to increase the accuracy of the predictions, the parameters associated with successive stress and strain increments are considered. The results show that the suggested two and three hidden layer models appropriately characterise the stressstrain variations to produce accurate results. Moreover, the UCS values derived from this method are much more accurate than those provided in previous approaches. Moreover, the UCS values derived from this method are much more accurate than those provided in previous approaches which simply proposed the UCS values based on the content of the chemical binders, compaction, and/or curing time, not considering the relationship between stress and strain.Finally, GMDH models can be considered to be a powerful method to determine the mechanical properties of a soil including the stress-strain relationships. The other novelty of the work is that the accuracy of the prediction of the strain-stress behaviour of zeolite-cement-sand samples using the GMDH models is much higher than that of the other models.

Low plasticity clays are found in abundance worldwide, exerting undue stresses on civil structures, road pavements and railway infrastructure, owing to the periodic settlement caused by their low bearing capacity and slight swelling potential. They are often encountered as natural soil when constructing road subgrade and have the potential to compromise the integrity of the entire pavement system unless improved appropriately. Furthermore, the accumulation of vast quantities of non-biodegradable glass waste is identified as a challenge in many countries. Considering the above, this paper aims to provide a sustainable solution by studying the effect of crushed glass (CG) at varied inclusions of 0, 5, 10, 15 and 20% in a clay subgrade. The testing procedure implemented includes three distinct testing phases, namely, material properties, microstructural properties and mechanical strength tests. The material property tests involved particle size distribution, X-ray fluorescence (XRF) and X-ray diffraction (XRD) testing. Microstructural tests considered include scanning electron microscope (SEM) and micro-CT (CT) testing, which enabled a vital understanding of how the introduction of glass affects the internal structure of the clay matrix, where an increase in the porosity was evident upon adding CG. The mechanical testing phase involved standard compaction, unconfined comprehensive strength (UCS), California bearing ratio (CBR), resilient modulus and swelling–shrinkage tests. It can be concluded that introducing CG improved the clay’s mechanical strength with respect to UCS, CBR and resilient modulus whilst also reducing its swelling potential, where the optimum inclusion of CG at 15% best enhanced the mechanical strength properties of the low plasticity clay.

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