Properties of compressed lateritic soil stabilized with a burnt clay–lime binder: Effect of mixture components

In this study, a pozzolanic binder containing lime and a common thermally activated kaolinitic clay, at 750 °C, was formulated. The chemical, mineralogical and pozzolanic properties of raw materials were determined. The percentage of lime in the binder varies between 20% and 30%. The binder was used as a stabilizer in compressed lateritic soil in which water–solid (laterite and binder) and laterite–binder ratios vary, respectively, from 0.12 to 0.20 and 4 to 9. Sodium hydroxide (NaOH) was added as a chemical activator in the mixture. The NaOH–binder ratio varies from 0.02 to 0.04. The average effect of each component of the mixture on compressive strength, water absorption and apparent density of compressed laterite after 7 or 28 days of conservation at 40 ± 1 °C in an atmosphere saturated with water vapour was evaluated in a screening design of the “design in graeco – latin squares” type. It was observed that water–solid and laterite–binder ratios are the factors that influence more the properties of the products. Compressive strength increases up to a water–solid ratio of 0.16 then decreases for higher ratios. Compressive strength decreases with the increase of laterite–binder ratio. Water absorption decreases with the increase of water–solid ratio up to 0.16 then sharply increases for higher ratios. However, water absorption decreases slightly with the increase in the lime content of the binder and sodium hydroxide–binder ratio. The maximum apparent density is observed at water–solid ratio of 0.16. It increases when sodium hydroxide–binder and laterite–binder ratios increase.     

Improving hydraulic properties of lime–rice husk ash (RHA) binders with metakaolin (MK)

To improve long-term hydraulic properties of binders from RHA and lime, 25–75% MK was added to RHA. Binders were formulated and properties were compared to that containing RHA or MK as only pozzolans. The lime–pozzolan ratio was 1:3. The properties tested after 7, 28 and 56 days were: absolute density and fineness of the binders, initial setting time, chemical and mineralogical composition of hydrated binders, flexural and compressive strengths and water absorption of mortars. The micrographs of the hardened binder pastes at 56 days permitted to evaluate the densification of different matrixes and the development of pores. From the results obtained, it was concluded that, MK increased the density of mixtures and decreased their grindability. The presence of MK decreased the SiO₂ content of binders and increases their Al₂O₃ and Fe₂O₃ contents. Calcium-silicate hydrates (CSH) gel and gehlenite (C₂ASH₈) were the main phases formed during the pozzolanic reaction in the presence of MK. No reduction in flexural and compressive strengths was observed after 28 days for binders containing MK. The mixture of 25% MK and 75% RHA which is recommended gave flexural and compressive strengths higher than binder with RHA or MK as the only pozzolan. Water absorption of mortars was less than 20%.     

Effect of mixture constituents on properties of slaked lime–metakaolin–sand mortars containing sodium hydroxide

In the present study, percentage of slaked lime (20–30%) in binder with metakaolin, water–binder ratio (0.8–1.0), sand–binder ratio (1–3) and sodium hydroxide (NaOH)–binder ratio (0.02–0.04) were factors varied to investigate properties of fresh or hardened mortars. Sodium hydroxide was used as a chemical activator in the slaked lime–metakaolin binders. Properties studied after 7 or 28 days of curing mortars at 40 ± 1 °C were consistency, compressive strength and water absorption. The physical, chemical, mineralogical and pozzolanic characteristics of materials used in study were determined. It was concluded that water–binder and sand–binder ratios are the most influential factors for consistency and water absorption of mortars. Compressive strength is influenced by all mixture constituents but NaOH–binder ratios less than 0.03 are recommended for use in mortars.     

Synthesis of Volcanic Ash‐based Porous Inorganic Polymers Using Biomass as Pore Inducing Agent: Phase Evolution and Descriptive Microstructure

Silicon - In the present study, multi-scale sized porous inorganic polymers were produced by alkaline activation of volcanic ash. Rice husk ash, an agricultural biomass, was used both in the...