Abstract
In the present work, the effect of mineral aggregates (pumice stone and expanded clay aggregates) and chemical admixtures (superplasticizers and shrinkage reducing additives) as an alternative internal curing technique was investigated, to improve the properties of high-performance concrete. In the fresh and hardened state, concretes with partial replacements of Portland cement (CPC30R and OPC40C) by pulverized fly ash in combination with the addition of mineral aggregates and chemical admixtures were studied. The physical, mechanical, and durability properties in terms of slump, density, porosity, compressive strength, and permeability to chloride ions were respectively determined. The microstructural analysis was carried out by scanning electronic microscopy. The results highlight the effect of the addition of expanded clay aggregate on the internal curing of the concrete, which allowed developing the maximum compressive strength at 28 days (61 MPa). Meanwhile, the replacement of fine aggregate by 20% of pumice stone allowed developing the maximum compressive strength (52 MPa) in an OPC-based concrete at 180 days. The effectiveness of internal curing to develop higher strength is attributed to control in the porosity and a high water release at a later age. Finally, the lowest permeability value at 90 days (945 C) was found by the substitutions of fine aggregate by 20% of pumice stone saturated with shrinkage reducing admixture into pores and OPC40C by 15% of pulverized fly ash. It might be due to impeded diffusion of chloride ions into cement paste in the vicinity of pulverized fly ash, where the pozzolanic reaction has occurred. The proposed internal curing technology can be considered a real alternative to achieve the expected performance of a high-performance concrete since a concrete with a compressive strength range from 45 to 67 MPa, density range from 2130 to 2310 kg/m3, and exceptional durability (< 2000 C) was effectively developed.
Highlights
Nowadays, reinforced concrete structures are susceptible to chemical attack caused by some elements from the environment
Since the principle and design method of the combined use of mineral aggregates with chemical admixtures are still unclear, the goal of this study is to evaluate the effect of mineral aggregates pumice stone and expanded clay aggregate along to the chemical admixtures superplasticizers and shrinkage reducing additive as internal curing agents to improve the physical, mechanical, and durability properties of high-performance concretes
The results show that the concrete elaborated in stage 1 with clay aggregate, registered a volumetric weight ranging from 2100 kg/m3 to 2400 kg/m3 [60]
Summary
Nowadays, reinforced concrete structures are susceptible to chemical attack caused by some elements from the environment. These elements mainly include chloride ions and sulfates. Concrete specialists have been trying to increase the service life of the concrete, avoiding the penetration of these harmful agents To accomplish this tough task, many researchers have focused their efforts on the development of less permeable concrete with low water/cement ratios. In this regard, the use of certain chemical admixtures and supplementary cementitious materials (SCMs) such as pulverized fly ash (PFA) as a synthetic pozzolanic material has contributed to the development of a denser cementitious matrix; a less permeable concrete by porosity reduction. The substantial improvement in the properties of the concretes due to the particular addition of chemical admixtures and SCMs have made the concrete, being classified as high-performance concrete (HPC) [1]
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