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Effect of natural pozzolan content on the properties o engineered cementitious composites as repair material

Frontiers of Structural and Civil Engineering 2018年第3期12卷 261-269页

作者： Said CHOUCHA Amar BENYAHIA Mohamed GHRICI Mohamed Said MANSOUR Geomaterials Laboratory Civil Engineering Department University Hassiba Benbouali of Chlef BP 151 Chief02000 Algeria

In order to determine the effect of natural pozzolan （NP） content on the mechanical properties and durability characteristics on Engineered Cementitious Composites （ECC） as repair material. This study focused on the evaluation of the most factors influencing compatibility between the repair material and the base concrete including mechanicals properties such as, compressive and flexural strengths, elastic modulus, capillary absorption and drying shrinkage. The experimental results showed that natural pozzolan reduces the compressive strength and the flexuraI strength of ECC at all ages. The elastic modulus of ECC was remarkably lower than that of normal-strength concrete. This lower ~oung＇s modulus is desirable for repair concrete, because it prevents the stresses induced by restrained shrinkage. In addition, the incorporation of high-volume natural pozzolan decreases significantly the coefficient of capillary absorption at long term and increases the drying shrinkage. Generally, based on the results obtained in the present experimental investigation, ECC can be used effectively as an overlay material over existing parent concrete.

关键词： natural pozzolan engineered cementitious composites mechanical strengths elastic modulus capillary absorption drying shrinkage

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Study on the Influence of Alkali Activator Solutions on Strength Improvement of pozzolan Calcium Hydroxide Binders

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Journal of Geoscience and Environment Protection 2022年第12期10卷 313-330页

作者： Asson Sifueli Malisa Duwa Hamisi Chengula Department of Civil Engineering Mbeya University of Science and Technology Mbeya Tanzania

Alkali activated binder, commonly known as geopolymer cement, has replaced Portland cement in the production of mortar and concrete globally over the past few years. The density, particle size distribution, and specific surface area (SSA) are important physical parameters affecting strength and durability of alkali activated binders. This study carried out tests for physical and chemical properties of the natural pozzolan and calcium hydroxide and then determines the influence of alkali solution (sodium silicate and sodium hydroxide) on strength development of natural pozzolan calcium hydroxide binders. The particle size distribution (PSD), relative densities (RD), and specific surface areas (SSA) of powder natural pozzolan and calcium hydroxide materials and for the mixture of natural pozzolan and calcium hydroxide were determined by using Blaine air permeability apparatus. The optimum proportion of 75% natural pozzolan and 25% calcium hydroxide was obtained which produces the compressive strength of 7.5 MPa at 28 days cured paste. The mixture of natural pozzolan and calcium hydroxide were further grinded at three different finenesses and the particle size gradation, specific densities, specific surface areas and mean particles sizes for the mixture were determined. The compressive strength of alkali activated binders increased with increasing curing period and fineness. The maximum compressive strength for 28 days cured specimens was 26.1 MPa which was obtained at a solution of 8 moles sodium hydroxide concentration. The test results showed that natural pozzolan materials can be used to make geopolymer binders for mortars and concretes. The geopolymer binders for mortars and concretes reduce green gas emission from cement factory but also it can be used to produce durable mortar and concrete with comparable strengths with mortars and concrete made from conventional Portland cement.

关键词： Alkali Activated Materials natural pozzolan Calcium Hydroxide Geopolymer Binders Material Properties Compressive Strength

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