Effect on Concrete Surface Water Absorption upon Addition of Lactate Derived Agent

Abstract

Water tightness of a concrete cover layer is important, as it is typically used as a protective coating of the steel reinforcement. Water tightness can be impaired by crack formation or by permeability. A bacteria-based lactate-derived healing agent (HA) can be added to concrete to enhance the potential for restoration of water tightness. Bacterial conversion of the included carbon source results in CO 2 production and subsequent CaCO 3 precipitation, similar to the mechanism of concrete carbonation. Carbonation is known to densify concrete, particularly when using ordinary Portland cement (OPC), but to a much lower extend in slag-based concrete (CEM III/B). To identify the effect of HA addition on concrete properties, this study focusses on the ingress of moisture in non-cracked concrete surfaces by assessing capillary water absorption. Surface properties were determined for sealed and unsealed surfaces of concrete-either based on OPC or CEM III/B-before and after curing under three different conditions: Dry, wet, or humid. HA addition to concrete containing slag cement generated a surface less prone to continued drying, but resulted in higher water absorption. In contrast, surface water absorption significantly decreased upon HA addition to OPC-based samples, independent of the curing regime. It is therefore concluded that HA in its current form is suitable for application in OPC, but less in CEM III/B-based mixtures.

A Review of Self‐Healing Concrete for Damage Management of Structures

“…Jonkers et al developed since 2006 in a series of studies a bacterial spore and an organic compound–based healing agent for providing autonomous healing potential to concrete under aerobic conditions (see and references therein, and). The specific healing agent contains organic compounds in the form of calcium salts of fatty acids such as calcium formate, calcium acetate, calcium glutamate, calcium propionate, and calcium lactate or lactate derivatives . In latter study, it was found that upon addition of a lactate‐derived bacteria‐based healing agent, surface water absorption of mortar specimen was decreased in the OPC‐based (CEM I) specimen but not (increased) in the blast‐furnace slag cement‐based (CEMIIIb) specimen …”

Bacteria-based self-healing concrete: evaluation of full scale demonstrator projects

“…Published lab-based studies have shown that, depending on the dosage of bacteria and lactate-based nutrients, cracks of up to 0.8 mm width can be sealed autonomously [14,16]. Healing of 0.8 mm wide cracks requires a dosage of 15 kg of B. alkalinitrilicuscomprising self-healing agent per m 3 of concrete mix , while a dosage of 5 kg/m 3 leads to the autonomous waterproofing of 0.4 mm wide cracks ( Figure 2) [17]. The composition of the healing agent used was 0.1% (w/w) dried B. alkalinitrilicus spores and 2% Yeast (w/w) extract both embedded in a lactate-based polymer matrix (97,7% w/w), latter functioning both as nutrient source and protective coating for the bacterial spores [21] and is commercially produced and marketed by Green-Basilisk B.V., The Netherlands.…”

“…A next generation selfhealing agent was therefore developed by the Delft group and in this one the active healing agent components (bacterial spores, yeast extract and lactate-derivatives) were pelleted using combined powder compression-and extrusion techniques which made the use of expanded clay carriers redundant [14]. Major advantage of the new generation healing agent is that it consists of 100% bio-based active ingredients not resulting in decrease of compressive strength of the resulting concrete if dosed correctly [21]. Activator of the healing agent is crack-ingress water what initiates germination of the bacterial spores.…”

“…Self-healing of an 0.8-mm wide crack in concrete at a dosage of 15 kg of self-healing agent per m 3 takes up to two months[17].…”

Properties of low-density cement-bonded composite panels manufactured from polystyrene and jute stick particles

“…This negative impact can be minimized by drying of lignocellulosic particles [17,18] or washing the particles or using additives such as calcium chloride and sodium silicate [19,20]. Alternatively, injection of carbon dioxide in the mixture can significantly improve the wood-cement compatibility [13], which also reduces the water absorption properties of the panels [21], and promote rapid strength development for the composites [22]. However, larger amount of cement is used in the CBCs for bonding in comparison to particles (cement:particles ratio is higher than 3:1), thus, the final products have higher density (> 1.3 g/cm 3 ) [2,4,23].…”