Replacement of Natural Sand with Expanded Vermiculite in Fly Ash-Based Geopolymer Mortars

Increasing the thermal insulation of building components to reduce the thermal energy loss of buildings has received significant attention. Owing to its porous structure, using expanded vermiculite as an alternative to natural river sand in the development of building materials would result in improvement of the thermal performance of buildings. This study investigates the properties of fly ash (FA)-based geopolymer mortars prepared with expanded vermiculite. The main aim of this study was to produce geopolymer mortar with lower thermal conductivity than conventional mortar for thermal insulation applications in buildings. A total of twelve batches of geopolymers were prepared for evaluating their different properties. The obtained results show that, at a given FA and expanded vermiculite content, the geopolymers prepared with a 10 molar NaOH solution exhibited a higher flowability, water absorption and porosity, as well as a lower dry unit weight, compressive strength, ultrasound pulse velocity and thermal conductivity compared with those prepared with a 15 molar NaOH solution. As is also shown, the geopolymers containing expanded vermiculite (15%) developed a lower flowability (~6%), dry unit weight (~6%), compressive strength (~7%), ultrasound pulse velocity (~6%) and thermal conductivity (~18%), as well as a higher apparent porosity (~6%) and water absorption (~9%) compared with those without expanded vermiculite at a given FA content and NaOH concentration. The findings of this study suggest that incorporating expanded vermiculite in FA-based geopolymer mortar can provide eco-friendly and lightweight building composites with improved sound and thermal insulation properties, contributing toward the reduction of the environmental effects of waste materials and conservation of natural sand

Performance of concrete containing pristine graphene-treated recycled concrete aggregates

Upcycling recycled coarse aggregates (RCAs) in concrete is a promising way to decrease the environmental effect of construction and demolition waste and improve concrete sustainability. Pretreatment of RCAs helps to enhance the quality of the resulting concrete and results in an increased level of confidence for material suppliers to systematically use RCAs to replace virgin aggregates for concrete production. This study demonstrates the utilization of pristine graphene for pretreating RCAs with the aim of effectively alleviating the loss of mechanical and durability performance of concretes when compared to virgin aggregate concretes. The RCAs were presoaked in water solution containing graphene concentration ranging from 0 to 0.5 %. Then, 50 % of natural coarse aggregates were replaced with the RCAs for concrete production. Different properties of concrete including slump, axial compression, splitting tension, water absorption and drying shrinkage were measured. In addition, microanalysis of the aggregates was performed by x-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Based on results, treating the RCAs with 0.2 wt% pristine graphene results in increased workability (13 %), compressive strength (21 %) and tensile strength (12 %) and decreased water absorption (22 %) and drying shrinkage (20 %) of the RCA concrete. Increasing the concentration of the graphene beyond 0.2 wt% is found to decrease the workability and strength properties and increase the water absorption and drying shrinkage. This is attributed to the agglomeration of the graphene at high concentrations, leading to non-uniform filling effects and ineffective microcrack and void filling. It is also found that 0.2 wt% is the optimum pristine graphene concentration, which can lead to an RCA concrete with similar mechanical and durability properties to the conventional concrete

A novel causative functional mutation in GATA6 gene is responsible for familial dilated cardiomyopathy as supported by in silico functional analysis

Funding Information: This study was supported by grants from the Mashhad University of Medical Sciences (Grant Number 980955). The authors thank the management of advanced computational centre, Khayyam Innovation Ecosystem, Mashhad, Iran for providing the facilities and encouragement to carry out this research work.Peer reviewedPublisher PD

Development of Eco-Friendly and High Performance Construction Materials and Technologies

Because of global environmental concerns for concrete and waste materials and increased awareness of non-renewable natural resources, there is an urgent need to find ways to develop eco-friendly concretes. This is reflected in the large number of recent studies undertaken toward this end. However, the existing studies lack some of main parameters and points, such as the influence of the quality of recycled aggregates, influence of the full replacement of dry constituents with waste-based alternatives, influence of high performance graphene nanomaterials, and influence of the lateral confinement at the material level on the properties of concretes. This thesis contains a series of journal papers focused on the development of eco-friendly and high performance construction materials. In this research the behaviour of different types of concretes and mortars, including recycled aggregate concrete (RAC), geopolymer mortar, waste-based concrete and mortar, and graphene-based cement mortar, is studied. In addition, this thesis presents the behaviour of geopolymer concrete and steel fibre-reinforced concrete (SFRC) under active confinement and high-strength concrete (HSC) under shape memory alloy (SMA) confinement. The experimental study on time-dependent and long-term mechanical properties of RACs shows that high-strength RACs, prepared with full replacement of natural aggregates with recycled concrete aggregates having a high parent concrete strength (110 MPa), exhibit the properties similar to or better than those of companion natural aggregate concretes. Using gene expression programming (GEP) technique, new empirical models are developed to accurately predict mechanical properties of RACs. In addition, analytical studies on RACs reveal that multivariate adaptive regression splines (MARS), M5 model tree (M5Tree), and least squares support vector regression (LSSVR) models provide close predictions of mechanical properties of RACs by accurately capturing influences of key parameters. The experimental study on waste-based concrete reveals that concretes containing ground granulated blast furnace slag (GGBS) at up to 90% cement replacement exhibit nearly similar mechanical properties to the conventional concrete after 28 days of curing age. The experimental studies on geopolymer and waste-based mortars show that mortars with full replacement of sand with lead smelter slag (LSS) and glass sand (GS) and up to 80% replacement of cement with GGBS exhibit nearly similar mechanical properties to the conventional mortar. The study on the influence of graphene oxide (GO) dosage on physiochemical and mechanical properties of cement mortars shows considerable dosage dependence with the optimum dosage of 0.1% GO (by weight of cement) that increases 28-day tensile and compressive strength of the composite by 37.5% and 77.7%, respectively. The study on the influence of oxygen functional groups of graphene on the properties of cement mortars reveals that an addition of 0.1% reduced GO (rGO) prepared by 15 min reduction and 0.2% (wt%) hydrazine results in a maximum enhancement of 45.0% and 83.7% in the 28-day tensile and compressive strengths compared to the plain cement mortar, respectively. The experimental study on the behaviour of ambient- and oven-cured geopolymer concretes under active confinement reveals that oven-cured geopolymers exhibit a less ductile behaviour and lateral dilation than their ambient-cured counterparts. The experimental study on the compressive behaviour of SMA-confined HSCs shows that confinement of HSC by 9.5% prestrained SMA spirals leads to 23.6% higher peak axial stress and 346% higher corresponding axial strain than that of unconfined HSC. The experimental study on the compressive behaviour of actively confined SFRC reveals that an increase in the steel fibre volume fraction leads to an increase in ductility of SFRCs. A finite element (FE) model is also developed to accurately predict the compressive behaviour of fibre-reinforced polymer (FRP)-confined SFRCs. The promising findings of this research point to the possibility of the development of eco-friendly and high performance composite members for structural applications in the construction industry.Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 201

Damage-Plasticity Model for FRP-Confined Normal-Strength and High-Strength Concrete

This paper presents a modified damage-plasticity model for fiber-reinforced polymer (FRP)-confined normal-strength and high-strength concrete (NSC and HSC). The proposed model is based on a concrete damage-plasticity model from the literature, which is improved through accurate incorporation of the effects of the confinement level, concrete strength, and nonlinear dilation behavior of FRP-confined concrete. The proposed model uses a new and accurate failure surface and flow rule that were established using a comprehensive and up-to-date experimental test database and it incorporates an analytical rupture strain model for the FRP jacket. Finite-element (FE) models incorporating the proposed damage-plasticity model are developed and validated for concretes having up to 110-MPa compressive strength confined by different types of FRP under a wide range of confining pressures. Comparisons with experimental results show that the model’s predictions of (1) axial stress-axial strain, (2) lateral strain-axial strain, (3) axial stress-volumetric strain, (4) plastic volumetric strain-axial plastic strain, and (5) plastic dilation angle-axial plastic strain relations are in good agreement with the test results of FRP-confined NSC and HSC. The accurate predictions of the compressive strength and ultimate axial strain of FRP-confined concrete were achieved by establishing the hardening/softening rule and flow rule based on the level of confining pressure and modeling the failure surface of the confined concrete by incorporating the effect of unconfined concrete strength

Physical and mechanical properties of foam concretes containing granulated blast furnace slag as fine aggregate

In recent years, industrial by-products have been considered as a promising waste-based material in the production of concrete for development of an eco-friendly construction material. An experimental study on the properties of foam concretes, made with a protein-based foam agent, containing fly ash (FA) as binder and granulated blast furnace slag (GBS) as fine aggregate is presented in this paper. A total of nine batches of foam concretes were manufactured and tests were performed to evaluate the porosity, bulk density, compressive strength, water absorption, ultrasound velocity, and thermal conductivity. To explain the reasons for the obtained experimental results microstructural analysis was also conducted. The results show that an increased water-to-binder ratio (w/b) owing to a decreased binder content results in an increase in the porosity of the foam concretes, which consequently leads to a decrease in the bulk density, compressive strength, ultrasound velocity, and thermal conductivity, and an increase in the water absorption of foam concretes. It is also found that foam concretes with 100% GBS as sand replacement, at a higher w/b exhibits a lower bulk density, ultrasound velocity, and thermal conductivity than those of the companion control foam concrete, and they provide a higher compressive strength at a lower w/b. The results indicate that the foam concrete with 100% GBS at w/b of 0.68 develops superior properties than the companion control foam concrete by exhibiting a lower porosity, bulk density, ultrasound velocity, thermal conductivity, higher compressive strength, and a similar water absorption compared to those of the companion control foam concrete. These results are promising and point to the significant potential of developing an eco-friendly light-weight concrete by full replacement of natural sand with GBS industrial by-product material

Sustainable mortars containing fly ash, glass powder and blast-furnace and lead-smelter slag

The aim of this study was to develop sustainable concrete using waste products to reduce both the carbon dioxide emissions associated with concrete production and the extraction of non-renewable natural resources. The development of the new sustainable concrete involved the replacement of cement with industrial by-products (fly ash, glass powder and ground granulated blast-furnace slag (GGBS)) and the replacement of natural river sand (NS) with waste-based sand (lead-smelter slag (LSS)). Twenty-four batches of mortar mixes were produced and tests were performed to determine the flowability, compressive strength and direct tensile strength of each batch. Microstructural analysis was undertaken to explain the experimentally obtained properties of the mortars. The compressive and tensile strengths of waste-based mortars containing LSS were found to be similar to those of mortars containing NS. Mortars with 80% replacement of cement with GGBS and 100% replacement of NS with LSS showed minimal strength reduction (4%) compared with the conventional mortar. The strength reductions of the waste-based mortars compared with the conventional mortar increased at 90% and 100% cement replacement levels, but remained limited to approximately 20% (at 90% GGBS) and 30% (at 100% GGBS). The findings of this study are promising and point to the potential development of new structural-grade mortars using full or near-full replacement of cement with industrial by-products and full replacement of NS with waste-based sand