The cause, effect, and prevention of cracks in latex-modified concrete (LM) overlays were inve ligated. The types or crack that occur in concrete, whether the concrete i LM or conventional, are divided into 1wo ca1egorie: internally caused and cxlernally caused. Internally caused cracks are pla tic and hrinkage cracks. A in any qunliry c ncre1e, LM i ubjec1 to borh of the c if good construction practices are not followed. In uddition, because LM ha a low water content. ii ha'little bleed water available 10 evaporate and thu should be protected during placement if extreme drying conditions exist. Exrcnrnlly caused crack include cracks cau ed by phy ical 1e< 1ring, and nexural. reflective. and thermal cracks. All of the e proce. es can be minimiz. ed or avoided by foll wing proper construction practices. If cracking ccurs in an LMC overlay, ir i. necessary first to determine the extent of the cracking before deciding on the remedy. racks that are hallow, Ys in. deep or less, do nor affect the permeability performance f the verlay. Deeper racks, however. hould be sealed. Laboratory studie of crack-sealing techniqu indicate that the low-viscosity eaters are capable or filling most cracks and are recommended when full-depth penetration i required.

Because overlays are designed to provide protective concrete layers on bridge and parking garage decks, it is desirable to produce a concrete layer that has integrity and uniformity, and minimize any condition that will cause cracks, thus compromising the barrier properties of the overlay. Latexmodjfied concrete (LMC), like any other concret. e, will crack when the tensile stresses exerted on it exceed the tensile strength of the material itself. Like any other concrete, these ten ile stresses can be produced both by external and internal sources. Typical of these internal source are plastic and drying hrinkage. Examples of external source are tructural movement, reflective crack. $ from the deck, thermal expan· ion, and tearing while finishing.