Volcanic Scoria as Cement Replacement

Numerous volcanic scoria (VS) cones are found in many places of the world. Many of them have not yet been investigated, although few have been used as binders for a very long time. The use of natural pozzolans as cement replacement could be considered as a common practice in the construction industry due to the related economic, ecologic and performance benefits. This chapter highlights the advantages and disadvantages of the use of volcanic scoria as cement replacement in concrete mixes in terms of fresh and hardened concrete properties. The chemical and mineralogical composition of volcanic scoria samples collected from 36 countries is presented in this chapter, with some further analysis. The effects of using volcanic scoria as cement replacement on some paste, mortar and concrete properties, such as the setting times, the heat of hydration, the compressive strength, the water permeability and the chloride penetrability, have been studied. The improvement in resistance against the chemical attack of volcanic scoria-based cement mortar has also been highlighted. Some estimation equations depending on the data available in literature have also been derived from the analyzed data. The modification of the microstructure of VS-based cement paste has been confirmed, as well

Effect of intrinsic microscopic properties and suction on swell characteristics of compacted expansive clays

The complex swelling mechanism in expansive clays during moisture ingress can be succinctly explained by an examination of their core mineralogy, microfabric, grain size and suction response. This note has attempted to investigate these influential factors on five different expansive clay samples to enable further understanding of swell behaviour. Laser diffractometry tests were performed on the expansive clays to determine the clay-sized particle structure (<2 μm). One-dimensional vertical swell and swell pressure tests were carried out using the standard oedometer to establish the extent of swell. The filter paper technique was adopted to determine the matric suction values for the compacted samples. Pore sizes of the expansive clays were analytically derived and utilized to describe the swell characteristics of the clays. Further microstructural studies were conducted using the scanning electron micrograph (SEM) to better understand the pore and aggregate structure of the samples. Results of analysis of one-dimensional swell under inundation revealed an increase in swelling with increase in the montmorillonite content in the expansive clays. Swell behavioural concepts formulated to describe and predict the volume change characteristics of the clays by accounting for the clay-particle size, pore morphology and suction showed estimates of coefficient of determination exceeding 0.90 hence buttressing the critical significance of the intrinsic properties considered. This approach was tested and validated against a previous model which considered the micro-internal factors influencing swell. Very satisfactory relationships were also achieved between the inherent expansive clay properties such as plasticity index, clay activity and specific surface area

Experimental study on the use of RoadCem blended with by-product cementitious materials for stabilisation of clay soils

This work presents an experimental study on the physical, mechanical and microstructural characteristics of two clay soils treated with by-product materials (GGBS and PFA) blended with a nano technology-based additive called RC (RC). The soils were initially treated with 8% of cement in the first phase of mixing, and in the other phases of mixing, the cement content was reduced by 50%, 60% and 70% and substituted with GGBS or different combinations of GGBS and 1%RC or PFA and 1%RC. Further, the paper discusses the shear strength, stabilisation mechanism, microstructural characteristics, and swell of the treated soils based on results of series of strength, scanning electron microscope and swell test. The results show that the inclusion of 1%RC increases undrained shear strength and reduces swell of the treated soils due to encapsulation effects associated with the formation of the crystalline reaction product in the hydration process and the resulting modification of cementitious product to bind very heavy clays together. The soil treated with 1%RC combined with 4%Cem and 3%GGBS, produces the best performance in terms of undrained shear strength and microstructural characteristics and the stabilisation mechanism of cement, RC and GGBS shows that it is due to interlocking of particles and wrapping effect

Wpływ czasu utwardzania na wydajność betonu na bazie scorii wulkanicznej

The objective of the presented paper is to investigate the performance of concrete containing volcanic scoria as cement replacement after 7, 28, 90, and 180 days curing. Five performance indicators have been studied. Compressive strength, water permeability, porosity, chloride penetrability, and reinforcement corrosion resistance have all been evaluated. Concrete specimens were produced with replacement levels ranging from 10 to 35%. Test results revealed that curing time had a large influence on all the examined performance indicators of scoria-based concrete. Water permeability, porosity, and chloride penetrability of scoria-based concrete mixes were much lower than that of plain concrete. Concretes produced with scoria-based binders also decelerated rebar corrosion, particularly after longer curing times. Furthermore, an estimation equation has been developed by the authors to predict the studied performance indicators, focusing on the curing time and the replacement level of volcanic scoria. SEM/EDX analysis has been reported as well.W Syrii znajdują się ważne obszary wulkaniczne o szacowanych rezerwach wynoszących około trzy czwarte miliardów ton wulkanicznej scorii. Jednakże, ich potencjalne zastosowanie w produkcji betonu nie jest powszechnie znane. Powszechnie uznaje się, że jakiekolwiek zwiększenie wydajności konstrukcji żelbetonowych zwiększa stabilność branży budowlanej. Prawdopodobnie jednym z najskuteczniejszych podejść jest zastąpienie pucolanów częścią cementu portlandzkiego. Wytrzymałość betonu jest powszechnie uważana za jego najcenniejszą właściwość, chociaż jego inne właściwości, takie jak trwałość i przepuszczalność, mogą być w rzeczywistości ważniejsze. Obecnie uważa się, że korozja indukowana chlorem jest najpoważniejszym mechanizmem niszczenia konstrukcji żelbetonowych. Korozja stali zbrojeniowej jest istotnym problemem spotykanym w branży budowlanej w Syrii, zwłaszcza w środowiskach przemysłowych i morskich. Wiele konstrukcji żelbetonowych zetknęło się z tym zjawiskiem, co znacząco skróciło ich żywotność. Celem niniejszej pracy jest zbadanie wpływu wykorzystania scorii wulkanicznej jako zamiennika cementu, w odniesieniu do niektórych właściwości użytkowych cementu. W szczególności zbadano wytrzymałość na ściskanie, przepuszczalność wody, porowatość, przenikalność chlorków i odporność na korozję zbrojenia osadzonego w betonie zawierającym cement na bazie scorii, po utwardzaniu przez 7, 28, 90 i 180 dni

Producción de hormigones más durables y sostenibles utilizando escoria volcánica como sustitutivo de cemento

The objective of the study is to investigate strength and durability-related properties of volcanic scoria-based cements. Compressive and tensile strength development of mortars and concretes containing volcanic scoria with replacement levels ranging from 10 to 35% was investigated. Water permeability, chloride penetrability and porosity of concretes cured for 2, 7, 28, 90 and 180 days were also examined. Results revealed that volcanic scoria could be suitable for making blended cements. The strength of mortar/concrete containing volcanic scoria was lower than that of plain cement mortar/concrete at all ages. However, at 90 day curing, the strengths of volcanic scoria-based mortars/concretes were comparable to those of plain cement. In addition, water permeability, chloride penetrability and porosity of scoria-based concretes were much lower than those of plain concrete. Further, the results were statistically analysed and estimation equations have been developed to predict the studied properties. SEM/EDX analysis was employed, as well.El objetivo del estudio fue investigar la resistencia y durabilidad de cementos basados en escoria volcánica. El desarrollo de resistencias a flexión y compresión, se estudió en morteros y hormigones con escoria volcánica en porcentajes de reemplazo desde 10 al 35%. Se realizaron ensayos de permeabilidad al agua, penetración de cloruros y porosidad de los hormigones a las edades de 2, 7, 28, 90 y 180 días. Los resultados revelaron que la escoria volcánica podría ser adecuada para la fabricación de cementos con adiciones. La resistencia de morteros/hormigones que contiene escoria volcánica fue menor que la de los correspondientes morteros u hormigones sin adición a todas las edades. Sin embargo, a los 90 días de curado, las resistencias de los morteros/hormigones con escoria fueron comparables con las del cemento sin adición. La permeabilidad al agua, penetrabilidad de cloruros y porosidad de los hormigones con escoria fueron mucho más bajos que los del correspondiente hormigón sin escoria. Los resultados se analizaron estadísticamente y las ecuaciones de estimación se han desarrollado para predecir las propiedades estudiadas. También se empleó el análisis SEM/EDX

Effects of Curing Time on the Performance of Volcanic Scoria-Based Binder Concretes

The objective of the presented paper is to investigate the performance of concrete containing volcanic scoria as cement replacement after 7, 28, 90, and 180 days curing. Five performance indicators have been studied. Compressive strength, water permeability, porosity, chloride penetrability, and reinforcement corrosion resistance have all been evaluated. Concrete specimens were produced with replacement levels ranging from 10 to 35%. Test results revealed that curing time had a large influence on all the examined performance indicators of scoria-based concrete. Water permeability, porosity, and chloride penetrability of scoria-based concrete mixes were much lower than that of plain concrete. Concretes produced with scoria-based binders also decelerated rebar corrosion, particularly after longer curing times. Furthermore, an estimation equation has been developed by the authors to predict the studied performance indicators, focusing on the curing time and the replacement level of volcanic scoria. SEM/EDX analysis has been reported as well