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

Effect of nanosilica addition on the fresh properties and shrinkage of mortars with fly ash and superplasticizer

The ongoing use of various mineral additions along with chemical admixtures such as superplasticizers justifies the need for further research. Understanding and quantifying their effects and possible synergies on the fresh and hardened properties of cement-based materials is necessary, especially if some of these components are known to have a pozzolanic effect. This paper describes and models the fresh and hardened properties of cement mortars including nanosilica and fly ash, and relates their properties to the proportioning of these materials and the superplasticizer dosage. Mini-slump, Marsh cone and Lombardi cone tests were used to examine the properties of the fresh mortars, and to assess density, plastic shrinkage, and drying shrinkage up to 20 days. The equations presented in this paper make it possible to optimize mortar proportionings to the required levels of performance in both fresh and hardened states

Lightweight concrete incorporating pumice based blended cement and aggregate: Mechanical and durability characteristics

This paper presents the development of lightweight volcanic pumice concrete (VPC) using pumice based ASTM Type I blended cement (PVPC) and aggregates (both coarse and fine). The performance of VPC mixtures was evaluated by conducting comprehensive series of tests on fresh and hardened properties as well as durability. Fresh and mechanical properties of VPC mixtures such as slump, air content, compressive strength, tensile strength, density, and modulus of elasticity are described. The durability characteristics were investigated by drying shrinkage, water permeability, mercury intrusion porosimetry, differential scanning calorimetry and microhardness tests. The variables in the study include: % replacement (0%, 50%, 75% and 100% by volume) of normal weight coarse gravel aggregate by coarse lightweight volcanic pumice aggregate (VPA), replacement (100% by volume) of fine aggregate (sand) by fine VPA, constant (0.45)/variable (0.37-0.64) water-to-binder ratio by mass, variable (1.3-3.7) aggregate-to-binder ratio by mass and cement types (ASTM type I cement and PVPC). The investigation suggests the production of lightweight VPCs for structural applications having satisfactory strength and durability characteristics. The use of PVPC induces the beneficial effect of reducing the drying shrinkage and water permeability of VPC mixtures. The presence of coarse/fine/both VPA is also associated with lower permeability due to the development of high quality interfacial paste-aggregate transition zone and the progressive internal curing in VPCs. Development of non-expensive and environmentally friendly VPC with acceptable strength and durability characteristics (as illustrated in this study) can be extremely helpful for the sustainable construction and rehabilitation of volcanic disaster areas around the world. © 2010 Elsevier Ltd. All rights reserved

Characterisation and standardisation of different-origin end-of-life building materials toward assessment of circularity

YesConstruction and demolition waste (CDW) management and recycling practices are crucial for transitioning to a circular economy. This study focuses on the detailed characterization of CDWs, including hollow brick (HB), red clay brick (RCB), roof tile (RT), concrete (C), and glass (G), collected from seven different sites. The CDWs were characterized based on particle size distribution, chemical composition, and crystalline nature. Pozzolanic activity was evaluated through compressive strength measurements of cement mortars with 20% cement replacement by CDWs at 7, 28, and 90 days. The results showed that clayey CDWs exhibited similar physical/chemical properties and crystalline structures. Compositions of Cs varied significantly based on their original materials. CDWs satisfied the minimum strength activity index for supplementary cementitious materials, with pozzolanic activity influenced by fineness and SiO2+Al2O3 contents. The average strength activity indexes for HB, RCB, RT, C, and G were 84.5%, 86.3%, 83.4%, 80.7%, and 75.8%, respectively. Clayey CDWs contributed to mechanical strength development, while Cs' contribution was related to hydration of unreacted cementitious particles. G exhibited the weakest pozzolanic activity due to its coarser particle size. Overall, CDWs demonstrated suitable properties for use as supplementary cementitious materials in PC-based systems