Deterioration and corrosion in scoria based blended cement concrete subjected to mixed sulfate environment

The use of blended cements incorporating supplementary cementing materials and cements with low C 3 A content is becoming common to prevent the deterioration of concrete structures subjected to aggressive environments. This paper presents the results of an investigation on the performance of finely ground volcanic scori

STR-920: STRUCTURAL BEHAVIOUR OF REINFORCED HIGH PERFORMANCE CONCRETE COLUMNS SUBJECTED TO MONOTONIC AXIAL LOADING

This paper presents the results of experimental and analytical investigations on the structural performance of high performance reinforced concrete (HPC) columns subjected to monotonic axial loading. Reinforced columns made of self-consolidating concrete (SCC), engineered cementitious composite (ECC) and ultra-high performance concrete (UHPC) were tested to failure under axial loading. The test variables included concrete strength and length/slenderness of columns (classified as short and long columns). The UHPC and ECC columns demonstrated excellent ductility and higher energy absorbing capacity compared to their SCC counterparts. UHPC columns also illustrated higher ultimate load capacity compared to both ECC and SCC columns. The efficiency of UHPC and ECC columns was also judged based on strength and ductility ratio compared to their SCC counterparts. Existing models and other Code based equations were used to predict the axial load capacity as a part of analytical investigation. The predictions suggested the need for the modification of existing models/Code based equations for UHPC and ECC columns

STR-928: SHEAR RESISTANCE OF COMPOSITE BEAMS WITHOUT SHEAR REINFORCEMENT

This paper presents the shear behaviour of composite beams made of combinations of high performance concretes (HPCs) such as self-consolidating concrete (SCC) and ductile Engineered Cementitious Composite (ECC). The variables in this experimental and Code based study was shear span to depth ratio, concrete types, longitudinal reinforcement and depth ratio (of ECC and SCC layer). The performance of ECC-SCC composite beams was compared with full depth normal SCC beams based on load-deformation response, stress-strain development, shear strength, failure mode, energy absorption capacity and aggregate-dowel action. The performance of American code in predicting shear strength of SCC beams including ECC-SCC composite beams was studied based on experimental results

STR-927: SHEAR RESISTANCE OF LIGHTWEIGHT SELF-CONSOLIDATING CONCRETE BEAMS

This paper presents the shear behavior of lightweight self-consolidating concrete (LWSCC) beams without shear reinforcement compared to those made with normal weight self-consolidating concrete (SCC). The variables in this experimental and Code based study was shear span to depth ratio, concrete types and longitudinal reinforcement. The performance of LWSCC was compared with normal SCC beams based on load-deformation response, stress-strain development, and shear strength and failure modes. LWSCC beams showed lower post-cracking shear resistance and the shear strength of LWSCC/SCC beams increased with the decrease of shear span to depth ratio. LWSCC beams showed higher number of cracks and wider crack width at failure than their SCC counterparts. American, Canadian and British Codes were conservative in predicting shear strength of LWSCC beams

MAT-712: MICROSTRUCTURAL INVESTIGATIONS ON THE SELF-HEALING ABILITY OF ENGINEERED CEMENTITIOUS COMPOSITES INCORPORATING DIFFERENT MINERAL ADMIXTURES

The present study investigates the impacts that self-healing has on the microstructure characteristics of microcracked Engineered Cementitious Composites (ECC). These have two contrasting maturity levels and, furthermore, they involve three varying mineral admixtures that have very different chemical constituents. The impact of self-healing on the transport characteristics was examined by employing rapid chloride permeability tests (RCPT). The findings indicated that, if the appropriate mineral admixture type and conditioning were chosen, it would be possible to enhance the majority of the chloride ion penetrability levels following a 30-day period of water curing. As a result, the majority of the findings were in range of the low penetrability level over the 30 days, as set by ASTM C1202. The microstructural indications corroborated the findings from the experiments and provided weight to the notion that the causal factor of the healing was the appearance of calcium carbonate and C-S-H. These served to fill the crack owing to the hydration of the cementitious particles. In summary, the results indicate that the degree of self-healing is subject to variance in accordance with the contrasting chemical compositions that dominate within a certain infrastructure type over the course of its service life

MAT-731: MECHANICAL & DURABILITY PROPERTIES OF ENGINEERED CEMENTITIOUS COMPOSITES WITH DIFFERENT AGGREGATES

This paper presents the outcome of a study conducted to exhibit the effect of micro-silica sand and mortar sand on fresh, mechanical and durability properties of Engineered Cementitious Composites (ECCs). ECC is a ductile concrete characterized by strain hardening and multiple-cracking behavior under tension and shear. This study used locally available aggregates instead of standard micro-silica sand to produce cost-effective, sustainable and green ECC mixtures to be used for construction applications. ECCs prepared by both types of sands exhibited almost similar behaviour in terms of fresh, mechanical and durability properties which indicated the viability of producing ECC mixtures with mortar sand. In addition, the behaviour of a standard ECC can still be achieved when producing ECCs made of high volume fly ash (up to 70% cement replacement) along with local mortar sand. By employing results of this research, correlations were derived between mechanical and durability properties

Rechargeable metal-metal alkaline batteries : Recent advances, current issues and future research strategies

Over the past few decades, remarkable advancement has been attained in the field of rechargeable metal–metal alkaline batteries (RABs). In terms of safety, energy density, charge-discharge capacity, and long-term storage capability, metal-metal RABs (e.g., Ni–Zn, Ni–Fe, Ni–Bi, Ni–MH, Ag–Zn, Co–Zn, Cu–Zn, and Bi–Zn systems) are contemplated as the promising energy storage devices for the applications in electric vehicles (EVs), hybrid EVs, grid-scale energy storage, as well as various implantable and wearable electronic devices. Especially, Ni-MH batteries become competitive with Li-ion batteries for EVs and hybrid EVs applications due to their high tolerance against mechanical abuse, stability under wide temperature ranges, and considerable charge/discharge capacity. Meanwhile, earlier works reviewed only specific topics, so, as a rapidly growing research topic, providing a deep understanding on metal–metal RABs is timely and worthwhile. So, in this work, we discuss the electrochemistry of all metal-metal RABs, then full cell designing with their performance will be discussed thoroughly. Further, issues associated with the existing metal–metal RABs and corresponding impro

Optimizing Precursors and Reagents for the Development of Alkali-Activated Binders in Ambient Curing Conditions

Alkali-activated binders (AABs) are developed through the activation of aluminosilicate-rich materials using alkaline reagents. The characteristics of AABs developed using a novel dry-mixing technique incorporating powder-based reagents/activators are extensively explored. A total of forty-four binder mixes are assessed in terms of their fresh and hardened state properties. The influence of mono/binary/ternary combinations of supplementary cementitious materials (SCMs)/precursors and different types/combinations/dosages of powder-based reagents on the strength and workability properties of different binder mixes are assessed to determine the optimum composition of precursors and the reagents. The binary (55% fly ash class C and 45% ground granulated blast furnace slag) and ternary (25% fly ash class C, 35% fly ash class F and 40% ground granulated blast furnace slag) binders with reagent-2 (calcium hydroxide and sodium sulfate = 2.5:1) exhibited desired workability and 28-day compressive strengths of 56 and 52 MPa, respectively. Microstructural analyses (in terms of SEM/EDS and XRD) revealed the formation of additional calcium aluminosilicate hydrate with sodium or mixed Ca/Na compounds in binary and ternary binders incorporating reagent-2, resulting in higher compressive strength. This research confirms the potential of producing powder-based cement-free green AABs incorporating binary/ternary combinations of SCMs having the desired fresh and hardened state properties under ambient curing conditions