Enhanced Mechanical and Durability Performances of Low Cement Concrete with Natural Pozzolan Addition

Abstract

The decarbonization of concrete structures sector is a priority due to the world climate. Since Portland cement is responsible for approximately 7% of the anthropogenic emissions worldwide, it is decisive to partially replace it by products with lower environmental impact. Fly ash has become highly demanded, due to its proven advantages, however, has announced end by the developed countries. The purpose of this research is to develop and characterize low cement concrete (LCC) with natural and ecological pozzolan additions as an alternative to fly ash. The main objectives are: define several structural concrete mixtures with low cement dosage, ranging from 125 to 175 kg/m 3 ; characterize the workability and the mechanical properties, beyond the durability performance of those concretes; study the influence of pozzolans additions on LCC performance, as an alternative to fly ash; assess the service life of structures produced with the developed LCC. It is possible to produce LCC with natural pozzolan additions, instead of fly ash, with improved mechanical properties and enhanced durability performances. Results also show that the structural LCC produced with pozzolan from Cape Verde provide a great protection against steel corrosion, achieving values 50% higher than concrete with fly ash, and even higher margins when compared with the minimum concrete covers recommended by standards, which highlights the benefits of its use from the sustainability point of view.

Development and Characterization of Eco-Efficient Ultra-High Durability Concrete

“…The average electrical resistivity of SK7 (UHDC with Cape Verde pozzolan) is higher than that of SK4 (UHDC with fly ash) up to 90 days. From this age onward, there was a contrary trend, confirming the trend recorded in the study with LCC-low carbon concrete [61]. Comparing these values to those obtained in the chloride migration test in a non- Comparing the electrical resistivity results of the developed eco-UHDCs, with the reference values proposed by AASHTO T358-15 [60], presented in Figure 18, it appears that the eco-UHDCs have a very low chloride penetration rate, but only after a long curing period (about 90 days for fiber-free concrete, 150 days for polymer fiber concrete, and 250 days for steel fiber concrete).…”

“…The average electrical resistivity of SK7 (UHDC with Cape Verde pozzolan) is higher than that of SK4 (UHDC with fly ash) up to 90 days. From this age onward, there was a contrary trend, confirming the trend recorded in the study with LCC-low carbon concrete [61]. Comparing these values to those obtained in the chloride migration test in a non-stationary regime, this trend was not registered at the corresponding ages, although the graph presented in Figure 17a shows a convergence of results of the two concretes.…”

Effect of Natural Pozzolana on Physical and Mechanical Properties of Concrete

“…NPs are widely used as a supplementary cementing materials which can establish promised outcomes in grasping the expansion of cementitious materials [28,29]. That is through using as a partial substitution of cement by NP to reduce cement consumption and at the same time improve concrete performance [30][31][32][33][34][35][36][37][38]. Besides these, the employment of NP is beneficial in the reduction of deformations while improving the compressive strength of concrete [14,30,35,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53].…”

“…That is through using as a partial substitution of cement by NP to reduce cement consumption and at the same time improve concrete performance [30][31][32][33][34][35][36][37][38]. Besides these, the employment of NP is beneficial in the reduction of deformations while improving the compressive strength of concrete [14,30,35,[39][40][41][42][43][44][45][46][47][48][49][50][51][52][53]. Also, NP can improve concrete resistance to chloride ion penetration which is directly indicated by electric resistivity and durability of concrete by reducing shrinkage cracks and significantly reducing crack width of concrete matrices [1,12,[54][55][56].…”

Comprehensive Review of Direct and Indirect Pozzolanic Reactivity Testing Methods

“…Approximately 7% of the anthropogenic emissions worldwide (i.e., CO 2 ) are related to the production of ordinary portland cement [1] To reduce the economic and environmental costs of portland cement production and to improve the durability of concrete, supplementary cementitious materials (SCMs) are commonly used to partially replace cement in concrete. According to Suraneni et al [2] SCMs are classified into three types: inert, hydraulic, pozzolanic, and highly pozzolanic materials.…”