Increase In Replacement Of Cement Research Articles

Influence of Nano Silica on Mechanical and Durability Characteristic of Mortar made by Partial Replacement of Natural Fine Aggregate with Recycled Fine Aggregate

To implement sustainability concepts in the construction industry, the possibility of utilizing the recycled fine aggregate obtained from the crushing of coarse aggregate debris of concrete was explored in this paper. As there are no specific codes for mortar made by utilizing this recycled fine aggregate (RFA), experimentation was carried out to find out its mechanical and durability properties by partially replacing natural fine aggregate (NFA) with recycled fine aggregate in the percentages of 0, 10, 30, 50 and 70 by weight along with an admixture Nano Silica in liquid form by partial replacement of cement with the percentages of 0, 0.75, 1.50 and 3.00 by weight for each percentage replacement with RFA. The study indicates that, for all percentages of partial replacement with RFA, there is an enhancement in the mechanical and durability properties of the mortar with the increase in replacement of cement with Nano Silica.

Pozzolanic and mechanical properties of Date Palm Seed Ash (Dpsa) concrete

This paper presents the findings of a research work conducted on how to improve the mechanical properties of concrete using Date Palm Seed Ash (DPSA) as partial replacement of cement. The DPSA used was obtained by controlled burning of date palm seed in a kiln at a maximum temperature of 630oC for eight hours and air cooled afterwards. The ash obtained was sieved through 75μm sieve and its oxide composition analysed using X-ray fluorescence (XRF) procedures. DoE method of mix design was used to produce concrete ingredients for grade 30N/mm2 giving a water-cement ratio of 0.53. The effect of partial replacement of cement with DPSA on cement paste and concrete using 0, 2.5, 5, 7.5, 10, 15 and 20% DPSA was investigated through consistency and setting times tests, workability test, compressive strength test (at 7, 21, 28 and 56 days curing duration), pozzolanic activity index evaluation and water absorption test. Results show that DPSA has high silicon dioxide (45.50%), aluminum oxide (20.75%) and Iron oxide (7.25%). Findings indicate that the consistency and setting times of cement-DPSA paste increased with increase in the replacement of cement with DPSA. The workability of DPSA concrete decreased with increase in cement replacement. Compressive strength test results show that cement can be replaced with DPSA up to 10% as the compressive strength at 10% replacement is 31.5N/mm2 as against the 31N/mm2 of the normal concrete, at 56 days. The pozzolanic activity index result also show that DPSA concrete meets up the minimum requirement of 75% specified by ASTM C618-15. Also, the water absorption capacity of DPSA concrete at the highest replacement (20%) is 11% less than that at 0%.
 Keywords: Cement, Compressive strength, Concrete, Date palm seed ash, Partial replacement, Pozzolana

Rice husk ash as a partial replacement of cement in high strength concrete containing micro silica: Evaluating durability and mechanical properties

The preliminary and inevitable interest in the use of partial replacements or by – products as complementary pozzolanic materials was mostly induced by enforcement of air pollution control resulted from cement production industry. Rise husk is by- product taken from rice mill process, with approximately the ratio of 200kg per one ton of rice, even in high temperature it reduces to 40kg. This paper presents benefits resulted from various ratios of rice husk ash(RHA) on concrete indicators through 5 mixture plans with proportions of 5, 10, 15, 20 and 25% RHA by weight of cement in addition to 10% micro- silica (MS) to be compared with a reference mixture with 100% Portland cement. Tests results indicated the positive relationship between 15% replacement of RHA with increase in compressive strengths by about 20%. The optimum level of strength and durability properties generally gain with addition up to 20%, beyond that is associated with slight decrease in strength parameters by about 4.5%. The same results obtained for water absorption ratios likely to be unfavourable. Chloride ions penetration increased with increase in cement replacement by about 25% relative to the initial values (about less than one fifth).

Comparative environmental life-cycle analysis of concretes using biomass and coal fly ashes as partial cement replacement material

Nowadays, the concrete production sector is challenged by attempts to minimize the usage of raw materials and energy consumption, as well as by environmental concerns. Therefore, it is necessary to choose better options, e.g. new technologies or materials with improved life-cycle performance. One solution for using resources in an efficient manner is to close the materials' loop through the recycling of materials that result either from the end-of-life of products or from being the by-product of an industrial process. It is well known that the production of Portland cement, one of the materials most used in the construction sector, has a significant contribution to the environmental impacts, mainly related with carbon dioxide emission. Therefore, the study and utilization of by-products or wastes usable as cement replacement in concrete can supply more sustainable options, provided that these types of concrete produced has same durability and equivalent quality properties as standard concrete.This work studied the environmental benefits of incorporating different percentages of two types of fly ashes that can be used in concrete as cement replacement. These ashes are waste products of power and heat production sectors using coal or biomass as fuels. The results showed that both ashes provide a benefit for the concrete production both in terms of environmental impact minimization and a better environmental performance through an increase in cement replacement. It is possible to verify that the incorporation of fly ashes is a sustainable option for cement substitution and a possible path to improve the environmental performance of the concrete industry.