Life Cycle Assessment (LCA) is applied to develop a methodology for calculating Environmental Disturbance Indicators (EDI) for six concrete mix designs of varying constituents (general use cement, limestone cement, and supplementary cementing materials). The objective of the study is to quantify the sustainability of concrete mix designs by LCA and to understand the interplay between cementitious material selection, weighting schemes applied to four environmental impacts and transportation distance (worst and best case) scenarios. The results reveal that selection of cementitious materials has the greatest effect on the EDI in comparison to the weighting schemes and transportation scenarios, in this study.
There has been a significant push in the direction of reducing carbon footprint of concrete through the development of alternative binders. To that end, calcium sulfoaluminate-belite (CSAB) cement is a promising alternative due to its lower carbon footprint and higher resistance against shrinkage cracking. Lower burning temperature and lesser amount of limestone requirement for CSAB cement manufacturing can provide up to 30% reduction in carbon footprint of concrete. Moreover, the porous nature of CSAB cement clinker lowers the grinding energy requirement. The main constituents of CSAB cement are ye’elimite, belite, ferrite, and calcium sulfate. Hydration of ye’elimite in presence of calcium sulfate results in the formation of ettringite, leading to early-age expansion. For shrinkage-compensating property, CSAB cement can be formulated as an expansive cement system. Nonetheless, the use of CSAB cement in concrete has been limited to niche applications. This paper reviews the manufacturing, composition, mechanical properties and durability characteristics of CSAB cement. The current challenges with respect to its wider application in concrete are also discussed.
The scarcity of traditional Supplementary Cementitious Materials in the region Latin America is compromising the strategy for sustainability in the sector. The large availability of kaolinitic clays and limestone in the region paves the way for the introduction of a new cementitious system named after “LC3”, which uses the synergy established between calcined clays and limestone during cement hydration. The Technology Research Center, TRC Cuba has been very active in the development and introduction of the technology throughout the region, and several industrial trials have been carried out. Experience on clay characterization has been increased through the study of more than 100 clay deposits. Applications at the level of concrete prove that despite its low clinker content, concrete made with LC3 cement achieve similar strength to concrete made with type I Portland cement at all ages, and the increase in water demand due to the presence of calcined clays does not have a high overall impact. Assessment of durability on a natural, high chloride concentration site has proven the benefits of using calcined clays and limestone systems in concrete, with a much better performance than Portland cement concrete.
This paper presents a summary of the major findings from the studies conducted at Indian Institute of Technology (IIT), Madras on Limestone Calcined Clay Cement (LC3), in comparison with plain portland cement and fly ash-based binder. The study attempts to delineate the chemical and physical effects of binder components in LC3 on hydration and hardening, property development, binder chemistry and durability indicators to evolve fundamental understanding on the performance of such low clinker binders. Such an assessment can drive the practical adoption and extend the applicability of such binders in various domains of cement-based materials. The experimental strategy involved the assessment of the pore structure evolution and electrical properties on cementitious pastes, along with measurement of the durability parameters on concrete for resistance to ingress of moisture by absorption, and chloride ions by migration and diffusion mechanisms. The synergistic interactions of the blend of calcined clay and limestone impact the physical structure positively at early ages as opposed to fly ash systems, which require prolonged curing to realise their potential. The study reveals a combination of calcined clay and limestone can be a potential combination for producing high-performance concrete, more specifically in a chloride laden environment, along with the beneficial alternative resource utilisation and sustainability prospects.
This article reviews our current understanding of the efficient and durable usage of Limestone Calcined Clay Cement (or LC3 in short). In around a decade, this cement has gone from the laboratory to the field and is on the verge of becoming a commercially available product. However, given that the properties of this cement are different from those of conventional cements, this article compares the design and performance of concrete using conventional cements with those using LC3. It has been seen that while the water demand of concretes with LC3 is relatively higher, the cement imparts higher cohesion. It has also been observed that the strength of concretes with LC3 develop faster than concretes with fly ash. While the transport of water has been seen to be comparatively slower in LC3, carbonation is seen to be faster. However, moisture transport is seen to increase in carbonated concrete. The rate of corrosion is, therefore, likely to be different from other cements and to depend on a multitude of factors. LC3was also seen to be more sensitive to temperature than the other cements. This article discusses some important findings regarding the performance of concretes produced using LC3.
Due to rapid industrialisation, a large amount of industrial waste are produced which needs efficient and effective disposal mechanism. In this study, fly ash bottom ash combination was activated with sodium-based activators for preparation of alkali-activated concrete under ambient curing condition. Consistency and setting time of paste with fly ash bottom ash combination was determined. Process parameters which affect the compressive strength of alkali-activated concrete were identified. Microstructural studies were also undertaken to study the product developed due to alkali activation. Observations indicate that there was a decrease in compressive strength of alkali-activated concrete with the increase in bottom ash, while an increase in activator content leads to an increase in compressive strength. The experimental investigation also shows that an equal proportion of fly ash and bottom ash can be used for the development of concrete up to 25 MPa strength.
In present research investigation, Fly ash based Geopolymer Concrete (FGPC) has been manufactured by full substitution of cement with unprocessed and processed fly ash. The effect of variables such as Ratio alkaline liquid to fly ash, sodium silicate solution to sodium hydroxide ratio, Concentration of sodium hydroxide, in Molar; Addition of superplasticiser, additional Water content, Curing temperature and time, Rest period on compressive strength of FGPC was examined. The results reveal that the optimum compressive strength of FGPC was obtained with sodium silicate to sodium hydroxide ratio as 2.5, plasticizer content of 2.0%, water content of 10%, curing time for 48 hrs, curing temperature at 90ºC and a rest period of 1 day.
The studies and applications of Engineered Cementitious Composites (ECC) in China have never been stopped ever since it was introduced. As a representative improvement, ECC with characteristics of low shrinkage (LSECC) was developed and field used. In this paper, recent applications of LSECC in China, covering link-slab in jointless pavement, protective panel of external insulation wall and prefabricated irrigation channel of farmland water conservancy, are briefly reviewed. For each application, the driving force behind the adoption of LSECC is first described. Emphasis is centered on the specific design principle and field construction. The experience in China should inspire wider application of ECC in future.
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