Effects of Blended-Cement Paste Chemical Composition Changes on Some Strength Gains of Blended-Mortars

Effects of chemical compositions changes of blended-cement pastes (BCPCCC) on some strength gains of blended cement mortars (BCMSG) were monitored in order to gain a better understanding for developments of hydration and strength of blended cements. Blended cements (BC) were prepared by blending of 5% gypsum and 6%, 20%, 21%, and 35% marble powder (MP) or 6%, 20%, 21%, and 35% brick powder (BP) for CEMI42.5N cement clinker and grinding these portions in ball mill at 30 (min). Pastes and mortars, containing the MP-BC and the BP-BC and the reference cement (RC) and tap water and standard mortar sand, were also mixed and they were cured within water until testing. Experiments included chemical compositions of pastes and compressive strengths (CS) and flexural strengths (FS) of mortars were determined at 7th-day, 28th-day, and 90th-day according to TS EN 196-2 and TS EN 196-1 present standards. Experimental results indicated that ups and downs of silica oxide (SiO2), sodium oxide (Na2O), and alkali at MP-BCPCC and continuously rising movement of silica oxide (SiO2) at BP-BCPCC positively influenced CS and FS of blended cement mortars (BCM) in comparison with reference mortars (RM) at whole cure days as MP up to 6% or BP up to 35% was blended for cement.WoSScopusPubMe

Fresh and mechanical properties of concrete made of binary substitution of millet husk ash and wheat straw ash for cement and fine aggregate

Now-a-days, many researchers use priceless industrial or agricultural products as the main raw material for the construction industry. However, these wastes are inexpensive and easily available everywhere to utilize for commercial purpose and also helpful in reducing the environmental pollution. This experimental study aimed to evaluate fresh (workability) and mechanical properties (density, permeability and split tensile strength, compressive and flexural strength) of concrete with 0%, 5%, 10%, 15% and 20% of millet husk ash (MHA) and 10%, 20%, 30% and 40% of wheat straw ash (WSA) to replace Ordinary Portland Cement (OPC) and sand respectively at conditions: a) concrete with MHA; b) concrete with WSA; and c) concrete with MHA and WSA. 525 concrete specimens were prepared with 1:1:2 mix proportions with 0.55 water/cement ratio and cured at 28 days. The increase of combined MHA and WSA contents to produce concrete decreased the workability of fresh concrete and decreased density and permeability of hardened concrete. Compressive strength, split tensile and flexural strength are increased with addition up to 15% of MHA and 30% of WSA combined. Same behavior is observed to compressive strength after chloride attack. Those results were better when compared to those of conditions a) and b). Therefore, it is possible to produce eco-friendly concrete with MHA replacing OPC and WSA replacing sand, individually or combined, which contributes to less environmental impact. (c) 2021 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

The effect of content and fineness of natural pozzolana on the rheological, mechanical, and durability properties of self-compacting mortar

Mineral admixtures are used in ordinary and self-compacting mortar to reduce carbon dioxide emission and enhance the performance of mortar at the fresh and hardened states. This paper reports the effect of the content and the fineness of natural pozzolana (NP) on rheological, compressive strength, total and autogenous shrinkage properties of self-compacting mortar. Capillary water absorption of self-compacting mortar was also investigated. Natural pozzolana was used as a partial cement replacement with two levels (15%wt. And 30%wt.) and ground to three specific surface Blaine (SSB) fineness measurements 350 m(2)/kg, 420 m(2)/kg and 500 m(2)/kg. Cement content, water to-binder ratio and superplasticizer content were kept constant for all self-compacting concrete mixtures. Rheological tests were conducted by measuring slump flow and V-funnel flow tests as well as using a rheometer to measure plastic viscosity and yield stress. Compressive strengths of self-compacting concretes were determined at 1, 7, 28, 56, 90 and 180 days of curing. Total and autogenous shrinkage were measured during three months and capillary water absorption of self-compacting mortar was also investigated after 90 days of water curing. The results indicated that the increase of replacement level of natural pozzolana affects negatively the rheological properties of self-compacting mortar. The same tendency is observed as the specific surface Blaine fineness increased. However, in the long-term (beyond 28 days of curing), the compressive strength of NP mixes exceeds that of control mortar. The increase of the fineness of natural pozzolana enhances compressive strength at later age but increases both the total and autogenous shrinkage compared with control mortar. It was observed that increasing the percentage of natural pozzolana generates an increase in water capillary absorption. However, increasing the fineness of natural pozzolana results in slightly lower water absorption of mortar

Fresh and mechanical properties of concrete made of binary substitution of millet husk ash and wheat straw ash for cement and fine aggregate

Now-a-days, many researchers use priceless industrial or agricultural products as the main raw material for the construction industry. However, these wastes are inexpensive and easily available everywhere to utilize for commercial purpose and also helpful in reducing the environmental pollution. This experimental study aimed to evaluate fresh (workability) and mechanical properties (density, permeability and split tensile strength, compressive and flexural strength) of concrete with 0%, 5%, 10%, 15% and 20% of millet husk ash (MHA) and 10%, 20%, 30% and 40% of wheat straw ash (WSA) to replace Ordinary Portland Cement (OPC) and sand respectively at conditions: a) concrete with MHA; b) concrete with WSA; and c) concrete with MHA and WSA. 525 concrete specimens were prepared with 1:1:2 mix proportions with 0.55 water/cement ratio and cured at 28 days. The increase of combined MHA and WSA contents to produce concrete decreased the workability of fresh concrete and decreased density and permeability of hardened concrete. Compressive strength, split tensile and flexural strength are increased with addition up to 15% of MHA and 30% of WSA combined. Same behavior is observed to compressive strength after chloride attack. Those results were better when compared to those of conditions a) and b). Therefore, it is possible to produce eco-friendly concrete with MHA replacing OPC and WSA replacing sand, individually or combined, which contributes to less environmental impact

Effect of wheat straw ash as cementitious material on the mechanical characteristics and embodied carbon of concrete reinforced with coir fiber

The use of supplementary cementitious materials has been widely accepted due to increasing global carbon emissions resulting from demand and the consequent production of Portland cement. Moreover, researchers are also working on complementing the strength deficiencies of concrete; fiber reinforcement is one of those techniques. This study aims to assess the influence of recycling wheat straw ash (WSA) as cement replacement material and coir/coconut fibers (CF) as reinforcement ingredients together on the mechanical properties, permeability and embodied carbon of concrete. A total of 255 concrete samples were prepared with 1:1.5:3 mix proportions at 0.52 water-cement ratio and these all-concrete specimens were cured for 28 days. It was revealed that the addition of 10 % WSA and 2 % CF in concrete were recorded the compressive, splitting tensile and flexural strengths by 33 MPa, 3.55 MPa and 5.16 MPa which is greater than control mix concrete at 28 days respectively. Moreover, it was also observed that the permeability of concrete incorporating 4 % of coir fiber and 20 % of WSA was reduced by 63.40 % than that of the control mix after 28 days which can prevent the propagation of major and minor cracks. In addition, the embodied carbon of concrete is getting reduced when the replacement level of cement with WSA along with CF increases in concrete. Furthermore, based on the results obtained, the optimum amount of WSA was suggested to be 10 % and that of coir fiber reinforcement was suggested to be 2 % for improved results