一、混凝土的凝結時間
根據水(shui)泥的具體(ti)性質及混凝(ning)(ning)土(tu)所摻外(wai)加劑的性能不(bu)同(tong),混凝(ning)(ning)土(tu)的初(chu)(chu)凝(ning)(ning)時(shi)(shi)(shi)間(jian)及終凝(ning)(ning)時(shi)(shi)(shi)間(jian)會有差別。為便于(yu)(yu)(yu)施(shi)工,常態混凝(ning)(ning)土(tu)的初(chu)(chu)凝(ning)(ning)時(shi)(shi)(shi)間(jian)不(bu)得小(xiao)(xiao)于(yu)(yu)(yu)3~4小(xiao)(xiao)時(shi)(shi)(shi);終凝(ning)(ning)時(shi)(shi)(shi)間(jian)不(bu)得大于(yu)(yu)(yu)12小(xiao)(xiao)時(shi)(shi)(shi)。一(yi)(yi)(yi)般控制在(zai)6~10小(xiao)(xiao)時(shi)(shi)(shi)。根據施(shi)工需要,選擇適合的外(wai)加劑,可以在(zai)一(yi)(yi)(yi)定(ding)(ding)的范圍內改變混凝(ning)(ning)土(tu)的初(chu)(chu)、終凝(ning)(ning)時(shi)(shi)(shi)間(jian)。國(guo)家標準規(gui)定(ding)(ding)水(shui)泥初(chu)(chu)凝(ning)(ning)時(shi)(shi)(shi)間(jian)不(bu)得早于(yu)(yu)(yu)45分鐘,一(yi)(yi)(yi)般為1~3小(xiao)(xiao)時(shi)(shi)(shi);終凝(ning)(ning)時(shi)(shi)(shi)間(jian)不(bu)得遲于(yu)(yu)(yu)12小(xiao)(xiao)時(shi)(shi)(shi),一(yi)(yi)(yi)般為5~8小(xiao)(xiao)時(shi)(shi)(shi)。
二、混凝土一方多少噸
普通混凝土因為強度和等級的不同,在重量上也有一定的差異,常規的混凝土一般有C10、C15、C20、C25、C30、C35、C40等級,最高的能達到C80。以C10為例,一立方C10混凝土通常需要用到水泥100公斤,砂石780公斤,碎石1025公斤,水160公斤,摻合料220公斤,總重量2285公斤。通常混凝土的等級越高,重量約大,選擇的混凝土品牌以強(qiang)度等級高為宜。
三、混凝土配合比
混(hun)(hun)凝(ning)(ning)土(tu)(tu)施工(gong)配合比是指(zhi)混(hun)(hun)凝(ning)(ning)土(tu)(tu)中(zhong)各組成(cheng)(cheng)材料之間的(de)(de)(de)(de)比例關(guan)系,混(hun)(hun)凝(ning)(ning)土(tu)(tu)配合比設計(ji)是混(hun)(hun)凝(ning)(ning)土(tu)(tu)工(gong)程(cheng)(cheng)中(zhong)很重(zhong)要(yao)的(de)(de)(de)(de)一項工(gong)作,它直接影響到混(hun)(hun)凝(ning)(ning)土(tu)(tu)的(de)(de)(de)(de)順利施工(gong)、混(hun)(hun)凝(ning)(ning)土(tu)(tu)工(gong)程(cheng)(cheng)的(de)(de)(de)(de)質量和混(hun)(hun)凝(ning)(ning)土(tu)(tu)工(gong)程(cheng)(cheng)的(de)(de)(de)(de)成(cheng)(cheng)本。設計(ji)混(hun)(hun)凝(ning)(ning)土(tu)(tu)配合比的(de)(de)(de)(de)基本要(yao)求(qiu)(qiu)是滿足混(hun)(hun)凝(ning)(ning)土(tu)(tu)設計(ji)的(de)(de)(de)(de)強度等(deng)級、施工(gong)要(yao)求(qiu)(qiu)的(de)(de)(de)(de)混(hun)(hun)凝(ning)(ning)土(tu)(tu)和易(yi)性(xing)、混(hun)(hun)凝(ning)(ning)土(tu)(tu)使(shi)用要(yao)求(qiu)(qiu)的(de)(de)(de)(de)耐久(jiu)性(xing),在(zai)滿足以上要(yao)求(qiu)(qiu)的(de)(de)(de)(de)基礎上降(jiang)低(di)成(cheng)(cheng)本。
四、混凝土強度低怎么辦
混凝(ning)(ning)土(tu)強(qiang)(qiang)(qiang)度(du)(du)低(di)可(ke)通(tong)過(guo)提(ti)高水泥強(qiang)(qiang)(qiang)度(du)(du)等級(ji)來增(zeng)大混凝(ning)(ning)土(tu)強(qiang)(qiang)(qiang)度(du)(du);施工(gong)時,一般通(tong)過(guo)降低(di)水灰(hui)比(bi)(bi)來提(ti)高混凝(ning)(ning)土(tu)強(qiang)(qiang)(qiang)度(du)(du)。適當降低(di)水灰(hui)比(bi)(bi),可(ke)有效控制(zhi)漿集比(bi)(bi)和(he)水泥漿層厚(hou)度(du)(du),使集料的骨架作用得到(dao)充(chong)分發揮,最終(zhong)能增(zeng)強(qiang)(qiang)(qiang)混凝(ning)(ning)土(tu)強(qiang)(qiang)(qiang)度(du)(du)。此外,還可(ke)以通(tong)過(guo)優化(hua)設(she)計(ji)工(gong)藝(yi)流程、選擇(ze)級(ji)配(pei)優良、砂率(lv)適中的高強(qiang)(qiang)(qiang)度(du)(du)碎石、采用濕(shi)熱處理養護混凝(ning)(ning)土(tu)、適量添加(jia)外加(jia)劑和(he)摻合(he)料等方法來增(zeng)加(jia)強(qiang)(qiang)(qiang)度(du)(du)。