Sustainable Cements Containing Sugarcane Bagasse Ash and Limestone: Effects on Compressive Strength and Acid Attack of Mortar

Development of sustainable interlocking concrete paving blocks using bamboo leaf ash and metakaolin

Eco-friendly interlocking concrete pavement block was developed using the admixture of bamboo leaf ash and metakaolin. This was done to develop an eco-friendly interlocking paving block for sustainable pavement construction. Bamboo leaf ash and metakaolin were added as a supplementary cementitious material. The supplementary cementitious material (bamboo leaf ash and metakaolin) were admixed and added at 0, 5, 10, 15, 20, 25 and 30 % replacement of cement. The workability of the fresh concrete (slump) at the varied percentage additions, and the mechanical properties of the concrete at 7, 14, 28, and 56 days of curing were assessed, including their microstructural characteristics. The outcome of the research showed that increasing the percentage of (bamboo leaf ash + metakaolin) reduces the workability of the concrete. With a 20 % addition of this cementitious material, the developed fresh concrete became unworkable. In addition, replacing up to 10 % of the concrete in the pavement with bamboo leaf ash and metakaolin increased the mechanical strength of the concrete by 28.7 %. At 30 % a percentage increase of 3.6 % was recorded. However, the strength at 5 % was still adequate for pavement construction with a 13.62 % increase in mechanical strength. The compressive strength at 5 % and 10 % addition of the supplementary cementitious material at maturity met the criteria for constructing a semi-rigid pavement, using IRC standards. The microstructural assessment showed that the number of pores in the mature concrete samples decreased at 10 % addition of bamboo leaf ash and metakaolin. The research data provides construction workers, researchers, and highway engineers with vital information regarding the viability of these sustainable materials for pavement improvement.

Study of the Pozzolanic Reactivity of Sugar Cane Straw Ashes (SCSA) Burned under Controlled Conditions

The aims of this work were to evaluate the reactivity of sugarcane straw ashes (SCSA) burned under controlled conditions and to analyze their reactivity in blended cement and hydrated lime pastes by thermogravimetric analysis (TG) and calorimetry. Four different ashes were produced, and burned at 600 °C, 700 °C, 800 °C and 900 °C (SCSA600, SCSA700, SCSA800 and SCSA900, respectively). These ashes were characterized by X-ray fluorescence spectroscopy, X-ray diffractometry, particle size distribution by laser diffraction and specific area surfaces to assess their potential interest in the partial replacement of inorganic binders (Portland cement (OPC) and hydrated lime). The hydrated lime pastes were subjected to scanning electron microscopy (SEM) and TG. The blended cement pastes were analyzed by TG and calorimetry, compressive strength testing and mercury intrusion porosimetry. High lime fixation percentages were observed in the hydrated lime and OPC pastes and were higher than 75% and 50% for the ashes burned at 600 °C and 700 °C, respectively. Calorimetry showed a delay in the heat release of SCSA600 and SCSA700 compared to the control paste. These pastes also had higher compressive strength and a smaller total pore volume. The results indicate the positive response of preparing sugar cane ashes under controlled conditions (mainly for straw calcined within the 600-700 °C range) for their use as pozzolanic addition by partially replacing inorganic binders.

A Numerical Model for the Optimization of Concentrated Suspensions for Sustainable Concrete Proportioning

Concrete has a large environmental impact due to CO2 emissions related to cement manufacturing and the consumption of natural aggregates. More sustainable concretes can be developed, replacing part of the cement with mineral admixtures or natural aggregates with recycled ones. However, recycled materials are less regular than natural ones, and using new deposit changes concrete properties, which necessitates the re-optimization of mixture proportions. For small/medium-size waste deposits, the expensive experimental work needed to adapt concrete formulation containing these particular wastes is not profitable, which prevents from their valorization. The aim of this study is to develop a numerical model to optimize the mixture proportions of concentrated suspensions based on very limited entry data. In the model, spheres of small radii are seeded in the porosity and allowed to swell until reaching a target radius/density. On monosized suspensions, it is shown that the ratio between the number of random displacements to the number of particles varies with density, following a classical viscosity–density relationship, which allows identification of the packing fraction. The model is extended to bidisperse systems, with the viscosity of the whole suspension calculated by combining the viscosities of each granular class. The model is applied to bidisperse systems of size ratios 4:1 and 2:1 with varying proportions of large particles. The optimum proportions identified numerically are compared successfully to experimental results from the literature.