Effects of limestone powders on pore structure and physiological characteristics of planting concrete with sulfoaluminate cement

Abstract

Limestone powders generated during the production of machine-made sands were widely used as supplementary cementitious material in making concrete, which affected concrete properties. In this paper limestone powders were added to prepare low-alkali planting cementitious material. Its alkalinity, compressive strength and fluidity were investigated to evaluate their suitability for planting concrete. Water permeability coefficient of planting concrete was investigated to make clear pore connectivity. The physiological characteristics, such as root length and relative water content of leaves, of plants grown in the planting concretes were analyzed to investigate their effects on plant growth. The results indicated that limestone powders had no effect on the alkalinity of PCMs at the early hydration ages of 1d and 3d. But the 28d alkalinity of PCM with 20wt.% limestone powder decreased to 9.67 because they reacted with CH from clinker hydration and anhydrite. Adding of limestone powders into PCMs contributed to the increase of fluidity of PCMs, but too high fluidity caused that the pores in the bottom of concrete were blocked and water permeability coefficient was decreased. The water permeability coefficient of concrete with 20wt.% limestone powders was the highest of 17.9mm/s. At 20d after sprouting root length and relative water content of leaves of plants in concrete with 20wt.% limestone powders were 11.8% and 3.2%, respectively, higher than that in concrete without limestone powders. But much more than 20wt.% limestone powders caused too high fluidity and holes at the bottom of planting concrete blocked, such as concrete with 30wt.% limestone powders, so most plants died in it.

Urban structure degradation caused by growth of plants and microbial activity

“…This is quite significant because fungi from this genus are very active in organic acid production (e.g., citric acid, oxalic acid, malic acid), which is responsible of major bioweathering and biodeterioration (1). This result is relevant because previous investigations showed that organic acid could dissolved concrete and release the calcium (27), and in this way concrete structure can be degraded. It is possible that this soluble calcium came from the dissolution of calcium carbonate and hydrated products of cementitious systems (24).…”

“…Organic acid + (Carbonates, CH, C-S-H) Very insoluble → Calcium salts very soluble → Ca 2+ + H 4 SiO 4 (in solution) [4] On the other hand, the isolated bacteria and fungi were similar to those commonly found in soils (27). These microorganisms could cause concrete degradation by producing organic acid and mineral dissolution, thus releasing nutrients (16,26).…”

“…Moreover, higher plants that establish in urban structures can also generate structural damages, but it has not been fully studied (Figure 1). However, planting concrete as an ecological concrete was conducive to prevent soil erosion and desertification, but high alkalinity of the traditional planting concrete severely limits its application (27). The hypothesis of Urban structure degradation caused by growth of plants and microbial activity • 3 this paper is that some microorganisms associated to plant roots grown in surface-deteriorated concrete of urban structures are capable of dissolving concrete and therefore release elements into solution that could be taken by plants.…”

“…The concrete biodeterioration process is particularly relevant, given the large amount of existing buildings, monuments, and different structures that have been exposed to aggressive environments for long periods of time (3,26,27). Therefore, it is necessary to establish control measures to mitigate the impact of biodeterioration (16,17).…”

Nano Titania combined with micro silica reinforced limestone cement:Physico-mechanical Investigation

“…Limestone filler knowing as inert and when added to clinker might fill the pores or spaces in the granulometric of cement without an increase in water demand, improves cement packing and blocks all the capillary pores. Hence, many researchers proved that addition of limestone to cement slightly decreases water demand, setting times and total porosity; whereas increases combined water content and compressive strength up to 15% of cement paste [7][8][9][10][11]. Whew limestone reacts with aluminate and ferrite phases from cement to form monocarboaluminate it act Egyptian Journal of Chemistry also as a nucleating sites for cement hydration products due to its high specific surface area and incorporates into the calcium silicate hydrates (C-S-H) themselves and accelerating the hydration of clinker particles especially the C3S improving early strength also may lead to the formation of some calcium carbosilicate hydrate, and reduces the potential cementing material causing a decrease in later strength and reacts with C3A forming monocarboaluminates [12][13][14][15].…”