TITLE:
Study on the Influence of Alkali Activator Solutions on Strength Improvement of Pozzolan Calcium Hydroxide Binders
AUTHORS:
Asson Sifueli Malisa, Duwa Hamisi Chengula
KEYWORDS:
Alkali Activated Materials, Natural Pozzolan, Calcium Hydroxide, Geopolymer Binders, Material Properties, Compressive Strength,
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.10 No.12,
December
30,
2022
ABSTRACT: 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.