Diatomaceous Earth—Lightweight Pozzolanic Admixtures for Repair Mortars—Complex Chemical and Physical Assessment

Abstract

The presented research is focused on the complex assessment of three different types of diatomaceous earth and evaluation of their ability for application as pozzolana active admixtures applicable in the concrete industry and the production of repair mortars applicable for historical masonry. The comprehensive experimental campaign comprised chemical, mineralogical, microstructural, and physical testing of raw materials, followed by the analyses and characterization of pozzolanic activity, rheology and heat evolution of fresh blended pastes, and testing of macrostructural and mechanical parameters of the hardened 28-days and 90-days samples. The obtained results gave evidence of the different behavior of researched diatomaceous earth when mixed with water and Portland cement. The differences in heat evolution, initial and final setting time, porosity, density, and mechanical parameters were identified based on chemical and phase composition, particle size, specific surface, and morphology of diatomaceous particles. Nevertheless, the researched mineral admixtures yielded a high strength activity index (92.9% to 113.6%), evinced their pozzolanic activity. Three fundamental factors were identified that affect diatomaceous earth’s contribution to the mechanical strength of cement blends. These are the filler effect, the pertinent acceleration of OPC hydration, and the pozzolanic reaction of diatomite with Portland cement hydrates. The optimum replacement level of ordinary Portland cement by diatomaceous earth to give maximum long-term strength enhancement is about 10 wt.%., but it might be further enhanced based on the properties of pozzolan.

Green Pervious Concrete Containing Diatomaceous Earth as Supplementary Cementitous Materials for Pavement Applications

“…The excess amount of C-S-H can replace the pore holes in the concrete mix and refine and densify the interfacial transition zone (ITZ) between aggregate particles and cement paste [53]. The immediate filler effect of DE was also reported by [52]. Moreover, a similar kind of split tensile strength increment at an early-age strength increment was recorded by [54].…”

“…Beyond 15%, there is a decrease in compressive strength that may be caused by an inadequate amount of calcium hydroxide (C-H) in blended cement, which would be needed to react with much more silica following DE addition [51]. It was also reported that mechanical parameters could be improved by up to 15% substitute for Portland cement [52]. The design shows that partially replacing cement with DE by up to 20% enhanced the compressive strength compared to the control mix.…”

“…In addition, a direct relationship between the adhesion of aggregates with paste that occurs because of the excess hydrated products from the pozzolanic reactions between SiO 2 and Ca(OH) 2 contributed to the bending resistance, thereby increasing the flexural strength [56]. Saidi et al proved that the addition of DE in concrete enhanced flexural strength at early ages [52]. However, beyond 15%, a decline in flexural strength was observed, which could be due to the agglomeration of amorphous silica and high water absorption that led to a reduction in consistency.…”

Diatomites from the Iberian Peninsula as Pozzolans

“…In their extensive scientific review, Becerra-Duitama and Rojas-Avellaneda [ 16 ] highlight, along with other materials, the positive influence of diatomites on the cement-pozzolan interface, mainly in mechanical properties, durability, water absorption, and permeability. Pavlíková et al [ 17 ] have focused their research on the improvement of mortars with diatomites intended for the repair and restoration of historic buildings and monuments and found that the optimal ratio of Portland cement to diatomite is 10%. Ince et al [ 18 ] have monitored the mechanical properties of cement mortars previously reinforced with cellulose fibers, which have been introduced into the mixtures as a substitute for fine aggregate, resulting in a significant increase in mechanical compressive strength and an evident physical and chemical stability of the specimens.…”

Experimental Study on the Mechanical Properties of Diatomite-Modified Coastal Cement Soil

“…To promote cement soil strength stability and alleviate environmental pollution, natural materials can be used to modify cement soil. Studies have found that diatomite can improve the mechanical properties of cement-based materials [ 12 , 13 , 14 ]. Diatomite is a biosilicite formed by ancient unicellular diatoms through long-term geological processes.…”