Impact of Fly Ash on Time-Dependent Properties of Agro-Waste Lightweight Aggregate Concrete

The utilization of by-products and waste materials to substitute for the natural or manufactured resources is considered as a practical way to obtain green building materials. In concrete mixtures, amongst the many available options, Fly Ash (FA) as a by-product pozzolan has been used as a partial replacement of cement. As for the aggregates, lightweight agro-waste oil palm shell (OPS) can be used as a replacement to conventional aggregate for the production of lightweight aggregate concrete. The present communication aims to investigate the impact of FA on time-dependent development properties of OPS lightweight aggregate concrete, including density, water absorption, compressive strength up to 120-days, and drying shrinkage up to the age of 365-days under standard moist curing, partially early curing, and non-curing conditions. Additionally, drying shrinkage crack development was investigated. In this study, two series of concrete mixtures with different substitution levels of OPS (0%, 50%, and 100%) and FA were tested. From the obtained results, it was concluded that the incorporation of fly ash in OPS concrete reduces the density and compressive strength values. Dually, the initial and final water absorption values plus the rate of drying shrinkage at early and long-term ages increased. On top of that, a high potential of drying shrinkage crack, especially for mixtures with 100% OPS, was identified.

The reintegration of losses in a wooden late baroque polychrome crucifix: issues and ways to approach the selection of materials

This work will review two different interventions of plastic and pictorial reintegration that a wooden late baroque polychrome sculpture has undergone. The Crucifix of Monte Giove, restored in the laboratory of the University of Urbino Carlo Bo, has unveiled large losses of the wood, some of which have altered the plastic forms and polychromy, and a shrinkage crack that has caused a deep vertical split in the torso and an alteration of the original volume. These issues have presented an opportunity for further discussion and study, relating to the potential solutions for each type of damage: the use of magnets to make the reconstructed elements movable and reversible and a filler for the wood’s crack to solve both the structural and the aesthetic issues. These two choices have been discussed analysing the critical approaches, the materials selection and the aesthetic results.

To the Problem of Assessing the Level of Self- Stresses during the Formation of the Structure of Self-Compacting Concrete

Conditional quantitative criteria characterizing the shrinkage crack resistance of various concretes and a model describing the change in the proposed criteria depending on the magnitude of shrinkage deformation, creep coefficient, tensile strength kinetics and shrinkage strain kinetics for ordinary concrete and self-compacting concrete are proposed. The proposed criteria for the class C40/50 concrete have been calculated and it was shown that self-compacting concrete can potentially have higher crack resistance during shrinkage. To ensure high cracking resistance during shrinkage when choosing superplasticizers and mineral additives, attention should be paid to their effect on shrinkage, creep and E-modulus of the cement stone. It should exclude additives that increase the shrinkage and E-modulus and reduce creep of cement stone.