Physicochemical Properties of Hydrated Portland Cement Blended with Rice Husk Ash (original) (raw)
Related papers
Strength and Carbonation Model of Rice Husk Ash Cement Mortar with Different Fineness
Journal of Materials in Civil Engineering - J MATER CIVIL ENG, 2010
This paper presents a study of the strength and carbonation resistance of mortar made with portland rice husk ash cement by some accelerated short-term techniques in 5% carbon dioxide. Three finenesses of rice husk ashes, viz., original rice husk ash ͑RAO͒, medium rice husk ash ͑RA1͒ with 15-20% by weight retained on a sieve No. 325, and fine rice husk ash ͑RA2͒ with 1-3% by weight retained on a sieve No. 325. Ordinary portland cement was partially replaced with RAO, RA1, and RA2. Compressive strength, porosity, and carbonation depth were determined. The result indicated that the RA2 decreased the water requirement to a lesser extent as compared to that of the RA1 and RAO. The use of RA2 produced mixes with good strength and low porosity of mortar. The carbonation depth increased with an increase in the replacement level for all rice husk ashes. The carbonation depth of RA2 was lower than those of RA1 and RAO. The carbonation depth increased with a decrease in compressive strength and with an increase in amount of water requirement.
A Study on Ordinary Portland Cement Blended with Rice Husk Ash and Metakaolin
Path of Science
This paper tries to investigate the effect of replacing Ordinary Portland cement (OPC) with Metakaolin (MK) and Rice husk ash (RHA) on the physicomechanical properties such as consistency, setting times, soundness and mortar compressive strength of ternary cement up to 40 % cement replacement. The soundness of the blended cement pastes and compressive strength of the blended mortars were conducted using Le Chatelier apparatus and Tonic Technic compression machine while the initial and final setting times were conducted on the blended cement paste using Vicat apparatus.. Nineteen ternary cement mortars were prepared to comprise of OPC, RHA MK at different proportions and tested at 2, 7, 28 and 60 days. Results indicated that as RHA was gradually increased up to 25% at constant MK content, the volume expansion of the ternary cement paste increased gradually. On the other hand, as MK was increased from 5-25% at constant RHA, the volume expansion diminished. The water consistency of ternary cement paste experienced a variation as MK was increased up to 25 wt% at constant RHA up to 10 wt%. However, at 10 wt% constant RHA as MK was increased the water demand gradually increased. Similarly, an increase in RHA at constant MK increased the water demands of the ternary blends. An increase in RHA from 5-25 wt% at 5-25 wt% constant MK resulted in acceleration in the initial and final setting times of cement blends. These accelerations could be attributed to the pozzolanic activity leading in shorter setting time. Whereas a series of accelerations and retardations of both setting times were experienced as the MK was increased from 5-25 wt% at 5-25 wt% constant RHA. It was observed that increment in the MK or RHA up to 10 wt% at constant RHA/MK up to 10 wt% resulted in improved mortar compressive strength of the ternary blend in comparison with control. This improvement was attributed to the high silica/alumina contribution to the matrix by MK inclusion, the C/S ratio in the cement matrix and RHA pozzolanic reactivity despite its unburnt carbon. All mortar compressive strength of the cement blends and control experienced an increase as the curing days were lengthened from 2 to 60 days. The enhanced strength compared with the control especially beyond 28 days could be attributed to the slow pozzolanic reaction resulting from the formation of additional CSH and CAH from the interaction of the residual CH and the silica available in the MK and RHA. The best compressive strength at 60 days was obtained at cement replaced with 15 wt% and 20 wt% at MK 5 wt% RHA producing a mortar compressive strength of 40.5 MPa.
Chemical Composition and Physical Characteristics of Rice Husk Ash Blended Cement
International Journal of Engineering Research in Africa, 2017
Applications of agricultural by-product as substitute for non-renewable material in cement production are desirable in stimulating socio-economic development. In this study, Rice Husk Ash (RHA) blended cement was produced by replacing 5%, 7%, 11.25%, 15%, 20.25% and 25% by weight of Ordinary Portland Cement (OPC) clinker with RHA. The cement without RHA serves as the control. The chemical compositions of RHA, OPC-clinker and the blended cements were determined using X-ray fluorescence analyzer. The physical characteristics of RHA blended cements that were considered are fineness, soundness, consistency, initial and final setting times and compressive strength at 2, 7, 28, 56 and 90 curing ages. The results showed that RHA is a suitable material for use as a pozzolan as it satisfied the minimum requirement by having the sum of SiO2, Al2O3 and Fe2O3 of more than 70%. Incorporation of RHA led to an increase in the composition of SiO2 and reduction in that of CaO. An increase in RHA con...
Advances in Civil Engineering Materials, 2013
In this study, low-and high-carbon rice husk ash (RHA) in their as-received and ground forms were characterized by means of different methods in order to evaluate their performance in Portland cement mixtures. RHA-cement pastes and mortars, at three different RHA replacement levels of 0 %, 10 %, and 20 %, were prepared at a constant water/cement ratio of 0.485. Results from this investigation indicate that the material characteristics of low-and high-carbon RHA were significantly different in most of the tests conducted. In the as-received condition, the high-carbon RHA had a greater bulk density than low-carbon RHA, but their bulk densities were comparable after grinding. The low-carbon RHA was more effective in its pozzolanic reaction than high-carbon RHA in both ground and as-received conditions. The microstructures of both lowcarbon and high-carbon RHA cement pastes were denser than those of control pastes. At a given dosage of RHA and superplasticizer, the ground and the as-received low-carbon RHA mixtures performed significantly better than the high-carbon RHA mixtures. Similarly, mixtures with low-carbon RHA showed significantly higher strength activity indices than those with high-carbon RHA at both dosage levels investigated. Grinding RHA was found to be beneficial in all the tests conducted, as the ground RHA mixtures depleted more calcium hydroxide, registered higher flow values, and possessed greater strength than unground RHA mixtures at all replacement levels. Thus, the grinding process significantly helps in utilizing both high-and low-carbon RHA in concrete.
Advances in Materials Science and Engineering, 2017
The aim of this work is to better understand the physical and chemical phenomena involved in hydrated mix (clinker + addition) during the natural carbonation process, to characterize cement with supplementary cementitious materials (SCMs) under various curing environment. The prepared cement pastes were characterized by thermogravimetric analysis. The results showed a considerable influence of the environment on the properties of mortars and cement and a perfect correlation between compressive strength, natural carbonation, nonevaporable water, and portlandite content. It was observed that the reduction of the curing period makes the mortars more sensitive. The kinetics of process was evaluated from Ca(OH)2 content and nonevaporable water contained in mortars. These two parameters reflect the hydration progress of the water/cement ratio studied. The weight loss due to Ca(OH)2 decomposition, calculated by DTA/TG analysis, shows the effect of the pozzolanic reaction and the natural ca...
Fresh and Mechanical Properties of the Cementitious Materials Containing Rice Husk Ash
The effects of using rice husk ash (RHA), as a cement replacement material, on the flowability, rheology, rate of flowability loss and compressive strength of cementitious materials were extensively studied in a controlled experimental program. The possibility of using RHA for producing high strength concrete (HSC) was also attempted. Various 0.5 w/c OPC mortar mixes containing different contents of RHA were therefore prepared and subjected to the mortar flow test at different elapsed periods from mixing. Cubical specimens were taken from these mixes, cured with different curing regimes (air, moist and sealed) and finally tested for compressive strength at age of 56 days. Concrete specimens made with different RHA contents and water cement ratios (0.4, 0.3 and 0.25) were also prepared and tested for compressive strength. It was found that the incorporation of RHA in OPC mixes has led to a notable reduction in the initial flowability, rate of flowability loss and parameters of rheology, and an increase in the compressive strength. RHA can be used for manufacturing HSC provided that w/c ratios of less than 0.30 are avoided.
Characterization of flat sheet cement containing rice husk ash
2007
Rice husk ashes (RHA) from two local sources, Mahaphant Fibre-Cement Public Co., Ltd. (crystalline SiO2 as cristobalite) and A.T. Bio Power Co., Ltd. (amorphous SiO2), were characterized for chemical composition and mineral phases by XRF and XRD, respectively. Then 10-25 wt% of RHA were mixed with Portland cement (Type I), sand, water and plasticizer to form into 2-in cubes of mortar. After wet curing (3-28 d) the specimens were tested for compressive strength and morphologies of the hydrates were observed by SEM. Although the water demand to attain normal consistency increased with the content of RHA, it was found that the strengths of A.T. Bio Power RHA added cement mortars were respectively higher than those of reference cement mortars (Portland cement type I : sand : water) and Mahaphant RHA added cement mortars at all curing ages. The highest compressive strength obtained at 28 d was from 20 wt% A.T. Bio RHA added cement mortars. This suggested the optimal content of RHA be 15-...
Cement and Concrete Composites, 2015
The effectiveness of unground low-carbon rice husk ash (URHA) as a pozzolan and the effect of grinding the URHA to finer fractions for use in portland cement system were investigated. The properties investigated include the setting time and calcium hydroxide depletion of rice husk ash (RHA) pastes; microstructure and flow behavior of RHA mortars; strength and durability of RHA concretes. Results from this investigation suggested that the URHA and ground RHA (GRHA) mixtures performed better than the control mixtures in all tests conducted except water demand and setting time. The URHA mixture revealed denser microstructure compared to the control mixture. The internal porosity created by the coarse RHA grains in the matrix and their inability to completely participate in pozzolanic reaction may be the reasons for the poorer performance of the URHA mixture than compared to the GRHA mixture. The effect of grinding the RHA to finer fractions either substantially or slightly improved all properties except final setting time. With the performance of the GRHA concrete somewhat similar to that of the SF concrete, the use of ground RHA can be concluded to provide acceptable performance in portland cement systems.
Carbonation and hydration of mortars with calcium hydroxide and calcium silicate binders
Hardening of calcium hydroxide and calcium silicate binders composed of cement, rice husk ash (RHA) and lime in different compositions were studied with mortars using thermal analysis, mechanical strength and SEM. When cement is partially replaced with RHA and lime, hardening occurs as a result of combined hydration, pozzolanic reaction and carbonation reaction. While hydration of cement contributes to the early strength development of the mortars, carbonation is much more pronounced at later stage with the decrease in the cement content and increase in the porosity of the mortars. RHA-cement mortars indicated a long-term strength development, which is lower than that of the reference cement mortar. This was attributed to their higher porosity due to the high water demand of the porous RHA grains. Strength reduction was recorded at the very early stage for RHA-cement-lime mortars containing 10%-wt cement as well as RHA-lime mortars. This has been explained with the insufficient ceme...